How to Succeed With Citrus

At one time Southern California was covered with citrus. Groves blanketed the valley floors and crept up into the hills.

Yet today in these same soils, people are having trouble growing good oranges, tangerines and even lemons.

At least that’s the impression I get from looking at the questions sent to The Times’ “In the Garden” question and answer column. Many of the writers wonder why their citrus are doing poorly.

Los Angeles County’s Master Gardeners hotline also gets lots of citrus questions, particularly about lemons.

In the last four years, 332 questions had to do with lemons alone, making it by far the most popular topic. The only contenders were tomatoes (186 questions) and roses (100).

Program manager Yvonne Savio said the most common questions about citrus problems are usually easy to answer. For instance:

*

Question: What is the black stuff on my citrus leaves?

Answer: It is sooty mold fungus, which grows on the sticky, sugary excretions of aphids, white flies, scale and other sap-sucking pests.

Get rid of the pests and the mold will follow. Pests are often carted onto the trees by ants, and the ants protect them from predators. Sticky barriers will keep ants off.

Q: Why don’t I get any oranges on my tree?

A: Maybe snails ate the flowers. Copper barriers keep snails off. Or moisten the soil and bait around the tree.

Q: Why are my lemons so ugly?

A: Grotesquely misshapen lemons are caused by bud mites, which can be controlled with the oil sprays sold at nurseries (they also safely control many other citrus pests).

Q: How should I prune my citrus?

A: You don’t. Unlike many other fruit trees, Savio said, they don’t need it. Just keep branches from touching the ground or ants will scale them.

Some questions--on general poor health of a tree, for example--are harder to answer:

“I have two Valencia orange trees that were here when we moved in 1958,” a Whittier reader wrote to Garden Q&A;, “but about two years ago we noticed that the trees looked kind of sick. The leaves were scarce and the fruit very small.

“I feed them regularly with citrus and avocado fertilizer and they get regular water,” he continued, “and the trees to either side of us look healthy. How come?”

Or, “We have four citrus planted in a row in a sunny bed,” said a Lomita resident, “but one of them has begun to lose its leaves at an alarming rate.

“We took it to the nursery and they said it wasn’t getting enough water, though we water every week. Please help me.”

Without seeing the tree, the soil or the spot where it’s planted, it’s difficult to know for sure what the causes of the problems are.

For a definitive answer, leaves or roots would need to be analyzed by a soil and plant laboratory, or the soil tested or an arborist called.

But in a majority of cases, the problem is often that the tree is too pampered: It’s getting too much water and too much fertilizer.

When people ask Joan Citron, who has a garden-sized grove of 15 different citrus, why their trees are sick or aren’t producing fruit, her surprising answer is to stop watering. She’ll even suggest they quit fertilizing.

“Just turn your back on them and go read a book,” she said.

This doesn’t apply to trees that are under 2 years old (see the accompanying story for advice on planting and caring for new trees) or to trees grown in containers, but to larger trees growing in average garden soil.

If you could see Citron’s fruit-laden trees, you’d know she must be doing something right. They’re loaded with juicy, sweet fruit.

It’s amusing that someone named Citron should be growing citrus in her garden. She and her husband, Jack, have been growing citrus since 1957, when they bought their house in Reseda and decided, “We live in California, let’s plant citrus.”

They started with a ‘Robertson’ navel orange and a ‘Kara’ tangerine, and through the years they’ve added a ‘Bearss’ lime; ‘Eureka,’ ‘Meyer’ and ponderosa lemons; ‘Clementine,’ ‘Dancy’ and Satsuma mandarins (tangerines); a ‘Sampson’ tangelo and ‘Tarocco’ blood orange; ‘Trovita,’ ‘Valencia’ and ‘Shamouti’ oranges; a ‘Nagami’ kumquat; even a lemon named ‘Pink Lemonade’ (it does have pink juice).

There are citrus in the frontyard, backyard and on the property they own next door. They make juice from a lot of the fruit (not just the oranges, but the tangerines as well), and even have a few extra juicers to back up their trusty, old Proctor-Silex. They also give much fruit away.

When the Citrons began, they watered often because the summers seemed so hot and dry, but they soon learned to water established trees only once a month during spring, summer and fall, and not at all in winter. And this is in one of Southern California’s hotter climates.

They put a fan sprinkler (or a bubbler) on the end of a hose and water each tree for two hours, moving the hose to a slightly different spot every 20 minutes so they cover all the ground under the citrus. This long irrigation lets the water sink several feet into the soil.

But they do this only once a month.

