All vegetable plants produce optimum results when they can achieve rapid, uninterrupted growth. As gardeners, it’s up to us to provide our vegetable plants with conditions that enable that rapid, uninterrupted growth.
Tomatoes absolutely insist on warm soil and warm air when they are placed in the garden. They will languish if planted out before being totally hardened off. The ideal growing temperature for tomatoes is between 65°-81°F (18-27 C). When temperatures exceed 80°F (26.7 C), the phytochemical lycopene, which gives the tomato its red color, is suppressed; at 85°F (29 C), production of lycopene is nil. Beta-carotene, which creates an orange color in vegetables, is also present in tomatoes and develops rapidly when temperatures reach 90°F (32 C). So if you find that your tomatoes are looking more orange than deep red at harvest time, you can probably blame the temperature rather than the variety you selected. (An independent gene controls yellow-colored varieties.) High temperatures also cause more sugars to change to starch, so optimal growing temperatures will result in sweeter tasting tomatoes.
As young transplants, tomatoes can also suffer leaf scald if planted out too soon. In my tomato growing days, I always secured small pieces of row cover material to my tomato cages (hinged clothes pins work well) to protect the tomato plants during their first two weeks in the ground. Thereafter, they seemed to manage the intensity of the sunlight pretty well on their own.
Non-compacted soil, containing 2%-5% organic matter, is ideal for growing tomatoes, as are raised beds. Tomatoes require a steady supply of water, so good drainage is important. Also, since healthy leaves are critical for fruit shading, bottom watering–either with a drip or soaker hose system–is a safer method of watering than using hand-held hoses or sprinklers which can cause leaf burn when water droplets act as a magnifying glass for the sun’s rays.
As for fertilizer, I will share with you the recommendations of my oelericulture professor, and then I’ll share what has worked well for me. The professor’s recommendation: Work a 10-10-10 fertilizer into the soil one month before planting (13-13-13, or slightly higher if this is the first time you are planting vegetables in a particular location), then side-dress (place granules 6″-12″ (15-30 cm) from the base of the plant) with granular nitrogen in late June or early July. Here’s my experience: tomatoes are heavy users of soil nutrients, requiring a constant supply throughout the growing season, both for maintaining that uninterrupted rapid growth and for staving off disease. Indeterminate tomatoes, in particular, with their long growing season, require a ready supply of nutrients as long as the plants continue producing. I prefer to use the 9-12-6 Jobe’s Bulb and Perennial Spikes, supplemented by additional applications of liquid fish emulsion (mostly nitrogen) shortly after planting and once again just before the 4th of July. The Jobe’s spikes last for two months, at which time I add new spikes. I don’t recommend any of the organic tomato fertilizers on the market, simply because they don’t have the correct balance of nitrogen, phosphorus and potassium.
Tomatoes possess perfect flowers (male and female parts exist on the same flower) and are highly self-pollinating, so there is little risk of out-crossing when planting different varieties next to each other. However, several conditions can cause unsuccessful pollination, in which case the flower(s) will abort: unfavorable weather (especially low nighttime temperatures, but also daytime temperatures exceeding 95°F (35 C)), faulty nutrition (particularly low light intensity combined with high moisture plus high nitrogen), or injury by insects or disease. Nighttime temperature is the most critical factor in pollination and fruit set: the optimum nighttime temperature range for pollination and fruit set is 59°-68°F (15-20 C); nighttime temperatures of less than 59°F (15 C) will cause failure of fruit set.
Planting depth for tomato transplants can either be at soil level or with the first set of leaves buried below the soil line. Some tomato growers swear that the main stalk is stronger with the first set of leaves buried; I’ve planted both ways and can’t really say I’ve noticed a difference. Once the plants have started growing, you will want to consider pruning and staking. For information on pruning and plant support, I recommend an excellent article from Fine Gardening Magazine.
Part III of Dreaming of Tomatoes will address tomato insects, diseases and growth abnormalities such as Blossom End Rot and Cat Facing.