Get your seeds out! Astronomical spring arrives on March 20 and unbelievably, daylight savings time begins one week earlier on March 12! The warmer temperatures, rain and melting snow, has many gardeners itching to get something started–anything! Seed starting can give you a jump start on and extend the growing season–and at a fraction of the price. It’s not too early to get started!
Most seed packets will tell you how many weeks prior to the time you can put plants outdoors that you should start your seeds. The date, of course, varies by zone and in the Twin Cities (zone 4) you should aim for planting outdoors on May 15 — which is the average date of last frost in our area. (I myself never plan on planting before Memorial Day.) Counting backwards the appropriate number of weeks from May 15 (or whatever date you plan on planting) should tell you when to start each type of seed. Timing is very important. If seedlings are too young when they are planted outside they may not survive. If they are kept indoors too long they may become too large and overcrowded, competing for light, water and nutrients.
For best results start your seeds in peat pots or plastic cell packs of four or more cells. You can buy new cell packs at garden centers or use some that you saved from previous years. If you use old ones make sure they are clean. You can sterilize them by soaking them in a solution of 1 part bleach and 9 parts water for 30 minutes. The advantage of using the cell packs is that the seedlings roots will not grow together and be damaged when you try to separate the plants for planting.
Seeds should be started in a seed ‘starting’ mixture that is lightweight, clean and free of weed seeds. “Soilless” seed starting mix can be purchased at garden centers or you can create your own mix with equal parts of peat moss, perlite and vermiculite. Regular potting soil is too dense for the seedlings’ delicate roots to penetrate.
The seeds will germinate faster and better in warm soil, so be sure your seed starting mix is at least at room temperature before you sow the seeds. You can ensure that the soil stays warm by using a warming mat or if you are lucky enough to have radiators placing your cell packs on them.
Most seeds do not need light to germinate — all the energy they need is contained in the seed itself. There are exceptions such as ageratum, impatiens, oriental poppies, snapdragons, Shasta daisy, dill and lettuce. And there are also some seeds that require darkness to germinate such as bachelor buttons, periwinkle, pansy, verbena and sweet peas. The seed packets should tell what each seed requires to germinate and if darkness is required. You can accomplish that by placing the cell packets in a black plastic bag. All seeds require moisture and warmth to germinate. Temperatures between 60° and 70° are usually sufficient. Lacking radiators and warming mats, a good place for germination is on top of the refrigerator! Keep the soil moist but not wet.
Once your seeds have germinated they will need 14-16 hours of light each day. Inadequate light is the main reason for tall spindly plants. If you have only a few seeds placing them in a south facing window may provide some of the light needed, but it will have to be supplemented by artificial light for satisfactory growth. The best way to provide adequate light for your seedlings is through the use of fluorescent lights. You can purchase garden lights, but two bulb shop lights will do just as well. Use cool white or a combination of cool white and warm daylight tubes. Hang the lights 2” above the tops of the plants, raising them up as the plants grow. Plants also need a period of darkness each day to grow properly, so using a light timer will ensure that the plants get an adequate amount of light and dark each day.
Your seedlings need moisture, but allow the top of your planting medium to dry out between watering. There is no need to fertilize until the ‘true’ leaves emerge and then you can water with a solution of ¼ strength soluble plant food once a week. If your seedlings outgrow their cell packs, you will have to transplant your plants into larger pots. (Another reason to not start them too soon.)
One threat to starting seeds indoors is what is called “damping off.” This is when a seemingly healthy seedling suddenly collapses and dies. Closer inspection will show that the stems appear to be rotted at the soil line. Damping off is actually caused by several species of soil-borne fungi and can be avoided by good cultural practices. This why it is recommended that you start with sterile pots and clean seed starting soil.
Before planting your seedlings outside they will require a period of hardening off. A couple of weeks prior, bring your plants outside for increasingly longer periods of time each day. Begin by placing them in a protected shady spot in the warm afternoon and bringing them in at night. After two weeks they can stay outside.
Enjoy your seed starting adventures and before you know it, it will be time to plant those seedlings outside!
“The love of gardening is a seed once sown never dies” – Gertrude Jekyll