Starting and Growing Tomatoes

With so many tomato varieties and uses for them in the kitchen, it’s no wonder tomatoes are one of the most popular vegetables to grow at home!      

Choosing Tomato Varieties

Tomatoes are grouped into types according to their growth habit and production rate. 

Determinate types grow in a compact, bush form, requiring little or no staking. Fruit is produced on the ends of the branches and most of the crop ripens at the same time. One or more successive plantings will ensure an extended harvest period. Determinate types are best for those who want to produce a large supply of ripe fruit at once for canning. 

Indeterminate varieties continue to grow and produce fruit all season until the first frost. Tomatoes in all stages of development may be found on the plants at any time. The plants set fruit clusters along a vining stem, which grows quite vigorously. Under optimum conditions, some can grow to 15’ in length, but in most home gardens they generally reach about 6.’ Some indeterminates have a bush form with stockier vines, which set fruit clusters closer together. In between these two types are the semi-determinates. These plants will grow larger than determinate varieties, but not as large as indeterminate ones. They produce a main crop that ripens at once, but also continues to produce up until frost. 

Tomatoes are also grouped by function, shape, and size. Slicing tomatoes are large and juicy, while paste (sauce, roma, and plum) tomatoes are drier and have a concentrated flavor. They have fewer seeds, which makes them ideal for sauce and for slicing. Cherry tomatoes are bite-sized and come in several shapes such as oblong, pear-shaped, and round.

General Sowing

When to start tomatoes

Start tomatoes indoors 4 to 6 weeks before the average last spring frost. Ideal soil temperature for germination is 70–90°F. Use a heat mat to help control germination temperatures. Transplant seedlings when air temperature is at least 45°F to avoid stunting their growth.

Seed Starting Mix

Use a lightweight seed starting mix/media, and sow seeds at a shallow, 1/8″–1/4″ depth. Seed-starting mix is sterile, unlike garden soil, and lighter than potting mix. This creates an ideal air-to-moisture ratio. Expandable seed starting pellets work well, too.

After plants are hardened off, it is time to transplant them. Transplanting on a cloudy day or in the evening is best. The method for planting tomato seedlings is quite different than with any other plant. When covered with soil, the stem will develop additional roots. A large number of roots will increase the uptake of nutrients and water, resulting in a healthier, more resilient plant with improved drought-tolerance. There are two methods for transplanting seedlings outside. The first is to plant them deeply, burying the stem and leaving 1–2 sets of leaves above ground. The second is to set each plant almost horizontally in the ground, leaving 1–2 sets of leaves above ground. The buried part of the stem will sprout roots and develop a strong, extensive root system. The top of the seedling above ground will naturally reach toward the sun and right itself.

Place stakes, cages, or any other type of support in the ground at transplant time to avoid root damage. While determinate tomatoes are usually stockier, you may still find a cage helpful in keeping them upright and supported when they are loaded with fruit. Indeterminate tomatoes can easily reach 6′ in height. 

Water

Tomatoes need about 1″–2″ of water per week, depending on the type of soil they are growing in. One or 2 deep soakings per week in mild weather, and 2 or 3 soakings per week in hot weather should be sufficient. If tomatoes are cracking, reduce the water. Too much water can cause the fruit to burst and weaken the flavor.

Fertilizer

Tomatoes are medium feeders and may benefit from fertilizer during the growing season. Start out using a balanced or mild growth formula until the plants are large enough to bear fruit. Then switch to a fertilizer higher in phosphorus to encourage flower and fruit set. This method ensures plants will get the nutrients they need to grow large and prolific. As always, test the soil of your growing area so you know what nutrients are actually needed. 

Growing Temperature

Temperatures above 55°F at night are required for fruit set. However, night temperatures above 75°F in the summer inhibit fruit set and can cause blossom drop -- a lack of fruit production. If you live in a high-heat area, choose heat-tolerant varieties. 

When transplanting, wait until night temperatures are at least 45°F. If your spring warm-up is lagging, use plastic mulch or season extension products like hot caps or walls-of-water to warm the soil. If your tomato leaves take on a purple tinge soon after transplant, it is a sign that cool temperatures are preventing phosphorus absorption. They will grow out of this deficiency once temperatures warm. Fertilizing with kelp or seaweed can help plants dealing with stress from heat, drought, or transplanting.

Special Care

Do not mulch too early when the weather is still cool; the roots of young plants need to be in soil that is warmed by the sun. When the weather warms up over 55°F at night and plants are established, mulch to a depth of 2″ or 3″ with a material such as straw, leaves, or compost. Mulch helps to conserve moisture and reduce weed growth.

Harvesting

Each variety is different when it comes to color. Check your seed packet to know what color the tomato will be when ripe. Tomatoes may also be picked at the “first blush” stage, when colors just begin to change, and ripened at room temperature without decreasing flavor or nutrition. Picking often and early increases yield, and decreases the risk of cracking and pest damage. Another tip to prevent cracking is to pick near-ripe and ripe tomatoes ahead of rain, as excess moisture causes cracking.

At the end of the season, about 1 month before the average first fall frost, clip all blossoms and any undersized fruit off the plant. This will steer all the plant’s remaining energy into ripening what’s left. If you have a lot of unripe tomatoes near the end of the season and a frost is approaching, pick, clean, and store them indoors in a single layer away from direct sunlight to ripen.

Enjoy your homegrown tomatoes!