Establishment and Maintenance of Blueberries

The rabbiteye blueberry (Vaccinium ashei) is native to the southeastern United States. Its native habitat ranges northward from central Florida to eastern North Carolina and westward to eastern Texas and southern Arkansas. The highbush blueberry (Vaccinium corymbosum) is native to the eastern coast of the United States and is the type grown commercially in New Jersey, Michigan, and other northern states as far south as North Carolina and northern Arkansas. Southern highbush types resulted from crosses between the highbush blueberry and native Southern blueberries. Rabbiteye and southern highbush are the two types that can be grown in Mississippi.

The Mississippi blueberry industry presently consists entirely of rabbiteye blueberries, with southern highbush being recommended for trial plantings. The industry began in the mid-1970's with very small acreage and had grown to more than 1,000 acres in 1990. The potential for further growth of the blueberry industry in Mississippi appears promising.

The rabbiteye blueberry differs in several ways from the highbush blueberries grown in northern states. The berries themselves, however, closely resemble those of the highbush, and the two are essentially the same in the market place. Rabbiteye plants are very vigorous, and yields are high in comparison with northern varieties.

Blueberry plantings are relatively expensive to establish when compared to short-term crops, but they generally remain productive for a long period of time. You should plan carefully when preparing to establish a blueberry planting. Carefully consider site selection, varieties, water source and quality, harvesting, and marketing. This publication looks at these and other factors.

Establishment

Site Selection and Preparation

Rabbiteye blueberries require acid well-drained soils with a pH of 4.0 to 5.5. The optimum pH is thought to be about 4.8. You should take a soil sample to determine the pH and the nutrient content of the soil. As a general rule, blueberries grow best on land that has been recently cleared or never planted in crops. Blueberries do not grow well in soils high in calcium (greater than 900 pounds per acre). Plants growing on land with an improper pH may become yellow and grow poorly.

Avoid planting blueberries in soil containing large amounts of wood ash as found in windrows burned on newly cleared land. Burned wood deposits minerals and salts that raise the pH above the acceptable range for good blueberry growth. If windrows have been burned, sample such areas separately and apply sulfur as indicated by soil test results.

Soils with a native pH above 5.5 are difficult to adapt to blueberry culture, and you should avoid them. On the other hand, cultivated land that has been limed in the past may have an artificially high pH, which can be lowered by adding sulfur. You should work the recommended amount of sulfur into the soil six months before you plant the blueberries.

Low-lying areas with a high water table are not recommended for blueberries, but you can use such sites if the water table stays at least 2 feet below the soil surface year-round. If you plant blueberries on poorly-drained soils where the water table is less than 2 feet deep, you should form raised planting beds. The bed should be 8 to 12 inches high. Blueberries will not tolerate standing water or grow well in excessively wet areas.

You should kill perennial weeds in the summer before planting. This usually requires cultivation and using a systemic herbicide. Weed control is difficult in blueberries for the first two years after planting. Eliminating perennial weeds before planting greatly reduces later problems.

Irrigation

Blueberry plants require from 1 to 2 inches of water per week. Newly established plants have the most critical water needs and can be damaged by either over watering or under watering. Upland soils in the Gulf States region are well drained but have low water-holding capacity. Short periods (one to three weeks) without rain can stress blueberry plants severely. Irrigation during such periods is required for optimum plant performance.

Irrigation of producing blueberry plants during dry periods before harvest results in larger berries and higher yields. Also, irrigation in August and September will stimulate growth and fruit bud formation, thus increasing the potential yield for the next blueberry season.

A rapid decrease in soil moisture during dry periods increases the concentration of fertilizer nutrients in the soil solution, which may damage roots. Irrigation lowers the concentration of nutrients in the soil solution and reduces the risk of fertilizer damage.

