Over the last fortnight, I’ve looked at getting free plants from perennials, but with annuals and biennials, you have to save seed. As insurance, plants produce a huge surplus so at least some seeds will germinate and make adult plants. Why not lend a helping hand by saving and growing some of your favourites.

Of course, double-flowered plants don’t contain pollen so can’t set seed, F1s won’t breed true, and many varieties are cheaply and easily available. But it’s a cinch with quite a few.

Hybrid seed is the result of pollen exchanged with neighbours, so you can never guess what shade or colour[s] the resulting gene mix will throw up. With the likes of aquilegias this colourful lottery could be great and often mirrors what you’ll get from a seed packet. If a particular colour offends, despatch it to the compost heap.

This hybridisation can be problematic with some species, like brassicas. They freely exchange pollen with any other brassica variety. Even though saving this seed couldn’t be easier, I don’t think I’d fancy a kale-cauliflower cross. And this random outcome also applies to tomatoes.

But this doesn’t happen with self-fertile species, like sweet and edible peas. I know I can rely on the highly scented ‘Painted Lady’: her old-fashioned pink and white flowers sit beautifully in a patio with that colour scheme. And ‘Cupani’, another old variety, is said to be closely related to a wild species found in Sicily and southern Italy. It’s named after Brother Frances Cupani, who sent the first seeds to England in the late 17th Century.

Turning to the edible kind, I need to religiously save the Parsley Pea seed I received from Garden Organic’s Seed Library some years ago. Instead of the usual tendrils, these plants produce tender little leaves that add - forgive the pun - a touch of pea to a salad.

The more seed ripens and dries on a plant the better. And although this means we have to put up with non-too-attractive sweet pea seed, others definitely pay their way. Any Nigella variety is a real bonus, adding great visual impact to a border. And this applies to annual poppies and Calendula.

Add some biennials, such as wallflowers, to your list. You’ll not only get the colour you want for a bed but also be confident the young plants will be ready to plant with autumn bulbs. Fiery wallflowers sit nicely with orange tulips and hyacinths partner Sweet William nicely, giving pots a longer flowering season..

There’s no shortage of annuals and short-lived perennials like Verbascum, Malva moschatum and Lychnis coronaria that seed fairly freely. Sometimes I simply wave the dried seed heads over part of a border and weed carefully to safeguard the emerging seedlings I want.

If you’re starting some annuals or short-lived perennials like Polemonium caeruleum in a different bed, pot up that seed and plant out in the spring.

If weather permits, leave seed to ripen naturally on the plant before harvesting, but during an extremely wet autumn, you may need to cut flower stalks once seed has fully swollen but not yet ripened.

If you have to finish the drying process under shelter, choose a a cool, dry place. Tie stems together and with seed pods facing downwards, suspend over a sheet of paper. When fully dry, pods will open and seed should be easily shaken out.

Store in a paper bag in a cool, dry mouse-proof drawer. Ideally, put 2 or 3 desiccant bags in the drawer to help keep the seed as dry as possible.

Plant of the week

Apple ‘Katy’. Bred in Sweden, this early eater is beautiful on and off the tree. Sweet, juicy and delicious, it also keeps for a couple of months.