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Don Kinzler, Published May 03 2013

Growing together: A little logic makes knowing when to plant easier

If William Shakespeare had been a gardener, Hamlet’s line pondering the meaning of life would have been “To plant, or not to plant, that is the question.”

Early spring, late spring, when is a gardener supposed to plant to avoid the dreaded frost?

Advice from other parts of the country might tell us which movie is Oscar material or how skinny your jeans are supposed to be, but they can rarely tell us how and when to garden. What works in Los Angeles or Tuscaloosa probably won’t work here.

Nowhere is this more obvious than in spring planting dates. Our parents and grandparents commonly planted garden on Memorial Day (which was May 30, until 1968). One reason was the need to get the wheat, barley and corn in first. Afterward, there was time to garden. But this also wisely put the task into a fairly frost-free period with warm soil.

Setting a yearly target date for planting reduces the peaks and valleys of early spring/late spring fluctuation. But the old Memorial Day rule is probably later than necessary for most of our area.

Let’s examine the calendar’s possibilities. On May 5 there is still a 50-50 chance of a hard freeze. May 12 is the average date of Fargo’s last spring frost, according to North Dakota State University. The regional last spring frost occurs between May 11 and May 20 on the average. May 21 is Fargo’s 90 percent frost-free date, according to the National Weather Service.

Keep in mind that these dates are only averages. Frost has occurred in Fargo after these dates, as late as June 20 in 1969.

Based on all the probabilities and to minimize risk, I believe the 10 days between May 15 and May 25 are the “sweet spot” of planting for much of our region.

Mary and I have always planted the vegetable garden, installed the annual flowers, and potted up the containers during this period with very few brushes with frost.

Cool crops, warm crops

For gardeners who want to start early, there are some vegetables that can tolerate freezing temperatures between 28 and 32 degrees. These cool season crops are broccoli, cabbage, carrots, lettuce, onions, peas, radishes and potatoes. They can be planted as early as mid-to-late-April.

Warm season crops, such as tomatoes, peppers, eggplant, beans, corn, cucumbers, melons, pumpkins, and squash, are easily damaged by frost. Planting between May 20 and May 25 is best unless you are prepared to cover plants when even light frost threatens.

Although a few annual flowers such as pansy, viola, alyssum and petunia will tolerate light frost, most are best planted between May 15 and May 25.

Garden location

Most vegetables grow best in full, all-day sun. Half-day sun is marginal. Leafy vegetables such as lettuce, spinach, kale and herbs will tolerate shade better than “fruiting” vegetables like tomatoes and peppers.

Soil workability

To decide if soil is dry enough to roto-till, squeeze a handful. If it stays in a mud ball, it’s too wet. If it crumbles out in pieces, it’s ready. Working soil when too wet ruins its structure, especially with heavy soil types.

Seeds versus plants

Vegetables that are typically seeded directly into the garden soil include carrots, beets, beans, peas, lettuce, radishes and spinach.

Vegetables that are best planted from pre-started transplants include tomatoes, peppers, eggplant, cabbage, cauliflower, broccoli and melons. They require a season too long for direct seeding.

Squash, pumpkins and cucumbers can be either direct seeded or started transplants for an earlier crop.


Vegetable and flower plants will suffer less transplant shock and are more likely to tolerate a little frost if they have first been “hardened-off.”

Whether you have started your own plants or purchased greenhouse plants, gradually expose them to sun and breeze outdoors in a sheltered spot close to the house. “Harden” all your transplants for five to seven days before your desired planting date.

Remember to watch the watering because the plants will tend to dry out during this exposure.

An important question was frequently posed to Mary and me during our greenhouse years: If you purchase plants but are not ready to plant them, is it OK to keep them in the garage for a week or two until you are ready?

No, it’s really not. Greenhouse plants were grown in sunlight, and if stored in a dim garage all day, they will weaken. Instead keep them outdoors in a sheltered spot receiving sun. Move them in at night if necessary.

Remember that passing along our gardening heritage helps new gardeners avoid trial-and-error mistakes, such as being deceived by false spring warm-ups. Learning from one another is a big part of “growing together.”

This column was written exclusively for The Forum.

Don Kinzler writes a weekly yard and gardening column in SheSays. Readers can reach him at donkinzler@msn.com.