Sowing Seeds Indoors in March: A Guide for Southern Ontario Gardeners

As winter fades and spring beckons, it’s time for us gardeners to start sowing select seeds indoors! March is a crucial month for getting a head start on your garden so you can have a fresh harvest come BBQ season. Get ready to start your crops, especially those that require a longer growing season, indoors this month. For best results, check out our short guide to some popular seeds to sow indoors this March.

Artichoke

• Sowing Time: Early to Mid-March
• Growing Time: 8-10 weeks before transplanting outdoors
• Special Instructions: Start seeds in coir based pots that do not need to be peeled off to plant, or straight in our Coir fibre soil (Beats Peats) as Artichoke don’t like root disturbance 

Asparagus

• Sowing Time: Early to Mid-March
• Growing Time: 8-10 weeks before transplanting outdoors
• Special Instructions: Soak seeds overnight before sowing

Broccoli 

• Sowing Time: Early to Mid-March
• Growing Time: 5-7 weeks before transplanting outdoors
• Special Instructions: Keep soil consistently moist for best germination 

Celery

• Sowing Time: Mid-March
• Growing Time: 10-12 weeks before transplanting outdoors
• Special Instructions: Requires consistent moisture and light

Celeriac

• Sowing Time: Mid-March
• Growing Time: 10-12 weeks before transplanting outdoors
• Special Instructions: Keep soil temperature around 70F (21C) with a heat mat for best results 

Leeks

• Sowing Time: Mid-March
• Growing Time: 10-12 weeks before transplanting outdoors
• Special Instructions: Start seeds in trays and transplant them when the stems are pencil-thick 

Onions

• Sowing Time: Early to Mid-March
• Sowing Time: 10-12 weeks before transplanting outdoors
• Special Instructions: Use a well-draining seed-starting mix like ‘Fafard Seeding and Sprouting Mix’ and keep soil moist but not waterlogged. 

Peppers

• Sowing Time: Mid-March
• Growing Time: 8-10 weeks before transplanting outdoors
• Special Instructions: Requires warm soil for germination (use a heating mat if necessary)

General Tips for Sowing Seeds Indoors

Containers: Use seed trays or pots with drainage holes to prevent waterlogging. 

Soil: Use a well-draining soil mix to promote healthy root growth.

Light: Place trays in a warm, sunny location or use grow lights to provide adequate light. 

Watering: Keep soil consistently moist but not waterlogged to avoid damping off. 

Transplanting: Transplant seedlings outdoors after the last frost of the season. 

Read the Packets: Check the back of each seed packet, as every seed is distinct and may require slightly different timing. 

By starting these seeds indoors this March, you’ll be well on your way to a bountiful harvest later this year! To learn more, stop by our ‘Seeding Celebration’ event on Saturday, March 2nd, to celebrate everything seeds, including talks, demos & a potting bar. Happy Gardening!