Rhubarb-qa

RHUBARB QUESTION AND ANSWER

Article by David Marks
Our main rhubarb article can be found here. But sometimes our readers ask specific questions which are not covered in the main article. This page lists their comments, questions and answers. At the end of this page there is also a form for you to submit any new question or comment you have.

COMMENTS / QUESTIONS LEFT BY OUR READERS

Date: 07 May 2020 From: Bob
QUESTION: My rhubarb was ok the second year when I picked it but for the last three years the stalks are short and never get any thicker than a pencil. I bought another crown but that one is worse never had any stalks I could use.

ANSWER: My guess is that the poor production of stalks is due to environmental factors. Here are a couple of ideas.

Water – the saying goes, albeit a slight exaggeration, “water rhubarb even when it’s raining”. They wont appreciate being waterlogged but they do prefer a constant supply of water especially in the summer.

Position – rhubarb do well in partial shade. They will not do well in full sun, this will cause them to be far less productive the next year.

Feed – rhubarb do best when well fed, they are greedy plants. In clay, which is rich in nutrients, they should receive most of what they need with only a couple feeds a year. The lighter the soil, the higher will be their need for feeding. Well rotted manure (keep it away from the crown of the plant) is good – not only will it feed the plant but it will also conserve water. If you cant get any of that, feeding with a long lasting fertiliser such as blood, fish and bone is an excellent alternative and maybe as an addition to well rotted manure.
 

Date: 04 July 2019 From: Scott
QUESTION: What time of the year should I transplant and split my plants? I had crown rot on several plants, one really nice plant is starting to show signs of rot, Can I dig it up and transplant it?

ANSWER: The best time to transplant rhubarb is when it is dormant in winter – late November to mid-February is ideal.

Crown rot is a fungal infection and if the plant is suffering from it, recovery may well never be possible. So dividing a rhubarb with signs of crown rot runs the risk of the divisions also suffering the same problem.

 

Date: 14 June 2019 From: Annie
QUESTION: Having split the rhubarb, I am not pulling any this year. Do I leave leaves and stalks to all die down until Autumn ? Not sure what to do next!

ANSWER: Yes, leave the leaves and stalks to die down. All the time the leaves have some green on them they are absorbing energy from the sun (what sun!) and feeding that energy into developing a good root system. When a leaf turns mostly brown, pull it and the stalk off to reduce the risk of bugs and disease getting to the rhubarb crown.
 

Date: 14 June 2019 From: Alister
QUESTION:: I have Rhubarb successfully growing in containers but blighted by by these Vine Weevil pests. Will they be merrily be laying eggs when I’m sleeping and the Grubbs eating the roots now or later, or is the plant to toxic, will the leaves kill them of?

ANSWER: I haven’t heard of vine weevil affecting rhubarb in containers. It may that the poisonous leaves deter them or that the fleshy structure of rhubarb roots are not to their liking.
 

Date: 14 March 2019 From: Bill P
QUESTION: I have moved to Hampshire and am surprised to see yellow clay at spade depth. I am in the process of planting six different rhubarbs in raised beds. I wish to use removal crates with the base removed.

I am aware that 90cm is the recommended planting distance but if I plant two in each crate in blood, fish and bone will this be OK? Is the planting distance because of the foliage or because of the roots?The upper dimensions are 1100 x 480 and the base 990 x 400. The planting distance will only be 50cm.

ANSWER: I’ve never grown rhubarb in containers so any advice has to come from elsewhere. The RHS write the following below about growing rhubarb in containers:

“Rhubarb can also be planted in very large pots at least 50cm (20in) deep and wide.”

They say very little else about the subject. From that small comment I would think that you may well succeed with your plan as far as the roots are concerned. Clearly the foliage will spread wider than 50cm and I simply don’t know the effect that overlapping foliage will have on the plants. My concern would be that so much foliage will prevent air circulation and increase the risk of Crown Rot.
 

Date: 1 May 2018 From: Hannah
QUESTION: I planted some rhubarb crowns with leaves starting to grow in late March and the leaves now have quite a lot of holes and the stems seem to be scarred, sometimes to the point of the stalk breaking, is this slug damage and how do I control it?

