This evening's lecture at the garden club was by a National Collection holder of Agapanthus, Nerine, and Tuhlbagia (and Clivia, but he didn't talk about them, which was a pity, but you can't cover everything in one evening). It was a very good and instructive talk, and by the end of it I had learned several things that might explain why some of my plants were doing or not doing various things.
I was pleased to discover that I had pretty much worked out the correct principles of growing Agapanthus in pots from experience, including the point that while young plants flower earlier if moderately pot bound, mature plants do not flower well once their roots are completely congested in their pot. The collection holder's rule of thumb was to move them on to a larger pot every two years until they were in as large a pot as you could handle, at which point you split them and started again, which is the answer I eventually came to. I had to smile inwardly at the question from the audience as to whether you really chopped them up or teased the roots apart, as I should like to see anyone tease the root ball of a thoroughly pot bound clump of Agapanthus apart. I blunted a bread knife sawing mine up, and tonight's speaker produced an array of the knives he uses for the task, the largest of which was a full-blown cleaver.
I had not thought of leaving the chopped up root ball exposed to the air for twenty four hours to callus over before potting the pieces, to reduce the chance of it rotting. On the other hand I had discovered empirically that you could divide evergreen Agapanthus in the autumn. During the talk we were told to do it in the spring, but chatting to the grower afterwards he said that of course on the nursery they split plants throughout the year to keep up with demand. I had got my winter watering regime pretty much spot on, which is to keep them dry in the coldest months when they are not growing at all. Where I fell down totally was on feeding. It turns out that Agapanthus like their feed to be phenomenally high in phosphate. Tomato food, said the lecturer, did not have the right mix of the main nutrients, let alone the necessary trace elements, and was really designed for annual crops (like tomatoes) rather than long term projects like potted Agapanthus.
Nerine are one of my gardening bugbears. The hardy outdoor form, Nerine bowdenii, almost never flowers for me despite being on well drained soil in sunny parts of the garden, while the tender varieties leave me anxious about when I am supposed to water them and when I should withhold water, so that they end up scarcely getting watered at all, and barely surviving in their pots. Following the talk I suspect that my problem with the hardy ones is that I don't feed them enough and that I have tried to cram them into areas where there are already so many other plants that they get shaded. I am on the right track now with the watering regime for my pots of tender varieties, but ought to feed them.
The hybrid between Nerine and Amaryllis belladonna sounded very promising, with flowers like Nerine only bigger on taller stalks, and a reasonable degree of hardiness inherited from the Nerine side of the family. On the other hand the question of why my non-flowering Amaryllis belladonna only flowered about one year in four remained unanswered, because apparently Amaryllis are notoriously fickle and even the experts don't agree on how to get them to flower. Some say to give more water while others say to give less. At any rate it is not a simple question of correct feeding. A bulb merchant in the audience had a theory that the flower buds of Amaryllis grown in the open ground could be vulnerable to frost, which sounded as good as any other theory, though it would not explain why my Amaryllis never flowered when it was in its pot, which is how it came to be planted out in the open ground in the first place.
Something I would never have guessed was that big mature clumps of Tulbaghia tend not to produce many flowers, so instead of merely moving my overcrowded plant into an even bigger pot I ought to cut the root ball up into halves or quarters and pot each of them individually. I should do that in the spring, however.
I was so inspired by the end of it that I bought three pots of specially formulated food, blue for Agapanthus, pink for Nerine and yellow for Clivia. Apparently there is still time to give the Agapanthus one feed before putting them away for the winter.