Freezing temperatures hinder fruit production on fruit trees

We had a pretty good freeze in parts of the valley recently. If your lemon tree or other citrus had flowers or very small fruit at that time, then that’s why.

The entire citrus tree is tender to freezing temperatures in the first place. It’s considered subtropical. The most tolerance to freezing temperatures starts with kumquat, then Meyer lemon and grapefruit, followed by some of the oranges, true lemons and finally limes. Freezing damage results in temperatures ranging from about 22 to 32 degrees.

As soon as growth starts, tolerance to freezing temperatures decreases in entire trees. That holds true of all fruit trees. There is no temperature discrimination when the tree is flowering. All fruit tree flowers and young fruit, whether apple or citrus, will die when it freezes. Freezing occurs at 32 degrees. No exception.

All flowers are tender to freezing temperatures. All fruit trees flowering during freezing temperatures result in dead flowers and no fruit. The tree survives at 32 degrees, but the flowers don’t. Young fruit trees are more sensitive to cold temperatures than older ones.

Add a light wind to this formula, and flowers and fruit for that year are history. There is a debate about whether plants succumb to wind chill like humans and animals. Let the debate rage. But I guarantee you, if there is wind associated with any freezing temperature, there is more damage than if there were no wind at all. Protect food production areas of the landscape from the wind.

You are lucky. If you don’t like a cold north wind, you go inside the house and get warm. Plants can’t. They must suffer through it. Therefore, let them occupy protected spaces in the landscape, and they will be more productive and produce better quality food.

Remember, there are microclimates in a landscape. South and west sides are warmer locations than north and east sides of the home. Protect the tree from the wind, and you have a nice small, warm microclimate that produces better food.

Q: I have a dwarf Lisbon lemon tree that grew fine and produced lots of lemons in a whiskey barrel. When the barrel began breaking apart, I planted it in the ground. It did fine at first, but last year — and it looks like this year — I have no fruit. I’m not sure what to do.

A: Lisbon lemon is a true lemon, unlike Meyer, so the tree is more tender to freezing temperatures. It flowers around the same time as Meyer lemons, so any freezing temperatures when it has flowers eliminate the fruit for that year.

Trees grow differently in containers than they do when planted in the ground. They are generally happier growing in the ground than in a container. If you have a fruit tree growing in a container for more than a few years, the roots grow in a contained mass rather than spreading into surrounding soil. The distribution of roots is different when a tree is grown in a container compared with tree roots growing in the ground.

When trees are taken from containers and put in the ground, they are moved to a new location that has a different kind of environment. That might compound the problem.

Light distribution is different, and water distribution in the soil is different. It takes awhile for a tree to adjust, both the canopy and the roots, to this new environment. The older the tree, the longer it takes the tree to adjust.

Because they might be happier growing in the ground, you might see them grow more vigorously as the roots and new growth adjust to this new environment. If top growth is vigorous, this can be at the expense of flowering. When they are moved from the container to the soil, flowering might stop until the tree has finished adjusting.

Another possibility could be that the roots were in such a tangled mess, and possibly growing in continuous circles, that the tree is root-bound. If the tree is root-bound, it will have difficulty establishing in its new environment. It will grow slowly and easily fall over when the fruit becomes heavy. Staking the tree makes no difference in its establishment.

If the tree was growing vigorously when it was planted, leave it alone. If the tree was struggling after planting, the plant might be root-bound. If you conclude it is root-bound, replace the tree.

Q: I am changing over to desert landscaping. Should I bother with landscape fabric under the rock if I will have desert plants and small rock covering the soil surface? Do I need to rototill my entire bare yard or just amend the soil under the succulents or cacti?

A: Landscape fabrics are laid on the surface of the soil to prevent weeds from growing through the surface rock mulch. Personally, I have not been a big fan of landscape fabrics, aka weed barriers.

Some people use black plastic for a weed barrier, but this is a huge no-no. If you are bound and determined to cover the soil with something before adding rock, pay a bit more money and use landscape fabric. Or my favorite, use nothing at all.

Landscape fabrics have not lived up to their marketing tout. Bermuda grass and nutgrass, two of the worst landscape weeds, still grow straight through it.

Secondly, we live in a very dusty environment. Windblown dust settles through the rock and on top of landscape fabric, making a very nice raised bed for growing weeds. In my opinion, landscape fabrics are not worth the money.

Instead, spend a bit more and put 3 to 4 inches of rock covering bare soil instead of the 2 inches most landscapers use. The greater depth of rock mulch provides a pretty good weed barrier. Bermuda grass and nutgrass will still grow through it, particularly close to the plants where irrigation is located. They’re going to do this anyway if you have landscape fabric or not.

No need to rototill the entire yard. Dig and amend the soil no less than three times the width of the container and the same depth as the container. Add compost to the soil where landscape plant roots are growing: 50/50 mixed with the backfill soil around the roots.

Dig no deeper than that unless you are sure you have a caliche or drainage problem. Then you must re-compact the soil underneath the container, so the plant doesn’t sink after planting and watering.

Q: After six years of trying to have a beautiful lawn in Las Vegas, I finally give up. The water company has offered me $3 per foot to convert to water-smart landscaping. What should I do? Do I add more rocks and plants? Artificial turf? What trees should I use, if any?

A: If you do nothing else after removing the lawn, plant some trees or large shrubs that shade to the west and south exterior walls and windows of your home. That will help reduce air conditioning costs during the summer. These plants should be deciduous, in other words, drop their leaves for the winter.

Select trees that grow to about the same height as your home. Avoid trees that grow huge. They use more water and don’t really provide any extra savings in air-conditioning costs. I would steer you toward trees that are adapted to desert environments.

Regardless of the trees you select, plant them a distance from your home no closer than half of their mature height. Plant them no closer together than this either.

Dig the holes for the trees at least three times the width of their container and no deeper. Smaller trees establish more quickly and grow more rapidly in the beginning than larger trees.

Irrigate the soil around plant roots no closer than 3 feet away from the foundation of the home.

Personally, I don’t care for artificial grass unless it’s used for a specific purpose other than just covering the ground. It gets terribly hot to the touch during the summer if it’s in the sun, and it requires upkeep. If you go in that direction, start asking some questions because it is not maintenance-free.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.