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Saving Seeds from Herbs

Bob Wildfong

Easy to grow, delicious, and beneficial to the garden and the body, herbs are a favourite for gardeners everywhere. Even in a small space you can grow wonderful flavour, fragrance, zest for every meal, and healthy tea for afterward. But there's even more that you can do - you can save your own herb seeds and never run out of your favourites.

Herbs come in many forms, from tender annuals to woody perennial shrubs. You might not have to save seeds from the perennials, such as sage or lovage, because you can enjoy them for years without replanting, but refreshing your supply of annual herb seeds can be expensive. It can even be difficult if you have a favourite variety that's hard to find. Fortunately, most herbs produce easy-to-save seeds, so you can supply them yourself!

Herbs in the mint family

You might be surprised at how many herbs are related to mint: basil, bee balm, hyssop, lavender, marjoram, oregano, rosemary, sage, savory, thyme, just to name a few!

These are all categorized in the same family because of the shapes of their flowers, and their seeds ripen in similar ways. Take the basil images below. Tiny flowers fade into green bumps that eventually turn brown, and each brown capsule contains a seed.

The flowers are pretty and edible, but if you don't eat them they develop into green capsules that eventually turn brown and papery. Many people trim the flowers because that improves the flavour of the leaves (more on that below), but if you want seeds, wait until the capsules are fully brown and dry, then strip them with your fingers. You'll get a small handful of brown chaff that contains a few basil seeds.

You can sift through the brown papery husks to separate the tiny, black seeds, or you can just keep all of it in a paper envelope and plant it indoors or outdoors. The seeds will know what to do, and the husks just turn to compost.

You can use a very similar procedure for any member of the mint family, from lavender to savory, but you usually have to make a choice between harvesting leaves, flowers, or seeds. The reason is that the leaves of mint-family herbs (e.g. mint, basil, marjoram) usually have the best flavour before flowers form, and if you want to harvest flowers (e.g. lavender) then you obviously can't also get seeds from those flowers.

The image above has purple basil plants at different stages. In the background are plants with full flowers, and to the right is a plant with no flower yet. Of these the flower-less plant has the most flavourful leaves. The reason is that the flavour comes from oils in the leaves that take a lot of energy to produce. When the plant starts to grow a flower, it diverts energy away from producing flavour oils. If you harvest your basil leaves after the flowers have fully grown, or started to ripen seeds, you might be disappointed with the poor level of flavour!

That's why it's best to grow several plants. You can harvest delicious leaves from some, and let other plants ripen seeds. 

Here's a trick. The image below shows how to get more flavour from your basil (and other mint family) plants. When flowers start to grow, any new leaves will be less flavourful. Instead of cutting the whole plant, cut it about half way down and let it grow back. The small leaves will turn in to big leaves, with full flavour because there are no flowers competing for energy. Then cut again, and get double the harvest of full-flavoured herbs. Though of course, you won't get seeds this way.

Herbs in the daisy and carrot family

Almost all herbs have similar seed-saving methods to garden flowers, because they are simply flowers that we use for food and medicine. The key with most flowers is to wait until their seed heads turn brown and dry, and to gather seeds only when they're at that stage of ripeness on the plant.

Here are a few examples:

The classic Calendula flower turns into green "fruit" (which aren't viable seeds), and if you wait a few more weeks those turn brown and hard (ripening into fully viable seeds). Wait until you see them brown and dry on the plant, then harvest and keep the seeds dry until you sow them.

Other daisy-family herbs like chamomile, costmary, feverfew, and tansy work the very same way.

Dill makes a scented umbrella-shaped flower

Wait until the seeds are fully brown, but collect them before they drop off!

Will herbs cross-pollinate?

One of the biggest obstacles that new seed savers encounter is the need to isolate plants from others. It's difficult to grow squash far enough away from other squash to prevent cross-pollination, so is it similarly difficult with herbs?

Technically, all mint-family, daisy-family, and carrot family herbs are crossed by insects with other members of the same species. Basil won't cross with marjoram, but green basil can cross with purple over a distance of about 100m because of pollinating insects.

However, your results depend on what you want to do. If you want to grow two kinds of basil and save their seeds separately, that will be an isolation problem. But if you don't mind a purple-green mixture next year, go ahead and save your own mix. It will taste great, and maybe it will look interesting!

Moreover, a lot of herbs are not named varieties anyway. There are specific cultivars of dill, but most people just grow the common kind and it doesn't matter whether that crosses with your neighbour's ordinary dill. The same goes for the common versions of coriander, cress, marjoram, chamomile, anise, and other annuals as long as you aren't trying to save a specific named variety.

Finally, an interesting fact about mint

Did you know that there are hundreds of named varieties of mint available? Pineapple mint, mountain mint, chocolate mint, strawberry mint, in addition to the old-fashioned peppermint and spearmint. The interesting thing about mint is that it's quite genetically diverse, so every saved seed will grow into an entirely new individual variety with a different flavour. Just like people, every mint plant is different from every other mint plant. We multiply named varieties by cuttings, not seeds, but if you grow mint seeds you can taste a new mint flavour and name it if you want to!

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