Trickle irrigation is the most common system growers use. This is the most efficient way to distribute water to blueberry plants. The trickle irrigation system operates on low water pressure and consists of polyethylene tubing laid down the row with an emitter placed under each plant. The emitter discharges a calculated amount of water on the soil surface beneath each plant. The recommended rate is 8 to 12 gallons per week per plant, which may be divided into three applications. Water requirements increase as plants age and grow and vary due to soil type, organic matter, and natural climatic conditions. Most trickle irrigation systems are buried to eliminate deterioration from ultraviolet light and protect them from damage by animals or equipment.

The water source may be ground water or impounded water. Regardless of the source, the water should be tested to determine suitability for blueberry irrigation. To prevent the clogging of emitters, you should filter impounded water.

You should check water quality before planting to see if it is suitable for blueberry production. Mississippi State University Extension Service county agents or the State Chemical Laboratory can do this. Specify that the water will be used for irrigation of blueberries.

Rabbiteye Varieties

Proper variety selection will determine, to a large extent, the profitability of the blueberry operation. Select varieties based on the targeted market, desired harvest interval, and location (Tables 1 and 2). Certain varieties are not adapted to machine-harvest or fresh market sales, but these same varieties may be excellent choices for pick-your-own operations. Among rabbiteye varieties, Climax, Premier, Brightwell, Tifblue, Beckyblue, and Powderblue are the best suited for mechanical harvesting for the fresh fruit market. Recommended varieties are listed in ripening categories. Many other varieties are available but are either obsolete or no longer recommended. Because most rabbiteye blueberries require cross pollination for maximum fruit set, plant two or more varieties in each field.

Early Season

Bonita - A pick-your-own and fresh shipping variety from Florida that you can harvest mechanically for the fresh market. The bushes are moderately vigorous and ripen about three days after Climax. The fruit has good color, size, and firmness with a dry picking scar. 350-400 chill hours. (Florida, 1985)

Climax - Upright, open plants. Berries are medium in size, medium dark blue in color, have a small scar, and good flavor. Early season, ripening three to five days before Woodard. Concentrated ripening, excellent for machine harvest and fresh market. 450-500 chill hours. (Georgia, 1976)

Woodard - Ripens early, seven to ten days before Tifblue. Bush size shortest and most spreading of Georgia varieties. Produces many suckers. Berries are light blue, firm, large, with excellent quality when fully ripe but very tart until ripe. Has wet scar, not well suited for shipping. 350-400 chill hours. (Georgia, 1960)

Brightwell - Early, same season as a Woodard. Berries are medium in size and blue in color, with small dry scars and good flavor. Plant growth is vigorous, upright, and produces enough new canes to renew the plant. Plants may be mechanically harvested for the fresh market. Fruit ripens over a relatively short period beginning after Climax. 350-400 chill hours. (Georgia, 1981)

Premier - Matures earlier (two to three weeks) than Tifblue. Large fruit with good flavor. Vigorous, disease resistant, productive. 550 chill hours. (North Carolina, 1978)

Beckyblue - Early ripening, has a low chilling requirement. Extends the cultural range of rabbiteye blueberries into south-central Florida and southern Mississippi. Bush is moderately vigorous and fruit has good color, size, firmness, and a dry picking scar. It can be mechanically harvested for the fresh market. 300-400 chill hours. (Florida, 1978)

Mid-Season

Briteblue - Bush is moderately vigorous, grows upright and open. Mid-season, generally ripening before Tifblue. Berry firmness, heavy bloom, and small dry scar combine to make this a good shipper. Fruit has good flavor when fully ripe. Berries are easily hand picked because they grow in clusters. Mature berries have a long retention on the plant, making it attractive for pick-your-own operations. 500-600 chill hours. (Georgia, 1969)

Late Season

Centurion - Later than Tifblue. Adds one or more weeks to the rabbiteye ripening season. Bush is vigorous, upright, with limited suckering. It blooms late and the flowers are self-fertile. Ripening season begins in late July and extends through August into September. Fruit is medium sized, medium to dark blue, good quality with aromatic flavor. Recommended for pick-your-own operations. 550-650 chill hours. (North Carolina, 1978)

Baldwin - A productive, late ripening variety with good flavor and firm dark blue fruit. Has lengthy ripening period, adapted to pick-your-own and backyard plantings. It is not recommended for mechanical fresh market harvest. 500 chill hours. (Georgia, 1985)

Southern Highbush Varieties

Several new varieties have been developed recently that show promise of producing early ripening blueberries. Rabbiteye varieties ripen in June or July. The new southern highbush varieties should produce ripe blueberries in May.

