You will need trays or pots, potting soil, soluble or liquid fertilizer, a sprinkling can and some labels to start your seeds inside. You can start a few plants in pots, but a seed tray or “flat”, as nurserymen call them, gives room for more. All containers should have holes for drainage to keep the soil from becoming waterlogged or soggy. For the same reason, it is important to have a well-drained soil mixture. Your safest bet is to buy indoor potting soil from a nursery or garden store. My favorite mixture for starting seeds is half sphagnum peat moss and half horticultural vermiculite. These can usually be found in most nurseries and garden stores separately or as a mixture called “Peatlite.”
Seed Sowing Inside
Seeds can be scattered over the surface, but I prefer to make slight row indentations with a pencil or ruler and plant in rows an inch or so apart. You can sow the seed fairly uniformly by handling the seed package as follows: open the packet and make a crease parallel to the length on one side half way between the two folded edges. Hold the packet by its folded edges between thumb and last three fingers. Tap one edge lightly with your index finger as you move the packet down the row. With the packet tipped slightly downward, seeds will come sliding or rolling down the crease one or two at a time. With a little experience you can space even the tiniest seeds uniformly. You may want to practice first on a piece of paper. If seeds get bunched too closely together, move them apart with a pencil.
Care after Sowing
After planting the seeds, cover with soil approximately twice the seed diameter. With fine seeds no covering is needed since they settle between the soil particles. The top of the soil should be kept constantly moist with room temperature water until the seeds have sprouted. Cover with clear plastic to increase humidity and reduce water evaporation. Plastic covered containers should not be placed in direct sunlight because tender seedlings can be burned by heat buildup. Placing containers in a warm location such as the back of a refrigerator or near a heat outlet will speed germination. I use an electrical seed starting mat which is set at 70 degrees. As soon as the seeds begin to sprout, the plastic should be removed and the flat or pot placed in direct sunlight. Watering once or twice a day may be necessary on sunny days until roots have grown down into the soil.
If you have spaced seeds an inch or more apart they may be able to stay in the original container until outside planting time. If seedlings are too crowded, some or all of them can be transferred to other containers such as peat pellets (Jiffy 7’s), peat or plastic pots, or compartmental “cell packs.” The best time to move seedlings is just after they have developed their second pair of leaves. Loosen the soil carefully around the roots with a pencil and use one of the leaves as a handle. Do not handle plants by the stems since they are easily crushed. Place the root system into a previously made hole and gently firm soil around it. Plants should be watered thoroughly immediately after transplanting so the soil is completely wet to the bottom of the container.
Place flats or pots so they will get maximum direct sun exposure. If you do not have enough direct sunlight, use artificial lights. They can grow for 3 to 8 weeks with a 1 to 2 inch space depending upon variety. They can be *Although cucumber, melon, squash and pumpkin plants are often started inside 3 to 4 weeks before outdoor planting, they mature just as fast from direct sowing outdoors if covered with clear plastic, spun fiber row covers, hotcaps or plastic milk jugs with the bottom removed to warm the soil. This makes it possible to plant seed before the average last frost date. When starting these vegetables inside, seed should be planted directly into individual pots or compartments since they do not transplant well if roots are disturbed. The above vegetables plus eggplant, pepper and tomato are all frost tender and may need protection from late frosts.
Supplementing With Artificial Light
Vegetable plants need at least five hours of direct sunlight to grow. If they receive less, they are likely to become tall and spindley. One way to give them extra light is to place them outside on warm days when the temperature is above 50 degrees and then bring them in again at night. You can also supplement with artificial light. If you have some natural daylight, almost any artificial light can be used to supplement. The brighter and closer the light is to the plants and the longer it is left on the more effective it will be.
