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Growing Guide
SOWING NOTES
Tomatoes require a long growing season, and are best started indoors 6 weeks before the anticipated transplanting date (after the final frost of the spring). For best results, sow seeds ½" deep in a well-drained, soilless starting mix. Seeds require warm soil between roughly 65-90 degrees F. Warmer soils will promote faster germination. Keep soil moist, but not soggy while awaiting germination. Moderate watering slightly once seedlings break through the soil.
SOIL & GROWING NEEDS
Tomato plants prefer well-drained, fertile soil, high in organic matter. Fertile clays and loams produce the highest yields, but lighter soils that drain and warm quickly can produce earlier harvests. It can tolerate slightly acidic soils, and is most productive with pH 6.0 to 6.8.
Tomato is a heavy feeder and should be fertilized with an organic blend rich in phosphorus and potassium, and containing moderate nitrogen.
Tomatoes need at least 8 hours of direct sun daily, and will develop faster with increased exposure. If possible, grow on a slight slope with southern or southeastern exposure. Tomatoes are native to tropical regions, and have the greatest light needs of any standard garden vegetable.
Staked and pruned plants can grow to well over 6 feet tall in favorable growing seasons, can be trained to narrow spreads. If space is limiting, use smaller determinate varieties.
Tomato is very labor intensive if you stake, prune or use plastic mulch and row covers.
Maintaining
TRANSPLANTING YOUR STARTS OUTSIDE
Once the last frost has passed and temperatures do not drop below approximately 50 degrees F at night, you can begin to consider transplanting. Don't rush to transplant. Cold soil and air temperatures can stress plants. Wait at least a week or two after the last frost. When considering candidates for transplanting, look for sturdy, short, dark green plants. Avoid plants that are tall, leggy, or yellowish, or have started flowering. Transplants that are too mature often stall after transplanting while younger, smaller plants pass them by, producing earlier and more fruit.
Harden off plants before transplanting by reducing water and fertilizer, not by exposing to cold temperatures, which can stress them and stunt growth. Transplants exposed to cold temperatures (60 F to 65 F day and 50 F to 60 F night) are more prone to catfacing. This (misshapen, deformed fruit) is caused by incomplete pollination, usually due to cold weather. Don't rush to transplant until weather has stabilized and soil is warm.
Unlike most plants, tomatoes do better if planted deeper than they were grown in containers. Set them in the ground so that the soil level is just below the lowest leaves. Roots will form along the buried stem, establishing a stronger root system.
To reduce root disease risk, don't plant on soils that have recently grown tomatoes, potatoes, peppers or eggplant for at least two years.
Use black plastic mulch to warm soil and/or row covers, hot caps or other protection to keep plants warm early in the season. Remove covers whenever temperatures exceed 85 F.
SPACING & COMPANION PLANTING CONSIDERATIONS
Depending on the nature of your starts, recommendation on spacing vary slightly:
12 to 24 inches apart for determinate varieties
14 to 20 inches apart for staked indeterminate varieties
24 to 36 inches apart for unstaked indeterminate varieties
Tomatoes can be cultivated in close proximity to carrots, onions, chives, garlic, asparagus, roses, and nettle. In some cases, tomatoes will help to deter parasites or other harmful conditions to the above-mentioned plants.
Avoid planting tomatoes near cabbage, kale, horseradish, broccoli, turnip, rutabega, arugula, cress, radish, mustard, kohlrabi, cauliflower, or any other members of the Brassicaceae family. Also keep tomatoes away from corn, potatoes and fennel herb.
MULCHING, STAKING & PRUNING TOMATO PLANTS
Mulch plants after the soil has warmed up to maintain soil moisture and suppress weeds. A reflective mulch, such as red plastic that will reflect light, can be help to promote more complete development if light conditions are not ideal. Tomatoes need a consistent supply of moisture. If it rains less than 1 inch per week, water to make up the difference.
Many factors (in addition to your choice of variety) affect total yield, first harvest and fruit quality. Raised beds, black plastic mulch and providing consistent moisture by watering or through drip irrigation are good ways to improve all three.
How you provide support to plants can also affect performance. Determinate varieties do not need staking. But staking and pruning indeterminate varieties can hasten first harvest by a week or more, improve fruit quality, keep fruit cleaner, and make harvest easier. Staking and pruning usually reduces total yield, but fruits will tend to be larger. Staked and pruned plants are also more susceptible to blossom end rot and sunscald. Allowing indeterminate varieties to sprawl reduces labor, but takes up more space and plants are more prone to disease.
Wooden tomato stakes are typically about 6 feet long and 1 ½ inch square, but you can use similar materials. Drive stakes at least 8 to 10 inches deep at or soon after transplanting so as not to damage roots.
