Small Fruit Fertilization and Maintenance Schedule
Regular maintenance of fruit-producing shrubs and vines maximizes quality and yield of fruit. A holistic maintenance program involves proper irrigation, fertilization, insect and disease management and pruning. Plant health depends upon healthy soils and weed management. Regular disease and insect pest scouting are critical issues for many fruit crops. The schedule in Table 1 identifies the cultural practices involved with caring for small fruiting shrubs and vines and the appropriate timing of maintenance. In addition to practices listed in the table, weed management is necessary throughout the year. For pest management strategies and more specific information regarding care of individual fruits refer to the Fact Sheets listed at the end of this document.
Fertility management is important to maintaining the health of perennial fruit crops during their life span. Because fruit crops are long-lived, it is important to assess and improve soils prior to planting. Improving soil tilth, adjusting pH and addressing fertility needs prior to planting will result in stronger plant growth and production. Nutrients such as phosphorous and potassium do not move through the soil readily and are best managed prior to planting. Soil pH is particularly critical for blueberries, which require acidic soils. It is worthwhile to take time to adjust pH prior to planting.
Fruit crops growing in soil that was properly prepared prior to planting generally require only small additions of nitrogen throughout the life of the planting. It is important to treat each crop individually — not all fruit crops have the same nutritional requirements. Specific nitrogen requirements and appropriate fertilizer rates for each fruit crop are outlined in Table 2. These rates represent average annual nitrogen needs for mature plants. Refer to specific Fact Sheets for fertilizer rates of immature plants. Visual growth inspections will help tailor nitrogen needs. If plants are growing too vigorously, reduce nitrogen application rates. Slow growth may indicate a need for higher nitrogen rates.
Soil tests deliver more accurate nutrient requirement recommendations based on the specific growing location and are recommended every three years. Some crops require applications of macronutrients or micronutrients in addition to nitrogen. If a nutrient deficiency is suspected, conduct a soil test to determine if additional fertilizer is needed.
Consider soil characteristics and plant requirements when selecting fertilizer. For example, blueberry and kiwi crops require acidic soils (low pH) for optimum plant nutrition. Specifically, blueberries perform best in soils with pH between 4.0 and 5.5 and kiwi performs best in a pH of 5.0 to 6.5. Soil pH can be amended through applications of sulfur prior to planting (Extension Fact Sheet HLA-6248, Blueberry Production for the Home Garden). Clay soils are more difficult to amend than sandy soils. It is also beneficial to utilize a sulfur-based fertilizer for these crops if soil pH is high. The sulfur will help lower soil pH to more appropriate levels. Fertilizers useful for acid-loving plants include sulfur-coated urea, ammonium sulfate and cottonseed meal.
Apply fertilizers uniformly around the drip line of the plant and one foot outward, but never near the base of the plant. Be careful to ensure fertilizer does not come in contact with the trunk or branches as this will damage the plant. It is best to apply fertilizer when the foliage is dry. Avoid getting any on the leaves. If the fertilizer does come in contact with leaves brush it away immediately. Gently work fertilizer into the soil with a rake, taking care to avoid plant roots. Apply one inch of water if rain is not expected within one or two days. Failure to work fertilizer into soils will result in loss of nitrogen to the atmosphere when air temperature is high.
Some gardeners prefer organic sources of nitrogen. The fertilizer chart includes blood meal and cottonseed meal as organic fertilizers. It is important to note that cottonseed meal also contains small amounts of phosphorous and potassium. Manure is often used as an organic fertilizer, but care must be taken. Only use manure from a reliable source and be sure it has been composted at least six months. Growers must also be cautious of herbicide residues in composted manure. Manure is most effectively used in pre-planting soil preparation or in fall applications. Incorporate 0.5 pounds of manure per square foot into soil or apply as a side dressing for established fruits. For vines and shrubs, spread manure in a four-foot circle around each plant, keeping the manure at least one foot away from the base of the plant. If using poultry manure, apply only 2.5 ounces per square foot.
This guide includes care of common fruit crops that can be grown throughout the state including strawberries, blackberries, blueberries, grapes, elderberry and gooseberries. Other crops are best suited for only portions of the state. Raspberries are not heat tolerant and will perform best in northeastern areas of Oklahoma. Kiwi and passionflower are best suited to wetter areas of the state in the east and southeast.
Table 1. Calendar of maintenance and fertilization needs by fruit crop.
Table 2. Fertilizer application rates by fruit crop. Rates are given for each appropriate fertilizer; use only one fertilizer for each application. Rates are given for MATURE plants; refer to specific Fact Sheets for application rates for young plants.
OCES Fact Sheets on Small Fruit Production:
HLA-6229 – Pollination Requirements for Fruits and Nuts
Former Assistant Extension Specialist