Growing dahlias with relative ease is one of the joys of having a glasshouse. Not that it is impossible to grow them without one – you can stick the tubers straight into the ground if you like – but starting them in the greenhouse gives them the best possible head start, and means that the plants that I sunk into the soil at the allotment at the weekend are robust and have a fighting chance of seeing off the encroaches of the inevitable slugs. I have grown them by sticking them straight into the earth before, but if you do this you really need to arm them to the teeth, and there is every chance that whatever slug defences you put in place will have washed away (pellets) or been knocked aside (slug pubs and barriers) at the crucial moment that the tasty growth emerges from the ground. You also have to wait until frosts are over, and that means later emerging plants and so later flowers. Those plants that start off in the greenhouse and are planted out around now are slightly more likely to outrun slug damage anyway just by dint of being bigger, but more importantly we can protect them at the moment they are likely to be damaged (eg the very first night they go out and every night from there on until they are big bruisers).
I am growing ‘Cafe au Lait’ with its huge dinner peaches and cream flowers, blackcurrant coloured ‘Senior’s Hope’, and vibrant lavender pink ‘Rosella’, which I hope will rub along happily next to each other. A few weeks ago all of them were pinched out, to stop the leading shoots from reaching for the sky and to encourage them to bush out from below: potentially this might give smaller flowers and there is a chance that I have dashed my chances of winning first prize in a dahlia show, but what i am really after is stocky, sturdy plants and lots and lots of flowers, and so pinching out is the way. Incidentally if you were a competition dahlia grower these pinching out would be turned into cuttings, albeit earlier in the year.
Plants from cuttings make bigger flowers than those grown from tubers, and so those who really mean business will only start tubers as a means to creating lots of cuttings material. My very non-professional plants were brought out of the greenhouse a few weeks ago and have been hardening off on the back step, but now half of them have gone to the allotment to take their chances up there and half have stayed behind. At the allotment they will have high levels of light but they will also get a battering from the wind – they have been given plant supports to grow through to give them a chance of staying upright and bushy. The conditions might make them sturdier plants but it might also finish them off: trial by plot. At home they be in pots on my deck, close up for easy admiring, and they will be far more sheltered, but as the summer goes on and the growth around them thickens up the deck will get a bit shady and I may get fewer flowers because of that. But never mind, I want these flowers to hand, to admire for myself, as well as to the others gather from the plot to give away in bunches. We will see which plants do best, though my money is on the allotment plants, at least once they have made it through the tricky settling in phase, and outrun the slugs.