Don't toss wilted flowers yet – late August is prime time to collect free seeds

Late August is a good moment for gardeners to pause before cutting down all their spent flowers. Many plants are ripening seeds right now that can be gathered, dried and kept for next season, meaning new plants next year won't necessarily cost anything.

Wait for the flower to fully fade

Morris Hankinson, founder of the Hopes Grove Nurseries plant nursery, explains that a spent flower head should be left on the plant until seeds form and ripen inside it. The seed head gradually turns dry and brown, and that is the right moment to harvest. If the seed head is still green and moist, the seeds are likely not yet fully developed.

How to collect the seeds properly

Once seed heads are fully dried, they can be carefully cut off. One simple method is placing the flower head in a paper bag and shaking the seeds loose inside it; depending on the plant, seeds can also be carefully removed by hand. A paper bag works better than a sealed plastic one, since it doesn't trap as much moisture. Before storing, it's important to make sure the seeds are completely dry, otherwise mould can develop over winter.

Where to store them until spring

Collected seeds should be kept in a cool, dry, dark place until the next growing season — in paper envelopes or bags, or in a dry glass jar. Labelling the packaging with the plant's name and the year of collection helps avoid guesswork in spring. Protecting seeds from moisture and sharp temperature swings is especially important.

Which plants to collect seeds from in August

In August, seeds are often ready to collect from poppies, marigolds, snapdragons, sweet peas, French marigolds (tagetes), cornflowers, and various herbs. Rather than going by the calendar, the safest sign is a fully ripe, dry seed head.

Gardeners should also keep in mind that seeds from hybrid varieties won't necessarily grow into plants identical to the parent — flower colour, size or other traits may differ, while seeds from traditional, stable varieties tend to retain the parent plant's characteristics. For many gardeners, that unpredictability is part of the fun, which is another reason not to automatically cut and discard every spent bloom in late August.