Southern highbush varieties require somewhat different cultural practices from rabbiteye and are more specific in their requirements. Southern highbush blueberries need well-drained soil and irrigation. Growth will be poor in wet fields and plant losses high from root rots. You will need to use raised beds or drainage if you have wet conditions. You will also need to practice annual winter pruning to reduce the number of flower buds per plant. Some varieties will be stunted if you do not remove flower buds when the plants are young.

Spacing of southern highbush blueberries should be closer than rabbiteye, since they are not as vigorous. For most varieties of southern highbush, a spacing of 4 feet by 10 feet or 4 feet by 12 feet should be ideal. Most southern highbush varieties are self-fertile, but cross pollination may improve production.

The following is a list of some southern highbush varieties available for Mississippi. These are listed in probable ripening order.

O'Neal - Very early, ripens in early May in south Mississippi. Vigorous, semi-upright, productive; fruit very large, medium blue, excellent firmness, picking scar, and flavor, blooms over an extended period. Adapted for pick-your-own or hand harvest for commercial shipment. Chilling requirement, 400 hours. (North Carolina, 1897)

Gulf Coast - Ripens in mid-May in southern Mississippi. Vigorous, semi-upright, medium productivity; fruit medium in size, firm, small stem scar, and good flavor. 400-500 chill hours. (Mississippi, 1987)

Cooper - Ripens in mid-May in southern Mississippi. Moderately vigorous, upright, productive with medium-sized fruit. Flowers later than Climax but ripens two weeks earlier than Climax. 400-500 chill hours. (Mississippi, 1987)

Georgiagem - Ripens in mid-May in southern Mississippi. Moderately vigorous, upright, productive with medium-sized fruit that has good color; small scar, firm. 350 chill hours. (Georgia, 1987)

Cape Fear - Ripens in mid-May in southern Mississippi. Vigorous, semi-upright, very productive; fruit large to very large, light blue, excellent firmness and picking scar and good flavor. Recommended for pick-your-own and hand harvest for commercial shipment. 500-600 chill hours. (North Carolina, 1987)

Blue Ridge - Ripens mid-to-late May in southern Mississippi. Vigorous, upright, productive; large to very large, firm, high acid flavored fruit. Adapted to pick-your-own and backyard plantings. Has wet stem scar. 500-600 chill hours. (North Carolina, 1987)

Selecting, Handling, and Setting Plants

You should get healthy true-to-name plants from a reputable nursery. You will propagate blueberries from cuttings taken in the spring of the year. Blueberries for commercial use are usually purchased as a two-year plant or one that has grown through two growing seasons. You may buy plants in containers or as bare-root plants.

You should buy container plants in one-gallon or larger containers. Water them when you get them and keep them moist until you plant them. If plants are still in containers when freezing weather arrives, saturate the root media in the containers before each hard freeze. This will help to insulate the roots from freeze damage. When you set container plants into the field, it is important to break up the rootball or make several vertical slashes with a knife. In transplanting blueberries, be careful to keep roots from drying out.

Check bare root plants when they arrive to see if the roots are still moist. Blueberry roots are naturally brown on the outside and white on the inside. Plant bareroot plants immediately after you get them. If you cannot plant them within a few days, heel them in.

Before planting, cut plants back to a height of 6 to 12 inches or remove at least 50% of the top, including all flower buds. Do not allow newly set plants to flower and fruit the first year.

