When to harvest potatoes


July 04, 1999

Q. I'm trying white potatoes and sweet potatoes for the first time in my small vegetable garden. How do I know when to harvest these underground crops?

A. You can begin digging small, tender new potatoes when the plants are blooming. Gently dig up a single plant with a garden fork and check tuber size for desired eating quality. For larger potatoes that you want to eat fresh or store, wait and harvest when the plants begin to die.

Keep soil hilled up around the plants to increase the number of tubers formed and to prevent sunlight from turning your spuds green.

Q. Our 4-year-old peach trees are loaded with fruit. Should I let them get completely ripe before I start picking?

A. You may have few fruits to enjoy if you wait that long! Squirrels, birds, yellow jackets and other creatures will beat you to them. Harvest peaches when they are still firm -- several days before they become fully ripe. The background color will be cream or yellow, and the fruit will twist easily from the tree.

Handle peaches very carefully to reduce bruising, which allows the entry of rot organisms. You should also spray a fungicide two weeks before harvest to prevent brown rot infection in the fruit.

Q. My irises looked terrible this year. The foliage was streaked and then it wilted down. Is this a virus disease? Will I have to dig them up and throw them out?

A. Your plants are probably infested with iris borer. The larvae begin feeding in the foliage and then tunnel down and feed on the rhizome, causing the foliage and flower stalks to wilt. Cut the affected flower stalks and foliage down to the crown; dig up the rhizomes; cut off rotted and infested portions, and re-plant the healthy portions.

The best control is prevention. Do not mulch your irises; plant rhizomes high in the planting bed, and select full-sun sites.


1. Pick and discard tomato plants with brown or black bottoms. They've been afflicted with blossom-end rot, which is caused when plants don't get enough water to allow them to absorb calcium from the soil. Water plants deeply and regularly, especially during drought conditions, and keep them mulched.

2. Sweep granular fertilizers off plant leaves to avoid burning them. Liquid fertilizers can also burn foliage, particularly on hot, sunny days.

3. Support your sweet corn, eggplant and pepper plants with wooden stakes or cages to keep them from getting blown down or damaged in storms.

Garden tips are provided by the Home and Garden Information Center of the Cooperative Extension Service of the University of Maryland. For additional information on these questions, or if you have questions of your own, call the center's hot line at 800-342-2507, or visit its Web site at www.agnr.umd.edu/users/hgic.

Pub Date: 07/04/99

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