By Rod and Rachel Saunders
The life of South African bulbs and corms is finite, so it is important to hand pollinate this season’s flowers to obtain seed for re-sowing the following season. This is particularly important for species of Sparaxis and Gladiolus which are quite capable of flowering themselves to death. After one has pollinated the flowers and the seeds have set and ripened, the next step is to harvest the seeds and store it until the correct season for sowing.
In Iridaceae, most seeds take about 6 weeks to ripen, with some exceptions eg Watsonias which take longer and some Moraea species which are ripe in 4 weeks. Ornithogalum, Albuca and Bulbinella seed is ripe about a month after flowering. As the capsules ripen they will change colour slightly, take on a shrivelled appearance and splits will appear in the capsules at the tips. At this stage the capsules may be harvested. Under certain conditions green spikes may be harvested and ripened in a jar of water to which a pinch or two of sugar has been added. As it is difficult to estimate the degree of ripeness of the seeds, I do not recommend this method unless one is desperate! If the seed is well formed in the capsules and the endosperm is solid and no longer milky then it is reasonably successful. Having said this, some seeds such as those of Lachenalias, with L. rubida a good example, have a long after-ripening period. The flowering stem dies off soon after seed set, and the whole spike separates from the bulb. In cases such as this, the spike with the green capsules can be collected, placed in a paper bag and left in a cool place to ripen.
Seed is very nutritious and is host to a number of parasites. It is therefore very important to treat the seed with an insecticide immediately it has been harvested. I always use Karbadust – it is freely available from nurseries and is relatively non-toxic to warm blooded animals. Do not use any product containing Gamma BHC as this will inhibit seed germination. The seed should be placed in a paper bag, Karbadust added, and the bag should be well shaken to ensure good coverage of the seeds. On sowing the seeds, the excess dust can be sieved off.
Seed longevity varies from genus to genus, and it can be increased by storing the seeds at 4°C. If stored at room temperature, most Irid seeds will germinate well for up to 2 years, for Gladioli and some Moraeas, it is less. As a rule, their viability is short. I have sown some 10 year old Dierama seed and obtained germination, but this is an exception. Agapanthus seeds are notoriously short-lived (about 3 to 6 months) and should be stored in a refrigerator. A cool dry place should be used for seed storage, away from light – better still, if you have the space, use a fridge.
In closing I have to stress how important hand pollination and seed collection is if you want to maintain the integrity of your bulb collection.