Plants may be spaced 6 feet apart in rows 12 feet apart; this will require 605 plants per acre. If you are planning to harvest the fruit with an over-the-row mechanical harvester, setting the plants 5 feet apart in the row may increase harvesting efficiency. The 5-foot by 12-foot planting arrangement will require 726 plants per acre. Southern highbush blueberries grow slower than rabbiteyes and may be planted as close as 4 feet by 10 feet. This spacing requires 1,089 plants per acre.

Plant blueberries during the dormant season, which is mid-November through February in southwestern Mississippi. It is generally more desirable to plant before the end of December because that gives the plants more time to establish roots before spring growth begins.

To prepare for planting, disk or work the soil well within the planting row. Use a subsoiler if a hardpan exists. Open a planting furrow with a middle-buster. Studies have shown that burying 2 gallons of moist peat moss beneath each plant at the time of planting will result in faster plant growth. Do not use sawdust or wood chips this way because they take nitrogen from the soil as they decay. If you are planting on ideal blueberry soil, you may reduce the amount of peat.

If you are planting where soil conditions are not optimum (high pH, heavy soil, very poor sandy soil), you may use more peat. Sometimes you may use fine pink bark as a peat substitute. Mix the moist peat moss well with soil and then place the soil-peat mixture around the blueberry roots.

Set the plants at the same depth they grew in the nursery or one-half inch deeper. Do not expose the shoulder of the rootball because this will cause a wicking effect and dry out the rootball. Never put fertilizer in the hole at the time of planting.

Another system of planting is to dig individual holes about 2 feet in diameter and 2 feet deep with a soil auger or shovel and fill the hole with a mixture of soil and peat moss and set the plants as described previously.

Pollination

Rabbiteye blueberries require cross pollination between different varieties for good fruit set. Plant varieties in alternating rows so that each row is bordered by a row containing a different variety. Planting the same variety on a row is advantageous for ease of harvesting, so do not mix varieties within the same row, but plant so adjacent rows have different varieties. Two schemes for a six-row planting are shown below:

Southern highbush blueberries are self fertile, but planting with other varieties may increase fruit set and size.

Insects are necessary to pollinate blueberries. Wild bees and honeybees are primarily responsible for blueberry pollination. In plantings of one acre or larger, it is usually beneficial to have one or two hives of honeybees per acre present at flowering.

Management

Fertilization

Fertilization of blueberries is very important, and you should carefully consider it because excessive or incorrect use of some fertilizers may cause damage. Blueberries have a low tolerance for fertilizer and young blueberries are often killed by over-fertilization by using the wrong type of fertilizer. For this reason, no fertilizer is recommended the first year. Blueberries prefer the ammonium form of nitrogen instead of the nitrate form. Ammonium sulfate is most often used. You should avoid ammonium nitrate and other nitrate-containing fertilizers because nitrate ions are very damaging to blueberries on certain soil types.

Fertilizers of any kind can damage or kill blueberries when applied in excess. Fertilization rates that are ideal for other crops may kill blueberries. A number of factors influence the effect of fertilizer on blueberry plants. These include soil moisture, soil type, plant age, mulching practices, and plant growth status. Because of this, it is hard to give a simple rule for fertilizing blueberries that will work in every case. General guidelines are listed, but each grower needs to adjust his fertilization rate based on the plant response he observed on his farm. Mild fertilizer injury is indicated by brown colored leaf chlorosis, particularly around leaf margins. More severe fertilizer burn causes leaf drop and possibly plant death.

The primary goal in fertilizing blueberries is to promote rapid vegetative growth in young plants so that they reach maturity as soon as possible. After plant size has been achieved, the primary goal is to maximize fruit yield.

The USDA Small Fruits Laboratory in Poplarville, Mississippi has developed two blueberry fertilizers that have shown good results:

1. An acid-forming fertilizer, 14-8-8, with a nitrogen source of ammonium sulfate and diammonium phosphate. Use this formulation on soils with a pH above 5.2.
2. Non-acid-forming formulation, 18-10-10, with the nitrogen source being urea. Use this formulation on soils with a pH below 5.0.

The filler material in both formulations is cottonseed meal. Contact your county Extension agent or state Extension specialist for sources.

