Seed Starting Vegetables in March -- Harvest to Table (2024)

To get a head start on the growing season, start your vegetable seeds indoors. Cold soil and unsettled weather will challenge seeds sown directly in the garden in early spring.

Cool-season crops that are the easiest to start from seed indoors are broccoli, Brussels sprouts, cabbage, cauliflower, leeks, and lettuce.

Warm-season crops to start indoors are beans, cucumbers, eggplant, melons, tomatoes, and squash. Start these crops 6 to 8 weeks before you plan to set them in the garden.

Start crops indoors in bio-degradable peat or paper pots that can be planted whole into the garden (that way you won’t disturb their roots at transplanting).

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Seed Starting Vegetables in March -- Harvest to Table (3)

Supplies You Will Need to Start Seeds Indoors

Containers: individual pots or cell packs at least 3 to 4 inches deep.
Seed-starting mix: most commercial seed-starting mixes contain fine compost, perlite, and milled sphagnum moss (Note: sphagnum moss and peat moss are non-renewable resources and are not sold in many countries). Later you will need a commercial potting mix or you can make your own: 1 part garden soil, 1 part perlite or builders’ sand, and 1 part fine compost.
Lights: adjustable up and down fluorescent lights to keep plants growing.
Heat mat with a thermostat: these will keep the starting mix and seeds warm as seeds germinate and then begin to grow.
Capillary mat or a tray for water: place these under containers to hold water; the starting mix will wick up moisture to the seeds and roots of seedlings.
Half-strength fertilizer to get seedlings growing: fish or seaweed fertilizer or compost tea.

Seed Starting Schedule for March (warmest zones first)

USDA Zone 10: (Where average low winter temperature is 30°F /-1°C or warmer.)

Direct-sow in the garden and or transplant crops started indoors last month; leafy vegetables and root vegetables.
Sow in the garden summer vegetables and tender herbs when all frost danger is past: basil, beans, corn, cucumbers, and melons.
Set out in the garden tomato and pepper transplants when nighttime temperatures average 55°F or warmer
Plant tender summer vegetables and herbs in containers
Thin seedlings.

USDA Zone 9: (Where the average low winter temperature is 20°F /-7°C.)

Sow outdoors cool-season root crops: carrots, beets, broad beans, Brussels sprouts, carrots, cauliflower, onions, parsnips, radishes, and spinach.
Plant early potatoes, onion sets, and shallots.
Make second sowing of early peas.
Start indoors with warm-season crops including tomatoes, peppers, and eggplants.
Warm garden soil for warm-weather crops by placing plastic sheeting over planting beds.
Sow sunflowers and nasturtium seeds outdoors.
Start sweet potato slips indoors.
Thin seedlings both indoors and out.

USDA Zone 8: (Where the average low winter temperature is 10°F /-12°C.)

Prepare planting beds when the soil can be worked; remove weeds, rake soil to a fine tilth, and add aged compost.
Sow in the garden beets, broad beans, Brussels sprouts, carrots, cauliflower, kohlrabi, lettuce, green and spring onions, parsnips, peas, radishes, shallots, spinach, and turnips.
Plant asparagus crowns and onion sets when the soil is dry and workable.
Prepare potato trenches adding a layer of well-rotted manure or aged compost. Plant early potatoes.
Plant new strawberries then put cloches over strawberries if you want an early cop.
Top-dress existing asparagus beds with well-rotted manure or aged compost.
Sow cool-season herbs: chervil, dill, fennel, parsley, pot marjoram, and sorrel.
Lift and divide overgrown clumps of bergamot, chives, and fennel.
Direct sow nasturtiums.
Prepare celery trenches by digging in well-rotted manure.
Prepare runner-bean trenches by digging in compost or well-rotted manure.
Late in the month, sow indoors tomatoes, peppers, and eggplant; also start sweet potato slips indoors.
Adjust the height of seed-starting lights or turn seedlings in the windowsill daily; water and fertilize indoor seedlings.
Warm garden soil by laying down plastic sheeting weeks in advance of planting.

