Seed collection and storage

Ghaf Tree seeds

Occasionally you may find that a friend or neighbor has an interesting plant or color of plant that you would also like to have in your own garden, or you may simply want to collect seeds from seasonals or vegetables that you have grown in your own garden and replant them next year.

In order to replicate the plants you can either take a cutting of the parent plant and try and root that at home, or you can collect seeds from the parent plant and sow these.

Seeds offer the luxury of time as they are dormant, you can harvest, store, and then sow them when you have time; cuttings on the other hand need to be handled correctly from the time you take them till the time you plant them into the garden as they are already living. Additionally, you cannot take cuttings from all seasonal species, and the only way to replicate them is by means of cuttings.

Some background that you may recall from school biology, cuttings are essentially clones of the parent plant, genetically identical in every respect, so if the parent plant has a specific lilac color flower, the flowers of the cutting will have the identical color. Propagation from cuttings (or division) is referred to as asexual propagation for this reason.

Seed on the other hand is referred to as sexual propagation as two parents are involved (the male part of the flower and the female part of the flower), these combine through pollination to produce a seed, which is a hybrid of the two parents. In brief, this means that if you have a really nice lilac Petunia, but if you collect the seeds and germinate them you may not get the same color flowers as the seeds are a hybrid mix and can also revert back to the parent (and even grandparent) lines - the same applies to vegetables.

• Not all plants produce viable seeds, commercial bananas, for example, have unmatured seeds in the fruit, but possibly only 0.0001% may germinate this is why all commercial banana varieties are produced by cuttings/ asexually.

• Grafted species such as lemon and orange cultivars, will produce seedlings which are the offspring of the scion (the top part), when germinated they will have their own natural root system - in some cases, the root systems are not suited to local conditions or the soil, which is the whole reason why they were grafted in the first place.

With that all out of the way, let's get on.

Seed Collection

• Some seeds are fine/ small and require more specialized collection processes, this may involve placing small nets or cloth bags around the flowers or fruit to prevent the seeds from dropping to the ground; others are large and easy to harvest by hand.

• Seed should always be collected from a fully dried seed head, pod, or fruit, do not collect green seeds as these may not be fully matured and will not germinate.

• Remove any visible debris from the seeds, husks, petals, stalks, etc.

• Remove any seeds which have visible signs of beetle holes - these are quite easy to spot.

• If the seed is contained within a fruit, then clean and separate the seeds out by rubbing or washing the excess dried fruit tissue off.

• If you have to wash the seed for any reason before storage then make sure to lay them out on some absorbent paper directly afterward to dry them completely so that they don't start germinating. Once the germination process is initiated it cannot be stopped and drying the seeds at this point will kill them.

• A good "protocol" to follow is to write a small label indicating the type of seed and date when it was harvested, this can then be either attached to the storage container for reference; add any other notable characteristics that made this seed special "Deep maroon flowers", "Extra large fruit", etc.

Seed Storage

There are many ways to store seeds, irrespective of the method or container that you use for storage there are a number of criteria that should be met:

• The seeds should be stored in a dry/low-humidity environment, this will prevent any fungal spores that may be on the seed coats from germinating infecting, or killing the seeds. This can be achieved in a number of ways, including adding humidity control sachets, including small envelopes containing bicarbonate of soda or even table salt (as long as these are not in direct contact with the seeds).

• The container should be sealed to prevent storage pests from getting, weevils and wood-boring beetles love seeds, their eggs are often found on collected seeds, and once they hatch could decimate your collection.

• Temperature-regulated storage. Seeds are prone to damage from high temperatures as well as extreme cold. The optimal storage temperature is 10 degrees Centigrade, but no less than 4 degrees Centigrade. For this reason, it is often suggested that seeds be stored in the fridge (not the freezer) as is done commercially. This has four benefits:

  • it slows the metabolism of the seed and extends its longevity

  • it also slows the metabolism of any storage pests that may be included with the seed - insect eggs will go into a form of hibernation at low temperatures and won't hatch as quickly

  • cold temperatures prevent humidity from forming in the container or on the seeds

  • it slows if not halts the germination of any fungal spores that may be on the seed

• Remember to label the seed

How long can the seed be stored?

There are two issues relating to seed storage.

The first is longevity, which is how long the seed will live for under normal natural or storage conditions. Just because the seed seems lifeless doesn't mean that it is, it is simply metabolizing very, very slowly, drawing on the stored food supply it contains within the seed coat, once this runs out the seed will starve and die. Depending on the species of plant, this can take between 14 days and 20 years! Many desert-dwelling species for example can survive years laying dormant in the soil waiting for a small bit of rain in order to initiate germination.

The second issue is vigor, as the seed ages and its internal food store is used up the vigor of the seed decreases, this means that it may germinate, but simply does not have enough stored energy to complete the germination process to the point that the apical parts of the plant can reach the sun and it can start producing its own food. This is also one of the reasons why you should never plant seeds too deeply, they can "run out of steam" before they even see the light!

Both of these factors contribute to the germination rate (or percentage) of the seed. For example, freshly harvested seed, planted within 3 to 6 months after harvest can have a germination rate of 100%, as the storage time increases this rate decreases.

The last factor to consider is the inherent germination rate, some species of plants simply have a low germination rate, even under the best collection, storage, and germination conditions, this is due in part to incomplete pollination, small seed size, and even incompatible genetics in pollination. Some common herbs such as Lavender and Rosemary have low inherent germination rates.

There are numerous charts and tables available online that will indicate the expected longevity of seed varieties but as a general rule of thumb, collect, store, and sow within 18 to 24 months.

Dried seed pod and seeds

Seed pod and Weevil