Planting Guide - Tomato Seeds
Tomatoes in Your Garden
So many to choose from – where do we start? Considering what you will use the tomatoes for (canning, preserving, snacking, slicing, sauces, salsas) will help determine which types of tomatoes to grow. For canning and preserving, it is ideal to have all the fruit mature at once and in that case, a determinate variety will suit your needs such as Ace 55, Beefsteak, or Bradley. For snacking, look to our cherry tomatoes that are offered in a variety of colors, especially Sweetie and Black Prince. For slicing, our big beefsteak-type heirlooms Big Rainbow, Cherokee Purple, and Amana Orange will brighten up that sandwich or salad plate. Sauces are best made with our medium-sized tomatoes such as Amish Paste, our various Romas, or Principe Borghese. Salsas will be at the ready all summer long as you can make them with any type you choose!
When & How to Plant Tomato Seeds
Gardeners find that they have the most success by starting their tomato seeds indoors where they can give their young seedlings the attention they need. Warm soil temperatures, an important piece of the germination process, is better achieved in a controlled environment. If you wait until your outside garden is at least 70 F to germinate your seeds, the growing season simply won’t be long enough to bring your tomato plants to maturity. This is why most gardeners are more successful starting tomato seeds in starter pots prior to the growing season, and then transplanting in the garden when temps are higher.
Tomato Seed Growing Guide
Soil & Early Germination
Choose a commercially prepared seed stating mix. These mixes usually contain a mixture of peat moss, vermiculite and perlite, and some gardeners even make their own homemade mixtures. Prepare your seed starting mix by combining it with warm water to make it arable. You might find that your mix can be difficult to wet, especially if it was a completely dry mix. Some gardeners let their mixes sit overnight to ensure that the water is evenly distributed. The final consistency should be damp and sponge-like. It should not feel soggy or water-logged.
Germinate your tomato seeds in the container of your choosing. Tomato seeds will germinate in any container as long as excess water can drain, and they are given enough moisture and warmth. Many nurseries and home gardeners use growing “flats” with different sized plastic cell inserts.
Fill your container with moist seed starting mix and plant the seeds ¼” deep. Place germination containers out of direct sunlight in a warm location. Although light is not needed in the germination process, it is not harmful as long as high temperatures are avoided. It only takes 5 to 10 days for tomato seeds to germinate if they are kept in their optimum temperature range of 70 to 80F. Lower temperatures delay germination and higher temperatures accelerate it. Extreme temperatures, below 50F or above 95F are damaging to germination. Cover the germination containers with a plastic bag or sheet of plastic. This will help preserve moisture, but you must ensure that air can circulate and the mix does not dry out.
Monitor your germination containers regularly. When the first seedlings emerge from the soil, they need to be moved into bright light. Tomato seedlings immediately begin reaching for light. If the light is not adequate, they will grow undesirable 3” long stems right after germination. If this occurs, you can try to transplant to a deeper container, but you might have to start over!
A heated greenhouse is the ideal location for seedlings to continue their development. Another good choice is a cold frame (preferably with supplemental heat for cool nights). While some home gardeners use south-facing windows, most agree that an easier option is to use fluorescent shop lights kept within inches of the leaves of the plant. Tomato seedlings need light for 16 to 18 hours per day, and they grow best at a temperature of 65F with some air circulation. In fact, you can turn a fan on your tomato plants for 5-10 minutes, two times a day. Moving and swaying in the breeze help your plants develop strong stems and prevent them from becoming “leggy”.
Most growers agree that the best way to water tomato seedlings is to soak the mix then let it get nearly dry before the next watering.
Continued Indoor Monitoring
Notice when the plants develop their first set of true leaves. Once these leaves appear, transplant the plants into their own, approximately 4”, container that drains well. This re-potting step is important as it helps the plant develop a strong root system. Do not be afraid to set the plants too deeply – plant them all the way up to their top leaves – tomatoes are able to develop roots all along their stems.
