Growing onion sets from seed involves planting onion seeds and nurturing them into small bulbs, which are then planted out the following season. Here’s how:
1. When to Start:
- Start your onion seeds indoors approximately 8-10 weeks before the last expected frost. This usually means starting in late winter or early spring.
2. Sowing the Seeds:
- Container: Use a seed-starting tray or small pots filled with a well-draining seed-starting mix.
- Depth: Sow the seeds about 1/4 to 1/2 inch deep.
- Spacing: Sow seeds relatively close together in rows spaced about an inch apart. Don't worry about precise spacing at this stage.
- Watering: Gently water the soil to moisten it thoroughly.
- Warmth: Keep the soil consistently moist and warm (around 70-75°F or 21-24°C) for optimal germination. A heat mat can be helpful.
3. Germination and Early Growth:
- Onion seeds typically germinate in 7-14 days.
- Once the seedlings emerge, provide them with plenty of light. A grow light is highly recommended, as indoor light may not be sufficient.
- Thin the seedlings if they are overcrowded, spacing them about 1/2 inch apart.
4. Hardening Off:
- Before transplanting the seedlings outdoors, you'll need to harden them off. This involves gradually exposing them to outdoor conditions over a period of 7-10 days.
- Start by placing the seedlings in a sheltered spot outdoors for a few hours each day, gradually increasing the amount of time they spend outside.
5. Transplanting:
- Timing: Transplant the seedlings outdoors when the soil has warmed up and the danger of frost has passed.
- Soil: Onions prefer well-drained soil with a pH of 6.0-7.0 and a high level of organic matter. Amend the soil with compost before planting.
- Spacing: Space the seedlings 3-4 inches apart in rows that are 12-18 inches apart.
- Depth: Plant the seedlings at the same depth they were growing in the seed trays.
- Watering: Water thoroughly after transplanting.
6. Ongoing Care:
- Watering: Keep the soil consistently moist, especially during dry periods.
- Weeding: Regularly weed the area around the onions to prevent competition for nutrients and water.
- Fertilizing: Fertilize the onions with a balanced fertilizer every few weeks.
- Bulb Development: As the onions grow, the bulbs will begin to swell. Stop fertilizing when the bulbs start to mature.
7. Harvesting Onion Sets:
- Harvest the onion sets when the tops begin to fall over and turn yellow-brown. This usually occurs in late summer or early fall.
- Gently pull the onion sets from the ground and allow them to dry in a warm, well-ventilated place for several days.
- Once the onion sets are dry, store them in a cool, dry place until you are ready to plant them out the following spring.
8. Using Harvested Onion Sets:
- The next spring, plant the sets 1 inch deep in well-drained soil, spacing them 4-6 inches apart.
- Water well and care for as usual.
By following these steps, you can successfully grow your own onion sets from seed and enjoy a bountiful harvest of delicious onions.
