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Index : Citrus and Other Fruits
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- 6. Helping Citrus Trees Recover - Top
- Our cold winter weather left many citrus looking very scarred and damaged. Temperatures in the teens caused citrus branches to freeze back. It also damaged flower buds. So in addition to brown leaves and frozen stems you may have noticed a lack of flowering.
Citrus flower buds are formed in the Winter, after a certain number of hours below 65 degrees has occurred. At this stage, the buds are microscopic and it takes warming weather in spring to cause them to grow and eventually bloom. However, this year, a great number of those microscopic buds froze, thus the lack of flowers now!
There isn’t anything that can be done to replace the frozen buds, however, citrus have been known to put out a second or even third set of flowers in the spring and summer. So don’t give up hope on getting a crop of fruit. But there are things that can be done now to help the tree, in general, recover from freeze injury.
By this time it should be clear what wood has been killed and what wood is still alive. If new growth has failed to emerge from those brown shoots and stems, it’s time to prune them off. Cut the wood back to where new growth has emerged. Use a sharp hand pruners and cut just above the newly emerged shoots. If stems or branches pencil-sized or larger must be removed, use a long-handled loppers.
If you’ve not yet applied a spring fertilization to your citrus, go ahead and do it now. Plant nutrients, particularly nitrogen will help the tree produce new growth to replace that lost in the freeze.
Contrary to popular belief, fertilizing citrus while they’re in bloom will not damage the flowers or young fruit. If you’re applying a special citrus food, use it at half the strength recommended. That’s because most common citrus fertilizers call for the addition of too much nitrogen. Over-fertilization with nitrogen can adversely effect fruit quality.
When applying fertilizer spread it evenly under the tree and out a few feet beyond the ends of the branches. Then water the fertilizer into the ground. If you have a basin for irrigation, just spread the fertilizer in the basin and fill it with water. If you have drip irrigation, use a soaker hose to slowly water in the fertilizer.
Sometimes, young leaves will be yellowed. If the yellowing occurs in between the veins, while the veins remain green, it's likely an iron deficiency. This is an excellent time to apply iron to the soil around your citrus trees. With warming temperatures the iron is taken up by the roots and distributed to new growth and deficient leaves. Be sure to buy chelated (water soluble) iron. It's more expensive, but it's the only type that works in our soil. The most commonly available type of chelated iron, and one that works very well is Sequestrene 130. Look for it listed on the label of chelated iron products.
In the spring, new growth may be attacked by small green, soft-bodied insects called aphids. Although they don’t do any significant damage, it’s a good idea to get rid of them on recovering citrus trees. Usually, a strong spray from a garden hose attachment is enough to knock them off the leaves. Soap sprays, made by mixing one tablespoon of liquid dishwashing detergent in a gallon of water, also work well.
Above all, recovering citrus trees must be kept well-watered! This means giving the tree more than ‘just enough’ if you want the tree to thrive. Adequate water is also critical to the development of quality fruit in terms of size and sweetness.
A broad and deep soaking is needed every 5 to 7 days for established trees in hot weather. At a minimum, water out to the edge of the branches and at 2 feet deep - 3 feet is better. If your using drip emitters, it may take several hours of running to get the water down that deep. Deep soil moisture provides a large reservoir for citrus roots to draw water from in hot weather.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona 520-626-5161. - Updated: April 11, 2004
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