Irrigation

Blueberry plants require from 1 to 2 inches of water per week in the first year or two of growth. Upland soils in the Gulf States region are well-drained but have low water-holding capacity. Short periods (one to three weeks) without rain can stress blueberry plants severely. Irrigation during such periods is required for optimum plant performance.

The rapid decrease in soil moisture during dry periods increases the concentration of fertilizer nutrients in the soil solution, which may damage plants. Irrigation lowers the concentration of nutrients in the soil solution, and this reduces the risk of fertilizer damage.

The most efficient method of irrigation is a drip or trickle system. This requires a filtering system for water from ponds or lakes. Excellent results have been obtained with in-line swimming pool filters that use a sand medium. Water from most wells can be filtered inexpensively unless it has a high iron content.

The trickle irrigation system operates on low water pressure and consists of polyethylene tubing laid down the row (buried or on top of the ground) with an emitter placed above ground near each plant. A calculated amount of water is discharged on the soil surface beneath each plant. The recommended rate is 8 to 12 gallons per plant per week, which should be in split applications. Water requirements increase as plants increase in age and size.

This system operates under low pressure and requires less water for a given area than an overhead system, thereby increasing efficiency of the pump.

Frost and Freeze Protection

Most rabbiteye blueberry varieties require 400 to 500 hours of chilling (below 45°F) to break dormancy. Until the cold requirement is achieved, an extended period of warm weather will not usually cause floral budbreak. Once the chilling hour requirement has been satisfied, extended periods of warm temperatures will initiate flower bud growth.

Susceptibility to cold damage in rabbiteye blueberry blooms is directly related to the stage of development. As flower development progresses, susceptibility to damage becomes increasingly greater. Flower buds that have visibly swelled but with flowers still completely enclosed can withstand temperatures as low as 21°F. Buds in which bud scales have abscised and individual flowers are distinguishable are killed at 25°F. Flowers that are distinctly separated with corollas unexpanded and closed are killed at 28°F. Fully opened flowers and fruit are severely damaged at 29°F.

Certain varieties seem to be more cold tolerant than others. This is primarily due to the predominant state of floral development at the time of the occurrence of the freezing temperatures. Earlier blooming varieties (those with a low chilling hour requirement) are the most prone to freeze injury, since they will have the greatest number of blooms at an advanced stage of development when freezing temperatures are most likely to occur.

The common method of determining if buds have been frost damaged is to cut through the bud several hours after a freeze. This gives time for browning of fruit or flower tissue that may have sustained injury. Sometimes the freeze injury is not severe enough to kill the fruit or flower completely but may affect some individual part, such as the pistil, stamen, or seeds, which may result in a reduction of fruit set or size. Blueberry fruits can develop and mature after a portion of the ovaries are damaged. However, since fruit size is highly correlated with seed number, fruits from seed-damaged flowers are usually smaller.

Freeze damage is also the cause of scarring on fruit, which results in reduced quality. The area of the fruit exposed to cold temperatures will desiccate and result in a brown ring around the calyx end. Since this tissue is desiccated, it is more brittle than surrounding tissue and may be the site of splitting during periods of unusually wet weather during harvest. At best, it will cause a discolored ring and possibly some disfigurement of the fruit.

Considerable work has been done to find methods of protecting flowers from freezing. The difficulty in making recommendations about freeze protection is that every freeze is different. Weather conditions, wind, weather, temperature before the freeze, and stage of growth of the plant are a few factors that affect the overall picture.

Overhead sprinkling is the most effective method of frost protection. However, it is also somewhat expensive to install and requires a large volume of water. Water volume is critical. Water must be consistently applied because ice is a very poor insulator and the protection comes exclusively from the constant application and freezing of water, which keeps the plant tissue at 31.5°F. The water must be continuously applied to the plants until the air temperature has risen to 32°F (34°F if conditions are windy). If the water is turned off too soon, the entire crop may be lost.

