Inadequate root system can cause plants to wilt

Q: My tomatoes are wilting. I don’t think I am overwatering or underwatering them. Besides they like water, don’t they?

A: Sometimes tomatoes wilt during midday when it is hot and plant roots cannot supply the water needed by their leaves. The plant recovers (stops wilting) during the cooler part of the day. The best time to correct this problem is at planting time.

About 40 percent of the water needed by plants come from the top 25 percent of its root system. A plant will wilt if the size and depth of its roots are inadequate compared with its top.

When first transplanting tomatoes into the ground, bury the roots about 3 to 4 inches below the surface of the amended garden soil. This means digging the hole for the transplant 3 to 4 inches deeper than its container.

Before planting, remove enough of the bottom leaves so these leaves are not buried in the soil. Ideally, wait 24 hours after removing the leaves before planting. It is best if fresh damage to the stem made by removing leaves is not below ground.

Once roots are placed this deep, amended soil fills the planting hole and it is watered in. Amended soil should contain fresh compost and a starter fertilizer high in phosphorus (the middle number).

Tomatoes are distinct in the vegetable world because they will grow new roots from the portion of the stem underground.

This type of planting technique provides for a deeper and larger root system capable of supplying more water and nutrients to the plant. This is particularly important with home gardeners who tend to “push” the growth of their tomato plants with heavy applications of nitrogen fertilizers.

A word of caution: The soil must be amended so it can drain easily.

Mulches applied to the soil surface also help reduce wilting. These surface mulches should decompose into the soil used for growing vegetables.

I prefer horse bedding made from wood shavings to most other mulches. It decomposes easily in the soil at the end of a growing season. Other types of mulches include straw and shredded paper.

Take handfuls of mulch and drop them on either side of plants so the mulch covers the soil with about a 2-inch layer. Surface mulches reduce evaporation from the soil and keep the soil cooler for improved rooting.

Q: My hearts and flowers ground cover is yellow green, not deep green. Why?

A: The primary reasons would be a lack of soil improvement at the time of planting, planting in extremely hot and bright locations, and not applying adequate amounts of fertilizer. Plants growing in amended soils and fertilized quarterly will have fewer problems than plants growing in soils with little or no improvement.

What you are calling hearts and flowers is probably Aptenia, a waxy leafed succulent with small red or purplish red flowers that have flower petals that are spiky. There is an ice plant also called hearts and flowers, but Aptenia is more commonly planted here. The most common is a variety called “Red Apple” with bright red flowers.

It originates from South Africa in regions with summer rains and sandy soils. This type of climate and soil is less extreme than our Mojave Desert. This is why our soils must be amended with a good quality compost at the time of planting if this plant is to look good.

This plant must be planted in soils with good drainage if it will survive. Again, soil improvement is a must.

In our climate, Aptenia takes full sun with amended soils but may look better, under some circumstances, if planted in full sun with shade or filtered light in the late afternoon.

Aptenia is a succulent and it will do well in rock gardens. But remember Las Vegas soils are an anomaly. Soil improvement is critical compared with other parts of the desert Southwest and even other parts of the Mojave Desert.

Yellowing can be caused from a lack of nitrogen so make sure fertilizers are applied at least quarterly. Use a light application of Miracle-Gro or similar product and apply an iron fertilizer at the time of planting just in case the yellowing is due from a lack of iron.

Q: Please walk me through the steps of planting trees or roses in containers on a balcony. Should the container be placed directly on top of a plate for drainage? I don’t want to stain my white balcony floor.

A: The first step is selecting the container. The larger the plant you want to grow, the larger the container you need to accommodate it.

Weight is an issue on balconies. Make sure your balcony can support the increase in weight from a plant and container full of wet soil. Expect the container to weigh about 8 to 10 pounds for each gallon capacity, plus the weight of the container and the weight of the plant.

Gravel isn’t needed at the bottom of the container. Although many people suggest using it, you run the risk of adding plant disease to your soil mix if the gravel isn’t clean or sterile.

Select a soil mix that is as light as possible. Light soil mixes are used for houseplants and usually contain a soil amendment called perlite.

Perlite is a lightweight, crushed volcanic rock that has been heat treated and expanded so that it contains a lot of airspace. Perlite adds bulk or volume to the soil mix without much additional weight. Plus it is good in holding water.

After buying the plant, gently remove it from its container and put it in a clean bucket of water. Let the roots soak submerged overnight. In the morning, remove the plant from the bucket. Gently rinse off the soil surrounding the outside roots.

It is not important to remove all of the soil. Just the soil from the outside inch of the root ball. Once the soil is removed, put the plant back in the bucket with fresh water covering the roots while you prepare the container.

Never put roots of any plants in direct contact with dry soil. Put enough wet potting soil in the bottom of the container so the top of the root ball of the new plant rests 1 inch below the top rim of the container.

Using wet potting soil, fill the void between the roots and the inside of the container. Use enough potting soil so that the top of the root ball is barely visible.

Add about 1 inch of water to the container to settle the potting soil around the roots. The potting soil will “disappear” as it fills the voids among the plant roots.

Add more wet potting soil and repeat this process until the soil barely covers the top of the root ball. You are finished potting the plant.

If you chose the plant for its flowers, such as a tree rose, apply fertilizer to the soil at the beginning of each growing season and once a month while the plant is flowering. Use a high-phosphorus fertilizer that promotes flowering.

If the plant selected was for fruit production, such as a lime tree, apply a fertilizer to the soil just before flowering begins and again after harvest. Use a fertilizer high in phosphorus, which promotes fruit production.

Water as needed and when the soil starts to dry out. An easy way to determine when to water is to use a water meter sold for houseplants. They are relatively inexpensive and give you a general idea how wet the soil might be.

Another tactic is to nudge or slightly lift the container to gauge its weight. Containers become lighter as they lose water. A third way is to push a pencil into the top of the soil. Pencils push easily into wet soil but are harder to push into dry soil.

You’ll water the container enough so that about 10 to 15 percent of the applied water runs out the bottom of the container. This is important to prevent the buildup of salts in the soil, which will damage the plant.

Any basin that collects water after an irrigation should be emptied soon after it fills. The container can rest directly in the basin if this is done.

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