March 2025 In the Garden
Welcome March 2025! This is the month when starting seeds indoors kicks into high gear for gardeners in Zone 3. Everyone is feeling the promise of spring arriving just a month away!
When starting your own seeds it is very important to plan well ahead and research your chosen seed varieties.
If you are unsure when to start your seeds indoors, find the last frost date for Zone 3b for spring 2025. The projected last frost for Saskatoon is June 1-10 with the first frost - September 11-20. These dates are not definite but are there to give us some idea as to when to plant our gardens and put out our containers. Your seed packets should tell you how many weeks to start ahead of transplant outdoors.
Once you know your last frost date, subtract ‘weeks to start ahead’ to determine your indoor sowing date. I would also factor in a week of hardening off the seedlings. Most seeds are usually started six to eight weeks ahead of the projected outdoor transplant stage. There are exceptions such as peppers that can be started in mid-February if you want to see mature peppers on your plants. Tomatoes can be started late March – early April. Seed geraniums (Pelargonium peltatum) can also be started at the beginning of March. You can start them indoors at least 12 weeks before your last frost date.
Most important things to remember when starting seeds.
Use a soilless seed starting mix. Most seed starting mixes and store bought ‘soil’ do not contain soil at all! A top quality seed starting mix provides three key components to ensure seeding success – good moisture holding capacity, proper drainage, and ample fertility. For plants that need extra drainage you can add perlite.
Floral Acres carries two brands of Seed Starting Mix which give all your seeds a great head start!
Scotts Fafard Seed Starting Mix (NPK Ratio - 0.11 – 0.07 – 0.07)
This lightweight seed starting mix is approved for organic gardening. It is also used for sticking cuttings and provides an outstanding base for microgreens. It contains sphagnum peat moss, coconut husk fibre (coir), natural organic matter, calcium and magnesium.
Pro Mix Organic Seed Starting Mix (NPK Ratio - 6-1-2)
Pro Mix Organic Seed Starting Mix contains Mycorrhizae which is a biological growth enhancer that promotes strong plant growth, root strength and stress resistance. It also contains an organic fertilizer that gradually feeds plants for up to 3 months. The breakdown of ingredients is as follows: Canadian sphagnum peat moss, coir (coco fibre), perlite, limestone, organic fertilizer and mycorrhizae.
Sanitize Your Seed Starting Supplies
Keeping your seeding area and supplies clean goes a long way in preventing damping off disease. This includes washing your hands and using gloves. Plastic seed starting supplies should be washed with soap and water, then run through a 10% bleach in water rinse and dry. Wash and sterilize all tools you need before you begin and after you are done. There are several methods of sterilization. Lysol All Purpose Cleaner Wipes are very handy to use and do not corrode metal.
Do Not Overwater!
Seeds (once planted) and seedlings should be kept moist – not wet. Use room temperature water that has sat on the counter for a day and bottom water your containers. If you find that there is extra humidity building up under your tray covering or dome, open it for a few minutes to keep the air flowing and reduce the excess humidity. A small fan in the room provides a bit of air movement which is especially good for the seeds once they have germinated. Do not point the fan directly at the plants.
Provide Proper Lighting, but not direct sun. Grow lights are a great investment and keep your seedlings compact and strong. Putting your seedlings in a window usually does not provide enough light resulting in stretched seedlings that are weak and do not transplant well.
Make Sure You Label Your Seedlings as you seed your pots and trays.
Seeds To Start in March
Some flowers and veggies do not transplant well and should not be started indoors unless you can be assured that the roots will not be disturbed. A way to get around this is to start the seed in coir pellets or coir pots. When it comes time to transplant into the garden, gently cut the bottom off the pot and plant.
Root vegetables do not transplant well at all - radishes, carrots, parsnips, turnips and beets. Other hard to move plants are corn, beans, peas, snow peas, parsley, dill, fennel, and cilantro. These are best direct seeded into the veggie garden. Vining vegetables can also be temperamental – pre-started varieties should be treated very gently.
Annuals and Perennials That Do Not Transplant Well – Lupines, poppies, statice, sweetpeas, nastursiums, nigella, bachelor buttons, sunflowers.
Herbs
Herbs that have a long germination period such as Rosemary can be started in early March. This also applies to Sorrel, Oregano and Thyme. Investing in a heat mat will help to speed up this slow germination time.
To Follow – A Short List of Garden Plants to Seed in March
Early March – Annuals - marigolds, zinnia, strawflower, black-eyed susan, phlox, snapdragons, seed geraniums.
Vegetables - kale, broccoli, brussel sprouts, cauliflower, eggplant, cabbage, celery, celeriac, leeks and onion.
Mid March – Annuals- Coleus, salvia, stocks, cosmos.
Toward the end of March - third week onward - Bok Choy, Asian greens, tomatoes, annual strawflowers.
Perennials- mid March – bellflower, blue flax, creeping thyme, delphinium.
-late March – Joe Pye Weed, Swamp Milkweed, and Helenium.
You may want to start Pansies for early flowering containers in March ( 8 weeks before transplant) as they can take the cool day and night temperatures of early May in containers on the porch or back yard deck.