Yard and Garden: Proper Spring Planting Windows For Garden Vegetables



AMES, Iowa – Spring planting season is upon us, and it’s time to think about how gardens will be populated with vegetables to yield a bountiful harvest later in the year. All vegetables have an optimal planting time that helps them properly mature and maximize their potential. How do those times shake out?

ISU Extension and Outreach horticulturists can help answer your questions about proper planting windows for garden vegetables. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

potato plants

When should I plant potatoes?

Potatoes should be planted in early spring. Appropriate planting times are late March or early April in southern Iowa, early to mid-April in central Iowa, and mid to late April in northern portions of the state.  

Since potatoes are susceptible to several diseases, buy certified, disease-free potatoes at garden centers or mail-order nurseries. Gardeners can purchase seed pieces (tubers that have been cut into sections) or whole potatoes. Small potato tubers may be planted whole. Large potatoes should be cut into sections or pieces. Each seed piece should have one or two “eyes” or buds and weigh approximately 1.5 to 2 ounces.

After cutting the tubers into sections, place the freshly cut seed pieces in a humid, 60 to 70 degree Fahrenheit location for one or two days. A short “healing” period allows the cut surfaces to callus or heal over before the seed pieces are planted. Healing of the cut surfaces helps prevent the rotting of seed pieces when planted.  

Plant seed pieces (cut side down) and small whole potatoes 3 to 4 inches deep and 1 foot apart within the row. Rows should be spaced 2½ to 3 feet apart.

When should I plant cabbage?

Cabbage, broccoli and cauliflower can be planted outdoors in early April in southern Iowa, mid-April in central portions of the state, and late April in northern counties. Harden (acclimate) plants in a protected location for a few days prior to planting. Cabbage, broccoli and cauliflower perform best in fertile, moist, well-drained soils. Space plants 24 inches apart within the row.  Rows should be 24 to 30 inches apart.

When should I plant onions?

Onions can be planted from early April to early May. Onions may be grown from seeds, sets and plants. Plant seeds in rows 12 to 15 inches apart. Cover the seeds with ½ to ¾ inch of soil.  When the seedlings are 2 to 3 inches tall, thin the planting. For large, dry onions, plants should be spaced 2 to 3 inches apart after thinning.  

Plant onion sets at a depth of 1 to 1½ inches in rows 12 to 15 inches apart. For dry onions, plant sets 2 to 3 inches apart. Sets grown for green onions can be planted closer together. Place plants 1 to 1½ inches deep in rows 12 to 15 inches apart. To produce large, dry onions, space plants 2 to 3 inches apart.

When should I plant radishes?

Radishes can be planted as soon as the ground can be worked properly in spring. When feasible, begin planting in late March in southern Iowa and mid-April in northern counties. Successive plantings can be made every 7 to 10 days through May. Several plantings can also be made in late summer (mid-August to late September) for a fall crop.  

Sow radish seeds one-half inch deep in rows that are 12 inches apart. When the seedlings emerge, thin the planting so remaining plants are 2 inches apart.

When should I plant peas?

Peas are a cool season crop. They should be planted as soon as the ground can be worked in spring. Appropriate planting dates are late March in southern Iowa, early April in central Iowa and mid-April in northern portions of the state.