8 Seeds You Should Never Start Indoors in Winter – Wait to Sow These Veggies Outside in Spring for Bigger Harvests

There are plenty of plants you can start indoors over the winter to get a head start on your garden. But there are other seeds you should never start indoors in winter. They languish, bolt prematurely, or roots tangle in ways that direct sowing outdoors prevents.

Seeds that are best sown outdoors in spring integrate effortlessly with seasonal changes. Instead of starting seeds indoors this winter, hold off until warmer weather for select types that prefer direct sowing. Forgoing the windowsill now will help you preserve plant vigor and maximize harvests come summer.

Waiting to plant seeds outdoors can also prevent pitfalls like fungal diseases and transplant trauma. Let's take a look at the types of seeds you should never start indoors.

1. Squash

Squash seeds like zucchini and pumpkins explode with growth once the soil warms, but they struggle when you start them indoors in January or February. The vines will quickly outgrow trays and the soft roots tear easily during transplant. This often leads to weak plants or even total failure.

Wait until the soil temperature hits 70°F (21°C) before planting squash outdoors – usually sometime in late spring. Work some compost into the bed for good drainage and plant your seeds 1 foot (30.5 cm) apart in small hills.

A floating row cover, like this one from Amazon, protects young seedlings from insects. This direct sowing method gives you tough, productive vines with none of the headaches associated with early planting.

2. Cucumbers

Cucumbers never do well when started indoors in winter. Dry air and weak light make seedlings leggy, leaving them fragile before they ever reach the garden. Their long taproots will circle inside small pots and endure too much damage when moved, delaying harvests. Instead, direct sow them outdoors in warm soil.

Plant seeds 1 inch (2.5 cm) deep once the nighttime temperatures stay above 50°F (10°C). Mulch to hold moisture and set up a trellis in your vegetable garden so those vines stay clean and lifted. Cucumber seeds sprout fast outdoors and deliver crisp fruit from strong, undisturbed roots.

3. Melons

Melons like watermelon and cantaloupe really need warm soil and steady heat from day one, something winter indoor setups just can’t provide. Cool drafts and uneven soil temperatures slow the seedlings and their big, roaming roots get frustrated fast in small pots. By the time you transplant seedlings outdoors, those roots are already stressed and the plants lag instead of taking off.

You can plant melons in the garden once the last frost is finally behind you. They take to raised mounds pretty well, mostly because the soil warms faster that way. Tossing in some compost before planting helps give melons a strong start as well.

When you water melons, try to hit the base instead of the leaves – wet foliage tends to cause problems like powdery mildew. Use a fertilizer made for melons, like this one from Amazon, for robust plants.

4. Carrots

Carrots often twist or fork when grown in containers because a shallow pot bottom can stop the root from going straight down. Transplanting also snaps the tiny feeder hairs carrots need to drink up nutrients.

Plant carrot seeds by scattering thinly in loose, rock-free soil in early spring and thin seedlings to 2-3 inches (5-7.6 cm) apart. A light covering of sand keeps the surface from drying and crusting. Carrot seed tape also makes perfect spacing simple and delivers straight, sweet roots every time.

5. Radishes

Radishes finish growing so quickly that starting them indoors is pointless. Warm indoor conditions make them bolt and turn woody instead of crisp.

Sow radish seeds in shallow rows as soon as the soil can be worked. Then harvest while plants are still small and tender. Plant a new row every 10 days for non-stop supply. Radish seeds pop up in days and thrive in cool spring weather.

6. Beans

Bush, pole, and other types of beans build their own fertilizer into the soil, but they hate having their roots disturbed. Indoor starts indoors often rot or produce weak plants.

Treat bean seeds with inoculant and plant in warm soil in spring. Give pole beans a trellis right away to make sure they have the necessary support. Water at the soil line to keep leaves dry. A bean inoculant from Amazon can also help them fix more nitrogen in the soil and produce heavier crops.

7. Peas

Peas love cool soil and cool air. Indoor heat and lack of light makes them stretch tall and weak. Then transplanting chills can kill the tender seedlings.

Sow peas in trenches as soon as the ground thaws, adding a trellis for vines to climb. Soaking seeds overnight speeds sprouting. Pea seeds give sweet, heavy pods when planted straight outside.

8. Spinach and Lettuce

Most varieties of lettuce and spinach bolt and turn bitter under grow lights and indoor warmth. Their shallow roots bruise easily when moved, so they often wilt or die after transplant.

Broadcast seeds in wide rows when soil reaches 40°F (4°C) and barely cover them with soil. A light shade cloth protects seedlings as the sun gets stronger. A lettuce mix provides weeks of fresh salads from sturdy, garden-grown plants.