So some of my rhubarb is just starting to show signs of life. A vivid yellow-green-red bud is starting to burst from the old brown husk. I'm planning to force some of the crop. Is now the right moment to start?
Do I have to wait for it to reach a certain size? Or could I have (should I have) placed my forcing jar (or whatever) over the dormant plant back in mid-winter?
It depends where one lives but I do it in December and leave it on the plant until May. Overfeed them with plenty of manure, but don't let it touch the new growth -- keep it a finger's width away from them as this will and can burn them. When they are a size you want them, then harvest them but leave all the leaves on during the summer to recharge the root for next year. It's a good idea to have several roots to expand the season and not overtax the one plant in your garden.
The professionals in the north of England's "Rhubarb Triangle" recharge their plants every year outside in the fields with tonnes of manure so they are literally force fed. In October they dig up the plants and place them in a very large dark shed on layered shelves with a constant temperature. The stems then grow rapidly in the dark.
A completely useless fact: rhubarb is officially the fastest growing plant in the world and one can actually hear it growing!
As you're in the UK, the timings olantigh mentions are more or less accurate - my info on rhubarb forcing says to cover the plants in December or January, then harvest as the stalks get large enough. I'm not a 'real' rhubarb grower, preferring to let mine grow perfectly naturally, but the info also suggests that the best time to topdress with well rotted manure is in May, which is certainly about the time I do mine. It also says that, if you force a plant one year, it must be let grow naturally the following year.
So, in answer to your question, yes, you are too late to force this year, sorry!
