It’s safe to plant onions and potatoes up to two weeks before the final frost is expected. In southern Ohio, I plant onions sets and seed potatoes the first week of April.
The difference between onion seeds and onion sets
Onion seeds are harvested from mature onion blossoms. It takes two years to grow a full-size onion from a seed.
Onions sets are small onion bulbs. Gardeners plant sets in spring to grow full-size onions by fall. Onion sets are the fastest, easiest way to grow full-size onions in a single season.
Onions are classified by day length. Short day onions need 10 hours of daylight to develop bulbs. Long day onions need 14 to 16 hours. Day neutral onions develop bulbs regardless of light conditions. Long day and day neutral onions grow well in southern Ohio.
How to grow onions
- Work spring soil, digging deeply and adding organic matter or soil amendments if desired.
- Plant each onion set pointed side up, 1-2” inches deep.
- Space each set 4” inches apart. Rows 12-18” inches apart.
- Backfill with soil.
- Onions are ready to harvest when the tops have bent over.
- Dig up onions.
- Dry cure onions in a warm, dry location for 2-3 weeks.
- Cut onion tops 1” inch above bulb. Store bulbs in a cool basement or cellar.
Plant seed potatoes, not supermarket potatoes
Unlike onions, potato plants do not flower to produce seed. Gardeners plant a small potato or a portion of a potato called a seed potato to produce a potato plant.
Supermarket potatoes are treated with chemicals to inhibit sprouting and maintain a longer shelf life in the store. Seed potatoes are not treated, making them superior for planting. Seed potatoes have been bred in isolation and carefully pollinated to produce offspring true to type. Most seed potatoes from reputable suppliers are certified disease free. Plant seed potatoes, not supermarket potatoes, for best results.
Potatoes are classified as early, mid and late season. Early potatoes are ready to harvest in 95 days or less. Mid-season potatoes take about 95-120 days to grow to maturity. Late potatoes require more than 120 days. Planting potatoes with staggered maturity dates can provide a continuous supply of delicious potatoes for an extended season.
How to grow potatoes
- Work spring soil, digging deeply and adding organic matter or soil amendments if desired.
- Each seed potato should have at least one eye. You can cut large potatoes into smaller portions; just make sure each portion has at least one eye, and allow cuts to heal a couple days in before planting.
- Dig rows 2-3’ feet apart, 6” inches deep.
- Plant potatoes 4” inches deep, 1’ foot apart within the row.
- Backfill with soil.
- When plants are 6” inches tall, hill up with soil to bottom leaves. Repeat every three weeks. Some gardeners prefer to use straw or mulch to hill up potatoes.
- Dig up a potato plant when variety reaches its target maturity date. If the potatoes are well developed, harvest the rest of your crop. If not, leave plants in the ground and recheck in a week or two.
