More info

For more on growing and canning garden fresh vegetables, join local Clemson Extension agents and area Master Gardeners for Seed to Shelf, a four-week course beginning in August. For more information and to register, go to www.regonline.com/seedtoshelf.For more on harvesting vegetables, check out the harvesting vegetables factsheet by Cory Tanner online at www.clemson.edu/extension/hgic.

Q How do I know when to harvest the vegetables in my garden?

A: There is nothing as gratifying as harvesting fresh vegetables straight from your own garden. Knowing the best time to pluck the fruit from the vine takes knowledge and experience. With some vegetables, it's no secret as to when they are ready to be enjoyed. A red tomato is the perfect example, but others can be a bit more difficult to figure out. Jonthan Croft, a Clemson Extension agriculture agent, and I put together these tips for some of the more secretive vegetables:

Okra

Okra (Hibiscus esculentus) is a Southern staple that is easy to grow. When harvested in a timely manner and prepared correctly, it's a delicious vegetable. Detractors have probably experienced the dark side of okra: tough, woody pods or gooey, mucilaginous preparations that are less than palatable. The secret to tender okra is to pick the pods when they are small, no more than 2 to 4 inches long.

For busy gardeners, this means harvesting daily during the peak season. Unless you plan to use older, woody pods for crafts or for harvesting the seed, do not allow the fruit to mature on the stalk. This will tell the plant to cease flower production and your okra harvest will come to an end.

To prolong the production period of okra, gardeners can give them new life by using a trick I learned from Croft called “ratooning.” This technique was historically used by cotton farmers (cotton and okra are botanically related) to coax an extra harvest out of the same crop.

Ratooning literally means cutting back the entire stalk to 8 to 10 inches above the soil line. The harsh pruning will force the plant to re-sprout and flower, thus producing more okra into late summer. Once you “ratoon” your okra, maintain soil moisture and add a little nitrogen-rich fertilizer to jump-start growth.

A late harvest is perfect for making pickled okra!

Sweet corn

Harvest sweet corn in the early morning and refrigerate it quickly to avoid losing the sugary flavor. You will know the ears are ready to be plucked when the husk is still green but the silks are dry and brown. A gentle squeeze should reveal plump kernels. Croft says that most home-grown sweet corn varieties take approximately 21 days from the time the first silks emerge until it is time to harvest the ears.

Sweet potatoes

Dig out sweet potatoes (Ipomoea batatas) before the first frost as cool soil temperatures reduce their quality. To make harvesting easier, cut and remove vines before digging. Sweet potatoes are easily bruised, so dig them carefully.

Sweet potatoes take time to convert all their starches into sugars. Store newly dug sweet potatoes at 85 degrees and 90 percent humidity for two weeks in the warmest room of your house. After curing, store them in a cool location but do not refrigerate them, which may cause them to rot. Sweet potatoes stored under good conditions will last for more than six months.

Watermelon

I hate to admit it but, my track record with picking watermelons is not the best. The anticipation is too great, and invariably I harvest too soon. Three key features, which should be present simultaneously, indicate that watermelons are ripe. First, the vine tendril closest to the fruit dies and turns brown. Then the underside of the fruit turns from white to yellow. Finally, thumping the melon should give a dull thud as opposed to a ringing, metallic sound.

Winter squash

Despite their name, winter squash are grown during the summer. When harvesting, be sure to cut, not tear, the fruit from the vine. Leave a long stem and avoid nicking or damaging the skins.

To determine ripeness, ensure skins are hard and cannot be punctured by a thumbnail. Harvest on a dry day, never when the fruit is wet. After cutting, Clemson University recommends dipping or wiping winter squash with a chlorine solution of 4 teaspoons of household bleach per gallon of water to kill bacteria and fungi. Allow fruit to dry with the chlorine solution on it, and rinse just before use.

Cure winter squash immediately after harvesting by maintaining temperatures between 80 degrees to 85 degrees with 75 percent to 80 percent relative humidity for 10 days. To store winter squash eight weeks or longer, keep them at 50 degrees to 55 degrees with 50 percent to 75 percent humidity, ensuring good ventilation to avoid spoilage.

Amy L. Dabbs is the urban horticulture extension agent and tri-county Master Gardener coordinator for the Clemson University Cooperative Extension. Send questions to gardening@postandcourier.com.