There is a disease of rhubarb called Red Leaf disease. You don't indicate your zone or location so I can't ell if it is prevalent in your location or not but it is primarily found in Canada and northern US.

But you can Google it by name for pictures and information to compare to your to see if that may be the problem.

Basically -

Red leaf disease of rhubarb commonly attacks the roots and crown areas of the plant. The leaves of the affected plants become reddish and later wilt and shrivel. New leaves cease to appear, and all that remains of the plant above ground is a few dry leaves. In some plants this process is slow, while in others it is rapid. Examination of the parts below the ground reveals decay in varying amounts. With plants showing only reddening of the leaves, the roots may appear normal on the outside, but their centers will be found to have rotted away. Some rotting in the crown will also be evident. In more advanced stages, when the leaves become dry, the greater portion of the root and crown will be found in a decaying condition.

There is still no good measure of control for this disease. The causal agent is not known, and until it has been found, no definite control measures are likely to be formulated. Shallow planting and a generous moisture supply may help to reduce the incidence of this disease. Affected plants should be completely removed as soon as possible after they show signs of this disorder. It is also good practice not to place new plants in soil where diseased plants have grown.

From U of Saskatchewan Ag Bioresources

Dave

My location is England. West Sussex

I can't find any UK sites that discuss it as a problem there but I would think it would be easy to find out from any local UK agricultural sources. But I have no idea what they are in your country.

Otherwise you'll just have to monitor the plants and see if the follow up symptoms detailed above develop or if the plant appears to recover. If it is Red Leaf disease then the plant will not recover and the crown will rot.

Sorry I can't be more help. Do you have access to any UK gardening forums that might be able to provide you more info?

Dave

Never heard of Red Leaf in rhubarb here. My rhubarb is only just emerging after this awful excuse for Spring. Many varieties are naturally reddish when they emerge. Can you post a picture? Is this newly planted? Have you been forcing it? Rhubarb is pretty much idiot proof so I'd be surprised if there was any real problem unless you've planted it on top of some sort of toxic rubbish dump. It has been very dry so you could try soaking it with the hose. But a picture would be great.

This is one of the leaves on my plant

This is the plant

Perhaps ask at http://mygarden.rhs.org.uk/forums/. I just discovered the site. It may or may not be useful.

Now I see the overall situation I would transplant it in the winter to a place away from that hedge bottom. Rhubarb needs a large space in good rich moist soil. And it would be easier if you could you keep to a single thread. Then we can follow the progress of the question.

I've just noticed several red leaves on some of my plants. They come away from the root very easily. I have plucked them and here's a pic before I binned them.

Will this spread to the other plants?

There is nothing at all wrong with that rhubarb except the leaves are rather small. It is nearly September and rhubarb is beginning to die down for the winter. It is doing exactly what it is meant to at this time of year. In the UK rhubarb is almost free of diseases. Just make sure it has enough moisture and rich soil for next year. Dropping a good dollop of manure on it in the winter will help. By late Autumn your rhubarb will have disappeared altogether and will re emerge next spring.

Phew ! Thanks for that.

Well... that was nine months ago - and now I find a bright red leaf on two of my otherwise healthy plants, and a yellow leaf on another. These coloured leaves have now started to decompose. Should I be worried?

Brutal but fixed the problem... Living in the UK: Mid season (June) after an infestation of small black dots (presumably eggs but I never worked out what they were and may not be relevant) the edges of the leaves started turning red and thicker than usual round the edges. After some searching it sounds like it had a fungal infection and the best solution was to dig it up and throw it away. As it is my only plant I thought I’d try some “kill or cure” first. I harvested all the stems and leaves so all that was left was closed buds. I then boiled the kettle, put it in the watering can (don’t melt your watering can) and watered the plant and the surrounding area with a radius of a foot. After a week I harvested and watered again. Apart from a few scorch marks on some of the leaves because some idiot poured boiling water on them the plant was cured. :)