Prune tomatoes to one or two vigorous stems by snapping off "suckers" (stems growing from where leaf stems meet the main stem) when they are 2 to 4 inches long. Tie stems to stake with soft string, twine or cloth, forming a figure-8 with the stem in one loop and the stake in the other. This gives the stem room to expand without being constricted. Start about 8 to 12 inches above the ground and continue to tie at similar intervals as the plant grows. As an alternative to using individual stakes, grow several plants in a row between heavy-duty stakes or posts spaced about 4 feet apart, and use twine to weave in and out around posts and plants.
Growing tomatoes in cages is a good compromise between labor-intensive staking and just letting them sprawl. You can purchase tomato cages at your local garden center, or simply bend a 6-foot-long piece of 4- to 6-inch wire mesh into a cylinder about 22 inches in diameter. (Cattle fencing or concrete reinforcing wire mesh work well for this.) Place cage around plants soon after transplanting and anchor with stakes.
FERTILIZING & WATERING TOMATOES
Avoid excessive N applications, which can cause excessive foliage and poor fruit set. Also avoid using fresh manure or high nitrogen fertilizers (those with three or more times nitrogen than phosphorus or potassium). Poor fruit set can also be caused by heavy rainfall or temperatures that are either too high (above 90 F) or too low (below 55 F).
On most soils, you can sidedress about 1/2 cup of 5-10-5 per plant and work shallowly into the top inch of soil when fruits are about 1 inch in diameter and again when harvest begins.
Keep soil evenly moist to prevent blossom end rot. This can also help prevent cracking when fruit absorbs water too fast after heavy rain following dry conditions.
CROSS POLLINATION
If tomato varieties are planted in close proximity, pollen from one variety can land on the female part of a blossom, the stigma, of a different variety and lead to some or all hybrid seeds being formed in that fruit. This is commonly referred to as a "cross-pollination" or simply as a "cross." When cross-pollination occurs, the fruit will look perfectly normal in the current season; however, the resulting seeds carry genes from each parent and will produce varying progeny in subsequent generations.
If you are not interested in saving seeds, then you can safely ignore cross-pollination issues. Tomato varieties will produce fruit consistent with the varieties planted. Again, any crossing in the current season affects the seeds within the fruit, not the fruit flavor or structure.
If you are attempting to save seeds and maintain a pure tomato variety, some efforts must be taken to avoid cross-pollination. The extent and seriousness of your efforts will depend on the importance of the variety and its intended usage. If the variety is typical, widely available, or intended for home use, then you may welcome a cross as an interesting diversion. However, if the variety is a rare family heirloom, or intended for distribution as a specific named variety, then crosses must be actively avoided.
If you want to be absolutely sure that your tomato seed line remains pure, then you will want to provide a physical barrier to prevent foreign pollen from being introduced. The technique most often used by home growers is called "bagging." It is quite simple but it also is limited with regard to seed production.
To "bag" a tomato means to cover the blossoms before they open. Various materials can be used. Some use floating row cover, others use tulle (bridal veil fabric), pieces of nylon stockings, sheer tricot or other lightweight fabric, or bridal favor bags. Depending on the size of the bags used, the bags must be monitored and removed after pollenization so that the tomato can grow to full size without restriction. After removing the bag, mark the fruit with yarn or a string to identify it when it has reached proper maturity for saving seeds.
It is difficult to collect large quantities of seed using bagging. Fruits do not always form inside the bag. High temperatures and the lack of mechanical movement can hamper pollenization. Lack of mechanical movement is easily corrected by shaking the bagged trusses.
If you are really serious, and you want a large amount of seed that is 100% pure, you could build isolation/screening cages as large as required to house the number of plants you desire.
There are no hard and fast rules to follow with regard to isolation. If you are knowledgeable about the pollinating insects in your locality, you may be able to design a system that reduces natural cross-pollination to a very low level with a small amount of isolation. If you lack specific knowledge about your locality, the following guidelines may be useful.
Generally, tomato varieties should be isolated 20 to 25 feet, and they should have a pollen-producing crop planted between. The objective of the inter planted crop is to divert insects away from the tomatoes. The amount of natural cross-pollination will depend on the factors previously discussed. Generally, organic gardening methods result in many more pollinating insects than would be present in a area where pesticides and tilling have been extensively used.
To obtain 100% seed purity by isolation distance, very large separations are required, possibly a 1/4 mile or more. Obviously, these resources and geography are difficult to achieve. Also, tomato volunteers from previous seasons could remain undetected within the isolation perimeter. Again, if you desire 100% seed purity, look to the physical isolation as provided by bagging or caging.
If you rely on isolation distances, it's best to grow several plants of the same variety and if in a row, harvest fruits from the inner plants and if in a square area, from the interior plants. If only a few plants, it's best to harvest several fruits from each of the two or three plants for seed saving so as to minimize the chance of getting nothing but crossed seed if you chose only one or two fruits.
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