Time to think about fall planting!

Wait… what?

It seems like you’ve just put that spring vegetable garden in… though actually, come to think of it, there are tomatoes reddening and squash burgeoning and summer is in full swing. But still, fall seems a long time away. Can’t we wait to think about it until it gets chilly again?

Well, if all you want to grow in the fall are lettuce and radishes, and maybe some spinach, sure. Given our tendency to long, warm autumns, you may be enjoying your summer vegetables well into October, or even November, if we don’t get a hard frost, so who needs to plant anything else? But those long autumns also mean we have an ideal situation for keeping our production going into winter. And if you planted broccoli or cabbage or cilantro this spring, or any other plant that prefers cool weather, and were disappointed when it went to flower early or began to taste bitter, let me tell you: fall is better. Temperatures that start a little warmer for tender seedlings and grow gradually cooler, resulting in frost-kissed sweetness and beautiful greens or root vegetables–terrific! You just need to do a little work to get there.

img_2299 by Robin
The author photographed after harvesting at the Derwood Demo Garden last fall, by MG Robin Ritterhoff

What can I grow in fall?

All of the same plants you grew in spring, but likely better! Anything in the cabbage family–broccoli, cauliflower, kale, collards, kohlrabi, radishes, turnips, mustard, arugula, bok choy, other Asian greens, etc. etc.–plus lettuce, spinach, chard, beets, and carrots. And just as you could plant all these before the last frost in spring, you can harvest them after the first frost in autumn. But you have to plant them well ahead of that.

So when do I plant them?

Here’s where you have to do a little math. Somewhere on your seed packet, or in the seed catalog, there should be a number called “days to maturity.” This is how long it takes between sowing and harvest time–or, in some cases, how long between planting out a transplant and harvesting. Your catalog (or online version) should tell you which is which, but in general, plants that are more commonly transplanted, such as broccoli, cabbage, cauliflower, or Brussels sprouts, will use days from transplant, and plants like lettuce that are more commonly direct-seeded will use days from sowing. (I know, confusion already. But you’ll get used to the conventions.)

Here’s a seed packet for an example:


This kale matures in 55 days, and in this case, that’s from sowing. Now, here’s where the math comes in. In the fall, days are getting shorter, and that means plants grow more slowly. So we add some extra days to allow for this slower growth. 14 days to be exact. This gives us a revised number: 69 days.

Okay, next step is: when do I want to harvest this plant? Kale can be harvested at any size, so “maturity” is a little arbitrary, but we’re talking about a good-sized plant that will continue to produce for weeks after that artificial “maturity” date. Kale is quite cold-hardy, but I’d like it to be mature around the time of the first frost. Which, on average, is October 20 for me. (See this page to calculate your own frost date.)

Subtract 69 days from October 20 and (if I’m counting right) you get August 12. So that’s the approximate sowing date for this kale. (No need to be that precise. Earlier is fine. A bit later is fine too.)

What if I’m growing broccoli? Let’s say the broccoli packet says 60 days to maturity, and that’s days from transplant this time, meaning transplanting on August 7. I need to grow transplants, which takes about another five weeks, so that gives a starting date of July 3.

Aha, that’s today! Better get those broccoli seeds planted right away! …more or less. The frost might be late, and the broccoli will come through a light frost just fine, so I’m not going to worry about an extra week or so (and I’m not planning to grow broccoli this year anyway) but this gives you an idea of how far ahead the planning needs to happen.

But it’s hot out. How do I get cool-weather plants to grow in the summer?

This is a challenge! Seeds will germinate faster in warm soil than they did in cold soil, but some won’t like really warm soil, and even if the plants grow, they may bolt early in the heat. Here are some ways you can stop this from happening:

  • Start your seedlings inside. This allows you to control the soil and air temperatures, and you can transplant outside when the nights are cooler. If you don’t have a setup with lights, you can use a sunny windowsill, but it’s a great time to learn about indoor seed-starting.
  • Cool your garden soil by using shade cloth on hoops over the bed where your cool-weather plants will grow.
  • Plant your seeds in a shaded bed and transplant into the sun later.
  • Water frequently with cool water!

And remember that some plants grow quite quickly, such as looseleaf lettuce, radishes, and spinach, so you can start those even in early September and have a good harvest. If you can get spinach to relative maturity before frost, it will often winter over and give you huge harvests in the spring!

What about bugs?

Once it gets cool outside, insect pests are less of a problem, but while it’s warm your crops may be invaded. Cabbage family plants, for example, are great favorites of harlequin bugs and various caterpillars. The simplest way to deal with these pests is using row cover. The supports you set up can do multiple duty: lightweight row cover and shade cloth, and then a heavier row cover to take your vegetables into the winter.

But I don’t have any seeds!

Start looking fast! A lot of seed companies are short-stocked in this crazy year when so many people have taken up gardening. This is a good time to be flexible; if the variety you wanted is gone, try another. Call up garden centers to see if they have seeds; start a neighborhood seed swap.

Also, remember you can buy plants. If all that seed-starting stuff sounded a bit challenging, make some calls in late August and you’ll probably find some garden centers stocked with seedlings ready to go in. Farmer’s markets are another good place to look.

And next year, plan ahead and do your fall seed shopping in the spring.

Just looking at that kale seed packet makes me feel a bit cooler. Now, to do some math…


By Erica Smith, Montgomery County Master Gardener. Read more by Erica.

9 thoughts on “Time to think about fall planting!

  1. Denise DeOrio July 5, 2020 / 11:43 am

    Hey Erica, so nice to see you using a High Mowing seed packet as an example AND recommending floating row cover. Way to go!!!

  2. Katherine July 28, 2020 / 3:44 pm

    Perfectly answered all my questions! Thank you 🙂

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