The most efficient light sources for starting seeds inside are metal halide, high pressure sodium and fluorescent. A fluorescent fixture which holds four tubes placed within six inches of plants can substitute entirely for daylight if left on for at least 20 hours per day. The light from four fluorescent tubes is not as bright as direct sunlight, but the extra time compensates for the reduced brightness. Although some plants respond well to continuous 24 hour per day lighting, most require at least an hour of darkness a day to grow normally. Timers are available which will turn lights on and off automatically. Light fixtures which can be moved up and down or tables which can be raised and lowered are effective in keeping the light close to the plants as they grow. Search for “indoor plant lights” on line for information and sources.
Plants should be hardened a day or more to acclimate them to the outdoor climate before transplanting. Place the containers outside where they are to be planted. The hardening process makes plants more tolerant to cold temperatures, dry air, and bright sunshine. Do not place plants in a garage or other dark area since they become soft and spindley in a short time.
Plants should be handled carefully when removing from pots or flats to avoid damaging the roots. The soil sticks together best if it has been watered an hour or so before transplanting. Most plants should be transplanted to the same depth they are growing in the container. Tomatoes can be planted an inch or two deeper. If plants have been in the container long enough so that several layers of roots have developed on the bottom, roots should be loosened or trimmed before transplanting. Water immediately after transplanting and keep the soil moist for a week or two until the root system has grown into surrounding soil.
containers and then move them to larger ones as they grow. Give plants liquid fertilization at one to two week intervals. It is usually safest to start with half the recommended strength until root systems are established. Water when the soil becomes dry on top. Use enough water so a little runs out the drainage holes.
Indoor Seed Sowing and Outdoor Planting Dates for Vegetables
Approximate Last Frost Date
April 15 May 1 May 15
Seed Outdoor Seed Outdoor Seed Outdoor
Vegetable Sowing Planting Sowing Planting Sowing Planting Time#
Broccoli 2/1-4/15 3/15-6/1 2/15-4/15 4/1-6/1 3/1-4/15 4/15-6/1 6 wk
Br. Sprouts 2/1-4/15 3/15-6/1 2/15-4/15 4/1-6/1 3/1-4/15 4/15-6/1 6 wk
Cabbage 2/1-4/15 3/15-6/1 2/15-4/15 4/1-6/1 3/1-4/15 4/15-6/1 6 wk
Cantaloupe 4/9-6/9 5/1-7/1 4/24-6/9 5/15-7/1 5/9-6/9 6/1-7/1 3 wk
Cauliflower 2/1-4/15 3/15-6/1 2/15-4/15 4/1-6/1 3/1-4/15 4/15-6/1 6 wk
Kohlrabi 2/1-4/15 3/15-6/1 2/15-4/15 4/1-6/1 3/1-4/15 4/15-6/1 6 wk
Celery 2/1-4/1 4/1-6/1 2/15-4/1 4/15-6/1 3/1-4/1 5/1-6/1 8 wk
Cucumber* 4/1-6/1 5/1-7/1 4/15-6/15 5/15-7/1 5/1-6/1 6/1-7/1 4 wk
Eggplant 3/1-5/1 5/1-7/1 3/15-5/1 5/15-7/1 4/1-5/1 6/1-7/1 8 wk
Onion 1/15-5/1 3/15-7/1 2/1-5/1 4/1-7/1 2/15-5/1 4/15-7/1 8 wk
Pepper 2/15-4/15 5/1-7/1 3/1-4/15 5/15-7/1 3/15-4/15 6/1-7/1 10 wk
Pumpkin* 4/9-6/9 5/1-7/1 4/24-6/9 5/15-7/1 5/9-6/9 6/1-7/1 3 wk
Squash* 4/9-6/9 5/1-7/1 4/24-6/9 5/15-7/1 5/9-6/9 6/1-7/1 3 wk
Tomato 3/1-5/1 5/1-7/1 3/15-5/1 5/15-7/1 4/1-5/1 6/1-7/1 8 wk
Watermelon* 4/9-6/9 5/1-7/1 4/24-6/9 5/15-7/1 5/9-6/9 6/1-7/1 3 wk
Most Pacific Northwest areas near sea level have average last frost dates around April 15.
Higher elevation areas have later average last frost dates.