This winter has been extremely cold in the Napa Valley. For several weeks before the end of January, temperatures dipped well below freezing. This rare extreme weather gave me a new appreciation for oranges.

Having lived surrounded by orange groves during World War II, I found an orange in my lunch bag every day, and that orange usually ended up in the garbage. Now I can’t even think about starting the day without a juicy orange.

This was a rough year in Southern California for the citrus industry, but here in Napa Valley we have many microclimates, so the prolonged cold produced varied consequences. Some neighbors’ trees experienced severe frost damage, while just next door, the same kind of tree was unaffected.

My neighbor and I both have “Eureka” lemon trees, and they are both thriving. Also, my kumquat and tangerine (mandarin) trees are doing well. Unknowingly, I had chosen the three most cold-hardy types of citrus for Napa Valley. “Meyer” lemons are even more frost tolerant than “Eureka” lemons, but I love the tartness of the “Eureka.”

Kumquats are the most cold-hardy type of citrus. The trees produce masses of small, smooth-skinned, tart fruits eaten skin and all. Actually the skin is sweeter than the pulp.

Citrus is a handsome evergreen plant, grown either as a shrub or tree. Most varieties have shiny, dark green leaves and fragrant white blossoms in the spring that attract honeybees. Trees on dwarf rootstock may grow 12 to 20 feet tall, and that is large enough for most yards.

Citrus needs are few. Provide moist soil with good drainage, full sun at least six hours a day and nitrogen fertilizer three times a year, and you will get enough fruit to feed a neighborhood. Fruits begin ripening in the fall through the winter. Because the fruit doesn’t continue to ripen off the tree, leave it on the tree until you need it. Some fruit may develop throughout the year.

Pruning isn’t necessary unless you want to keep the fruit at picking height or to give the tree a more appealing shape. Put copper bands on trunks to deter snails. Somehow snails find a way to be where you don’t want them. Try to keep trunks dry to prevent brown rot, a fungus.

When watering, consider that surface roots extend beyond the canopy, and deep roots may descend three to four feet. Water deeply once a week during Napa Valley’s hot summers. Never let the roots dry out. A three- to four-inch mulch of well-aged manure that extends well beyond the edge of the tree canopy will help keep the soil moist, conserve soil warmth, keep down weeds and eventually compost into the soil.

Sometimes your citrus may show yellowing leaves with dark green veins. This symptom indicates an iron deficiency, or possibly a deficiency of manganese or zinc. Treat with an application of chelated iron, found at any nursery. Buy fertilizers specifically for citrus, and read the labels.

The most common citrus pests are scales, mites and aphids. Give aphids a blast of water from the hose to wash them off. Mites look like black spots on the underside of leaves; to vanquish mites, apply a horticultural spray. Horticultural oil will help smother scales, the tiny, hard, six-legged “bumps” that feed on the branches. Close, humid air encourages them, so give citrus some breathing room.

Resist planting citrus varieties that don’t grow well in our area. I do have a “Navel” orange in a container, and I’ve seen venerable grapefruit trees loaded with ripe fruits and a few lime trees that are doing well, but for guaranteed success, they must be in well-protected, sunny locations.

When frost threatens, cover tender plants with burlap or other cloth supported by stakes so it doesn’t touch the leaves. Warm air under the cloth will rise and protect the plant. Or hang Christmas lights in citrus to supply warmth on cold nights. Cloud Cover, a spray available at nurseries, helps raise the temperature by a few degrees.

The most bizarre citrus I have seen is “Buddha’s Hand.” It is a type of citron, and it has no fruit pulp. It is all skin and looks like long, wrinkled fingers. Some people candy it, but it is mostly a conversation piece. Also, it is very frost sensitive, so you don’t want to plant it.

March is the best time to plant citrus. Not all winters here are as cold as this one has been, so if you follow these suggestions, you should have good luck and lots of lemonade.

The Master Gardeners’ Demonstration Garden at Connolly Ranch is open to the public on the first Thursday of each month through October from 9 a.m. to noon. Master Gardeners are on hand to answer gardening questions. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter at the Thompson Avenue gate.

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners (www.mastergardeners.org) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to noon, at the U. C. Cooperative Extension office, 1710 Soscol Ave., Suite 4, Napa, (707)253-4221, or from outside City of Napa toll-free at (877)279-3065. Or e-mail your garden questions by following the guidelines on our Web site. Click on Napa, then on Have Garden Questions?

source : www.sthelenastar.com