Depending upon the seed starting mix you chose, you might need to provide your tomato seedlings with a supplemental fertilizer. If so, fertilize minimally with a weak, diluted solution.
Evaluate your container size and your growing conditions. If necessary, repot your tomato plants a second or third time to keep them from becoming root-bound. The tomato plants still require good lighting; ensure they receive plenty of sunlight. If that is not possible, fluorescent lights or high-intensity grow lamps in combination with sunlight is the next best choice.
One to two weeks after the average date of the last frost for your region, slowly introduce your tomato plants to outdoor conditions. This is called “hardening off”. If you fail to harden off your plants, they may become shocked and temporarily cease to grow! When you first move them outside, avoid full sun and wind. The longer they remain indoors, the harder it is for tomato plants to acclimate to the outdoors. Cold frames provide another way to harden off tomato plants. Keep te covers in place during inclement weather and remove the covers on moderate days. Some gardeners build temporary structures from plastic sheeting, and others use buildings and fences to provide sun and wind protection while the tomato plants are adapting.
Transplant hardened off plants to their final outdoor growing location or into a large growing container. Master gardeners know that tomatoes love heat, and some of them preheat their soil by covering the planting area with plastic two weeks before they intend to plant. This will warm the soil by a few degrees and cause the plants to produce tomatoes earlier! Most also agree that any early blossoms should be plucked off prior to transplanting, as hard as that may be to do.
Tomatoes should be transplanted deeply. 50% - 75% of the plant should be buried. It is okay to bury some of the lower leaves too. Space the plants 18-36”; this is the recommended distance for plants allowed to bush out on the ground. If you live in a warmer climate or are using tomato cages, you may space them half the suggested distance. This closer distance allows caged tomato plants to shade each other’s fruit and helps prevent burning.
Each plant will need about a gallon of warm water (80F) within 10 minutes of transplanting. This helps avoid transplant shock. In the first 7 to 10 days after transplanting, give each tomato plant about 16 ounces of water every day. Drip or soaker hoses are better than overhead hoses which can encourage diseases. After 10 days, water 2 to 3 times a week, and give each plant 1 to 3 inches/2 gallons of water weekly. If you live in a hot or dry climate, you will need to give more water more often.
Mulch your tomato plants a week or two after transplanting to your garden. A good mulch will consist of straw, dried grass and/or pine needles to control weeds and help the soil preserve its moisture during dry weather. Your mulch should be an inch thick and surround each plant stem by at least a 12 inch circle. Pine needles can help raise the acidity of your soil.
Some good companion plants for tomatoes include carrots, leaf lettuce, nasturtiums, parsley, onions, chives, and marigolds. Poor tomato-growing companions are cabbage, fennel, potatoes, and kohlrabi.
Remember, it is difficult to keep large tomato plants under artificial lights. To avoid this, do not start too early! It is important to plan your seed start date so that your transplants are at a reasonable size at the same time the outdoor temperature becomes suitable for garden planting.
Freezing temperatures will kill plants quickly. Bring your tomato plants back inside if the forecasted weather is expected to drop below 40F.
Do not overwater. Keeping the soil soggy will smother and kill the roots and cause stem fungus – especially when it is really hot.
Other tomato problems include Blossom End Rot and Blossom Drop.
Check your crop daily once your tomatoes begin to ripen. Use shears to cut or gently twist off each tomato when they are at the peak of maturity – firm and fully colored. Six weeks before the first expected frost, pinch away all of the growing tips and new blossoms. This will terminate new growth and allow the plant to put its energy into ripening its last fruits. Once the first heavy frost is predicted, pick ripening fruit in all stages and set them on the kitchen counter out of the sunlight and allow to ripen there.
Preparing for Next Season
Pull tomato plants out by the roots and add to your compost pile. Rake soil into the newly formed hole where your tomato plant once was. Avoid planting anything in the tomato family in this area for 3 years to avoid crop-specific pests and diseases from building up and carrying over from one season to the next in the soil.