Other methods include creating heat or wind currents or a combination of the two. If windy conditions occur with a freeze, this method will prove ineffective. However, if an inversion frost situation occurs and a warmer layer of air exists 50, 100, or 200 feet above the ground, creating air currents to mix the air may achieve some protection. Air mixing may be accomplished with helicopters or by building fires throughout the planting. Even though the fires generate some heat, the protection is primarily derived from the air-mixing action that results from the heat-generated air currents.

Weed Control

Weed control during the first two years is probably the most difficult problem in establishing a blueberry plantation. Weeds compete with blueberry plants for water, nutrients, and sunlight. Weeds also decrease harvesting efficiency and interfere with maintenance operations such as pruning and fertilization. Effective weed control begins in the summer and fall before transplanting by using a combination of herbicides and cultivation. Planting rows should be thoroughly disked and weed-free at the time of planting.

You should maintain a weed-free strip, 4 feet wide, centered on the plant row, throughout the life of the blueberry planting (see here). Establish a sod in the middles between the rows and maintain it by mowing. Centipedegrass, carpetgrass, or some native grasses are better choices than bahiagrass or bermudagrass, which grow much faster and require higher maintenance.

Use herbicides, shallow cultivation, or mulching to control weeds in the weed-free strip. Several herbicides are labeled for use with blueberries. Always follow label instructions carefully when using any herbicide. County Extension agents or state Extension specialists can assist with specific weed control recommendations.

Mulching

Mulching with organic materials, such as pine bark, pine needles, leaves, hay, or other organic materials is expensive but very beneficial. Mulch helps control weeds and helps keep the soil moist and cool. A good mulch is 4 to 6 inches deep and covers a 4-foot band centered on the plant row. The mulch needs to be replenished as it deteriorates. A deteriorating mulch adds organic matter to the soil and creates a favorable environment for root growth but can cause damage from root exposure if not replenished.

The economic feasibility of mulching large commercial plantings is questionable but is highly recommended for small plantings, pick-your-own operations, and home plantings.

Pruning

Before planting blueberries, prune them back to a height of 6 to 12 inches, removing at least 50% of the top, including all weak shoots and flower buds. Additional pruning usually is not needed in the year of establishment.

Rabbiteyes

After the first year, rabbiteyes require very little pruning in comparison to other fruit crops. The objective is to keep the plant properly shaped and of a size that fits a particular harvesting method. If you use mechanical harvesters, the plants should be narrow at the base with excess suckers removed, and plant height should fit the parameters of the harvester. Height control and rejuvenation are generally needed when rabbiteyes become 6 years and older.

Pruning rabbiteyes in the second through fifth years consists mainly of removing the lower twiggy growth, dead or damaged shoots, and weaker growth. In the post-harvest season, remove the top one-third of tall shoots to encourage lateral branching and prevent excessive drooping in the next fruiting season. Shape plants for mechanical harvesting by removing all shoots growing outside a 12-inch crown within the row.

Prune plants immediately after harvest. This permits shoot regrowth and flower bud formation before plants become dormant (see here).

When plants become too tall to harvest easily, summer prune immediately after harvest to reduce top height by removal of about one-third of the older canes. This permits better light penetration into the center of the plant. You should do height reduction pruning annually after the plants are mature by raising the cutting height 6 inches from the year before. This allows new growth to form on previous year's wood, which will be the site of next year's crop. When the plant becomes too large for the desired harvesting program, make a rejuvenation cut at about 4 feet and begin the annual pruning process again as previously described.

Southern Highbush

Pruning methods and principles for southern highbush are similar to those used in northern highbush blueberry production. That is, mature plants are annually pruned to regulate fruit size and quantity plus the growth of new fruiting wood and not to maintain bush size for ease of harvest, as is usually the case in rabbiteye blueberries. Unpruned southern highbush plants usually have weak growth and small, later-ripening fruit.