ANSWER: Holes in leaves are caused by slugs and snails. Once the plant becomes established after a year or two these don’t really matter, the rhubarb plant can cope very well with the damage. I have heard of slugs and snails damaging the stalks as well and this sounds like what is happening to you. I would do whatever you can to control the slugs and snails this year. Next year I think you will find the plant grows so quickly that any further damage (aside from holes in leaves) is minimal or non-existent.
 

Date: 7 August 2017 From: Julia
QUESTION: My rhubarb is in its first year and was growing well until 2 weeks ago. After the rainy weather the leaves are now turning red and die down one after the other. Following the rain the plant was standing in quite a bit of water which I’ve now removed. Could it be the the plant was over watered? Is there anything I can do to save the plant?

ANSWER: Rhubarb hate being in water logged soil, it rots the crown. Reduce the amount of water to the minimum and then wait and see what happens next year.
 

Date: 11 May 2017 From: Hayley
QUESTION: This is the first year I’ve grown rhubarb and all of a sudden the leaves have done a purple/red colour. I’m not too sure what this is? Is it a disease or natural? Is my rhubarb safe to harvest and eat?

ANSWER: When rhubarb leaves turn red there are two common reasons. The first is that the plant is going into hibernation until next year, that is natural. The second reason can be that the plant is under stress.

You mention that this is the first year you have grown rhubarb, so I quote from our rhubarb page:

“Don’t harvest rhubarb in the first year of its life and go easy during the second year. The reason is that the plant will be building up its strength and removing the stalks will also remove the leaves – these are its source of strength.”

So, although it’s safe to harvest and eat, don’t harvest in the first year and only a small harvest in the second. I suspect your rhubarb plant is fine and next year it will have built up some strength.
 

Date: 21 February 2017 From: Letty
QUESTION: When I transplanted my rhubarb, I found hundreds of yellow ants throughout the roots and in cavities within the biggest roots. What should I do?

ANSWER: Ants are not known to attack rhubarb plants so I would guess your plant has crown rot (see main article above) and the ants are just feeding on the sweet liquid released by the damaged roots and stems.

 

Date: 1 November 2016 From: Janine
QUESTION: My rhubarb was so healthy but suddenly just all turned red and died. A few shoots have started to come up again and I was hopeful, but even the little shoots are turning red and dying?

ANSWER: I think this natural behaviour. You rhubarb is dying down for winter as it normally does. The new shoots are probably caused by the unusually warm weather in October. Now it is getting colder they are also dying off. I suspect that it will be fine next year.
 

Date: 2 October 2016 From: Angela
QUESTION: I have been given a large amount of rhubarb. I found that some had a red circle in the middle of the stem which went right up the middle of the stork plus one had a hole straight up the middle of the stem. is this ok to eat? I usually cook it with custard.

ANSWER: My guess is that stalks are past their best and starting to go woody. If that’s the case they are OK to eat but may not taste particularly good. At this time of year almost all rhubarb will be too old to taste good.
 

Date: 4 June 2016 From: Karen
QUESTION: I planted rhubarb for the very first time (I’m an extremely novice gardener) it’s growing really well but I’ve noticed lots of tiny green spiders on the underneath of the leaves that run to the soil when I turn over the leaf. The leaves have lots of holes in (I presumed were from slugs). Should I be worried and do I need to do anything about it?

ANSWER: It's difficult to diagnose without seeing this but I suspect the spiders and the leaf damage are not connected. The leaf damage is, as you thought, probably slugs. I know of no spiders which damage rhubarb so I assume they are just natural wildlife hiding from the sun. When you lift the leaf they don't like the sun and run for shade.
 

Date: 08 April 2016 From: Marilyn M
QUESTION: My rhubarb plant is 3 years old. This year the first of the stalks were woody and I cut them off now all the outer stalks are falling to the ground and I found one large stalk that was very weak and had some sort of slimy stuff in it when I tried to pick it off. Can you tell me what this could be?

ANSWER: This sounds very much like crown rot. Any signs of slime or rotting is the key sign. The woody stems are a sign that either the crown of the plant is failing or it is severely congested. You could try splitting the crown into three pieces (see here) and replanting. However, I wouldn't recommend it with signs of slime. You may well end up infecting even more ground. Best to dig it up, burn it and plant new rhubarb away from the original site.
 

