Planting potatoes, onions and other cool crops

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Minnesota gardeners, are you ready to plant veggies? Many vegetable plants require waiting until after last frost (usually around mid-May) to be planted, but there are some exceptions. So if you just can’t wait to plant, or you want to grow some cool season veggies, now is the time!

Cool season vegetables include onions, potatoes, peas, lettuce, kale, beets, radish, carrots, turnips and asparagus. These vegetables can be planted from seed (or tuber or set) as soon as the soil warms and is workable, early to mid-April in Minnesota. Broccoli, cauliflower, Brussel sprouts, and early cabbage are also cool season crops, and prefer to be planted before the weather gets too warm. These vegetables must be started from seed indoors or purchased as plants from a garden center.

Planting onion sets

Onion sets. From It’s Not Working, It’s Gardening

Planting onion sets

Onions can be purchased in sets. Onion sets are short day varieties and the bulbs usually grow as large as long day varieties. Onions need full sun and prefer a well-drained soil with plenty of organic matter. Plant the pointy side up, 1”-2” deep and 3”-4” apart. Firm soil around the bulbs. Soak the soil thoroughly when watering, to a depth of at least 1 inch each week during the growing season.

Harvest onions when about half the tops are falling over and dry. Undercut and lift bulbs with a spading fork.

Planting potatoes

Tonkadale Greenhouse: Planting potatoes

Potatoes from Univerisity of Minnesota Extension.

If you’d like to plant potatoes, be sure to purchase seed potatoes that are fresh and firm. Cut potato tubers into 2-ounce pieces. Make sure there is at least one eye per piece. Allow pieces to dry on newspaper overnight.

Prepare a deep and loose soil bed. Adding compost helps add needed nutrients to the soil. Plant potato pieces 4 inches deep, eyes facing up, and cover with soil. Space tuber pieces 12 inches apart, in rows 36 inches apart. Hill the soil around plants as they grow to keep potatoes covered with soil.

Harvest by gently loosening the soil with a pitchfork – 7-8 weeks after planting for “new potatoes” or when the foliage has dried out and fallen over for fully mature potatoes.

These veggies prefer cooler temperatures and will do best when planted early. As the weather warms, cool season vegetables will begin to perform poorly – some lettuces may become bitter, peas will stop growing, and radish may bolt.

Some cool crops can be planted again in late summer or early fall depending on the amount of time each variety needs to grow and the plants cold tolerance. Cool season crops will grow well in the cooler fall weather and you’ll have another harvest. Some vegetables, such as carrots, parsnip, and some kales can even be harvested through frost and snow when properly mulched.

For more information about spring and late summer plantings of cool season veggies, visit the U of M Extension website

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