When planting southern highbush blueberries, cut back about one-half of the plant top to remove all flower buds. The next year, remove all flower buds if plants are not growing vigorously. Both years remove all low and weak growth. In older plants, annually prune to produce new vigorous growth and to reduce flower bud numbers. Remove old (4- to 6-year-old) canes near the crown, and on young canes, cut back weak shoots to a strong lateral branch. Southern highbush blueberries are usually pruned when plants are dormant.

Disease Control

Diseases seldom are a serious problem in rabbiteye blueberries. Rabbiteye blueberries are more resistant to fungal infections than are highbush blueberries.

Root rot can cause problems, especially in wet, poorly drained soils. Stem blotch is characterized by red blotches on the previous season's growth, and anthracnose can cause stem dieback on more susceptible varieties.

These and other reported diseases are found only in isolated situations and are not considered serious problems at present. There is no disease spray program for rabbiteye blueberries.

Insect Control

Rabbiteye blueberries are more resistant to insect damage than are highbush varieties. Relatively few insect species attack the rabbiteye varieties and, as with diseases, damage occurs only in isolated cases.

Insects known to attack blueberries include stem borers, cranberry fruit worms, leaf rollers, mites, bagworm, orange-striped oak worm, yellow-necked caterpillars, and scales. Fire ants are a major problem. You should eliminate them.

An insecticide spray program is not necessary because insect infestations are infrequent. However, you should monitor your orchard and spray with an approved insecticide if you detect an infestation.

Harvesting

Rabbiteye blueberries in southern Mississippi normally begin ripening in early June and continue into late July. They continue to ripen into mid-August in northern Mississippi. Southern highbush varieties begin ripening mid-May and are usually finished by early June. Blueberry fruit will continue to ripen for several days after they turn blue. Maximum flavor and size are achieved 5 to 7 days after the fruit turns blue. This is the best time to pick for home use or pick-your-own operations. Fresh fruit that will be packed and shipped needs to be picked before the fruit reaches its natural peak in the field. If you leave the fruit until it has reached its peak, it will be too soft to handle and the shelf life will be shortened considerably.

You must harvest fruit every 5 to 7 days, and depending on variety, three to five pickings may be necessary to complete harvest. In order to reduce field heat in berries, you should harvest in the early morning hours, late afternoon, or at night. Delay picking each day until after the dew has evaporated to reduce post-harvest fruit rots. Some drying of dew-moistened fruit may be done in an air conditioned, low humidity room.

Excessive rainfall can cause splitting of ripe berries. If heavy rains occur, harvest berries at closer intervals. If rains continue long enough that the harvest intervals are extended to where fruit is overripe, you will have to harvest the overripe fruit and sell to the processing market. When you become current with harvesting again and the overripe fruit is out of the field, you can resume harvesting for the fresh market.

Where available, hand harvesting is used for fresh market berries. Roll ripe berries into your hand and place them into gallon buckets or directly into pint containers in which they will be sold on the fresh market. Usually some grading of hand-picked fruit is necessary, but be careful not to handle it any more than necessary during picking, sorting, and packing. Handling removes the "bloom" or surface wax, which gives the fruit its characteristic blue color. This can subject it to bruising and the spread of organisms that cause decay.

You can mechanically harvest blueberries with a catch frame or over-the-row harvester. Because mechanical harvesting removes some leaves, twigs, and immature and overripe fruit during the harvest operation, grading is necessary. A common blueberry grading line consists of a blower unit (removes leaves, small twigs, and immature berries), a tilt belt (removes soft and misshapen berries), and a sorting table. A conveyer belt moves the fruit along the sorting table for visual inspection and hand removal of the remaining undesirable berries. A greater percentage of mechanically harvested berries will go to the processing market, and mechanically harvested fresh market berries have a shorter shelf life than hand-picked berries.

Southern highbush berries are more perishable than rabbiteye berries and should be handled carefully during harvest and grading to assure marketing of high quality fruit.

Storage life of rabbiteye blueberries is quite good if you handle them properly. Store and transport packed blueberries at temperatures of 32°F to 35°F and 85% to 90% relative humidity. If you handle and refrigerate them properly, blueberries should have 2 weeks of storage and shelf life measured from the day of harvest.

