Extend the growing season

These tips will have you harvesting into October

A hoop house
Courtesy of Carol O\'Meara

The scorching weather of this past summer, one of the hottest on record, had a positive flipside for gardeners in that the growing season has been longer. A lack of frost in April meant that vegetables and herbs flourished in the early season, and if plants received proper watering during the summer, gardeners were able to reap a hearty bounty of fresh food.


As the summer winds down, cold weather looms, but there are ways you can prepare your garden to extend your growing season from the summer into the fall.

There are two ways to look at it. You can either plant fast-maturing vegetables like lettuce and kale for fall harvest or you can plant crops like multiplier onions (e.g., shallots and potato onions) and garlic for spring harvesting.

“Garlic, absolutely plant at the end of September and the end of October,” says Carol O’Meara, a horticulture entomologist with Colorado State University Extension Boulder County.

She says to plant garlic cloves and then mulch them, and then move the mulch aside to water the garlic bulbs every few weeks. O’Meara recommends using clean hay as mulch to keep the roots warm, as other commonly used materials such as straw and leaves each come with their own problems.

“Clean hay is a good choice. There have been some difficulties gardeners have been experiencing with some straws having herbicides on them. Raked up and fallen tree leaves can be a good temp fix, but … I’m not recommending a mulch of leaves,” she says.

If you plant now, even if you plant for the winter, you’ll reap benefits in the spring, says Ramona Clark, executive director of Growing Gardens.

“A lot of people will plant garlic and spinach in the fall and in the late fall, and it grows and then goes dormant during the winter, and then you’ll have a jump on the spring planting,” Clark says. “You’ll already have them in the ground. You’ll have bigger garlic because it will have a longer season. So you can plant crops in the fall for spring harvest.”

Of course, if you can’t wait until spring and instead want to milk an extra few weeks out of the growing season, you can take some simple measures to protect your crops.

One simple way to keep the frost off your plants is to build a “cold frame” that goes over the plants and traps heat from sunlight, keeping the roots warm. O’Meara says it’s pretty simple to do (for detailed instructions, visit www.cmg.colostate.edu/gardennotes/722.html).

“You can take some kind of PVC pipe or some kind of firm wires …and you basically build a ribcage over the bed where you’re going to plant. … Then you take 6-mm plastic that’s UV stable and put that over this and secure it to the frame you have, and it creates this tent of plastic that will capture heat.”

Plants like lettuce, kale, beets and certain peas will thrive in a cold frame, O’Meara says. The plants can potentially overheat during hot fall days, so she cautions you might have to open the cage during the day to allow cooler air to circulate through the plants.

“It’s a real balancing act in fall because in Colorado the weather gets really wacky,” she says. “You get these temps that will seesaw back and forth between the 80s and the 30s.”

In the end, planting a fall garden might require a little more careful attention than a summer one, but if there’s a will, there’s certainly a way. Mikl Brawner, owner of the Harlequin’s Gardens nursery, says potted herbs can be taken inside at night and grown throughout the fall.

Basil, for example, is very cold-sensitive and usually dies in the first frost, Brawner says, but if you take your potted basil inside, it can survive throughout the whole winter.

“There are various herbs [besides basil] that you can bring inside,” he says. “Rosemary, of course, is a classic. And there are other things too, you can bring in, [such as] chives, sometimes parsley.”

Several herbs can also be left outside, he says, including thyme and oregano. Mint will survive the whole winter if left in a shady spot free of winter sun, he says.

But if you have more veggies than you know what to do with, September and October are good months to start prepping your garden for spring.

Remove this year’s plants and dig in a layer of organic fertilizer or compost, O’Meara says. Brawner recommends using animal manure-based fertilizers and composts.

Another idea is to plant what’s called a “cover crop” over your garden, like clover or hairy vetch.

“It keeps the bed protected from soil erosion,” Clarkson says. “Then in the spring you plow it into the soil and it adds nutrients to the soil. They’re like a blanket in the winter and cake mix in the spring. You just mix it up in the soil, and it adds nitrogen and nutrients and protects it in the winter from the high wind and the rain and erosion that [can happen] in the wintertime.”

Cover crops also help promote healthy soil in a way that fertilizers might not.

“There are nitrogen-fixing cover crops that will add nitrogen to the soil,” Brawner says. “It’s like growing your own fertilizer.”

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