If you receive seeds from your garden or have bought some from a local garden centre, you may be wondering how soon you should use them. How long do seeds last before deteriorating?
This depends very much on the type of seed and the storage conditions. Some types of plant do not produce seeds that keep well; these have to be used much more quickly and may only last a year. Many seeds keep for between 2 and 4 years, while some can last up to 10 years if stored in ideal conditions.
In this article, we'll talk about the lifespan of certain types of seed and explore which types last longer than others. We'll also look at how to store seeds to optimise their lifespan.
How long do different seeds last?
It's difficult to predict the longevity of any seed, although perennials generally last longer than annuals. Annual seeds have a lifespan of 1 to 3 years, while perennials have a lifespan of 2 to 4 years. However, this is a generalisation and does not apply to all seeds in these categories.
The list below will give you an idea of the lifespan of most seeds:
Parsley seeds: 1 year
Aubergine seeds: 4 years
Cauliflower seeds: 4 years
Carrot seeds: 3 years
Pumpkin seeds: 4 years
Brassica seeds: up to 7 years
Tomatoes: up to 8 years
Onions: 1 year
Parsnips: 1 year
Lettuce: 1 year
Sweetcorn: 2 years
Peppers: 2 years
Spinach: 3 years
Watermelons: 4 years or more
Peas: 3 years
As you can see, lifespan varies considerably from seed to seed and, even then, these are only estimates and do not particularly guarantee that the seeds will remain viable, one way or another. How you store them has a huge effect on their longevity, and if you don't take steps to ensure good storage, even seeds that usually last well will quickly become non-viable.
So you need to harvest and store seeds using the right method if you want them to be plantable from one year to the next, or even the year after that. Poor storage can render seeds non-viable in less than 12 months. Storage is therefore very important, even if you usually plant your seeds in the spring.
How do you store seeds?
The first step in storing seeds correctly is to dry them. Many seeds, particularly those from fruit and vegetables, are enveloped in a pulp that needs to be removed before they can be stored. You need to wash off this pulp, then place the seeds on a clean sheet of paper towel or other absorbent surface.
Leave them to dry for a few weeks and they will then be ready for storage. Most people place them in small paper or plastic envelopes to prevent moisture from forming around the seed, then place them in an opaque container and put them in a cupboard for storage. The three essential conditions for viable seeds are as follows:
The seed must be perfectly dry
The seed must not be exposed to bright light
The seed must not be heated
Exposure to humidity, light or heat will favour the development of the seed.
Exposure to moisture, light or heat will encourage the seed to germinate, and if it does, it will expend its energy in a failed attempt to germinate. Once it has tried to germinate, it is no longer viable, as it has no energy left for a second attempt. This means that when you try to germinate it the following year, nothing will happen.
So make sure your seeds are stored in dry, cool, dark conditions. In this way, the seeds remain dormant and can remain so for many years. Many people opt for an opaque container in a cool cupboard, and some even use silica gel sachets to absorb atmospheric humidity.
What else do seeds need during storage?
Another thing to think about is protecting your seeds from pests. Many animals will happily eat seeds if they get the chance, which obviously kills them. Mice and rats are the main predators of seeds, but insect damage can also be a problem in certain circumstances.
So it's best to avoid storing seeds in an outdoor shed or greenhouse, unless you can place them in a locked metal box. Remember that rodents have very sharp teeth and will gnaw through many other materials if they think there is a food reward on the other side.
It's best to store seeds inside your home, away from rodents and other pests. Many people devote a cold cupboard in their kitchen to seed storage. It's worth noting that you can't always tell if seeds are no longer viable by looking at them.
Should seeds be frozen?
Some people choose to freeze their seeds to ensure that they last from one year to the next. You can do this, but if the temperature in your freezer fluctuates, there is a risk that this will prevent the seeds from germinating later. You need to be able to keep them reliably cool for this to be useful.
On the whole, freezing seeds is not necessary in a domestic setting. You may choose to do so for some seeds that have a shorter shelf life, but it's generally best to harvest some of the crop each year and store it as you normally would. Most people find they get better results this way, provided they store the seeds well.
How long you can keep seeds depends very much on the type of plant you're working with. Some last much longer than others, and it's important to know their average longevity when you start saving seeds. Put them in a dry, cool, dark place and they should last at least a year, if not much longer.