1 - High temperatures, excess nitrogen, shade and other factors can cause tomato plants to exhibit growth with no flower and fruit development.

Yard and Garden August 9, 2014

Q.

I am VERY frustrated!! I spent over $24 on tomato plants and they are all growing. They are about 1.5 to 2 feet tall, but have not produced a single flower, nor is even a BUD showing!!!!! They are all in pots. What am I doing wrong? Can I still save them? HELP, please.

A.

You did not tell me where you are growing your tomato plants, but I will assume they are in New Mexico. I also assume you planted them in July for them to be only this height. Of course, some varieties, especially determinate varieties, may remain short.

In New Mexico summer heat can have a tremendous effect on plant growth. Tomatoes my produce few fruit during times of high day temperatures. This is because the pollen may be killed or prevented from successfully pollinating for fruit formation under conditions of high heat. However, there should be some flowers produced.

When gardeners describe tomato plants that are growing well, but not forming fruit or flowers, the first thought is that the plants are over fertilized. Too much nitrogen fertilizer will stimulate vegetative growth at the expense of reproductive growth (flowering). If you used a commercial potting soil in the pots in which you are growing the tomatoes, the potting soil may be composed of manure or other sources of nitrogen. This may explain the problem. If you are also applying fertilizer, you may be increasing the problem. You may be further increasing the nitrogen that stimulates vegetative growth.

If the plants are in a shady location, they may not be getting enough sunlight to promote flower formation. The plants should have a minimum of 4 to 6 hours of direct sunlight each day.

If excess nitrogen fertilizer is the problem, you can use a "flowering houseplant" fertilizer that is high in phosphorus (second of 3 numbers on the fertilizer label). Phosphorus promotes increased flower and fruit production, balancing the vegetative growth enhancing nitrogen.

If the plants are not receiving enough sunlight, you can move the pots to a location with enough sunlight. This is a benefit of growing plants in large pots - them are portable and can be moved to appropriate environmental conditions as conditions change through the summer. Moving large, heavy pots may require a hand truck and assistance. Be careful not to hurt yourself or the plants when moving them.

Now that the highest heat of summer has past, flowering and fruit set should begin once nutrient and light conditions are modified. Varieties that do poorly in the heat should begin to perform much better. There is enough growing season left in most of New Mexico for fruit development and ripening. The fact that your plants are in pots will allow you to stretch your growing season by moving the plants to protected locations or into a garage, sunroom, or warm porch as fall frosts begin. This will allow you to mature and vine-ripen more tomatoes than if the plants were planted in the garden where they are more exposed to frost and immobile.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

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