What Seeds to Start Indoors Before Spring: 15 Easy Choices
Some seeds belong in the ground. You direct sow them in spring and they do fine. But a lot of the crops that make a vegetable garden worth tending need a head start. Starting them indoors gives them weeks of growing time before the last frost, and it puts transplants in the ground that are ready to produce fast once warm weather settles in.
Here are 15 seeds that do well started indoors, broken down by how to handle each one and when to start.
Tomatoes
Start 6 to 8 weeks before your last frost date. Tomatoes are the reason most people set up a grow shelf in the first place. A packet of 25 seeds costs around $3. Twenty-five nursery transplants cost $60 to $100. Start them indoors, sow 2 seeds per cell, thin to the strongest one, and pot up into 4-inch containers when the first set of true leaves appears.
Plant tomatoes deep at transplant time. The stem grows roots along any part buried in soil, so you end up with a stronger root system than a nursery plant grown in a small pot.
Peppers
Start 8 to 10 weeks before your last frost date. Peppers are slow. They germinate slowly, grow slowly, and they resent cold soil at transplant time more than almost any other vegetable. Give them a heat mat set to around 80°F for germination. Without heat, pepper seeds in a 65°F basement take 3 weeks or more to sprout.
Both sweet and hot varieties need the same treatment. Bell peppers, jalapeños, habaneros — all of them want the same long indoor head start.
Eggplant
Start 8 to 10 weeks before your last frost date. Eggplant has the same needs as peppers: bottom heat for germination, a long indoor season, and warm soil at transplant time. Don't put eggplant outside until nights stay above 55°F. Cold nights stall growth and the plants never fully recover their momentum.
Broccoli
Start 6 to 8 weeks before your last frost date. Broccoli is a cool-season crop, which means it actually goes into the garden earlier than tomatoes. You start it indoors in late winter, transplant it outside while nights are still cool, and harvest before summer heat arrives. A second fall planting is possible in many zones if you start again in midsummer.
Cabbage
Start 6 to 8 weeks before your last frost date. Same timing as broccoli. Cabbage tolerates frost once hardened off, so it goes in early. Varieties like Early Jersey Wakefield head up fast. Savoy types take longer but hold in the garden without splitting after maturity.
Cauliflower
Start 6 to 8 weeks before your last frost date. Cauliflower is the most finicky of the brassicas. It hates heat stress at any stage. Time the transplant so the heads form during cool weather. One hot week during head development and the cauliflower "buttons," breaking into small, separated curds instead of one tight head.
Kale
Start 4 to 6 weeks before your last frost date. Kale is probably the easiest thing on this list to grow. It tolerates cold, resists most pests, and the flavor actually improves after frost. Starting it indoors gets you larger transplants that establish faster than direct-sown seedlings. Lacinato and Red Russian are both reliable varieties for beginners.
Lettuce
Start 4 to 6 weeks before your last frost date. Lettuce seed needs light to germinate. Press seeds onto the surface of the mix and do not cover them. The cell stays moist under a dome and that's enough. Lettuce seedlings grow quickly and go out early, often 3 to 4 weeks before the last frost date.
Start a second round every 2 weeks for a continuous harvest through spring.
Celery
Start 10 to 12 weeks before your last frost date. Celery is on this list because it is almost impossible to grow from a direct sow in most climates. The seeds are tiny, germination is slow, and the plants need a long season. Start them early, keep them consistently moist, and give them steady light. They won't look like much for the first month.
Basil
Start 4 to 6 weeks before your last frost date. Basil germinates fast, often within 5 to 7 days in warm conditions. Do not rush it outside. Basil is the most cold-sensitive herb on this list. One night below 50°F turns the leaves black. Wait until nights are reliably warm before transplanting, and never put basil out during a cold stretch just because the calendar says it's time.
Parsley
Start 8 to 10 weeks before your last frost date. Parsley is notoriously slow to germinate, often taking 3 weeks even in good conditions. Soaking the seeds in warm water for 24 hours before sowing helps. The long indoor period compensates for that slow start. Once it gets going, parsley is tough and productive for the whole season.
Marigolds
Start 6 to 8 weeks before your last frost date. Marigolds started indoors go into the garden blooming, which means pollinators find your vegetable beds earlier. They also deter aphids and other soft-bodied insects when planted at garden edges. Direct sowing works too, but transplants give you flowers weeks ahead of schedule.
Zinnias
Start 4 to 6 weeks before your last frost date. Zinnias are fast growers and some gardeners prefer direct sowing. Starting indoors works well if you want the first flowers by early summer. Don't start too early. Zinnia transplants that sit in cells too long get root-bound and start blooming indoors, which stunts their long-term performance in the garden.
Snapdragons
Start 8 to 10 weeks before your last frost date. Snapdragons are cool-season flowers that go out early, similar to broccoli. They bloom in spring and early summer, fade in heat, and sometimes rebound in fall. The seeds are tiny. Scatter them on the surface of the mix and don't cover. Give them light for germination.
Leeks
Start 10 to 12 weeks before your last frost date. Leeks take the longest of anything on this list. The seedlings look like thin grass for weeks and barely seem to grow. Keep going. They pick up once transplanted and given room. Starting them indoors is not optional in most climates. There is no realistic way to direct sow leeks and get a full-size harvest in one season.
What to Skip Starting Indoors
Carrots, beets, radishes, turnips, peas, beans, corn, and squash all do better direct sown or don't transplant well. Squash and cucumbers are the exception: they take a 2 to 3 week indoor start in short-season areas, but no more than that. Transplanting too early creates root-bound plants that struggle more than seeds sown straight into warm soil.
For the full timing breakdown by crop, see the week-by-week guide to when to start seeds indoors.
Setting Up Your Indoor Growing Space
All 15 of these crops need the same basics: seed starting mix, cell trays, a humidity dome for germination, and a grow light. The light is the one thing that separates a successful indoor season from a shelf of leggy plants that never produce well.
A 4-foot LED shop light hung 2 to 4 inches above the trays, running 14 to 16 hours a day on a timer, handles everything on this list. For detailed shelf layouts and equipment, see the indoor seed starting setup guide.
If you're new to starting seeds indoors, the beginner's step-by-step guide walks through the full process from sowing to transplanting.
Seed starting season runs from January through April for most of these crops. The Seed Starting Club crewneck is heavyweight, forest green, and made for gardeners who are at the shelf before the ground thaws.