It’s only days away. I know frost-free days aren’t expected until May. However, mid-March is seed starting time — even if you’re starting yours on a sunny windowsill and not under grow lights.
The sun is much higher in the sky as we approach the spring equinox. The bare trees and the snowy ground allow the bright spring light to enter the home and encourage seedling growth. To get the most benefit from this light, be sure to clean the inside window panes.
So, why is mid-March an ideal time to start seeds? It’s basic arithmetic. Calgary’s traditional last frost date is May 18. Count eight weeks back from that day and where on the calendar do you get to?
March! This indoor growing period allows seven to 21 days for germination, then time to let those seedlings become large enough to handle being planted outdoors at the end of May. It also considers the transition time known as hardening off. Plants that are grown indoors won’t do well if they’re moved directly from the cozy indoor environment to the harsh reality of outdoor living. They need to be gradually acclimatized to outdoor conditions.
The timing of seed starting is a bit of a balancing act. You want to give the seeds time to grow to be vibrant small plants, but not have to keep them indoors so long that they become stress from being in containers that are now too small, and growing in less-than-ideal light. Regardless of the challenges that may be faced at the end of the indoor growing stage, March is a good time to start planting seeds.
For the home gardener, very little equipment is needed. The most important resource is a soil-less potting mix. It can be as simple as picking up a bag of potting soil from your local garden centre. You need a container with good drainage, something for that container to sit on to collect water passing through the soil, a cover to keep the soil moist until the seeds sprout, a place in the sun, and seeds, of course!
Many gardeners like to use peat pellets or small-celled seeding trays for seed starting. I’ve found these methods of growing very frustrating as I have difficulty keeping the peat pellet moisture level consistent, and I cannot cleanly remove seedlings from the small cells when it’s time to transplant (around the end of April).
Last year, I decided to try planting my seeds in the plastic containers that berries and plums are sold in. I started alyssum that grew into amazing plants this way. I used the bottom watering technique where the container is placed in a basin of water until the soil is saturated. I left the lid attached to the container to use as the moisture dome but found it was in the way later when I lifted the lid to allow airflow around the seedlings.
Cutting the lid hinge and placing the lid under the container solved my problem. I still needed to transplant, but even though I had to detangle the seedlings, they had a nearly 100 per cent transplant success rate. I grew more plants than I could use and gave them away to friends. They performed beautifully in containers all summer long.
Take care deciding how many seeds to start. Sowing too many seeds is a common problem for eager growers. I transplanted 80 seedlings from the little fruit container. Fortunately, I had room for that many plants which took more than ten times the space required by the fruit container. You do want to sow more seeds than you need, in case some do not germinate or survive. But if you usually only buy a six-pack of plants from the garden centre, you likely won’t have suitable growing spaces for 80 plants! However, it was nice being able to share them.
Come March 15, I’m going to try growing tomatoes this way. I’ve been saving my fruit containers, have soil, a basin, and space—everything’s ready to go. Now I just have to patiently wait—I don’t want to start them too soon. I want them to thrive, not just survive—it’s a balance.
To learn more about gardening, visit calhort.org.