How do I germinate seeds from my garden?
Aloe secundiflora
If recently harvested, filled, mature seeds have been placed on damp but not waterlogged compost and provided a little warmth but still won't germinate then the most likely causes are either inappropriate environmental conditions (particularly temperature and light) or dormancy. The conditions required for germination, although partly genetically determined in many cases, are strongly influenced by the environment under which the seeds developed. Two seed-lots of the same species may behave in quite different ways. This said, with a little detective work and some experimentation, it is often possible to increase the likelihood of successful germination.
The most important thing to consider is whether the seeds have a hard seed coat or some covering structure that might prevent water uptake or physically inhibit germination. If so, they may need to be scarified. Filing through the seed coat with a narrow file until the contents are just visible may be possible with larger seeds. Smaller seeds might be gently rubbed within a folded piece of fine sandpaper.
The next thing to consider is the ecology of the species. Where does the species naturally occur in the world and at what altitude? For instance, seeds of many temperate species that are programmed to germinate in the spring often respond to a period of moist chilling. After scarification (if appropriate), the seeds can be placed on wetted tissue paper inside a reasonably airtight container and left within a refrigerator (+ 4°c) for up to three months. The moisture should be checked occasionally. Alternatively, the scarified seeds could be placed in or on moist compost and left within a cold-frame over winter. Following this treatment, the seeds can then be germinated on moist compost and in the warm as usual. Many small-seeded species need exposure to light for germination and also benefit from experiencing temperature fluctuations each day. This is an adaptation to prevent germination until the seeds are brought to the soil surface by disturbance.
If none of the above work, it might be necessary to try different germination temperatures. Unfortunately, the temperature range over which seeds germinate may change as the dormancy status of the seed changes.
The Seed Information Database (SID) provides germination data on seed lots that have been successfully germinated by the Millennium Seed Bank. This may help provide a number of clues.
