Fall harvest

  • Article by: NANCY ROSE , Contributing Writer
  • Updated: September 27, 2005 - 11:00 PM

When should I harvest my pumpkins and butternut squash? Some look ripe but others don't. I also have some peppers that I hope will turn red. How long can I wait to pick them? Are there some vegetables I can plant next year to extend the growing season?

September often brings the final harvests for many vegetable gardens.

When to harvest depends in part on whether the vegetable has any tolerance to frost. Tomatoes, peppers, pumpkins, squash and cucumbers are sensitive to frost, so their fruits should be harvested before freezing temperatures arrive. You can protect these plants against light frosts (from about 28 to 32 degrees) by covering them with blankets or cardboard boxes overnight, but if temperatures lower than 28 degrees are predicted, it's time to harvest the remaining fruits and call it a year.

Pumpkins and winter squashes may survive a light frost without injury, but a freeze can limit their keeping quality. That's not a problem if you want to use them for decoration, but if you plan on storing pumpkins or squash for eating later, you should harvest the fruits when they are fully mature and before any frost. (Mature squash should be fully colored without obvious green background color. Pumpkins should also be fully colored. Immature fruits will not ripen after harvesting, so compost them.)

Peppers also are frost-sensitive and should be harvested before freezing temperatures arrive. Many peppers (including bell, jalapeno and Anaheim) can be used even when they are still green as long as they have reached mature size. However, they do develop additional flavors if allowed to attain their mature color.

Unfortunately, by late September the cooler days and reduced sunlight don't usually allow for much additional ripening. Peppers that are harvested when starting to turn red will continue to color indoors if kept in a paper bag on the kitchen counter, but they should be used fairly quickly.

Vegetables that will tolerate some frost make good season extenders in the garden. Brussels sprouts and collards tolerate below-freezing temperatures. In fact, some gardeners believe that a few light frosts improve the flavor of these cole crops.

Spinach, mustard greens and many leaf lettuces will also survive frosty midfall conditions. Root crops such as carrots and parsnips can be harvested up until the ground starts freezing. If you want to extend their season even more, you can mulch root crops with a thick layer of straw to slow the freezing.

How can I tell when my apples are ripe? The tree was here when we moved in, so I'm not sure what kind of apple it is.

The color of the fruit and how easy they are to pick are good clues to judge the ripeness of apples, but taste is the best indicator.

The skins of fully ripe apples should have a yellow background color, not green. It's easy to see this background color on yellow, light red or red-streaked apples such as Honeygold or Honeycrisp. It's more difficult to tell on solidly dark red apples, but check the shoulder area around the stem.

Ripe apples are also easier to pick than immature apples. Give the fruit a moderate tug with a slight upward twisting motion. Ripe apples should pull off without a lot of resistance. Be careful not to damage the short, spurlike branch the apples grow on, though, because this is where next year's apples will be produced.

As apples ripen, they develop more sugars and lose starchiness. If you sample an apple and it leaves a starchy taste or feel in your mouth, then the apple is not ripe. As the apples reach peak ripeness check them frequently and harvest as needed. Overripe apples don't store well, though they can be used for juice or cider.

Nancy Rose is a horticulturist with the University of Minnesota Extension Service. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.

Is it too late to seed my lawn?

The timing for fall lawn seeding varies according to where you live. Ideally, mid-September is considered our cutoff date in the Twin Cities metro area.

Getting the seeds to sprout is not a problem this time of year. But allowing the little plants time to develop a root system that is strong enough to survive winter's rigors is critical, and that takes longer. A good covering of snow will help protect any vulnerable seedlings, but we can't always count on that.

If you still want to seed this fall, try dormant seeding. Here's how: Prepare the area you wish to seed, then wait until just before the ground freezes to seed. It will be too cold for the seeds to sprout, but if we get good snow cover and if the area remains undisturbed over winter, the seeds should sprout in spring as snow melts and the soil warms.

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