Ask the Master Gardener: Be sure to harvest squash at the right time

If you leave very large squash fruits on the vine, plant yield will decline, so remove fruits that have grown too large even if you will not use them

Winter squash-2.jpg
A winter squash. Photo by Dave Boran

Dear Master Gardener: How do you tell when it’s time to harvest squash?

Answer: Pick winter squash and pumpkins before a hard freeze. A light frost that kills the vine will usually not harm the fruit. Cut the fruit from the vine, leaving a few inches of stem attached. Be careful not to cut or bruise the fruit. After cutting them from the vines, leave them in place in the garden for one or two weeks as long as the weather is dry and sunny. If the weather turns cold and/or rainy, cure your squash indoors in a warm (80 degrees), well-ventilated area.

The U of M Extension guidelines for harvesting summer squash, which include zucchini, crookneck, straight neck, patty pan, and other similar types are as follows:

  • Pick summer squash when they reach the size you prefer, but before they are too large.

  • Tiny “baby” fruits are more tender. If your squash planting is large, you may choose to pick some at the baby stage. In a smaller planting, it makes more sense to harvest medium-sized fruits.

  • Squash blossoms are also edible, and should be harvested the day they open. You can pick male flowers without hurting the yield of squash fruits. Female flowers have a miniature fruit at the base of the flower. Male flowers don’t.

  • If you leave very large squash fruits on the vine, plant yield will decline, so remove fruits that have grown too large even if you will not use them.

  • Harvest often, but be careful not to disturb the plants, as they often send out new roots from joints in the vine. Shifting the vine can break these roots.

  • Do not pick fruit when the vines are wet, because of the danger of spreading diseases.

  • Pick and eat summer squash as it ripens. It will keep in the refrigerator for up to four days.

Ask the Master Gardener: Managing powdery mildew on ornamental plants Powdery mildew is easy to recognize by its characteristic coating of “powder,” which is typically found on the upper sides of leaves. Although it is quite unsightly, it is rarely fatal to the plant.

Dear Master Gardener: I have an area next to my garage which faces northwest and is bare ground. Someone suggested lily of the valley as a ground cover. When should it be planted and what can you tell me about it?


Answer: Lily of the valley (Convallaria majalis), a member of the asparagus family, is an attractive and vigorous ground cover for a shady area, woodland garden, mass planting, or for naturalizing. It is hardy to zone 3a, relatively pest and disease free, and best of all - deer don’t like it! It is long-lived once established and can form dense colonies. It spreads by rhizomatous roots, which is advantageous if you want to fill in an area quickly. If you want to limit its spread in your garden area, you can bury edging to set boundaries. Lily of the valley grows to a height of 8-12 inches at maturity and a spread of 12 inches. It performs best in partial to full shade; moist, organic soil (although it will tolerate summer drought); and benefits from a sheltered location. The flowers are white, bell-shaped, very fragrant, and bloom in spring. Lily of the valley can be propagated in spring or fall by root division. Plant it so the bottom of the rhizome is three inches deep. Potted plants can be planted any time. Because it is an aggressive plant, there is no need to encourage it by fertilizing. Lily of the valley is toxic to humans and pets, but only if eaten in large quantities.

On a cultural note, on May Day (May 1) in France, the street corners overflow with lily of the valley being sold in bundles held together with a ribbon. Every May Day the French present each other with bunches or pots of lily of the valley to celebrate La Fête de Muguet -- Festival of Lily of the Valley.

If you are scared off by the aggressive nature of lily of the valley, another option is to plant the more well-behaved Solomon’s seal (Polygonatum biflorum). It grows taller (1-3 feet), performs similarly well in shade, and spreads by rhizomes to form colonies. It does need to be kept consistently moist, and unlike lily of the valley does not tolerate summer drought well. It has white, fragrant flowers that dangle from the bottom of arched stems, followed by blue-black fruits that are often enjoyed by birds. Some varieties have solid green leaves and some have variegated.

Ask the Master Gardener: Finding fresh fragrance from true lilies While many plants have "lily" as part of their names, they are not really lilies.

Dear Master Gardener: There are many clumps of strange-looking, white stems growing in my woods. Are they friend or foe?

Answer: This peculiarity of the plant world is called Indian pipe or ghost plant (Monotropa uniflora). It is a native plant found throughout the forested half of Minnesota, including Crow Wing County. Indian pipe completely lacks chlorophyll -- the stem, flower head, and petals are all white with small black flecks on the petals and sepals. The white stems occur singly or in dense clusters from the roots. The flower head points downward and is barely discernible. Since the plant doesn’t contain any chlorophyll you may wonder how it gets its nutrients. They come from mycorrhizal fungi, which are fungi that live symbiotically with trees and their roots. Because this plant needs no sunlight to survive, it can grow in the darkest areas of the woods. On your next stroll through the woods, watch for this anomaly of the plant kingdom and enjoy the display!

Dear Master Gardener: When can I start digging up potatoes? Do I have to wait for the tops to die back or can I dig some of them up sooner?

Answer: Harvest potatoes after the vines have died or when they have reached full size. Dig them up using a spading fork, handling them as gently as possible so they don’t get pierced. Try to harvest your potatoes on a warm, dry day. New potatoes may be dug before the vines die, about seven to eight weeks after planting, so go ahead and dig out a few now -- they will just be a little smaller than if you wait.


You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, emailing me at and I will answer you in the column if space allows.
University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.
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