Master Gardener: Temperature extremes, overfertilizing can cause tomato plants to stop producing
By BRIAN JERVIS Ask a Master Gardener on Jul 27, 2013, at 2:24 AM Updated on 7/30/13 at 9:44 AM
There are several reasons tomato plants may quit producing, including temperature extremes and excessive nitrogen fertilizer. BILL SEVIER/Courtesy
Home & Garden
All Helenium species are native to North America and were introduced to Europe in 1729 and, by the 1940s, many cultivars were available from German and English breeders.
Q:I have enjoyed the blackberries available at the local farmers markets. Are blackberries practical for the home gardener? M.D., Tulsa
Q: My tomatoes have quit producing. There are blossoms, but they fall off and don't make tomatoes. What does the plant need, more fertilizer? W. W., TulsaA:
Tomatoes originated in Central America and are classified as a subtropical plant. They do not tolerate cold temperatures, but they also do not like high heat. When daytime temperatures are consistently over 92 degrees and the nighttime temperatures are out of the range of 55-70 degrees most varieties stop producing tomatoes. Of these temperature extremes, the nighttime temperature may have the greatest effect on halting new fruit development.
These high and low temperatures cause the pollen to be infertile and blossoms are not pollinated. Blossoms that are not pollinated drop off the plant, and this is descriptively called "blossom drop." This problem is well-known to veteran tomato growers and is the reason commercial products have been developed to prevent blossoms from dropping.
We feel these chemical sprays have some usefulness in preventing blossom drop when the cause is cold nighttime temperatures but do not recommend them for heat-related blossom drop.
Another possible cause for tomatoes to stop producing is too much nitrogen fertilizer, rather than not enough. Excessive nitrogen tells the plant to grow tall, produce big green leaves and forget the blossoms and fruit.
An additional heat-related issue relates to lycopene - the chemical that produces the red coloring of tomatoes. It usually is not produced when temperatures are consistently above 86 degrees and tomatoes stop at either a yellow or pink stage. It is suggested they be picked at this stage as long as fully developed. They will ripen indoors at room temperature without a need for indoor lighting.
There is not much that one can do to combat the heat other than shading plants and making sure they are well-mulched and adequately watered (but not overly watered).
Selecting varieties of tomatoes that have shown some heat tolerance is an option, especially for next year. Varieties such as Bella Rosa and the heirloom variety Arkansas Traveler have shown superior heat tolerance by OSU Extension. There are many other varieties of tomato with superior heat tolerance. These varieties are available as plants and seeds locally and on the Internet. However, no variety can overcome temperatures similar to those of the past two summers.
If you are able to get the plants through the heat of summer and into the cooler temperatures of September, they will again start blooming, the pollen will once again be fertile and the fall tomato crop will begin production.
If you have a garden-related question you would like the Master Gardeners to answer in a column, call 918-746-3701.
Garden tips
- Fertilization of warm-season grasses such as Bermuda and zoysia can continue if water is present for growth.
- Cucumbers are often bitter this time of year, and vines quit producing. This is due to the heat. If you are able to get the vines through the summer, after it cools, they will be fertile again and the taste of the cucumbers will improve.
- Some trees such as sycamores and river birches lose large numbers of leaves in the heat of summer. Trees do this to reduce water loss from their leaves. The tree is not dying.
- Mowing heights for cool-season turf grasses should be at 3 inches during hot, dry summer months. Gradually raise mowing height of Bermuda grass lawns from 1 1/2 to 2 inches.
Original Print Headline: Why tomatoes stop producing
Home & Garden
All Helenium species are native to North America and were introduced to Europe in 1729 and, by the 1940s, many cultivars were available from German and English breeders.
Q:I have enjoyed the blackberries available at the local farmers markets. Are blackberries practical for the home gardener? M.D., Tulsa
