Free plants! What’s not to like? Let’s ignore for a minute the fact that I don’t have room for them. No, really, shhh. La-la-la not listening!
The starting point for this process is dahlia tubers. These can either be tubers, bought at great expense, or tubers that have been overwintered. Mine are the latter, ‘Bishop’s Children’ that I grew from seed last spring. To be honest, they’re a little bit garish, but that’s half the fun with dahlias.
I will be doing the same with some luverly dahlias I ordered recently but they’ve just arrived so I need to wait for them to produce shoots.
First thing to do is get the dahlia tubers into some fresh compost, either using trays or pots depending on how many you have, see here for an earlier post on this. It’s apparently best to leave the tops of the tubers sticking out, this is to make it easier to take a clean cutting later. I did not do this and am regretting it a little now. Water them a bit so they’re moist not wet, leave them somewhere warmish and light and wait till they throw up shoots. I had mine sitting on benches in the unheated part of the greenhouse, they started to show shoots after about 2 weeks. Don’t let them dry out but don’t leave them sitting in a puddle either.
I waited until they were a few inches long, with leaves at the top.
Watch out for slugs at this stage, by the way, they seem to be very partial to a juicy dahlia shoot. Using a sharp, clean blade, I cut the shoot away from the tuber, cutting as close as I could get to the surface of the tuber. If the tuber is undamaged it should throw up new shoots in the same place.
Although, interestingly, there is conflicting advice about this. Sarah Raven (see video link below) says you should try to take a piece of tuber as this helps with rooting. Seems to be a choice between better chance of the cutting striking properly and the parent plant getting a good deal. As you can see from the above photo, the base of the stem is buried which is why it’s better to bury the tubers initially with the top clearly showing. I took two or three shoots from each tuber, carefully cutting away the lower leaves so that there was a clean stem, also neatening the end if needed to avoid rot.
I used two methods for cuttings here.
- basal cuttings (from the base, close to the tuber).
- nodal cuttings (from below a leaf node)
They are similar generally, differing just in the place where the cutting is made.
When I had finished taking the cuttings it was time to set them up. If I was taking loads, or got interrupted, I would have put the cuttings in a damp plastic bag to keep them nice and perky. I didn’t need to on this occasion. I gave each one a dunk/shake in rooting hormone powder then popped them in cuttings compost.
For the cuttings compost, I have used an equal parts mix of grit, vermiculite, sand and multi purpose compost. The goal is to have a nice open mix.
I’ve used 7cm pots, three or four cuttings to a pot, but trays or modules could be used instead. I made a hole first with a dibber then popped one cutting in each hole, remembering to firm it down gently to ensure the stem is in contact with the compost. I gave the pots a good water with a fine rose..
I’ve put them in the heated bench without any additional cover, hoping that the main bench cover provides the needed humidity. A propogation unit with a vented lid would do, so long as it is somewhere warm, ideally with heat underneath.
The cuttings will allegedly root after a few weeks. We shall see. I’ll take more cuttings as the shoots develop on the other larger tubers I have on the go. Particularly looking forward to taking cuttings from the new ones.
I didn’t have much of a clue about how to go about this whole process with dahlias, but luckily there are some proper dahlia fanatics out there who have trodden this path before and given chapter and verse:
I’ll be back in a few weeks, with an update on rooting, I hope…