Top Job for September – Collecting hardy annual and perennial seeds

The general rule is to look for seed pods which have changed colour from green to brown.  Most collected before they’re ripe will not grow. However, there are some exceptions, like nasturtium and pot marigold (Calendula) which can be collected when well-developed but still green.

As a guide, seeds are generally ripe approximately two months after flowering. But if you’re unsure, open a pod.

If the seeds are undersized and light green in colour, or the right size or colour compared to those bought from seed companies, the chances are they aren’t quite ready.

Some plants like corn cockle (Agrostemma githago) and campion (Silene), make it much easier to tell when their seeds are ripe.

As the pod opens, it reveals dark black seeds ready for harvesting before they fall to the ground.

The seed pods of some other plants, such as poppies (Papaver), actually rattle when ripe.

Bear in mind when collecting that only seeds from pure species plants will ‘come true’ grown this way. This means they will produce mainly identical or similar-looking plants to the one the seeds were harvested from.

Although seeds from a hybrid plant should germinate and grow, many will look very different to the parent plant!

You can tell a hybrid plant by looking at the name on the label.  It will have words at the end of the name enclosed within single quotation marks, i.e. Fuchsia ‘Mrs Popple’.

Collect seed pods on a dry day as wet seeds will probably go mouldy in storage if not dried properly.

To ensure that you’re collecting good quality seeds make sure the plant you collect from is healthy and growing well.

Some seed pods, such as caper spurge (Euphorbia lathyrus), have an exploding mechanism.

This forces the pod apart, propelling the seeds in the air.  It’s best to place seed pods into separate sealed bags so you don’t lose the seeds when the pods burst.

Place the seed pods on a warm windowsill, or other warm place, like an airing cupboard. As this will help them further dry them before extracting the seeds.

Seed from berries needs to be extracted in a different way.  Mash them in a fine sieve before rinsing away the pulp in cold water.

The seeds will need to be placed on paper towels and left to dry for several days before storing.

Some seeds do not store for long and should be sown immediately.  Hellebore is a good example.

Most other seeds can be sown either in autumn or spring and should be stored in separate bags, ideally paper. Remember to label each bag with the seed name and date collected, including the year.

Store the bags in an airtight container placed in a cool environment out of direct light, ideally a fridge.

Some seeds last much longer in storage than others so it’s worth researching which ones can be stored for longer.

If in doubt there’s an easy test where you put the seeds into a cup of water.

If they sink they should grow when planted, if they float, the chances are they won’t!