by Cheryl Harrison, Master Gardener
March is the start of gardening season! Let the seed starting begin. My husband is the “seed starter” at our house. I am the “seed buyer”, the occasional “assistant transplanter” and a very helpful critic.
Husband has the seed packets organized by type of plant (e.g. perennials, vegetables – tomatoes, Brussel sprouts etc., and annuals – zinnias, marigolds etc.) and by the date that the seeds need to be started. The dates are calculated by looking at the back of the seed packets to find the length of time from seed planting to when the plant may be moved outdoors (i,e. the last expected date for frost), which is early to mid-May in the Peterborough area. For us, this means that the perennials are started first then the vegetables and the annuals.

In fact, the back of the seed packet will also tell you:
- How deep to plant the seed and how far apart to space the seeds when planting in a tray or for direct sowing in the garden. Planting in individual pots may be the way to go for some plants (e.g. tomatoes).
- The number of days from planting to when the seed sprouts (germination) and to when you may expect to harvest.
- The growing conditions required for the plant. This includes light, moisture and temperature. Seeds are often started in a special seed starting mixture which is sterile.
Husband and I check the seeds every day to ensure that moisture levels are adequate. The surface may be dry or barely moist but there should always be moisture below the surface. There is a fan set up to circulate air back and forth over the seeded areas. This helps prevent damping off. Damping off is a serious disease of seedlings that are grown in cool and wet conditions.

A heated home is usually warm enough to start seeds – i.e. 21-27 degrees C (70-80 degrees F). Seedlings need 14-16 hours of light a day. Sadly, we do not have that many hours of sunlight in a day until near the end of April. We use indoor grow lights which do work very well. Plants that do not have enough light will stretch and become weak and spindly as they stretch towards the available light. This makes them more susceptible to disease and they may not do well when they are moved outside.
The seedlings are transplanted from their tiny starter pots, or tray, into larger pots after they have 2-6 new leaves. These new leaves are in addition to the 2 small leaves (cotyledons) that are the first to emerge from the seed starter after germination. The soil in the larger pots is potting soil not seed starter.

We are grateful to have a homemade greenhouse where the plants, in their larger pots, are moved to continue growing until they are ready to be planted in a garden. Prior to the greenhouse, plants were kept inside under the indoor grow lights until the weather co-operated enough to plant them outside.
Tips
- If you are new to starting seeds, I suggest starting small. Seed starting, while fun, can be labour intensive with planting. There is also the cost of startup supplies.
- Remember to label your seeds with plant type and variety (e.g. tomato – Beefsteak). Nothing is more frustrating than when you plant seeds but do not know if you planted a tomato or a Brussel sprout.
- Ensure that you are not using old seeds. Old seeds may not germinate. Purchased seed packets will be printed with an expiry date.
- Moisten soil and seed starter before use.
- Seed starting is great for children. They get to plant seeds, then care for and watch their plants grow.
For more information:
- Seed Starting for Beginners – more detailed seed starting information
- Planning your Seed Starting – includes a short list of easy to grow plants
- Indoor Grow Lights – The 10 Best Grow Lights, Tested and Reviewed, by Jenica Currie, The Spruce 02/26/25




































