Spring is here and you’re raring to get your vegetable garden going. Well, hold on just a minute. Sowing seed or planting seedlings at the wrong time will bring nothing but heartache.

“One of the biggest mistakes people make is to plant too early,” said Weston Miller, a horticulturist with Oregon State University’s Extension Service. “They get excited when it’s sunny for a few days, put plants in the ground and think they will grow. But the seeds either rot from damping off fungus or germinate very slowly. Transplanted starts planted too early will be stressed for the rest of the season and likely won’t catch up.”

In early May, west of the Cascades, you can plant cool-season vegetables like carrots, beets, scallions, chives, parsley and cutting greens that are easy to grow from seed; or plant already-started transplants of kale, head lettuce, chard, leeks and onions.

An inexpensive soil thermometer helps keep planting time in perspective.

Fifty degrees is a good benchmark for cool-season crops,” Miller said. “And the soil should be 60 degrees or more for warm-weather plants like tomatoes, peppers and basil. In fact, for tomatoes it should ideally be 65 to 70. The soil won’t warm up to 60 or more until mid to late May or even June.”

If you can’t resist the urge to plant warm-season vegetables, Miller recommended using some sort of protection from the chill like floating row cover, individual glass or plastic cloches, or even milk jugs or soda bottles with the top cut off and turned upside down over plants. For directions on building a large, greenhouse-type cloche with PVC pipe and plastic, check out the OSU Extension guide on How to Build Your Own Raised Bed Cloche.

Keep those tomato seedlings inside a while longer — the ground needs to be 65–70 degrees for tomatoes to thrive. That won’t happen until late May or even early June. (Getty Images)

Whether the relatively warm winter will mean that the soil warms earlier this year is a matter of conjecture, Miller said. There still could be a cold snap this month.

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“Gardening depends on the weather, which is unpredictable,” he said. “But it pays to wait.”

You’ll find more information about vegetable gardening, including schedules for planting 45 vegetables, in the comprehensive Extension publication called Growing Your Own. You’ll also find information on how far apart to space plants and how much to plant for a family of four.

Weston Miller’s 5 tips for a successful vegetable garden

Prepare the soil: Before planting, add a moderate amount of compost — ¼-inch to 1-inch — and a balanced fertilizer (all three numbers on the bag are the same) according to package directions. Incorporate the materials into the top 8 to 12 inches with a digging fork or spade. Rake the bed before planting seeds or transplants.

For new garden beds, remove sod or weeds to expose the soil. Liberally add 4 to 6 inches of compost, agricultural lime and a balanced fertilizer and incorporate them into the top 8 to 12 inches with a digging fork or spade. Rake flat. Next fall, add 5 to 10 pounds per 100 square feet of lime to beds.

Fertilize: In addition to adding complete fertilizer to the soil, use a soluble fertilizer like fish emulsion around transplants, especially early in the season or if the plants are not thriving.

Use transplants: Crops that do best when seeded directly into the garden include carrots, parsnips, beets, radish, turnips, mustard and arugula. Most other crops can and should be transplanted to make the gardening process easier, particularly for weed control. Grow your own transplants or look for high-quality starts (not root bound, stunted or off-color) at the garden center for best results.

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Remove weeds: Control weeds early in the growth cycle of your veggies. Plan to weed your veggie beds at least once every two weeks for the first six weeks of the plants’ growth to keep an edge on this ongoing challenge.

Control pests: Monitor and control slugs and insect pests often. Keep an eye out for slugs. Find them under debris and in the folds of plants and dispatch them by dropping into soapy water. Look for aphids, imported cabbage butterfly larvae and other pesky critters on the underside of the leaves.