Seed-Starting Tips

Growing plants from seed is not always an easy job, and the following techniques to ensure that seeds get a healthy start.

1. Keep records to allow for better planning

An often overlooked aspect of plant propagation is the art of record keeping. Whether you are producing a few plants for your home flower and vegetable gardens or working at a larger-scale nursery, developing a propagation journal will prove indispensable.

2. Store seed properly to maintain viability

Seeds are a fragile commodity, and if not treated properly, their viability will sharply decline.

To maintain dormancy, keep seeds in a cool, dark location with low humidity, like a refrigerator. It's recommend to label them (seed name, source, year) and storing them in a small reclosable bag or empty film canister that is, in turn, kept in a larger plastic container. Once you are ready to sow, you can test the viability of many, but not all, seeds by soaking them in water for a few hours. The seeds that are still living will sink to the bottom, while the dead ones will float on the surface.

3. Use wide, flat containers to avoid overcrowding

Plastic pots or containers are preferable to clay pots when starting seeds, as they retain moisture more consistently. Wide, shallow containers prevent both overcrowding of seedlings and excessive moisture around fragile, young roots. Plants that resent root disturbance when transplanted are best sown into small, individual containers like cell packs or plug trays.

Recycled plastic containers, like empty yogurt or margarine tubs, work well, too, provided you've poked holes in the bottom for drainage. No matter what type of container you use, it must be clean and free of pathogens.

4. Prevent disease by providing air flow and drainage

The fungal infection often referred to as damping-off is usually caused by excessive moisture and poor air circulation. However, there are a few cultural techniques that will help to keep fungal agents at bay. After covering the seeds with planting mix and tamping them down, spread a thin layer of 50 percent milled sphagnum and 50 percent starter chicken grit (finely ground stone) over the surface to keep the soil around the emerging shoots dry and provide an inhospitable environment for pathogens.

5. Cover trays with plastic wrap to keep the moisture level constant

Seeds are very sensitive to the extremes of overwatering and underwatering. In addition, heavy-handed watering can disturb newly germinated seedlings. Securing plastic wrap over the surface of a freshly sown seed pot can help to keep the moisture level constant. However, the pot must still be checked daily for moisture and germination.

If you find that you need to rehydrate your seed container, place the entire pot in a basin with 2 to 3 inches of warm water and allow the planting medium to wick moisture from the bottom. If just the surface has dried, you can lift the plastic covering and spritz the surface with water from a spray bottle. As soon as the seeds germinate, remove the plastic wrap.

6. Keep seeds warm to encourage germination

Most seeds require temperatures of 65° to 75°F to germinate. Placing seed containers near an existing heater or using a space heater with the proper precautions can raise the ambient temperature as needed. In addition, a heating pad designed for plant use placed directly under the seed containers will warm the planting mix and encourage germination. When using any additional heat source, be sure to check for moisture often, since the seed containers may dry out more quickly.

7. Feed them well

Proper nutrition at a consistent rate will keep your seedlings growing strong. When the embryo inside a seed is developing, it relies on food stored in the endosperm to fuel its growth. As the shoot emerges from the soil and the true leaves develop, the initial nutrients supplied by the endosperm will be depleted and supplemental fertilization is then required.

Most seed-starting mixes contain a small nutrient charge to help make this transition while not burning the developing roots. However, once the true leaves emerge, it is time to begin a half-strength liquid fertilizer regimen on a weekly basis.

8. Acclimate seedlings to direct sunlight

Before seedlings can be planted outdoors, they need to be hardened off, or acclimated to direct sunlight and fluctuating temperatures. It is best to do this over a three-day period by placing them in direct sunlight during the morning only of the first day, then increasing their time outside by a few hours each day until they are vigorous enough to be transplanted.

9. Transplanting from pot to ground

Water the ground outside and the seedlings thoroughly before transplanting. This helps prevent transplant shock. It's preferable to transplant on a cloudy day so strong sun won't wilt your seedlings. Dig a hole about twice the size of the root ball and set the transplant into the hole so the root ball will be covered by 1/4 inch of soil. Press the soil firmly around the roots. A small depression around the plant stem will help trap moisture. Water immediately after transplanting and every day for the first week. Be sure to water deeply so you plants won't develop shallow roots.