Propagation

Blueberries usually are propagated from softwood or hardwood cutting selected from healthy, disease-free mother plants. Cuttings are placed in a propagation bed in a medium that holds moisture well but allows adequate aeration. Water is delivered with an intermittent misting system (see here).

Softwood Cuttings - Take softwood cuttings (4 to 5 inches long) in late spring from the tips of the current season's growth. Collect these when stems are still somewhat flexible and terminal leaves are half-grown to almost mature (see here). Cuttings taken too early (terminal leaves very succulent, stems very flexible) wilt readily. If cuttings are taken too late (mature leaves, second flush of growth initiated), poor rooting will occur. Rooting usually is more successful when you get cuttings from the first blush of spring growth. However, you can collect cuttings from growth flushes occurring later in the growing season.

Take cuttings from the upper part of the mother plant. Use sharp, clean pruning shears or knives disinfected in a solution of 1 part household bleach to 5 parts water. Disinfect tools between mother plants. Remove lower leaves by pulling them upward to avoid tearing the bark, leaving the two or three terminal leaves. Don't allow cuttings to dry; keep them moist and cool after collection. Place cuttings in the propagation bed as soon as possible at a depth of one-half to two-thirds of their length (see here). Cuttings are usually planted at a 2-inch by 2-inch spacing. Pre-punching holes in media is often advantageous. Firm media around the base of cuttings to avoid air pockets.

Hardwood Cuttings - Hardwood cuttings are taken during the dormant season after sufficient chilling has occurred, usually late January through February. Collect strong, healthy shoots or "whips" (usually 12 to 36 inches long) that grew the previous summer. Divide these "whips" into sections 5 to 6 inches (see here) long with a sharp knife or a bench saw with a fine blade. If the terminal of the shoot contains flower buds, remove the flower buds or discard the tip.

You can use the same beds and media for softwood propagation and for hardwood cuttings. Insert cuttings into the medium from one-half to two-thirds of their length. Press the medium firmly around the base of cuttings, which are usually spaced 2 inches by 2 inches. Keep the propagation beds moist, but be careful not to use too much water. You can water hardwood cuttings with a sprinkler until the leaf out, then mist-water them while in leaf but not yet rooted.

After cuttings are rooted you can apply a dilute complete liquid fertilizer weekly. Plants can remain in the propagation bed until winter (use little or no fertilizer in this case), when you should transplant them into pots or nursery beds and hold them for one year. If plants are strongly rooted by June or July, you can transplant them to pots, place under shade, and fertilize with a slow-release complete fertilizer two weeks after transplanting. This method often results in plants large enough for field planting the next winter.

Propagation beds need to be well-drained, under shade cloth (40%-70% shade), and have adequate ventilation. Avoid excessive wind movement that may interfere with mist control.

Propagation Media - A medium that retains moisture well but allows aeration is necessary. Media containing various propagation mixtures of coarse sand, ground pine bark, perlite, sawdust, and peat moss have proven satisfactory. Root development is best when the rooting medium contains at least 25-50% peat moss. Mixtures of coarse sand, ground pine bark, and peat moss (1:1:1) or perlite and peat moss (1:1) often are used.

Mist System - The mist system should keep the media uniformly moist but not soggy. If only a few drops of water can be squeezed from a handful of media, the amount of moisture is probably correct. An intermittent-mist system is needed to keep the humidity around the cutting near 100%, preventing wilting, and keep the medium moist. Starting with a porous medium that holds moisture well, adjust the mist system to maintain turgid (non-wilted) leaves and high humidity. Frequent (2 to 10 minutes) short misting intervals (2 to 10 seconds) are recommended.

By John Braswell, Horticulture Specialist, Mississippi State University Extension Service; James M. Spiers, Research Horticulturist, USDA-ARS; C. Pat Hegwood, Jr., Associate Horticulturist, Mississippi Agricultural and Forestry Experiment Station

Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex age, disability, or veteran status.

Publication 1758
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director