by Glenn I. Teves, County Extension Agent
UH College of Tropical Agriculture and Human Resources, Cooperative Extension Service
Tomatoes are a member of the Solanaceous family or Sun Lovers which include peppers, eggplant and Irish potato, and are native to Central and South America, especially Mexico, Peru, and Chile. There are many wild species adapted to a wide range of conditions, from the salty shore to dry high mountains. Wild species are used to create new disease-resistant and resilient varieties, as well as new colors.
Tomatoes prefer warm, sunny days with cool nights. Warm nights can affect flowering and fruit set while high rainfall conditions can create many fungal and bacterial diseases. Good air circulation or wind flow can help to dry off plants after rain episodes, including proper plant spacing. When growing on the ground, spacing plants about 3 feet apart in a garden row will give them ample space to grow. When growing on a trellis, a 2 feet spacing is adequate. (Right) A robust tomato growing in a planter.
If you’ve grown tomatoes before and they were successful, continue to maintain the same methods and conditions you’ve practiced. If grown on the ground, side shoots can be pruned to manage its growth and spread. If grown on a trellis, the side shoots need to be pruned to maintain a single leader or stem.
Sow seeds in potting mix or compost in cells at least 2” square. Some gardeners will grow them in larger pots to have larger plants for transplanting, but potting mix is expensive so planting in small pots or cells helps to conserve potting mix. One way of sowing is to place seeds in cells or pots in loose potting mix and shake the pots so seeds sink into the potting mix. Another way is to cover very lightly. A common problem that gardeners face is planting seeds too deep so they don’t emerge from the media. A rule of thumb is to sow seeds three times the thickness of the seeds, so just give them a very light blanket of potting mix.
Komohana tomato fruit clusters
Depending on the size of the pot or cell, seedlings will be ready for transplanting in 20-30 days. If plants are too pot-bound, roots will be tangled and seedlings will take a while to grab on in the ground. One way to determine if seedlings are ready for transplanting is to check the bottom of the pot or cell if roots are emerging. An additional test is to see if the potting mix stays together when removing seedling from the pot. If they pass both tests, they’re ready for transplanting.
For a good harvest of tomatoes, it’s important to prepare the soil with compost and adequate fertilizer. Ideally, collecting a soil sample would help to determine the nutrient status of your soil and what tomatoes need. Tomatoes grow best in well-drained soil with a pH of 6.0 to 6.8. If your soil is too acidic, it’s important to add lime or dolomite. Important nutrients for tomatoes include calcium, magnesium, phosphorus, and potassium. In most soils, it’s assumed that no nitrogen is present so adding nitrogen early in the growing cycle is important for good vegetative growth to create a large plant. If added late in the season after flowering, it may increase vegetative growth at the expense of fruit production. For fertilizers, use what you have since a range of fertilizers should work. Ideally fertilizer high in phosphorus added when transplanting and thoroughly mixed into the top 6-8 inches will ensure good growth.
Tomato is one of the few crops that’s transplanted deeper than when removed from the tray or cell. Seedlings can be planted up to the cotyledons or the first leaves. If it’s difficult to plant the seedling deep in a hole, dig a long trench and lay the seedling on its side in the trench, covering the stem. This will create additional roots for a stronger plant. Side dressing with fertilizer or compost at flowering and also at first harvest will increase productivity and extend the harvest. (Above) Black & Blue, an indigo tomato
Irrigation is important for good production of tomatoes. Erratic watering during flowering can cause flower drop, and decrease fruit production. Before fruiting, irrigate 2-3 times a week during periods of little or no rainfall. After the fruit has set, deeply watering 3-4 times per week is recommended. Insufficient water can encourage blossom end rot where the base of the fruit turns black. Watering at the base of the plant is recommended to minimize fungal diseases in wetter areas but is OK in dry windy areas as long as the plants dry before the sun goes down.
Tomatoes can face many disease, insect, and mite problems. However, the key to pest control is to grow a healthy plant. Sanitation is also important. Disposing of damaged or infested fruit is important; do not throw fruits in the bushes this will allow pests to complete their life cycle nearby and return to attack the crop.
A severe Spider Mite infestation: Symptoms include yellow specks on leaves. Colonies can be found on both sides of the leaf.
Strong plants can overcome some of the key problems.
