If you are reading this thinking you have already missed the season, you haven't. Late April in The North is exactly when a great many of your most important seedlings want to begin. Garden magazines that work on national timelines can make Northern gardeners feel perpetually behind, but our season has its own shape, and this weekend falls right where it should.
Here is how I think about it: we are roughly five to six weeks out from our safe planting-out window. Up here around Duluth, that is typically the end of May into early June, somewhere on the other side of Memorial Day for most of us. Count backward from your own last frost date (a little different depending on where you are in The North), and late April is prime time for starting a specific set of crops indoors.
Why timing matters and why The HEAT Compass™ points here
The A in The HEAT Compass™ stands for Available Frost-Free Days, and it is the number that shapes almost every seed-starting decision we make up here. Our frost-free window is short, so we stretch it at the front end by starting seeds indoors, giving warm-season crops a head start while the soil is still cold, and giving cool-season crops a jump on the calendar so they are ready to go out the moment the soil lets them.
Late April is the sweet spot for the crops that follow. Not too early (leggy, root-bound plants by transplant day), not too late (undersized starts that never quite catch up). Right on time.
Start these indoors this weekend
Nine crops belong in trays this weekend. Each has its own reason for being on the list now.
Tomatoes. Five to six weeks of indoor growth will give you strong, stocky plants for transplant day. A sunny windowsill is all they need this time of year; the house has warmed up enough that germination will move along on its own.
Peppers and eggplant. Both want warmth, patience, and a long runway. Start them now, keep them warm, and they will be ready to go out when the soil finally catches up in late May or early June.
Cabbage and kale. Tough, cold-tolerant brassicas that will harden off and go out early. Four to six weeks from now they will be ready for the garden, and they will take a light frost once they are established.
Lettuce and spinach. Start a tray of each now for early transplanting and you will be harvesting long before anyone who waited to direct sow.
Celery. A slow starter that benefits from every extra week you can give it. Keep the tray consistently moist; celery seed will stall in dry conditions and needs light to germinate, so press the seeds onto the surface rather than burying them.
Basil. Wants warmth through and through. A sunny kitchen window is perfect for getting it started this time of year.
What is coming, but not quite yet
As soon as the soil thaws enough to work, usually a couple of weeks out yet for most of The North, you will be able to direct sow peas, radishes, and arugula. These are crops that actually prefer cold soil and will reward you for getting them in the ground the moment it is ready.
Watch the soil rather than the calendar. It will tell you when it's ready.
Hold off another three to four weeks on cucumbers, squash, melons, and pumpkins. They grow fast once they get going, and starting them too early gives you sprawling vines in your living room by mid-May with nowhere to go.
One more thing
If this is your first spring starting seeds, hear this: you are not late. You are exactly on time for the crops that belong in April, and a little ahead of the ones that belong in May. Gardeners in The North learn to read the season as it actually is, not as the glossy calendars tell us it should be.
Clear a shelf near a sunny window. Label everything; you will thank yourself in six weeks. Water gently. The harvest is yours.
