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By C. Darren Butler and Ann Clary
For gardeners lucky enough to have citrus trees, fall is a time of anticipation. Citrus trees may be bulging with full-sized but unripe fruit. It may seem that the fruit remains green and unripe month after month – because it does! Unlike most temperate fruits, citrus may need several months to ripen.
Make the most of your harvest and keep your trees healthy by following these five simple tips. For early varieties, you might be harvesting home-grown oranges, lemons and grapefruits by the middle of December. Sweetness of citrus fruits improves if they’re left longer on the tree.
Rinse citrus leaves. After months of summer smog, ash from fires, and other pollution, citrus leaves need a shower. This gritty layer of silt and dirt on citrus leaves slows or inhibits the trees’ ability to perform photosynthesis. Trees need a lot of energy to ripen fruits, while pollution on leaves may limit how much sunlight they’re able to “eat.” So take out your garden hose and wash away the grit. Don’t worry if you can’t clean off every leaf – just washing off a portion of leaves will help your trees.
Acidify your soil with vinegar. Citrus trees generally prefer soil pH at about 6.0 or below. Iron and other nutrients become decreasingly available to trees when soil pH is above 6.0. Citrus trees tend to develop nutrient deficiencies at pH of 7.0 and above. Soils in Southern California are naturally alkaline, and watering over years with alkaline city water only makes them more so. Acidify your soil by adding 1/3 cup of vinegar to 2 gallons of water used as a soil drench after regular watering. Most trees will benefit from this extra acidity at least twice per month.
Remove mulch from the area immediately surrounding the trunks of citrus trees. Mulch may shift around during windy weather or be moved by the blowers of many a city gardener. Fall before rains is a good time of year to doublecheck that mulch hasn’t migrated toward tree trunks. Mulch traps moisture against tree trunks and major roots, and may encourage root rots, crown rots, and other diseases. Clear an area with no mulch and bare soil only around tree trunks to a minimum 6-inch radius from small tree trunks, and 1-to-2-feet or larger radius from the trunk for established and mature trees.
Monitor water needs. After the heat of the summer, many gardeners cut back on water in their yards. However, citrus trees still need regular, deep watering (usually every few weeks for established trees) while fruit is ripening. Slightly curled leaves on citrus trees usually indicate that trees need more water. If leaves are folded almost in half or drooping, this may indicate serious drought stress. Flat citrus leaves generally indicate that a tree is adequately watered.
Apply a minimal amount of a balanced fertilizer formulated for citrus trees or fruit trees. Citrus benefit from rich acidic soil. In most yards, they need regular fertilization about every month or two for optimal growth and yield. If you aren’t fertilizing regularly, do so at least once when citrus are budding and blooming, and again after they set fruit. Encourage a productive harvest by applying a small amount of a balanced fertilizer, generally with reduced nitrogen while fruiting. Beware: applying too much nitrogen will promote foliage growth at the expense of ripening fruit. Dr. Earth Fruit Tree Fertilizer is an excellent fertilizer formulated for fruit trees.
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