Date: 01 August 2015 From: Rosemary
QUESTION: My rhubarb leaves have developed red patches especially around the edges. On browsing web sites I think it is a very virulent virus and suggestion is all rhubarb should be removed and destroyed. Is it safe to plant any other type of fruit in the soil now, ie gooseberry or raspberry bushes or will I just have to leave this garden patch of soil bare?

ANSWER: I think you are jumping the gun here. Before you pull up your rhubarb, you need to identify the virus specifically. Firstly, what is the suspected name? Without that bit of information you really have no way forward.

I strongly suggest that your rhubarb is, in all probability, just suffering from stress. Follow the guidelines on rhubarb care first and see what happens. If you want to send me a picture of the affected leaves, send an email (see our contact us page for the email address) with a photo attached and I will do my best to diagnose the problem.

I have received your picture and decided to write a section about it above in the main article because others may well experience the same apparent problem and wonder what is causing it. See here for the full explanation.
 

Date: 12 June 2015 From: C M berckes/Sloan
QUESTION: I planted rhubarb this spring and it is growing yellow leaves..why? does it need what type of fertilizer?

ANSWER: The three key needs of rhubarb at this time of year are lots of nutrients (it is a gross feeder), moisture but not water-logging and partial shade. See the section above for more details. As for a specific fertiliser I would give it a normal dose of liquid general purpose plant food plus a couple of handfuls of blood, fish and bone to keep it fed later in the year.
 

Date: 9 June 2015 From: Ian
QUESTION: Rhubarb is in its first year but it has like rust marks on the leaves.

ANSWER: Then it's almost certainly the fungal disease rust. See the section for more details.
 

Date: 18 April 2015 From: Dotty
QUESTION: My rhubarb in its 2nd year grew a large flower head in the centre of the plant (it resembled a young cauliflower ) what is this?

ANSWER: Your rhubarb has started to produce seeds and that's the seed head. Sometimes it can be 20cm or more across. This year, cut it off in order to stop the plant putting energy into producing seeds you do not want. Next year, watch out for it a bit more closely and remove it as soon as possible.
 

Date: 7 April 2015 From: Terry
QUESTION: I started my rhubarb in a large pot because I was told that the plant roots need to
have 30 days of freezing weather per winter in order to grow. I live in South Carolina
and that just doesn't happen – thus the pot, which would not provide as much warmth as the ground. This is the second year for the plant. This spring the stalks emerged and then some started to "Bolt" sort of like lettuce does when the weather gets too warm. Also, only a couple of leaves have developed normally; the other stalks produce something that looks like a cauliflower head. The plant definitely doesn't look healthy. What is causing this and what can I do?

ANSWER: Your rhubarb has prematurely bolted and is producing a flower heads and later seeds. It doesn't like the warm weather and there's not a lot you can do about that. I'm from the UK so no expert in growing rhubarb in warm climates but I have heard that the only realistic solution is to grow it as an annual. This article here may give you some ideas on how to do that.
 

Date: 10 January 2016 From: Jeannette
QUESTION: About 12 years ago I transplanted a crown of rhubarb from where I used to live. The original plant(s) had been there for as long as I can remember (over 60 years) and always flourished next to the compost heap. Thank you

I have never forced it and have taken care not to harvest too much. It was fine until a few years ago when growth began to weaken. For three of the last four years there has only been one flower stalk, (I always remove them as soon as they appear). I dug up a piece of it and found that there was a large hole in the centre of the root, which seemed to be lined with black (though because of the black soil I'm not sure of that).

If this is a disease, how near would it be safe to plant new healthy rhubarb after disposing the old one? My garden is quite small. The soil is neutral or slightly alkaline, unlike the previous place where it was rather acid.

ANSWER: Sounds very much like crown rot. If the plant is not saveable (and that sounds the case) dig it up and dispose of it – burning if possible. Plant a new rhubarb 3m / 10ft or more away from the original position. This page here explains how to plant new rhubarb.
 

Date: 01 September 2014 From: Carmen
QUESTION: Hi, we have rust spots on our rhubarb leaves and stalks. Could you please tell me what the cause of it and would it harm the crown?Kind regards Brian

ANSWER: We have added a new section on rhubarb rust to help answer your question. Good luck.

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