How long packets of seeds last depends on type of plants

Tomatoes and runner beans.
Tomatoes and runner beans.

I’m often asked how long seeds can be kept in the packet before sowing.

That question occasionally comes from someone who’s discovered a cache of packets long forgotten.

The answer depends on the environment they’ve been in and what type of plants they came from.

When stored in a cool, dry place, they’ll keep longer than in a warm, damp area.

The viability of some seeds can be counted in days, but others will germinate after 1,000 years.

The seed of the Himalayan primula is often quoted as lasting only a few weeks after dispersal, but that of poppy could probably outlive Methuselah.

In general, seeds with an inherent low water content remain viable longest.

I was asked recently why we should not save seeds of F1 hybrids. It’s because the seeds saved have become F2 or second-generation hybrids and do not reproduce true to form. Rather than developing into plants identical to the parent, they become a diverse mixture.

Furthermore, many of the free-flowering F1 varieties are sterile.

Each year, we grow several tomato cultivars and collect seed from those that perform best in terms of taste and cropping.

This time, there were five traditional varieties, three cherry types, one beefsteak and one Italian.

Gardeners’ Delight is so reliable that it’s on the list once again. Golden Sunrise was the other star this year, with a sweetness superior to all others.

Third to be saved is San Marzano, the Italian plum tomato.

The kitchen was taken over for a short while to extract seeds from the inner pulp of all three with forceps.

They were spaced out on paper towels for 24 hours to dry, then packed and labelled in small, brown paper envelopes.

Bigger seeds are easily handled and go straight into a paper envelope once dry, but many of the smaller types are mixed with plant debris and need separating.

Winnowing is one option, and sieving is another.