Hundreds, possibly thousands, of plants are raised from seed each year in the greenhouse at Glyndebourne. These young plants, mostly annuals and tender perennials, help to keep the borders looking full and floriferous throughout the opera season. Seed sowing starts slowly in January and then builds to a crescendo in March and April. Biennials, such as digitalis, are sown later in the year and planted out in autumn.
A viable seed is equipped with everything needed to make a new plant; it is just waiting for the ideal environmental conditions to be met. On a basic level those conditions are: a plentiful supply of water, the optimum temperature and a well aerated compost.
Germination isn’t always this easy and some seeds require a physical action to break their dormancy. Scarification is the process of damaging the thick seed skin (testa) to allow water through. Nicking with a scalpel or rubbing on sand paper mimics the effects of harsh stomach acids, (some seeds actually need to be eaten first), or of the effects of freezing and thawing. Chemical inhibitors located just below the testa may occur; soaking the seed in water can wash these out. Exposure to cold temperatures also causes breaks in dormancy in some species – this is known as stratification and can be mimicked by placing your seeds once sown in the fridge or sowing early in the year and leaving outside covered by glass. Luckily seed companies have usually done all of the research for you and the instructions will be on the packet. If not, the research is down to you; it helps to know the conditions your plant grows in.
When sowing your seeds use a good sterilised compost, Glyndebourne use a 50:50 mix of peat free compost and John Innes No2. Firm down the compost, and sprinkle the seeds thinly on the surface. Larger seeds need to be sown deeper, usually twice the depth of the seeds diameter. Smaller seeds may just need to be surface sown. Cover with a fine layer of compost, sieving it works well, water and then place at the correct temperature for the species. Keep the compost moist.
Germination time varies from species to species, but as soon as germination has occurred reduce the heat if required. Once the seedlings have two true leaves prick out and pot on. Remember to hold the seedling from its leaves, not the stem, new leaves will grow but if the stem is damaged the seedling will probably die. Lift the seedling out with the aid of a dibber (a pencil will do). And be gentle!