USDA Zone 7: (Where the average low winter temperature is 10°F /-12°C.)

Finish winter digging and planting bed preparation; add aged compost to planting beds.
Place plastic sheeting, cloches, or plastic tunnels over planting beds to warm the soil.
Sow early cool-weather crops in cold frames, plastic tunnels, or beneath cloches if hard freezes still threaten.
Sow beets, Brussels sprouts, carrots, chard, dill, parsley, onions, parsnips, radishes, and spinach in a cold frame, plastic tunnel, or indoors.
Sow broad beans under cloches.
Sow early peas in a sheltered spot outdoors; make second sowing in two weeks.
Plant early potatoes when the soil is workable.
Sow onion and scallion seed. Set out onion and scallion sets when the soil is workable.
Transplant cabbage, broccoli, and onions to the garden; cover them with cloches if you expect a hard frost, or leave the cloches in place for a few weeks.
Chit (sprout) ‘seed’ potatoes (small tubers) of early varieties and prepare to plant.
Start indoors the seeds of tomatoes, peppers, eggplant, and basil.
Prepare runner bean and celery trenches; dig well-rotted manure into celery trenches.
Begin sowing herbs in a warm cold frame or greenhouse.

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USDA Zone 6: (Where the average low winter temperature is 10°F /-12°C.)

Turn undercover crops as soon as the soil can be worked.
Finish winter digging; add aged compost and manure to planting beds.
Place cloches, plastic tunnels, or plastic sheeting over planting beds to warm the soil.
Move broccoli, cabbage, and cauliflower seedlings to a cold frame or plastic tunnel.
Sow beets, Brussels sprouts, carrots, Swiss chard, dill, parsley, onions, parsnips, radishes, and spinach; cover beds with horticultural fleece if hard frosts persist.
Sow broad beans under cloches.
Sow early peas in a sheltered spot; make second sowing in two weeks.
Plant early potatoes as soon as the soil is workable.
Sow onion and scallion seed. Set out onion and scallion sets as soon as the soil is workable.
Transplant cabbage, broccoli, and onions to the garden; cover them with floating row covers or cloches if you expect a hard frost, or leave the covers in place for a few weeks.
Chit (sprout) ‘seed’ potatoes (small tubers) of early varieties and prepare to plant.
Start indoors with tomatoes, peppers, and eggplant. Time seed starting of these crops so they are ready to go in the garden when the nighttime temperature averages 55°F or warmer.
Prepare runner bean and celery trenches; dig well-rotted manure into celery trenches.
Begin sowing herbs in a warm cold frame or greenhouse.

USDA Zone 5:(Where the average low winter temperature is-20°F /-28°C.)

Harvest root crops such as parsnips in the garden from last fall.
Clean the garden of winter debris and spent plants.
Prepare the soil for planting cool-weather crops as soon as the soil is dry enough to work.
Plant new asparagus and rhubarb beds; fertilize established beds with a blanket of compost
Care for indoor seedlings; adjust the height of lights as seedlings grow, turn windowsill seedlings daily, water, and fertilizer.
Put seed potatoes on a warm, bright windowsill to encourage them to sprout
At the end of the month, move broccoli, cabbage, and cauliflower transplants outdoors to a cold frame or plastic tunnel. Cover the frame with a blanket or tarp if a hard freeze threatens.
Start tomato and pepper seeds indoors late this month.

USDA Zone 4 and 3: (Where the average low winter temperature is-30°F /-34°C in Zone 4 and -40°F /-40°C in Zone 3.)

Clean the garden of winter debris and spent plants for later planting.
Start cabbage, broccoli, Brussels sprouts, cauliflower, celery, leeks, onions, and parsley indoors beneath lights.
Trim the tops of onion and leek seedlings to an inch or so high, to keep them stocky.
At month’s end, start sprouting spinach and lettuce indoors.
Direct-sow earliest crops when the soil begins to warm.
Late in the month, start seeds tomatoes, peppers, and eggplants indoors; use individual peat pots.

Related Articles:

March Vegetable Garden Zone-by-Zone

Vegetable Garden Tips for March

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