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Is your citrus blooming? Yellow? Missing skin? Questions answered
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Posted: 01/23/2010 01:30:20 AM PST

One day this week, I dashed into a local garden center between rain showers. In a conversation with one of the horticulturists there, I learned that employees have been getting lots of questions about citrus recently. Are you curious about the following?

Why is my citrus blooming in the middle of winter?

Many citrus trees both bloom and ripen fruit in winter. What a treat to have fragrant flowers and ripe fruit in the slow season here! However, the flowers as well as tender tip growth are quite susceptible to cold damage so cover your tree with frost blanket or row cover if the forecast is for freezing temperatures. Most local nurseries carry these products.

Do yellow citrus leaves in winter indicate the need for fertilizer or iron?

Usually the answer is no. During winter, though the nutrients may be present in the soil, the citrus is unable to properly absorb them because of the colder temperature. Once the weather begins to warm up, the leaves should begin to turn green.

If they do not, fertilizer is probably needed at that point. Leaves that have green veins but are yellow between veins are telling you that they need chelated iron or zinc. Overall yellowing usually indicates a nitrogen deficiency.

In spring, take a leaf sample to your favorite nursery; a nursery professional will be able to recommend appropriate nutrients for your tree and tell you when to apply them for maximum effect.

Why am I finding missing patches of skin on my citrus fruit or missing areas of bark on the trunk and branches?

Snails or slugs are probably the culprits. Unfortunately, both of these pests relish citrus and can do major damage without ever being caught in the act unless you search for them at night with a flashlight or examine your tree on rainy days.

Their rasping mouth parts can remove skin and even mature bark; if they manage to girdle your tree, they might even cause its death. After removing as many of the slimy critters as you can find and be sure to search the undersides of leaves, make sure no branches or leaves touch a building, fence or other tree where the pests can gain access to your citrus.

Then wrap copper tape in a band around the trunk -- snails don't like to crawl across copper. You can place copper tape around major branches as well, to impede the movement of any snails or slugs that you didn't find during your first search. And monitor your tree for a few weeks; if you notice further damage, search again for snails and slugs hiding in the canopy that you missed the first time around.

Some gardeners like to use sticky Tanglefoot www.tanglefoot.com rather than copper tape. It definitely does deter snail and slug access to the tree but should be applied to a paper band wrapped around the trunk. If applied directly to the bark, the gooey substance can severely damage or kill the tissue that it touches. Both copper tape and Tanglefoot are available in local garden centers.

Can I remove the unsightly frost-damaged areas on my citrus?

It is a good idea to wait to prune away the blackened leaves and branch tips until after the last expected frost date in your area. If more frosts occur this winter, the damaged areas give some protection to the live tissues below, preventing them from being damaged as well. Also, pruning tends to stimulate new growth which is the most susceptible to frost damage.

If you want to learn more about fruit tree pruning, attend the free Fruit Tree Pruning Workshop with Matthew Sutton of Orchard Keepers and Orin Martin of the UCSC Farm and Garden. It is today, from 10 a.m. to noon at ProBuild Garden Center, 235 River St., Santa Cruz. These experts will answer questions about fruit tree culture and choosing varieties as well as help you understand pruning methods for various trees.

Garden tips are provided courtesy of horticulturist Sharon Hull of the ProBuild Garden Center. Contact her at 423-0223.