Garden Guru: Seed capital

Keep different pumpkin varieties separate, and (right) propagating from seed helps save money. Photos / Supplied

It's easy to get greedy wandering about in autumn with a paper bag and pencil, shaking pods and plucking bunches of berries.

As well as that peculiar joy of seeing green shoots sprouting from a seemingly lifeless capsule, propagating from your own seed saves money, helps to increase your plant stock and helps ensure the longevity of special plants that need a helping hand. However, it's only a select few that are really worth growing in this way.

We associate seeds with autumn and early winter, and certainly there are plenty of native tree and shrub berries about now, but plants are producing seeds all year round.

In early spring, three worthwhile subjects I always keep a beady eye on are hellebores, primulas and aquilegias.

Seeds of these ripen quickly and are best sown almost immediately.

Unusually, primulas and aquilegia seeds are better collected and sown while still green and not quite ripe but in general it's best to wait until seed pods rattle and turn brown - select only the sturdiest specimens to propagate, then pounce with your bags.

If you have wondered why you would bother to save the seed of a plant that is quite capable of multiplying unaided, hellebores are a good example.

If you have a named hellebore cultivar or form - perhaps a particularly fine, speckled yellow - they will, if left unattended, produce a forest of seedlings at their feet.

The result will be an overcrowded colony where all the offspring are mixed in colour and rarely as good as the original.

Most plants that are named hybrids (prefixed with an "x" in the name) or a cultivar (the name often seen in inverted commas), will not produce seeds identical to the original.

Simple, wild species tend to stay the same or "come true" if grown from seed. There are a few plant cultivars which do come true, such as Rudbeckia "Goldsturm", the red Geum "Mrs J Bradshaw" and the improved and beefy Echinacea "Magnus".

Vegetables are similar; those that self-pollinate also come true from seed so you can grow different varieties of bean or tomato together and be sure they will not cross with mixed results.

However, if you grow cross-pollinated plants together, such as different pumpkin varieties, and the bees get to work mixing all those genes up, the seed will end up like a bag of half-baked liquorice allsorts.

The only way to get pure seed off these is to grow your preferred cultivars in isolation.

Seed tips

* A gentle blow in the palm of your hand or in the hollow of a sieve will often remove much of the chaff, leaving cleaner seed for storing.

* Only take seed from healthy-looking plants. Sickly plants could have diseases.

* Not all seed in a pod will be fertile. In peonies, for example, the sterile seed is shrivelled and red while fertile seed inside the pod is white at first, turning to a plump black.

* Seed gatherers need two special areas in the house - a wide, sunny windowsill to lie pods that aren't yet ripe out on newspaper to let them shed their seeds; and a corner of the fridge to stash your dried and sifted seeds which have been put into little envelopes and sealed in a plastic air-proof jar.

* Many native tree and shrub seeds need a period of winter cold (stratification) to stimulate germination, so clean pulp from berries and sow direct into pots of soil-based compost covered with a thin layer of gravel. Leave out in the open through winter and be patient - it can take a year or more for some to germinate.