Seed Germination

Successful seed germination is one of the key factors in a great garden.

In order to start seeds and care for the transplants, it’s important to have an adequate amount of protected growing space and the correct equipment.

At a bare minimum, you need the following supplies for proper seed germination:

  • A workspace that is protected from the weather, preferably in a sunroom or other room with lots of natural light.
  • Seedling trays or containers: we use the portable mini greenhouse kits you can buy in any garden department. They are basically just peat pellets in a special self-watering tray. You can also use just about any container you want. We’ve used soda bottles cut in half, peat pots, black plastic pots, and old plastic yogurt containers. I find that since we are so dry here in Wyoming, the black plastic pots work the best for holding in moisture. You’ll have to experiment and see what works best where you are.
  • A table or level surface on which to place the seedling trays
  • Some sort of heating source; we use old water bed heating mats that we get at garage sales. You can also buy special heating mats for seedlings but they are expensive.
  • Supplemental lighting, such as a shop light which can be adjusted to hang at different heights over the table
  • A water source, and small watering canister.

Other Factors Which Affect Seed Germination

  • Growing mediums: You’ll want to use a clean soil-less medium to start your seedlings because regular soil can introduce insects, bacteria or fungus that will kill the seedling. The other reason to avoid using garden soil is that it tends to have drainage problems and may drown the seedlings. Common soil-less growing mediums for seed germination include:
    • Peat Moss: it provides the base for most commercial soil-less mediums. It consists of the decayed remains of sphagnum moss. It comes in pellets that can be expanded in a self-watering tray.
    • Vermiculite: this is a mica-like material that has been heated to high temperatures. It provides pore space and retains moisture and nutrients.
    • Perlite: This is an inert lightweight material that provides air space as well.
  • Light: This a key factor in seed germination. The light source must be bright and close to the seedlings. We hang shop lights about 2” above seed tray domes. Light is critical because it affects the temperature and moisture in the growing area. Too little light will cause your seedling to be weak and spindly, and they will be more susceptible to fungal disease. Also, be aware that vegetable seedlings need more light than standard houseplants.
  • Temperature: Another critical factor in seed germination rates. The seed packets should provide optimal germination temperatures for each seed type you buy. We use a water bed heater pad to warm seedling trays to proper germination temperatures.

    You can get old water bed heater pads at garage sales and auctions for much less than you would pay for a formal seed heating mat. Just make sure the heater bulb of the pad is under the seedling tray or you will overheat and burn out the pad, and probably melt your seedling tray in the process.

  • Moisture: Too much moisture is often associated with cool temperatures and dark conditions. It can lead to root rot and leaf spot diseases. You can avoid problems with diseases fostered by too much water by thoroughly watering when seeding, and then after germination, water the seedlings in the morning so leaves will be dry before night. Also, you can spot water only the dry places. Be aware of the opposite problem too; too little water will stop seed germination, and quickly kill young seedlings.

Hardening Off Seedlings

Hardening-off is the process in which the seedlings are subjected to a greater range in temperatures and light. This process helps them develop a tolerance to temperature changes and weather so they can survive being planted into the garden or greenhouse.

The hardening off process is critical for successful transplanting, especially if you have an outside garden. Basically, you just expose the seedlings to outside temperatures and/or higher levels of sunlight for longer periods each day. (Keep a close eye on them, especially for dryness).

Any breezes the seedlings encounter will strengthen the seedling stalks, and they also get the full spectrum of light from the sun, which will also make them stronger.

Transplanting Your Seedlings

Once the seedlings are hardened off, now they can be planted into soil. Here are a few tips to ensure a successful transplant.

  • Make sure the night time lows aren’t too cold for the warm weather plants. Tomatoes, peppers, and eggplant do not like night temps lower than 55 degrees.
  • Make sure the soil isn’t too warm for cool weather crops. If you plant peas in soil that is 70 degrees, they will immediately die.
  • Transplant on a cloudy day to minimize wilting from transpiration.
  • Really wet all of the soil in the container or area where you will transplant the seedling before you transplant it.
  • Follow the recommendations on the seed packets for planting distances. For instance, tomatoes should be planted no closer than 24 inches apart. That seems like a lot of space when the seedling is so tiny. You may be tempted to plant them closer together, but you’ll be sorry when you have to dig through a thick jungle of vines to get to your tomatoes at the end of the summer.
  • Be aware that certain plants will need trellises to support them as they grow. Tomatoes, peas, and cucumbers are good candidates for trellises.
  • When planting your garden, put the shorter plants on the south side of the garden, and the taller plants on the north side. Otherwise, the tall plants will shade the shorter plants and they won’t grow as well.

Here’s a great site with more detailed information about starting vegetables from seed.

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