How To Harvest And Save Onion Seeds

Learn how to save money and harvest your own onion seeds! There are on average 42 onion seeds per Onion Flower! Yep, from one Onion, you can grow 42 More! And it’s so easy! Follow my simple steps to ensure a successful Onion seed harvest…

harvest save onion seeds

Homegrown Onions!

Aren’t they wonderful! One of my favourite jobs on the Allotment is harvesting my onions at the end of the season! The satisfaction that comes from enjoying fresh, straight from the dirt, homegrown Onions is a treat that’s hard to beat!

It’s also a very economical way to feed your family, especially if you grow your Onions from Saved seeds! But that’s not all- harvesting your own Onion seeds allows you to select seeds from your very best Onions, ensuring a continuous cycle of healthy Onion harvests, year after year!

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Onion Seed Harvesting Basics

Rocket science it aint! However, there are a few things you should know about Preparing your Onion plants before seed harvesting can occur …

1. Onions Are Biennial Plants.

Which basically means, it takes them 2 years to complete their life cycle…

In the first year, onion plants direct all their energy in to developing lovely fat bulbs that can be harvested and eaten by us grateful gardeners! During this time, the plant absorbs and stores lots of fabulous nutrients within the bulb. This process prepares the plant for the flowers and seeds that will arrive in the second year…

In The Second Year, the onion plant produces one or more long flowering stalks. Atop the stalk, are clusters of dainty, star-shaped flowers that are typically pink or white, dependant on the Onion Variety you are growing. Each one of those tiny flowers contains a seed pod, each seed pod will eventually yield an Onion seed.

onion flower

2. Pollination

No pollination, No Onion Seeds! You may find, that not every seed pod will provide a seed. Certain important factors are necessary for a successful Onion seed harvest…Onion flowers must be pollinated by insects and bees that transfer pollen from one flower to another.

Their work ensures the successful fertilisation of the Onion flowers, which in turn influences viable seed development.

In short, we rely on the work of mini beasts to feed us! So provide them with a welcoming bee friendly environment and steer clear of harmful pesticides.

3. Bolting

Watch Out For Bolting! What is Bolting? Bolting is premature flowering and seed production, usually triggered by hot temperatures, temperature fluctuations and prolonged cold exposure.

But we want Onions to flower and set seed don’t we? Yes, we do! But collecting seeds from an Onion plant that has bolted (too early) can affect the quality and viability of the produced seeds.

So, it’s very important to allow the Onion to fully mature the first year, absorbing as many good nutrients as possible, before it flowers and produces seed in the second year. The result will be a far more healthy and viable seed harvest

Bolt Resistant Onion varieties to try:

Prepare Your Onion For Seed Production

Before you can even think about harvesting Onion seeds, you must first properly prepare your Onion for seed production!

  1. Select mature bulbs (mature bulbs are large with well formed layers of papery skin) The larger the bulb, the more energy it has absorbed, and the better the seed harvest will be.
  2. Trim the onion foliage down to around 1 inch above the bulb, then store the selected bulbs in a cool, dark, sheltered environment. This will allow the Onions a period of dormancy and halt any premature sprouting.
  3. Overwinter the Onion Bulbs for at least 8-12 weeks
  4. Transplant overwintered Onions in Early Spring when all risk of frost has passed.
  5. Plant in a well prepared bed with some organic matter dug in.
  6. Press the bulbs into the soil, making sure the neck of the onion is above soil level
  7. Keep the soil moist but not sodden, too much water can lead to bulb rot
  8. Wait for the flowers to arrive!

When To Harvest Onion seeds?

Onion Flowers are spherical clusters of flowers with leafless stalks. They can reach heights of 75 cm-180 cm Depending on the variety, onion flowers may arrive in late spring or early summer.

Timing is everything! Harvest too early and you will have immature seeds with poor viability, too late and the seeds become prone to shattering and germination rates will plummet! What is shattering? This is when the seed pods open naturally and release the seeds.

Onion seeds

When is the right time to Harvest Onion Seeds?

The perfect time to harvest Onion seeds is just before the seed pods fully shatter.You want to harvest Onion seeds just as the seed pods begin to open….

  • You’ll know it’s time for harvesting onion seeds when the flowering heads begin to turn brown. As the onion seed pods mature, they will transition from green to yellow to brown and become dry and papery in texture. This is your first indication that the seeds within the pods are reaching their full maturity
Onion seed pods
Developing Seed Pods
  • To determine readiness, gently squeeze the seed pods, If they feel firm and the seeds within are hardened and well-formed, they’re ready! If the pods feel a little soft, they need some more time
  • Try to avoid harvesting seeds during wet or humid periods. Moisture can reduce seed viability and also lead to fungal growth. Harvest on a fair, dry day if possible
  • Leave the seeds to dry completely in a cool sheltered spot and store in a paper envelope for future growing! Remember to label them :o)

*Another way to Harvest Onion seeds: Wait for the flowers to turn brown, clip the stalk a few inches below the flower head and place them in a paper bag. Set the bag in a cool, dry place for several weeks and collect the seeds following the steps above.

How Long will Home Harvested Onion seeds Keep?

If harvested and stored correctly Onion seeds can stay viable for several years! Check out my other seed saving posts!



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