Harvesting seed

Harvesting techniques and tips

Harvesting seeds to save is a simple and fun activity, although a bit of patience is required to ensure that the best seeds are harvested at the best time. To ensure you harvest seeds that will be viable and vigorous and produce plants with desirable characteristics when replanted, it’s good to understand a couple of simple principles:

  • Selection – follow the golden rule: ‘save the best, eat the rest’.
  • Maturity – seeds need to be completely ripe before harvesting.
  • Timing – the right time to harvest seeds depends on the type of seed and the weather

Selection

The golden rule of seed saving is to ‘save the best, eat the rest’. Although this rule may seem counter-intuitive and can be difficult to follow (it’s hard to resist eating the first or best tomato straight away!), there’s a very good reason for it. Seeds contain information, like programming, from the plant or fruit they have been produced by. Seeds produced by sickly, struggling plants are programmed to be more likely to reproduce those characteristics. Seeds produced by healthy plants with vigorous growth, ideal fruit, resistance to early bolting etc. will carry those characteristics into the next generation. As you continue selecting and saving seed from the best, you will ensure your seed – and plants – improve and get stronger season after season.

As your plants grow, you will have observed and decided which are the best – the earliest or biggest tomato, the sweetest lettuce that bolts to seed last, or the perfect pumpkin that grows on a healthy vine without mildew. Once the best plants and fruit are identified, they should be marked and protected from early harvesting and eating by humans, animals and insects. For example, slip a cut out old stocking over the tomatoes you want to save seed from before they fully ripen; stick a tag to the stem of a lettuce which is just starting to bolt; write on the skin of a pumpkin with permanent marker.

When harvesting time comes, collect seeds from the plants and fruit that you have selected for seed saving. Read on to find out more about when to harvest to ensure seed is most viable and ready to process, save and store for future planting.  

Maturity

Seeds need to be fully mature before harvesting. One way to think of this is to understand that seed production is the final stage of a plant’s life. Plants produce seeds to reproduce themselves: to ensure the next generation. Often this stage happens after the plant or fruit has passed the “ripe” or “mature” stage when we most enjoy eating it. This means that plants and fruit selected for seed harvesting will likely live in your garden for longer than those you just want to eat.

Leafy herbs and vegetables will turn bitter and tough when they start producing seeds. For example, a lettuce will bolt to seed after it has passed the stage of producing leaves and a full edible plant. When it bolts, it will send up a tall central stalk with smaller leaves and that stalk will progressively be crowned with small flowers, then fluff and eventually seeds. When a lettuce bolts, the leaves from the plant are no longer good to eat – they will usually be tough and bitter.

Fruit like zucchinis or tomatoes will produce seed early but that seed will be most viable and best for harvesting when the fruit is too ripe or too big or too tough for us to enjoy eating.

Root and bulbing vegetables like carrots, parsnips, onions will produce flowering stalks which will draw energy from the root or bulb to develop seeds. This means that roots and bulbs will start to soften and deteriorate once the plant starts to flower. Eventually the flowering head will set seeds. 

How and When to Harvest: how mature is mature enough?

Different plants will mature at different rates and have different signals for when they are mature. Below are some examples but this is not an exhaustive list.

A good rule of thumb for deciding the ideal timing to harvest fully mature seeds:

  • for seeds in fruits, let the fruits get very overripe;
  • for seeds on leafy plants or herbs, let the seeds or pods get as dry and brown or black as possible until they just start falling off in your hand;
  • for podding vegetables like peas or beans, let the pods get as brown, dry and brittle as possible before they start splitting open.
  • for bulbing and root vegetables, wait until the tiny flowers have produced seeds and the flower heads go brown and dry. 
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Lettuces will send up a central stalk which will eventually be covered in flowers, then fluff, then seeds contained within the fluff balls. Harvest the seeds by pulling up the whole plant by the roots (or cutting off at the roots) when more than half of the flowers have turned to fluff. Pop the plant into a paper bag, upside down, and set aside somewhere cool and dry with airflow for a couple of weeks. Seeds can be harvested from the plant by shaking or beating the bag vigorously and letting the seeds drop off the plant into the bottom of the bag.

Fruiting vegetables like cucumbers or zucchinis do not have reliably viable seeds when the fruits are small and tender and perfect for eating. Seeds in fruit will only become fully mature when the fruit has become too large and tough for people to want to eat. For example, a zucchini should be left on the plant until it becomes as large as it can and the skin thickens so that it is as tough as a pumpkin! This will ensure the seeds are mature enough to be viable. Cucumbers should be treated the same. To protect the fruit while it matures, you can slide a loose stocking over it or a paper bag.

Tomatoes, capsicums and eggplants should be left to mature on the plant for as long as possible. Slip a stocking or a paper bag over them when not quite ripe to protect from predators (human, animal or insect!). Leave the fruit on the plant for as long as you dare or until it looks like it wants to drop.  

Although it may seem that it is difficult to get this timing right – leaving the seeds until they are about to drop or disperse, seeds can be quite forgiving and harvesting before absolute peak maturity can still produce good seeds. Try these tricks:  

  • If your leafy green, herb or podding vegetable seeds are starting to brown and dry, you can pull up the plant by the roots and pop it upside down with a big paper bag or hessian sack to contain the seed heads or pods. This will allow the seeds to continue drawing some nutrients from the plant and maturing and ensure that any seeds or pods that are fully ready will fall into the bag or sack rather than scatter through your garden.
  • If your tomatoes, capsicum and eggplant are a bit more ripe than perfect for eating, take them off the plant and allow to continue ripening and maturing on a bench inside. Leave for a few days to a week. The seeds will continue to draw nutrients from the fruit. Save the seed from the fruit when the fruit starts to get a bit ‘past it’.

How and When to Harvest: Practical tips for collecting seeds

Dry Seeds (Herbs, Leafy Greens, Podding Vegetables, Brassicas etc.)

  • Watch the weather: collect dry seeds like herbs, leafy greens, brassicas, podding vegetables, when the weather is dry and sunny. Plants and seed heads should be as dry as possible. Collecting plants when there is rain or dew about or the plants are wet will increase the risk of mildew and mould.
  • Once collected, seeds should be given more time to dry: collect seed heads and pods in paper bags or hessian sacks to hang in a cool, dry and breezy place or spread out on old material like a sheet or towel or even on an old fly screen in a cool, dry spot. Make sure that seeds have good airflow, are out of the sun and heat and won’t escape by blowing away or falling through a screen. 
  • Herbs and leafy greens can be pulled up by the roots or the flower heads cut off; cut nitrogen fixing plants like peas and beans off at the base to leave roots to break down in the soil, pull pods off plant; brassicas and silverbeet/beetroot can become monstruously huge plants so snip off seed branches; snip off flower heads from onions and root vegetables like carrots and parsnips, compost or eat the rest of the plant.
 

Wet Seeds (seeds contained in fruit)

  • Take fruit off the plant. The rest of the plant and fruit can be left to continue growing. 
  • When removing fruit from the plant, take the stalk of the fruit as well if possible.
  • Set fruit aside indoors where it is protected from pests and animals and can continue to ripen. 

Contributors: LLoyd Sharp (?)

Last updated byLiz