Starting Plants Indoors

Growing Media

It is desirable to use a sterile plant-growing medium. Several kinds of soilless growing mixes, germinating mixes, potting soils, peat cubes and compressed pellets may be obtained from garden centers, seed stores and garden catalogs. These are usually free from insects, diseases and weeds and have enough fertilizer incorporated for the first three or four weeks of plant growth. They are easy to use and many gardeners and commercial growers believe that their extra cost is justified.

Outdoor soils may also be used for growing plants. Unfortunately, these soils often need improvement in fertility, aeration and drainage and they may harbor insects or disease organisms.

If you use outdoor soil, you should fertilize it and mix in rotted compost or manure the summer before you intend to use it. A good soil mixture for growing plants may be made by combining the following ingredients: one part fertile garden soil; one part shredded peat moss or well-decomposed compost; and one part vermiculite, perlite or sand. Mix thoroughly and pasteurize, if possible, before using.

Pasteurizing the Soil

Pasteurization (heating at 180°F) usually kills most diseases, weeds and insects in the soil. You can pasteurize soil at home in your oven. After making sure that the soil mixture has adequate moisture for seed germination, put the mixture in a pan or glass dish (the mixture should not be more than three to four inches deep). Place a thermometer in the center of the mixture, cover with aluminum foil and put in the oven.

Set the oven at 250° to 275°F, and heat until the soil temperature (as indicated by the thermometer) is 180°F. Lower the oven temperature and maintain the soil temperature at 180°F for 30 minutes. Remove the soil from the oven and allow it to cool before planting. Be careful not to contaminate the mixture with unclean tools, soil or seeds.

It is equally important to clean old or used plant containers, pots and tools with a disinfectant. You can use one part of household bleach (5.45 percent sodium hypochlorate) mixed in nine parts of water. Thoroughly was the container and tools outdoors and allow them to dry completely before use.

Sowing Seeds

The most common method of starting seeds is to sow them in shallow boxes in rows about two inches apart and cover lightly with vermiculite. Soon after the seedlings come up, they can be transplanted to trays, pots or other containers.

A simpler method of starting seeds is to sow the seeds directly into the final growing container. This method saves a step in handling the tender seedlings and avoids the transplanting shock. It requires additional space, however, because of the larger number of containers needed. The dates for planting various vegetable seeds indoors are shown in the following table.

Planting Dates for Starting Transplants Indoors

Temperature

The temperature of the medium is important for rapid and successful seed germination. Often the medium will have a lower temperature than the surrounding air. To ensure the proper temperature for seed germination, use a thermometer with a soil probe. The temperature can be increased by covering the seed containers with glass or clear plastic, or by adding heat with special heating cables or mats. Heating cables or mats are especially helpful when large numbers of plants are to be grown.

The optimum growing conditions chart shows the optimum temperature ranges for germinating seeds and for growing vegetable plants. Frost-tolerant plants can be hardened out-of-doors for one to two weeks before they are planted in the garden. Growing times for plants may be changed significantly by temperature, moisture and light.

Watering and Fertilizing

Next to proper temperature, uniform moisture is the most important requirement for seed germination. Some containers, such as peat pellets, dry out quickly and may need frequent watering. Water the plants as they grow in size, but do not water too much.

Your soil or growing medium should be fertile enough to sustain the plants for the first three or four weeks. You may supplement the fertility of the soil or growing medium by adding water-soluble fertilizer. Use the fertilizer (10-50-10, 20-20-20, 18-12-6) at rates of one tablespoon per gallon of water. Apply once a week, or less often, as needed for plant growth. It is good practice to use plain water between feedings because water prevents the accumulation of fertilizer salts that could injure the young plants.

Light

Vegetable plants need direct light. A window that receives sunlight only part of the day may not furnish enough light to grow the best plants. Many gardeners use plant-growing lamps to supplement the light coming in through a window or when there is no natural light.

Large lighting setups may require special electrical circuits and the wiring and ballasts may be separated from the fixtures themselves. Light fixtures may be purchased as complete units or they may be assembled at home. Ask an electrician for help.

Artificial light systems in a workroom, family room, kitchen, garage or basement may be the total source of light. Make sure that the temperatures are suitable for the plants you want to grow. For the best plant growth as well as for germination, you may need to provide supplemental heat in addition to light. An accurate thermometer is essential.

Two double-tube fixtures (a total of four tubes) placed side by side are preferable to one fixture with two fluorescent tubes. They will provide light for a 16 to 18 inch wide growing area. Long fluorescent tubes (48, 72 or 96 inches in length) will produce more light than shorter ones (18, 24 or 36 inches) combined to produce the same length. The standard 40 watt, 48 inch long fixture is the most popular and replacement parts for this unit are readily available.

Cool White is the most commonly used tube. Add one or two incandescent light bulbs with each four tube fluorescent bank of lamps. This simple addition provides light quality for plant growth that is superior to fluorescent light alone.

There are several kinds of "plant-growth" lamps designed for indoor light gardening. Their light will not appear as strong to the eye as light from Cool White tubes, however, and the color may be objectionable in a room environment.

Seedlings and plants should be lighted for 12 to 16 hours per day. Do not light onion plants for more than 12 hours. A timer that automatically turns the lights on and off is helpful.

Place the lamps close to the leaves of the plants. A distance of six to 12 inches is recommended. There is twice ass much light (intensity) six inches away from lamps than 12 inches from lamps. Make either the light fixtures or the plant shelf adjustable to permit spacing of lights as the plants grow in size. The total weight of lights, plants and growing media can be substantial. For this reason, be sure that the supports and tables are sturdy.

Before plants grown under lights are transplanted outdoors, they should be gradually hardened by exposing them to outside conditions. Place the plants outdoors a few hours each day, extending the period as you approach planting time. Frost tolerant vegetables can be left outdoors in cold frames for their final growth and hardening. The degree of success achieved in growing plants under lights varies with the kind of plants, the length of time that they are grown, and the mixtures of lights and intensities that are used.

Growing Time

The time required to grow plants to a stage suitable for transplanting to the garden varies with the kind of vegetable and the environmental conditions under which the vegetable is grown. If you cannot provide the best conditions, grow your plants for less time (three to six weeks, for example) than shown in the following table and then transplant the smaller, younger plants into the garden. Even though they may not be as large as they might have been under ideal conditions they are preferable to tall, spindly plants for transplanting outdoors.

You can also germinate the seed indoors until the seedlings are started and then place them outdoors in a protected location during the day. Bring the plants inside at night to protect them against cold temperature. A hotbed or cold frame is helpful if many plants are grown.

Growing plants out of season in a home greenhouse can be a rewarding hobby. The best plants are usually grown in greenhouses because light, temperature, ventilation and moisture are more easily controlled.

Optimum Growing Conditions

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