March in zone 7: peas in the ground, tomatoes under lights

March is the busiest planting month of spring in zone 7. The ground is workable, the last frost is a few weeks away around early April, and cool-season crops grow best now, before the heat arrives. Get peas, spinach, lettuce, onions and potatoes in, and start the summer crops indoors.

Think of the month in two halves. Hardy crops go outside all month. Tender crops stay indoors, from tomatoes in early March to squash and sweet corn at the end of it.

Sow and plant outside

Crop	What to do	When in March
Peas	Sow outdoors	All month
Spinach	Sow outdoors or plant out	All month
Radishes	Sow outdoors	All month
Lettuce	Sow outdoors or plant out	All month
Carrots	Sow outdoors	All month
Parsnips and turnips	Sow outdoors	All month
Onions	Plant sets or transplants	Until late March
Potatoes	Plant seed potatoes	All month
Beets and Swiss chard	Sow outdoors	From mid-March
Cabbage, broccoli, cauliflower	Plant out transplants	From mid-March
Kale	Sow outdoors or plant out	From mid-March
Leeks	Plant out	From mid-March
Cilantro	Sow outdoors	From mid-March
Strawberries	Plant	All month
Asparagus crowns	Plant	Until mid-March

Most of these are hardy enough to shrug off a light frost, but have row cover ready for a hard one, especially over transplants and the first potato shoots.

Start indoors

Crop	When in March	Goes outside
Tomatoes	Early March at the latest	Mid-April to mid-May
Basil	All month	Mid-April onwards
Zucchini, cucumbers, winter squash	Mid to late March	Mid-April to early May
Sweet corn	Mid to late March	Mid-April to early May
Green beans	Mid to late March	Mid-April onwards
Zinnias, cosmos, sunflowers	All month	After the last frost

Peppers and eggplant should already be up. If you haven’t started them, buy transplants in April instead, as they need eight weeks or more indoors.

Squash, cucumbers and sweet corn grow fast and dislike root disturbance, so sow them in individual pots, and don’t start them before mid-March. Many zone 7 gardeners simply sow them straight outside in late April.

Getting the timing right

These dates assume a last frost around April 3 and a first fall frost around October 29, typical for USDA zone 7. Zones are mapped from winter lows rather than frost dates, so check your own. Gardens at altitude, in valleys or in frost pockets can be two weeks later. Cities and coastal gardens often run earlier.

Jobs for March

• Prepare beds. Dig in compost once the soil has dried enough to crumble rather than smear.
• Harden off seedlings. Brassicas and onions raised indoors need a week of gradually longer spells outside before planting.
• Check row cover. Keep it handy all month for cold nights.
• Plan successions. Sow a short row of lettuce and radishes every two weeks rather than one big row.

Already picking: leeks, cabbage, spinach, overwintered lettuce, chard and the first asparagus spears.

For starting seeds, our seed starting guide is written for zone 5 but the method is the same. Just start each crop about four weeks earlier than it says. The sowing calendar shows every crop for zone 7 if you pick it from the frost menu.