Caring for Citrus Trees



Taking care of citrus trees can be hard work. We've accumulated some questions over the years and hope we can offer some insight to anything you might need to help grow your garden.

I am interested in starting an orchard or learning more about the business climate for Texas Citrus.
Probably the best source for the broad-spectrum questions like this is the Texas Agricultural Extension Service. Julian Sauls would be first on the list and then the Hidalgo County Agent is Brad Cowan. Julian's office number is 956/968-5581 and Brad's is 383-1026.

Where can I purchase a citrus tree?
Please visit www.acornspringsfarms.com for more information on purchasing citrus trees or seeds that can be shipped directly to your home.

How do I tell and orange tree from a grapefruit tree?
Identifying citrus varieties by their leaves can be complicated when you are looking at plants in containers because their care can have an influence on color and size--which are a couple of the characteristics you look for. In normal, well maintained citrus trees, you will find the grapefruit leaves larger and a couple of shades lighter green in color. Again, lack of fertilizer or over-watering can produce the same result.

Beyond color and size, and in normal leaves, the grapefruit leaf has a larger petiole than the navel orange leaf. If that term is new to you, this is a smaller second leaf between the large terminal leaf and the stem or limb to which it is attached. In a grapefruit with a main leaf spanning 2 1/2 inches in width, the petiole might be around an inch wide. A large navel orange leaf might be 1 1/4 inches wide in the middle and the petiole would be difficult to find or not much over 1/4 inch.

Color and size can vary with care and condition, but the petiole test is the most certain.

When is the best time to trim/prune an orange tree?
Right now. Pruning will induce growth--which is about to come with spring temperatures anyway. If you wait until warm temperatures, you will have wasted some of the tree's energy and if you prune in the fall, you will have it growthy at the wrong time of the year and make it more vulnerable to cold damage.

Why does a tree only have a few blossoms this year when it had lots of fruit last year?
Some varieties are naturally alternate bearers. For others, very often the nutrition necessary to provide blooms is used up by a heavy crop and it takes a while to recover. We see this in early oranges when much of the crop isn't harvested--the next crop is diminished. Extra nutrition is necessary when a big crop has been produced--and this needs to be available to the tree before the spring growth occurs. Commercial groves are usually fertilized in December and January.

Do citrus trees go dormant every year? For how long? Why?
Citrus is a sub-tropical plant which does not actually go dormant. However, the root system becomes inactive when the ground temperatures fall below 50 degrees F. With proper conditioning by sustained cool temperatures, citrus becomes inactive, but a few days of warmth can break dormancy very quickly. Drought conditions can have the same effect, but both conditions can be very damaging when carried too far.

A tree is 2 years old and its leaves are falling off...Why?
Falling leaves are a bad sign. In a yard it can mean that the trunk has been injured by a yard implement and a fungus has begun to infect the bark. Too much water in a poorly drained soil can do the same thing--and so can cold weather, but so far we haven't seen cold to that extent this year. Look closely at the trunk near the ground for a lesion. A systemic fungicide will control the fungus if it isn't too late.

How much and how often should they water their citrus trees?
Soil moisture a couple of inches below the surface should be maintained to feel damp to the touch. In a well-drained soil, this should be maintained by watering every couple of weeks--once the tree is established. A new tree might need to be watered every week. The soil type is the determiner. Heavy soils of course will hold the water longer. Some monitoring will let you develop a pattern. The tree will go into a wilt in the afternoon if it is running low on soil moisture. Overwatering can be a danger too. If the water still stands around the tree a couple of hours after you water, you have applied too much and the roots will be starved for oxygen. Citrus will tolerate a lot of variation, but avoid letting the leaves wilt for lack of moisture and puddling, which indicates excessive moisture--and stay somewhere in between.

Can I grow a Citrus Tree from a Seed?
For centuries the Chinese propagated citrus trees from seed and the Florida citrus industry still has some of the seedling groves which were planted around the turn of the last century. If you have the time and luck, you will have what you are after.

Four factors have changed the practice of orchard propagation to budding in modern times:

  1. By budding a piece of an outstanding tree that is true-to-type, you have a clone of the individual source tree. An orchard can be expected to have fruit which is consistent and the same throughout the grove.
  2. Seedlings are the results of cross-pollination. As the genes combine, the characteristics of the parents can display in ways which are somewhat different from the parent. And if the parent is of another variety (a bee visits a lime blossom just before he visits your parent grapefruit tree)--then your individual seedling can be very different from the one parent.
  3. There is a term in plant biology called "seedling vigor." It relates to the way seedling plants grow much more rapidly than budded plants or rooted cuttings. In citrus trees the rapid growth produces individuals with very long thorns, which most people don't care for; and secondly, the emphasis on growth usually delays fruiting. Many times a seedling variety in citrus will not bear for 6 to 8 years from planting while a budded tree will often begin bearing the second year after planting.
  4. Soil compatibility--some rootstocks are selected because they are adaptable to the soil conditions and weather factors where they must grow. Seedlings can be vulnerable to soil diseases and not impart much dormancy. As few areas use grapefruit as an understock, I must presume that they have good reasons.

If you are comfortable with these possibilities, you can certainly try your luck. If you want to be sure of what you will get, use a budded tree...

How do I get my citrus tree to bare fruit? Do I need another tree to cross pollinate? Or is there a chemical which I can spray on as a substitute?
Valencia orange trees do not need a pollinator. Tangerine varieties are generally the most dependent on cross pollination--so that isn't the problem.

