Seed collecting is perfect for the lazy gardener. Whenever someone looks sniffily at your bolted lettuces or wonders why you haven't been deadheading the flowers, you just have to say in lofty tones, "oh, I'm going to be collecting those seeds of course".
It is also a great garden activity for children so I made sure to include it in 101 Things For Kids To Do Outside. They can begin by creating their own homemade seed packets by decorating plain envelopes. When I do this activity with pre-school gardening club, the children tend to make fingerprint flowers which are simple but look really effective. Older children can get a little more artistic with paints or coloured pencils.
Also, very importantly, they need to include the name of the flower and some growing instructions (easy to look up if you're not sure).
Some of the best seeds to collect are from annual plants. Because they only live a year, they have lots of seeds they want to scatter. if you have plants like cornflowers (Centaura cyanus), pot marigolds (Calendula officinalis), poached egg plant (Limanthes douglasii) and nasturtiums, just leave the old flowers on after they have finished booking and wait unto the seeds are ready to be released.
I also like to leave the odd lettuce and radish to bolt as it's good for children to understand vegetables have flowers too and that this is how they can produce more seed.
The easiest way to check if they are ready to be harvested is by putting a paper bag over the seedhead and then shaking it inside the bag - if it releases its seeds, they're ready for collecting.
Next, cut off the seedheads into a labelled paper bag (use a different one for each type), and then, when you've finished collecting, carefully put the seeds into the correct packets.
One tip: some plant seeds are poisonous if eaten (although not those I've listed here) so to be safe I ask the children to follow the simple rule - never put any in your mouth and always wash your hands after handling seeds.