6 Seeds You Really Shouldn't Start During the Winter, According to Pro Gardeners

When the seed catalogs start arriving in the mail after the New Year, placing your order early is a good idea, especially if you are after more unusual varieties. But when it comes to starting seeds, whether it’s indoors to get a head start on the growing season or whether it’s direct-seeding outdoors, there is such a thing as being too early. 

Here's what gardening experts say about which seeds you shouldn't start in the dead of winter and why.

Tomatoes, Eggplants, and Peppers

These members of the nightshade family take several months to reach the harvest stage (some hot peppers require up to four months after transplanting). However, it is important not to start them too early because these highly cold-sensitive plants should only be moved outdoors after the last spring frost.

To determine when to start the seeds indoors, count back six to eight weeks from the last average frost date in your area. Owen Taylor, the founder of Truelove Seeds, starts pepper and eggplant seeds in late February or early March. This can be earlier or later for your location depending on your last frost date. 

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Cucurbits

The members of the cucumber family (summer squash, zucchini, cucumber, melon, and watermelon) are also warm-weather crops. Most cucurbits germinate and grow fast so if you start them too early, the plants will be in urgent need of transplanting even though it may be too cold.

“Hold off on starting the seeds of fast-growing crops such as squashes and melons until April,” Taylor says. “That way, they are ready for a mid-May transplant into the garden after the last danger of frost.”

Elise Pickett, the founder of The Urban Harvest, says waiting out the cold weather also applies to
southern crops like luffa gourd that thrive in the hot and humid Florida climate where she gardens.

Basil

Because basil is highly sensitive to cold—it needs daytime temperatures above 70°F—delay the seed starting until six to eight weeks before the last average frost date in your area to prevent scraggly transplants. The only exception is if you have a sunny windowsill or strong grow lights that let you bridge the time until it’s time to transplant basil outdoors. 

Beans

Because beans don’t transplant well, they cannot be started from seed indoors but must be directly seeded in the garden. They also need warm soil, at least 70 to 80°F, to germinate. For Taylor, this means that mid-to-late May is bean planting season, depending on the weather.

The same waiting period for beans applies in the south.

“Winter is prime growing season for much of the south but not for beans," Taylor says. "They need very specific conditions: warm soil temperatures, longer daylight hours, and warm days.” 

Sweet Potatoes

Vegetables that are grown from seed are not the only ones that may stretch the patience of an eager gardener.

“Sweet potatoes do amazingly well in our Florida climate," Pickett explains. "But, they need the warmer spring months to be planted in the garden, or they will not germinate.”

If you don’t want to wait for soil temperatures to reach 60 to 85°F, growing sweet potato slips indoors gives you a head start on the growing season.

Annual Flowers

Taylor explains how heat-loving annuals like zinnias, marigolds, and cosmos are also not suitable to start in the middle of the winter.

Just like the vegetables, you’ll need to wait six to eight weeks before the last average frost date and then plant them in the garden after the last danger of frost. 

Seeds to Start in the Winter and Early Spring

 “The only seeds I'd consider starting in December or January are seeds that benefit from a long period of cold (called cold stratification) in order to germinate successfully,” Taylor explains.

The plants he subjects to cold treatment include native plants like milkweed, purple coneflower, black-eyed Susan, and passionflower. The next round of planting starts towards the end of January and runs into February. During this period, Taylor suggests starting perennials like lower-growing herbs indoors: lavender, thyme, rosemary, oregano, and mints.

For Pickett, late winter and early spring is the time to plant cool-weather vegetables in Florida.

“In our climate, around March, we plant crops like fava beans, kale, arugula, chard, spinach, and other leafy greens that can take a list frost, as well as potato tubers," Pickett says.