When they watered frequently, some trees almost died from gummosis--a fungus disease that causes sap to ooze from the trunk. They also lost trees to root rot. So they backed off on the watering.

Vincent Lazaneo, the urban horticulture specialist at the San Diego Cooperative Extension, agrees that over-watering is a frequent cause of backyard citrus problems.

“A whole lot more trees are killed by over-watering than under-watering,” he said. “Lawns are a particularly bad spot for citrus.”

Yvonne Savio says that, when they ask callers with citrus problems, they often find that the trees are planted in the middle of the lawn, right next to it or in flower beds--parts of the garden that get way too much water for citrus (and most other trees).

Ben Faber is a Ventura County farm advisor who specializes in soils, water and subtropical crops. He agrees that mature backyard citrus growing in deep or clay soils need only monthly irrigations between the end of the rainy season and the beginning of the next, usually from April through November. That’s when commercial groves get irrigated.

If you suspect that you have been over-watering citrus trees, now is a good time to wean them. This winter’s rains will help cushion the transition from frequent to infrequent irrigations, allowing roots time to adjust.

Begin watering less often and you will encourage deeper rooting and better fruit production. Switch to weekly watering and then monthly, if you have a clay soil like the Citrons’.

Keeping the soil surface dry between irrigations will discourage disease, often the cause of citrus problems.

Not everyone agrees with this infrequent watering schedule. Several growers I talked to suggested watering every 10 to 12 days during our dry season. How often you water will depend on your soil, your particular climate and how old the trees are.

Lazaneo says you’ll know when you’ve overdone it and haven’t watered enough. The leaves begin to roll up at the edges, threatening to become little citrus-leaf cigars.

Many years ago the Citrons decided not to fertilize after they noticed that uncared-for trees were producing more fruit than theirs. Joan Citron can point to old citrus in the neighborhood that get absolutely no care at all and they are covered with fruit.

She uses compost throughout the garden, so these trees aren’t going unfed. Hers is also a naturally rich, valley-bottom clay soil.

There’s little competition for water or fertilizer in the Citron garden. They don’t attempt to grow other things around the citrus, things that might compete with the citrus’s roots, or that need more irrigation or fertilizing than citrus.

For instance, growing thirsty and hungry roses nearby would definitely affect the health of citrus.

The Citrons’ citrus grow much as they would in a commercial grove, with nothing underneath the tree’s canopy, except a thick mulch of leaves and compost.

“In a backyard,” Faber said, “trees don’t need much nitrogen, especially if they have a good mulch underneath. Older trees may not even need fertilizing if they’re thickly mulched with fallen citrus leaves.”

Still, he suggests fertilizing mature trees during and after the rainy season, in February and June, with about a half pound to a pound of actual nitrogen per year.

To find out how much of a fertilizer is “actual nitrogen,” multiply the percentage of nitrogen listed on the label (the “14” in a 14-8-2) times the fertilizer’s total weight.

For instance, a 3 1/2-pound bag of blood meal has 13% nitrogen (it’s labeled as a 13-0-0), so multiply 0.13 by 3 1/2 pounds to get 0.46 pounds, or about half a pound, of actual nitrogen. Give them half of this in early February and half in June.

But it’s important to qualify this advice.

Faber said citrus trees are a bit like children. “When they’re young, they need lots of nutrients, but as they get older, they need less and less.” So when they’re young fertilize frequently but lightly, even every month.

Fertilizing becomes more important on soils that are not as naturally rich as the Citrons’.

Many newer gardens are not on “soil” at all, but are built in tracts or on slopes that have been bulldozed, cut and filled or otherwise rearranged so that the native topsoil is gone.

These gardeners are essentially gardening on mineral subsoils, and the care for citrus would be quite different and more difficult. Ditto for especially sandy soils. In both cases, watering and fertilizing become more important.

On graded lots, good drainage can be a major problem. It may simply be impossible to grow healthy citrus without installing some kind of drainage at planting time. On sandy soils, drainage will be so quick that watering must be more frequent.

But with the average clay and loam soils in the majority of backyards, established citrus needs infrequent watering and little or no fertilizing.

And fertilizing should never be the first thing you do when a citrus looks ill. Fertilizing anything that is already sick is a bad idea, since the plant is probably unable to “swallow” its medicine.

If you suspect that the problem is with the soil--that the drainage is particularly poor or that there are not enough nutrients in the soil or too many growth-impeding minerals--have the soil, roots or some leaves tested by a soil or plant lab before you start throwing fertilizer on the problem.

* How to Plant Citrus, K2