Many factors affect tomato production

Q: I noticed last year that I didn’t get nearly the same number of tomatoes that I had harvested in previous years. I have a raised bed with a blend of about 4-to-1 cheap compost and our desert soil. Each year I have continued adding compost from my own yard and vegetable scraps. Last year the tomato plants themselves grew well and I saw lots of flowers, but the tomatoes just never developed.

A: Let’s look at the list of things that could affect fruit production. These would include the right temperature range, wind, good soil preparation, disease, pollinators such as bees, humidity, sunlight and a few other things as well. This topic is expanded much more in my blog.

I will tell you a little trick you can use, but first I want to make sure you read the rest of what I have to say. Little tricks do not work all by themselves. You have to do the whole package to be truly successful.

The spring months, as well as the corresponding fall weather, are the best times for tomato production here. If we have a long, cool spring, we can expect to potentially have good production of fruit.

If the spring is erratic and goes from cold to hot in a short period of time we can expect poor fruit production. When it gets too hot, tomatoes stop producing. Tomatoes are very sensitive to hot and cold weather and have a narrower acceptable temperature range than peppers or eggplant, which are in the same family.

You have to be very careful about using cheap compost in your garden. When I prepare our desert soil for production I use an equal mix of good compost and native soil to begin with and I construct raised beds with outside walls. I will use compost that I know is good quality or make my own.

The second year of production, I add about half of the amount I used the first year. The third-year, I add about the same amount as the second year. By the third year, that desert soil will become extremely productive. At that point, I only add compost to the area that I’m planting, not the entire growing area.

You don’t mention which varieties of tomatoes you are using and that can have a huge impact on production. Usually, varieties like Early Girl, Celebrity, Jet Star, Big Boy, Better Boy, grape tomatoes, yellow pear and cherry tomatoes will set when others do not. A couple of those plants are good indicators that you are getting pollination.

There are two ways of getting tomatoes to set fruit without pollinators. One is the use of hormones sprayed on the flowers to set fruit without bees. These are sprays you can buy in the nursery.

The second method is a technique that greenhouse growers use when they grow tomatoes because they don’t have pollinators in their houses either — an electric toothbrush. It appears that the physical visit of a bee to the flower is not the only thing that trips the setting of fruit; the vibration caused by the wings of the bees trips it as well.

When temperatures are cool and you see flowers, gently flick the flower clusters with your finger a few times or use an electric toothbrush and vibrate the flower clusters for a few seconds to improve flower set.

Q: I have an easement in the backyard where I cannot plant trees. I have decided to plant as much as possible in the space I have left, which is about a 10-by-10 area. I would like to plant fruit trees in a high density there and keep the trees small for easier picking.

A: I would really caution you on a high-density mini orchard unless you are truly committed to it. It will take more time and effort and require gaining some extra knowledge if you commit to any intensive gardening technique. If you are willing to spend a bit more time and effort (not a lot but the extra time is critical), then give it a shot.

A 10-by-10 area is quite limiting but you could still probably get about eight trees in there with a combination of multiple trees in a single hole and trellising them. You might consider planting fruit trees in a hedge with no space between the trees and letting them grow together.

I personally wouldn’t plant trees any closer than about 6 to 8 feet apart for a hedge or trellis. If you use apples or pears, try to make sure they are on dwarfing rootstocks such as M111 for apples and OHxF333 for European pears.

There really is no true dwarfing rootstocks for stone fruits such as peach, apricot or nectarine, but the Citation rootstock may give you a smaller tree. These stone fruits are normally planted full size and kept small through aggressive winter and summer pruning.

Another possibility instead of a hedgerow is trellising and I prefer it over hedging for small spaces. Trellising costs more because you have to construct the trellis but it gives you more control of the plant and helps you keep it smaller.

Q: I have three questions. How often should I water? Do I need to put mulch around the plants and then cover them with rocks or keep the mulch exposed? Do I need to fertilize plants with a desert-type fertilizer or can I use the same stuff I use on my regular plants and how often?

A. How often should you water? In the winter once every 10 to 14 days. In spring until May 1, water once a week. From May 1 through the summer, water twice a week. Then, from Sept. 15 through Dec. 1, water once a week. These are approximate dates. Adjust them with the weather.

Wood mulch is a substitute for rock mulch. Rock mulch will cause problems with some plants. If you want all rock mulch, then make sure the plants used can tolerate rock mulch. Wood mulch is used without rock mulch and should be 3 to 4 inches deep around plants.

Fertilizers are the same for all plants. If you want growth, use high-nitrogen fertilizers. If you want flowers and root growth, use a fertilizer with high phosphorus. Good fertilizers are more expensive than ordinary fertilizers and are frequently worth the money.

If you can’t afford good fertilizers, then make sure you use a good fertilizer at least once a year and use less expensive fertilizers the remainder of the time. Use them when you can and the first application of the season is usually the best time to use them.

One application per year is enough for most plants except lawns and plants that you appreciate for their flowers. In those cases four applications are best: Labor Day, Fourth of July, Memorial Day and Thanksgiving. If the plants are tender to winter cold, skip the last two fertilizers of the season.

Plants that turn yellow are usually iron deficient and will need a good iron fertilizer. Not all iron fertilizers work in our soils.

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at

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