string beans on pole

Photo: smereka/Shutterstock

The grill has barely cooled from the Memorial Day barbecue and tomatoes are just beginning to set fruit. So who’s thinking about fall and winter gardening?

Mail order seed companies are, and they think home gardeners should be, too. That’s why they began sending online catalogs for fall vegetable seed and ornamental bulbs to email inboxes at the end of May. Is that just smart marketing, or should home gardeners really be thinking that far ahead?

“You need to be thinking that far ahead,” said Susan Littlefield, horticulture editor at the National Gardening Association in Williston, Vt. “It’s hard to do,” she admitted, acknowledging that many people might have a roll-their-eyes moment and mutter to themselves, "'Oh, gee, I need to start something now to harvest in October.'"

“That’s the thing about succession planting for fall crops,” Littlefield added. You have to be thinking at least a month and probably two months ahead. There are several reasons for that.

One is that specific varieties you may want could be sold out if you wait until fall to place your order. “It’s important to order early to ensure a good selection,” she said.

Another is that you can’t wait until fall to sow seed because it won’t have time to germinate before the first frost date in your area. “You have to think about where you are in the country, how long a growing season you have and the number days the seed will need to reach maturity,” Littlefield said.

Some crops, such as kale and collards, need a fairly long growing period. Others are sensitive to frosts, she pointed out, citing broccoli and cabbage as two examples.

cabbage seedlingsTo figure out when to sow seed, Littlefield said the first step is to find out the predicted first frost date in your area. Once you know that, she said to look on the back of the seed package for the number of days to maturity. If it’s 60, for example, count backward 60 days from your frost date and that’s the last date you should sow the seed.

Even then, Littlefield advised allowing for a “fall fudge factor.”

“Fall days grow increasingly shorter and the nights more and more cool,” she said. Because fall can, and sometimes does, arrive earlier than expected, Littlefield advised adding up to 14 days to the time of maturity on the seed packet.

That doesn’t mean you need to sow fall seed in the garden when you’ve devoted all of your space to tomatoes, peppers, squash and beans and they are at their production peak. In fact, the garden soil in many parts of the country will be too hot for the seed of cool-growing lettuces and spinach to get a good germination rate.

“Start them in seed trays and flats,” Littlefield advised, “and be sure to keep the soil moist.” If it turns out you do have some space in the summer garden, you can even sow seed that can take warm temperatures directly into the open soil.

Again, the idea is to keep the soil moist. One way to do that is to moisten the soil after sowing the seed, lay burlap or a garden cover cloth directly on the seed bed and moisten the soil cover. Keep the ground and cover moist until the seed germinates. Depending on your temperatures and soil conditions, you can either remove the cover or put hoops of PVC pipe, wire or other material in place and drape the cloth over the hoops — lettuces especially will appreciate moderation from the summer heat.

It’s not difficult to start fall seeds in summer, Littlefield said; it just requires a little more attention.

Related gardening stories on MNN:

Cabbage seedlings photo: IrinaK/Shutterstock
Is it too soon to plan my fall vegetable garden?
Seed companies and garden experts say it's time to start thinking about cooler weather. (Yes, already.)