Did you know Onions are one of the easiest vegetables to Regrow from scraps? You can regrow most onion varieties, including grocery store-bought onions, in your garden or inside your house.
Onions thrive in a variety of temperature ranges but they produce the best at 55 to 75 F. (12-23 C.) and most varieties are hardy to 20 F. (-6 C.). Onions also need 12 and 15 hours of light to produce large bulbs.
Onions cost about a dollar apiece in the grocery store and I grew 10 new onions from the bottoms of 4 onions. I spent $4.00 on four onions and four months later I saved $10.00 by picking and using the ten onions I grew.
The onions can only be regrown about 3 or 4 times before the plant wears out and you will need to start fresh again. I guess the old idiom is true, nothing lasts forever.
10 Steps to Regrow an Onion
Time needed: 120 days.
How to Regrow an Onion
- Determine Time and Location to Plant
If you’re growing the onions outside, start your cuttings at the beginning of your growing season in the climate zone you live in. For onions grown indoors, any time of the year is fine. Find a location that will allow the maximum amount of sunlight during the day to grow your onions.
- Prepare the Onions
Cut the onion about 1 inch above the root and let set on the counter for 24 hours to dry. Put the onion on top of a jar filled with water. By day 4 the roots should begin to grow and they will begin to grow green sprouts. Most onions will grow 2 to 3 separate sprouts that must be separated before planting. Allow sprouts to grow 2 to 3 inches before separation.
- Make Nitrogen Fertilizer
Add chopped banana peels to a jar and fill to the top with water, enough to cover the banana peels.
Close the jar and allow it to rest for a few days. Remove the peels and water plants with the banana peel fertilizer. You will need this recipe for the next step.
- Separate the Sprouts
Peel back the outside layers of the onion and remove them from the root ball. Using a sharp knife separate the root ball evenly between the sprouts.
- Plant the Sprouts
You can skip this step and go directly to step 6 if you’re going to plant directly into the garden. Otherwise, plant the sprouts in starter cups filled with fresh potting soil about 1–2 in (2.5–5.1 cm) deep. Water the onion cutting with a nitrogen fertilizer mix immediately after planting and give the sprouts as much natural sunlight as possible. Supplement any lack of sunlight with light from a grow-lamp.
- Transplant to the Garden
If you are bringing the sprouts directly to the garden to plant, onions should be planted at a depth of 1 to 1 1/2 inches in rows 12 to 15 inches apart. Water the onion cutting with a nitrogen fertilizer mix immediately after planting.
- Caring for Your Onions
Water your onion once a week and fertilize your onions once every 3 weeks. Fertilizing your onion plant regularly helps it grow large, healthy bulbs. Spray the onion plant at least twice a month. Try and provide a full 12 hours of light if possible, onions thrive on light. Supplement with grow-lamps if necessary.
- Harvest Your Onions
Harvest your onion when it forms flowers. When your onion starts to grow flowers, it’s ready to harvest. Loosen the soil around the onion with your shovel and pull the onion by the base of its green foliage to pull it out of the ground. On average, it takes onions grown from cuttings about 90-120 days to grow a new bulb.
- Cure Your Onions
A properly cured onion stores the longest. Curing means the onion has dried thoroughly from the neck (where the stem meets the bulb) to the bulb surface. The onion skin becomes dry and papery. When tops are completely dry, they should pull right off the bulb. After curing your onions outdoors for a few days, move them indoors to a spot where they’re protected from weather and have good airflow. Lay them on screens to finish drying. When bulbs are completely dry, clip roots and either clip or braid tops.
- How to Store Cured Onions
Place onions in a cool, dry area with good airflow. Tuck bulbs into a mesh bag to increase air exposure. In a cool spot (45 F), onions store from three to 10 months. Sweeter onions usually don’t store as well, so plan to eat those first.
Because I live in Phoenix, my outdoor onion growing season is from November to March and I plant onions in my garden. The rest of the year I plant inside at a west-facing window. I supplement the 5 hours of sunlight the onions get with 6 hours of light from a grow lamp.
I use a planter that is 12″ wide by 36″ long and 10″ deep allowing me to grow 12 onions in the planter at the same time.