You planted your tomatoes in early June and the bushes are growing like weeds. But you’ve made it this far before and were left with grass green tomatoes at the end of the growing season.
Here are a few tips to increase your chances for those vine-ripened tomatoes all gardeners dream about.
Watering, fertilizing
Inconsistent watering can cause tomatoes to crack and contributes to blossom end rot and other problems. Do not let the soil become overly dry or overly wet.
Water your tomatoes when the soil is dry to the touch about 2 inches below the soil surface. When you water, water plants deeply, soaking the soil to a depth of about six inches.
Irrigate with a soaker hose to keep leaves dry and to prevent runoff. Apply mulch around plants to help to maintain a consistent moisture level and to discourage weeds.
Apply fertilizer, as indicated by a soil test, at the time of fruit set. Additional applications are not recommended. Too much nitrogen encourages vegetative growth at the expense of fruit.
Pruning
Tomato plants are aggressive growers and will produce suckers (that is side shoots that emerge between the main stem and where branches come off the main stem). If left, suckers will grow quite large, taking energy from the rest of the plant and decreasing fruit production. Suckers also inhibit good air circulation through your plants and prevent the leaves from drying, increasing the risk of fungal diseases.
On indeterminate tomatoes (tomatoes varieties with a vine-like growth habit), remove all suckers. For determinate tomatoes (tomato varieties with a more bush-like growth habit), remove suckers only below the first flower cluster. The earlier you prune out suckers, the easier. Small suckers can be snapped off with your fingers. Those thicker than a pencil should be cut out with pruners.
In addition to removing suckers, it is also good to remove all stems and leaves below the first flower cluster on your plants. This step improves air circulation through the planting and helps reduce contact with soil pests and pathogens.
Getting fruits to ripen
As your plants grow, check them regularly for pests and diseases. Diseases such as late blight can wipe out an entire tomato crop in a matter of days. (See sidebar.) If you see a problem, figure out what it is and act appropriately. Sometimes, it is necessary to remove and discard affected plants so that the problem does not spread to other plants. Do not compost diseased plants.
The optimum temperature for ripening tomatoes is from 68 to 77 degrees. The further temperatures stray from this optimum, the slower the ripening process will be. Not surprisingly, many gardeners in the Pacific Northwest are left with green tomatoes at the end of the growing season.
To hasten ripening before cool temperatures arrive, stop fertilizing your plants (if you have been fertilizing them) in early August and reduce irrigation. Root pruning (pushing a shovel into the soil halfway to three-quarters of the way around the plant about 8-12 inches from the main stem) will effectively decrease the amount of water a plant can take up and also hastens ripening.
Early August is also a good time to start removing young fruit and blossoms as they appear because they will not have a chance to mature before the season ends and will delay ripening of the rest of the crop. In early to mid-September, some growers also top their indeterminate plants (that is remove the growing tip of each main stem) which also redirects energy to the remaining fruit.
Finally, as the temperatures cool, cover the plants with plastic or a floating row cover at night to maintain warmer temperatures for longer. Use of covers can extend the ripening period by a couple of weeks and possibly get you the vine-ripened tomatoes you have been dreaming about.
For more information on growing tomatoes in the Pacific Northwest see “Growing Tomatoes in Home Gardens” (FS145E) available for free at cru.cahe.wsu.edu/CEPublications/FS145E/FS145E.pdf.
Jeanette Stehr-Green and Audreen Williams are tomato enthusiasts and WSU-certified Clallam County Master Gardeners.
Avoiding late blight
Late blight (Phytophthora infestans) is a serious threat to tomatoes and can kill plants in only a few days. Although it is called “late” blight, it can occur any time conditions are cool and wet. Prevention is better than treatment; steps that keep leaves dry and ensure adequate air circulation between plants will help prevent late blight.
The disease appears as brown to black spots on the leaves and stems and as grayish areas on green tomatoes. The blotches tend to occur where moisture collects. Older leaves close to the ground are usually the first to show signs of blight; the infection then moves upward. As late blight progresses the underside of leaves appear gray and dead and may show a margin of white cottony material.
If you find these symptoms, remove and destroy the affected leaves. If it has reached the fruit, the entire plant should be removed and destroyed. Do not compost the plant or fruit. Late blight is a soil-borne disease and thrives in cool wet weather (temperatures between 50-70 degrees, combined with rain, fog and heavy dew).
Late blight can be spread from the soil by wind, rain and insect and human contact. In mild climates late blight can overwinter in diseased potato tubers and contaminated tomato fruit.
