Because they are a warm season crop, knowing when to plant cucumbers will have a big impact on the quality of your harvest. Used fresh in salads or pickled, cucumbers are an easy-to-grow staple in every garden. How soon you get started will depend on how you’re growing your cucumbers: Starting indoors, direct sowing, or from nursery plants.
Cucumbers seeds need soil temperatures to be around 70° in order to germinate, so don’t plant until three weeks or so after last average frost. You can cover the area you’re going to plant with black plastic mulch to artificially increase the temperature, adding a week or two to your growing season, but remove mulch before planting. Sow seeds, root end up, ½ to 1 inch deep in either raised rows or in hills to help increase soil temperature. If planting in rows, thin seedlings to about 12 inches; if planting in hills, thin to three plants per hill. Succession plant every two weeks through mid- to late July for a continuous crop.
Get a jumpstart on the season by starting cucumbers indoors three to four weeks before last average frost. Sew two or three seeds, root end up, about a ½ to 1 inch deep. They can be fussy about transplanting, so use peat pots to reduce stress. Once seedlings emerge, thin to one per pot. Plant once seedlings have two or four sets of true leaves, but don’t wait too long. Larger cucumbers suffer more from transplant shock. Follow spacing for direct seeding.
When selecting cucumber plants in a garden center, look for full, squat plants that have thick healthy stems and glossy leaves. Don’t purchase any that look thin, yellowed, have flowers, or are already starting to vine. Plant in hills or rows according to spacing on plant label three to four weeks after last average frost date.