Garden Variety: Time to plant cool-season crops

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Mid-march is the ideal time to plant peas and other cool-season crops.

Mid-March is the beginning of vegetable gardening season in Kansas, with ideal temperatures to plant greens, peas, root vegetables and other cool-season crops.

Examples of greens that prefer the cool temperatures of spring are arugula, bok choi, chard, lettuce and spinach. Examples of root crops suitable for cool-season planting are beets, carrots, onions, potatoes, radishes and turnips.

Prepare the planting site by removing plant debris from the previous year as needed, adding compost or other organic matter to improve soil drainage, adding nutrients or pH amendments as prescribed by a soil test, and tilling or otherwise loosening the soil for planting. Follow these steps for container plantings and raised beds as well as any other planting site. If using potting media or soil in containers, mix new soil in with the old or replace it as needed.

When choosing your crops, consider the amount of space available, how long the crop grows through the season and the amount of labor required to grow the crop. Peas, for example, finish their growth season early enough to plant another crop in the same space in the same year. However, harvesting them is somewhat labor-intensive.

Most crops can just be grown from seed, but you shouldn’t try that right now for onions or potatoes. For onions, use sets or plants instead of seed this time of year. Seed is better if you’re starting onions early under grow lights and then transferring them outdoors in March. For potatoes, use certified seed potatoes. Don’t use potatoes sold in the produce section; they pose a risk of transporting plant disease organisms and may have been treated to delay sprouting.

When it’s time to plant, follow the package directions. For seed potatoes, cut the potatoes into sections with at least one eye per section. Potato eyes are small buds on the surface where a sprout will emerge. Cut the potatoes two to three days before planting and lay them out to allow the cut surfaces to suberize or heal over.

If planting peas, plan to use a trellis or grow them along a fence or other support structure. They take up less space this way and are much easier to harvest when the time comes. Install the trellis prior to planting or soon after plants emerge.

Greens should sprout quickly and be ready to harvest within a few weeks. Some can be clipped and allowed to regrow for multiple harvests. Pea plants will sprout quickly and be ready to harvest by mid- to late May or early June. Potatoes may take a month to sprout but then will grow quickly and be ready for harvest in June. The other root crops are variable in growth rate and days to maturity, and sometimes they can be harvested at different times for different results. For example, onions might be harvested small as green onions this spring or left to grow into the summer for larger bulbs.

Be patient with warm-season crops such as cucumbers, beans, melons, peppers and tomatoes. Wait until all chance of frost has passed and the soil has warmed to ideal temperatures for root growth. Mid-April is the average date of the last frost in northeast Kansas, but frosts have occurred into early May. Frost will kill or severely injure warm-season crops, and cool soil temperatures delay plant growth.

— Jennifer Smith works in regulatory horticulture and has worked as a horticulturist for various government entities. She has experience in landscape design and maintenance and as an educator.

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