Some of the worst pests include the following:
Fruit flies: These include the Oriental Fruit fly and the Melon Fly. If you have lots of fruit crops nearby such as mango, papaya, and guava, the Oriental Fruit fly can be a major problem. Covering fruit clusters with paper bags can minimize damage. The use of Methyl Eugenol baits can attract male Oriental Fruit Flies and minimize breeding. Methyl Eugenol can be found at farm supply stores. Here’s more information on Fruit Flies and how to control them: https://www.ctahr.hawaii.edu/uhmg/EastHI/fruit-fly.asp
Spider Mites: Leaves will have yellow spots with cupping and dry up from severe infestation. Mites are usually on the undersides of leaves. Spraying with sulfur can bring them under control, and the entire plant should be sprayed.
Russet Mites: The bottom leaves will turn yellow and stems will have a bronze color, and under severe infestation can defoliate plants. Spraying with sulfur can bring them under control, and the entire plant should be sprayed. (Right) Russet Mites damage includes yellowing of leaves starting with lower leaves followed by drying, progressively moving up the plant. Another symptom is bronzing of the stem.
Whiteflies: Many tiny white flies cause black sooty mold on plants and can also transmit serious virus diseases. Using insecticidal soaps such as Safers Soap mixed with Diatomaceous Earth at the first sighting of these pests will help to keep them in check. Be sure to spray the undersides of leaves.
(Left) Greenhouse Whiteflies. Courtesy Michigan State University
Treehoppers: These are found on the stems and can create large colonies. The immature tree hoppers are brown and have spines, while the adults are green and larger with three-sided heads. Sprays of Neem and Safers Soap should bring them under control. (Right) Tree Hoppers: Adults are green with a three-sided head while immatures are brown with spines. Large colonies can be found on stems.
Tomato Pinworm: Pinworms can be a major pest if tomatoes have been grown previously nearby. Small moths will lay eggs under the fruit calyx and will hatch into tiny caterpillars that will bore into fruits, usually under the calyx but sometimes on the top of fruits, and rot fruits. They are difficult to control but picking infested fruits can help to keep the population down. In commercial operations, a confusion lure that smells like the female moth is placed nearby to prevent the male from finding the female.
Harvesting: Harvesting can begin when tomatoes color starting at the base. If you’re growing in a wet area, it’s a good idea to harvest early to minimize cracking. Allowing fruits to fully mature on the vine will decrease total production, so when many fruits are ripening at the same time, it’s a good idea to remove some fruit at the half-ripe stage. It’s better to store fruits on a table in the kitchen until consuming them because refrigerating will decrease the flavor of tomatoes.
by Glenn I. Teves
These “tried and true” tomato varieties are currently in stock.
Disease resistance noted in italics.
AVTO 1350 Cherry Tomato – An open-pollinated, indeterminate red cherry tomato with genetic resistance to Tomato Yellow Leaf Curl Virus and Tobacco Mosaic Virus. Developed by breeder at the World Vegetable Center in Taiwan. Needs trellising and pruning as they are vigorous plants.
Gold Cherry Tomato – Developed over the course of 5 years in a participatory breeding project, this delicious bright orange, large cherry tomato is high yielding, e, and - most importantly - has tolerance to TYLCV (Tomato Yellow Leaf Curl Virus). In 2019 it won a blue ribbon in the Kauai County Farm Bureau Fair.
Jay’s Tomato – Discovered in a backyard garden in Kipahulu on the island of Maui, this large red cherry tomato is packed with flavor. The long vines prefer trellising and will continue to produce for 2-3 months with good fertility. This plant can take up a lot of space
Chadwick Cherry Tomato – Developed by farming expert Alan Chadwick, this sweet and delicious large cherry tomato is a winner for any home garden. The long vines prefer trellising and will continue to produce for 2-3 months with good fertility. With excellent disease resistance, the Chadwick Cherry has also proven to be naturally fruit fly resistant after over a decade of growing in Hawaiian soils.
Austin Red Pear Tomato – A full flavor pear tomato with a unique elongated neck that grows up to 2” long. The long vines prefer trellising and will continue to produce for 2-3 months with good fertility. Proven to be naturally fruit fly resistant after over a decade of growing in Hawaiian soils.
Tommy Toe Tomato - The flavorful Tommy Toe Tomato produces hundreds of one inch cherry tomatoes. The long vines prefer trellising and will continue to produce for 2-3 months with good fertility. Proven to be naturally fruit fly resistant after over a decade of growing in Hawaiian soils.
Large Red Cherry Tomato - The Large Red cherry tomato lives up to its name with 1.25” wide tomatoes. This sweet and juicy heirloom tomato is high in Vitamins A and C. The long vines prefer trellising and will continue to produce for 2-3 months with good fertility. Proven to be naturally fruit fly resistant after over a decade of growing in Hawaiian soils.