Most likely the tree is "root-bound." Citrus trees produce a very large root system and when it is confined in a container, it restricts the normal growth/fruiting of the tree. Successful long-term container-grown citrus usually involves at type of "Bonsai" technique where the roots which circle inside the container are removed on a regular basis and some of the top is also removed to balance the plant. Then the tree is re-potted into a larger container.

I have heard of some citrus trees bearing regularly for about 15 years in containers about four feet square and four feet deep, but I have not seen them. I understand they are in a greenhouse and are not moved like these in question. A friend of mine in Austin raised a lime tree in a garbage can for several years. He rolled it outside on his patio during the summer and kept it near a bright spot inside when cold weather was predicted. Every winter he would re-pot the tree and remove the circular roots. As lime trees or kumquats are normally smaller plants, they are probably better suited for pot plants that are grapefruit or Valencia's.

If your tree is blooming right now, I wouldn't disturb it. It might go ahead and stick some fruit. Then, when that fruit is harvested next February/March, you might try the re-potting technique. If no fruit sticks again this year, you can work on it this spring or when the weather cools off in early fall and it might do better next season.

What is the appropriate spacing when planting citrus trees?
"It all depends." Landscaping and citrus orchard culture can also have different requirements. But you have nailed the highest consideration--Equipment.

Most modern orchards are designed to be worked in a single direction--with 20 to 25 feet between the rows for the equipment. Grapefruit grow larger and need more room; most orange trees are smaller and can be spaced closer. Down the rows the spacing is usually from 10 to 15 feet--again depending on variety. This gives an orchard a tree density of around 120 to 160 trees per acre and is a good blend of first cost and potential production.

In a landscape situation, you will want to be sure that the equipment used to maintain the grounds will not mechanically damage the citrus trees. A break in the bark in the trunk area will offer an entry point for fungus disease and will probably lead to the death of the tree. Lawn mowers commonly cause this type of injury and the progress of the disease can take months or even years to circle the trunk and girdle the tree. Damage by string trimmers can also allow fungus to penetrate the bark.

For protection against mechanical injury of this type I would strongly recommend that no grass be allowed to grow within 2 to 4 feet of the citrus tree's trunk. You can accomplish this with various combinations of weed block fabric topped by rock, brick, wood chips, etc. Then there is no reason for the mowers or trimmers to go near the tree trunk. For citrus tree spacing in a landscape, you should consider the type of tree and its potential size. Kumquats and most ornamental fruits are semi-dwarfs and can be placed as close as eight feet and not touch each other for many years. Tangerines and most oranges need at least 10 to 14 feet between them to not touch for 10 years. Grapefruit will touch at 25 feet if given 12 or so years to grow. Of course, selective pruning will control the growth of all these varieties and is not prohibitively expensive in a landscape.

Probably the second most important consideration is to leave space for possible spray application. If trees are grouped too densely and certain insects become a problem, you may not be able to penetrate the foliage satisfactorily to achieve control.

Thirdly, you might give some consideration to some method of freeze protection. In a landscape situation it is fairly easy provide frost protection by using the irrigation system to provide heat when needed.

Our Texas orange fruit trees are bearing fruits but it cracks and falls. How will I overcome this problem?
The peel splitting problem you describe is common among thin skinned citrus varieties. In our area, the Hamlin orange and the N-33 navel orange are the most seriously affected. Normally the splits occur when the inside of the fruit (mostly juice sacs) grows more vigorously than the outside peeling. In fruits with heavier peeling (like grapefruit) you almost never see splitting unless something has weakened a spot in the outer skin.

I once had a N-33 navel tree in my yard that bore fruit for three years and I was never able to eat a one--they all split just before they were mature.

Some folks have suggested that a little heavier fertilizer program will thicken the peel and make it stronger. You might try that this coming season. Otherwise the tree may settle down and become less vigorous and you will lose fewer fruit. But I doubt if it will go away completely.

I have a citrus tree in the house that is about five years old. It seems to be doing quite well other than the sap that the tree is producing. It has also never produced fruit. What can be done?
I'm unclear about the nature about the "sap" which is "coming out of the tree." If it is a thick, honey-colored viscous material oozing from the trunk or a major limb, then the tree has become infected with a fungus disease, which will become more serious with time. The treatment is to apply a 12 to one mixture of water and Ridomil with a brush or sponge to the whole trunk and any limbs which might be affected. Another treatment is to spray the foliage with Alliette as directed on the label. These are both commercial orchard materials and may be available from a well-equipped garden center. Both materials are used in other crops and should be available somewhere in your area. Your county agent should be able to help.

If the "sap" is more watery and seems to fall to the area below the drip line, you may be actually seeing a sugary material emitted by sucking insects present on the tree. If that is the case, you will also see a black sooty mold on the leaves. The cure is to spray the tree with a something which is effective on aphids. These materials are commonly available at garden centers.

The presence of the black sooty mold can block sunlight from the leaves and retard photosynthesis--inhibiting fruit production. The thick gumming described earlier is usually a prelude to death and often stimulates blooming.

First, any sap coming from the trunk can only reach the outside through some lesion which penetrates the bark. The sap can be colorless, but a bark lesion of any type is not a healthy condition and shouldn't be a mystery. You should pay close attention to the source of the sap on the trunk. Seldom have I seen sap come from more than one or two small areas. When you are sure of the source, that area needs to be treated as described previously. Secondly, the liquid coming from the leaves is probably an insect by-product as the leaves do not normally exude sap.