Q: I am growing onions in raised beds and would like to harvest and sow the seeds. What is the best way to do this?
A: Onions are a staple in the kitchen and fun to grow at home. Collecting seeds to have a free harvest is also a great idea. Onions grow naturally, so the process is relatively easy, although it usually requires a bit of patience.
We spoke to some vegetable gardening experts to get tips on how (and when) to do it, as well as the best varieties to harvest from seed. Below, we share our insights on this budget-friendly gardening task.
Onions are an easy crop to grow.
(Image credit: Compassionate Eye Foundation/Natasha Alipour Faridani/DigitalVision/Getty Images)
A simple guide to collecting onion seeds for sowing
Whether you're growing onions in containers or in a larger garden, these tips will help you if you want to save seeds.
When to harvest onion seeds
If you want to collect seeds, wait for the onion plants to flower.
(Image courtesy: york010 / Alamy Stock Photo)
Drew Swainston, a former professional gardener and content editor at Homes & Gardens, points out that onions are biennial plants, meaning they flower and produce seeds the second year.
“If you want to harvest onion seeds, this may mean planning ahead a little,” he says. “You can leave some of the onions in the ground to get them through the winter, but if you have very wet ground over winter or frequent hard frosts, it can be effective to dig up the onions and keep them in a cool place over winter, then replant them in the spring.”
In very hot weather, onions can develop flower stalks during the growing season, Drew adds. “This speeds up the whole process – you can get them to flower and then harvest the seeds that result.”
Horticultural expert Tony O'Neill advises that you can harvest your onion seeds when the flower heads have dried and turned brown, and Drew adds that it's best to leave the seeds to dry on the plant – they're ready to harvest when they turn black.
Tip: If rain is in the forecast, Drew recommends cutting off seed heads earlier than usual (before they dry out completely), leaving some of the stems on. Roll the seeds into a paper bag and hang it upside down. “The seeds should dry out indoors and fall into the bag.”
Drew Swainston
Social Links Navigation
Content Editor at Homes & Gardens
Drew is a qualified journalist and wrote for a number of websites and publications before beginning his horticultural qualification. He worked as a professional gardener for many years, specialising in home gardening, and he now brings his expertise and passion to Homes & Gardens as a member of the team.
Tony O'Neill
Social Links Navigation
Founder of Simplifygardening.com
Tony O'Neill is a gardening expert, best-selling author and educator. He shares his passion for gardening and sustainability through his popular YouTube channel with 434,000 subscribers and over 1.4 million monthly views, and his award-winning website Simplifygardening.com. He is the author of Simplify Vegetable Gardening, Composting Masterclass and Your First Vegetable Garden, helping individuals cultivate their own green spaces.
How to Harvest Onion Seeds
Onion flowers eventually turn brown and turn into seed heads.
(Image credit: Hazrat Bilal/Alamy Stock Photo)
Tony recommends cutting the dried seed heads off the plant and placing them in a paper bag, “and leaving them to dry further in a cool, dry place for about a week.”
“Once dry, give them a good shake and the seeds will come out,” says Craig Wilson, co-founder, director and gardening expert at Gardener's Dream. Tony also suggests lightly crushing the dried seed tips. “Separate the seeds from the husks using your hands or through a fine sieve,” he adds.
Gonicc 8-inch Bypass Pruning Shears
With ergonomically designed titanium steel blades, these pruners are the perfect tool for cutting off old flower heads and collecting onion seeds, but can also be used to prune and deadhead other plants.
FAQ
How should I store onion seeds after harvesting?
Just like when storing tomato seeds or cornflower seeds, proper storage is essential to keeping collected onion seeds healthy.
“Make sure your seeds are completely dry before storing them, otherwise they will develop mold or mildew,” says Tony. He recommends storing your seeds in glass jars or seed packets, labeling them with the variety and date, and storing them in a cool, dark place. “The refrigerator is the best place to maintain the viability of your seeds,” Tony adds.
I love the clear window on these seed packets from Amazon, and they're also resealable.
What type of onion seeds should I harvest?
Make sure to collect seeds from heirloom onions, not hybrids, as this will increase your chances of growing a new crop with the same characteristics, just like when saving cucumber seeds.
The three heirloom varieties Tony recommends are ‘Yellow Sweet Spanish’ (“known for its large bulbs and mild flavor,” Tony says), ‘Red Burgundy’, and ‘Walla Walla’ (available from Seed Needs on Amazon).
Looking for more tasty crops to collect seeds from? Our guides on how to save watermelon seeds and how to save basil seeds are worth a look.
