There is a greenhouse dahlia trick that I am keen to try out this year, and that is taking cuttings to increase flowering. We all normally buy our dahlias as tubers, and quite right too: good, chunky tubers are very easy to grow, you just pop them into the ground or a pot and as long as you can get them past the slugs when they first shoot, they are away. However, I once spent some time with a competition dahlia grower, and this is not how he does it. Having lifted his tubers in autumn, come January he moves them to a hot bed in his greenhouse and starts them into growth. Once the new growth is well away he takes hundreds of cuttings, and the plants that these cuttings turn into are the plants that he puts into the ground once all danger of frost has past. It is these plants that will grow up to produce a crop of award-winning blooms. The reason for this, he said, is that cuttings will flower earlier and better. Most of us can’t be bothered with the fuss and are quite happy to wait until late summer or early autumn for ours, but if you are serious about your dahlia game then cuttings is the way to go.
I am not particularly serious about my dahlia game. I like them a lot and I have a few, but I pop them into pots and forget about them, apart from a little water and feed. But mine do seem to have got later and later to start into flower and I would really like some earlier flowers this year. Last summer they were planted out into big pots in fresh compost in one of the sunniest spots in my south facing garden and fed regularly with a liquid feed. They grew well all summer long and then as summer started to wane…nothing. Not a hint of a bloom. Autumn set in and a few buds reluctantly appeared. Finally these buds swelled and burst into flower in late November, about a week before the first frost started to blacken the foliage, and not very long at all until they were all killed back by a harder one. I am particularly fond of ‘Café au Lait’, which doesn’t help matters. Café au Lait, gorgeous cream and coffee and peach tones that it has, is notoriously slow and late and tricky, and so it is no huge surprise that my blooms came late, though I wouldn’t expect them quite that late. I suspect my tubers may be a little old and perhaps that is slowing them down too.
Anyway, café au lait will bloom again in my garden this summer, I hope. I have ordered some new tubers and am setting up the greenhouse ready for them. I imagine that the competition growers do this next bit in a heated greenhouse, but that is a huge amount of energy to be throwing at a whim for earlier flowers and so I am just using a propagation mat and a cloud of protective fleece for the tops. As long as you can warm the roots you will get good early growth even in a cold greenhouse, and heated propagation mats use a very minimal amount of energy. I am planning to plant them up into long tom style pots so that I can cram a good few onto my small matt, then water a little, just enough to make sure the compost stays moist, and sit back and wait for the growth to come, before taking my cuttings. By the time these are taken it will be a little warmer, but placing them on the propagation mat once you’ve vacated the mother plants will really help encourage root growth and get them to take quickly.