How to harvest & save seeds

A guide to harvesting and saving seeds from your most treasured plants, flowers and vegetables in autumn.

The autumn garden may seem daunting to some… Plants tower and flop, pests are plentiful and rusty seed heads seem to outnumber the blooms. It’s at this time of year that we can feel a tad agitated as we wander the garden. 

There is an urge to cut everything back and start fresh. If you, too, feel compelled to wipe the slate clean, don’t rush to toss it all into the compost bin and close the lid on the season. 

Instead, muster that last bit of energy to save a few seed heads from your most treasured plants. We promise your energy will return, along with the promise of spring, and those little gems are the ticket to a flourishing garden once again. 

Tips for saving seeds

• Select the healthiest plant(s) for seed saving. This is usually the first to flower or fruit, the tallest, tastiest, or most unique colour variation. 
• Do not cut off the flower or vegetable until the seed is ready for harvest. 
• If you’re saving seed from a flower, wait until the seed pod turns brown. 
• For fruits like tomatoes or pumpkins, wait until they ripen on the vine. 

Protect the seed pod with a mesh bag if worried about birds or animals getting to it first.

How to harvest seeds for saving

• Harvest on a sunny day, preferably in the afternoon or once morning dew has dried. 
• Cut off the seed pod and store in a breathable container (like a cardboard box or bag) in a cool, dry area for two weeks. 

You can begin to separate seeds from the chaff after this time.

How to sort seeds for saving

There are several methods to use for separating out the seed from the chaff: 

Manual removal
Some seeds are large and can be easily removed from the pod. 
This is the case for the legume family like sweet peas, peas, beans and lupin, or flowers like calendula, sunflowers or cornflowers. 

Shaking in a bag
Some seed pods can be placed into a sealed ziplock bag and given a good shake to loosen the seed. This is a helpful method for flowers such as hyssop, foxglove, nigella or poppy.  

Blowing or winnowing
Other pods, like cosmos, can be broken apart and given a gentle blow to separate the chaff from the seed.

Colander
Break up seed heads and let the seed fall through the gaps with the remaining chaff left at the top. This technique is helpful for brassicas, leek, parsleyor coriander seed. 

Paper towel
Seeds inside fleshy fruit like tomatoes or pumpkins can be washed and drained inside a sieve and left to dry on top of a paper towel. 

Tomato seeds will stick to the paper towel but remain viable. Simply sow the paper towel when the time comes to germinate.  

How to store your harvested seeds

• Store in an airtight container or ziplock bag and label with the plant name and harvest date. 
• Freshness matters. Use within one year for optimal viability. (Seeds can last for up to six years if stored correctly, although you may notice germination rates decrease the older the seed is.)
• Store in a dark, cool place away from direct sunlight and extreme heat to prolong seed life.

Cross-pollination of seeds

• Some types of vegetables and flowers can cross-pollinate, resulting in offspring different from the parent. This is more common in flowers than it is in vegetables.
• Flowers that are known to cross-pollinate are: Dahlias, cosmos, poppies and zinnias. 
• Legumes like sweet peas, beans and peasall self-pollinate, ensuring consistent traits in saved seeds. 
• Tomatoes are mainly self-pollinating but can be cross-pollinated by manually transferring pollen. 

Experimentation with cross-pollination can lead to new cultivars and exciting discoveries in your garden!

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Once you have squirrelled away some seeds, you can choose to scatter them around the  garden in autumn (only if they are hardy) or wait until spring. 

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Saving seeds is an easy and cost effective way of increasing the stock of the vegetables and flowers you love in your garden. There are many benefits to saving seed. It opens the door for you to appreciate the life cycle of plants and the possibilities of plant breeding. 

Seeds harvested from your own garden will be more suited to your garden’s climate and as a result, you will notice that the plants adapt and become more resilient to the environmental conditions and pests in your area.