In the 4 years since we moved in here I have never divided my Dahlias. I realised my mistake when, last Autumn, I lifted a writhing Medusa’s head from the soil. I neglect my dahlias terribly and popped them, sparsely covered with compost, in a cardboard box in my outdoor tool shed. Not frost-free, but out of the wet of winter which is enough to protect them from rotting. Most importantly they were out of sight and mind, and I adopted the standard British approach to a tricky problem of pretending it didn’t exist.
But by the first week of March, I found my mind straying to the monsters I had unearthed that lay in wait at the end of the garden and I knew I could put off surgery no longer. Step one was easy enough. I took all my dahlias to the sink and gave them a good rinse under the tap to see what was going on. This took rather a long time as the tubers were so large they had grown into each other in a knotted mess, providing habitat for large numbers of overwintering insects and retaining soil despite my best efforts. Our sink will never be the same again.
Much to my disappointment, Medusa was undiminished by a good hair-wash, her locks even more tangled than I had initially realised. In any guide to dividing dahlias you are shown a central stem or two with a ring of neatly arrayed tubers radiating from it. You then divide them up ensuring that each division has a little node or bud at the top and enough tuber to give it a kick start. The whole process looks encouragingly simple, and so it should be… if you do it regularly.
The gorgon had 7 stems many of which, confusingly, were growing from the bottom and sides of the mass, pushing their way up through the tubers. This made locating any kind of growth bud extremely difficult and gave the whole exercise much more of an intellectual ‘logic puzzle’ feel than I had anticipated. I set to with a bread knife, damaged two small tubers beyond repair and gave up for the afternoon.
That evening, with the help of some Dutch courage, I returned to the task and practiced on my tamer candidates fist. Once I had got into the swing, I tackled the gorgon with reckless abandon and I think we were both quite pleased with the results.
For anyone dividing Dahlias for the first time, here is what I have learned:
If you can’t see the nodes and that worries you, wait a little longer. The growth buds sit at the top of the tubers where they join and in general if you are keeping your divisions quite large (eg dividing a plant in half) then you will always have some nodes there. But if you want to see them to be sure, pop your tubers in some compost, water them a little and wait for a few weeks. As they prepare to burst into growth the buds become visible and you will still have time to divide them up.
If plants divide easily into 2 or 3 then you’re away.
If your dahlia is a mess like mine and you’re nervous about losing the patient, you’re better off being cautious and making sure that your central plant is strong and healthy. With Medusa in the end I found it easier to remove a few ‘babies’ here and there, each with one or two bits of tuber and a bud, and to leave the densest part of her untouched. This means I have one mother plant and several offspring, but dahlia plants bulk up really quickly and by next year they will all be a good size.
Don’t chuck your casualties. With a messy plant to divide, it’s quite hard to avoid the occasional tuber falling off by mistake. Even if you can’t see a node, it’s always worth potting it up in a small pot and seeing what happens. Of 7 casualties I had this year, 5 have started to sprout and are looking promising.
Don’t put it off till next year. I’ve been amazed at how quickly relatively small looking sets of tubers grow into really healthy flowering dahlia plants. They are a species with a lot of energy and vigour. You’re better off increasing your stock every year or so and lifting dahlias to check on their condition, remove rotten tubers, and tame them before they grow wild. You’ll have lots of plants in no time, and your hairdressing will be much simpler in future.
