Guy Barter

RHS Chief Horticultural Advisor

A key part of my work is making our advice actually fit the questions gardeners really want answered, and ensuring our advice is based on evidence.

I joined as superintendent of trials at RHS Garden Wisley in 1990, following experience in the commercial horticultural world after graduating with a degree in horticulture. Following this I went on to run the RHS Members' Advisory service.

We cover an enormous range of questions, and we learn nearly as much information and advice as we give, which we publish on our website and in our publications. A key part of my work is making our advice actually fit the questions gardeners really want answered, and ensuring our advice is based on evidence.'

I am a hands-on gardener who likes to get my boots muddy. I grow fruit and vegetables in my spare time, I am a bit of an experimental gardener, testing and trying new plants, methods and products, which helps in my work too

Guy's posts and conversations


  • Very many thanks for this up-to-date information. We will update this profile very shor

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  • Very many thanks for this up-to-date information. We will update this profile very shor

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  • Thanks for your comments. Do you have any evidence that insurance companies are erring

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  • Let them bide, brandlings won't survive in soil. If compost suitable for brandling

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  • Earthworms need oxgen and moisture so it mayt well be that the compost is wet but poorl

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  • Sadly even the rose finding authority

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  • You need at least 2 knotweedfree years before you can be reasonably sure it is gone. &n

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  • I think you will find what you need, and/or get better responses by posting this in our

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  • Thanks mango trees are unkown in Britain, sounds very exotic. Report trees threatening

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  • We feel that rather more than two weeks of covering is likely to be required to elimina

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  • Not every horse chestnut has horse chestnut scale and there are other scale insects tha

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  • Without seeing it hard to say but consider this guide: http://apples.ahdb.org.uk/d

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  • Sadly no fungicides are offered, so if cultural controls fail and/or the weather is aga

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  • Fungicides work best as preventative - consider if you can apply earlier in future year

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  • Like the idea of bark chips for kitty.

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  • Spraying is seldom 100% effective alas.  But it is likely that the problem would h

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  • I hope our words of not very great comfort help you manage this distessing occurance.

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  • Could be honey fungus bootlaces (rhizomorhs) best get stumps pulled, or surround with a

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  • Horses/courses all right - we have listed

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  • Consider this: http://www.ipm.ucdavis.edu/PMG/r584100511.html

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  • Two acres is more agriculture than horticulture - see if a local farmer or contractor c

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  • As a general rule one leaves woodchips stacked for three months - as February is the id

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  • No, because soil is heavy, solid stuff no disease travels far through soil. Unless ther

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  • All good comments but don't underestimate the resourcefulness and persistence of garden

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  • Thnaks for this.  We did have a page on vegetables, fruit and flooding but it appe

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  • It all depends but generally not worthwhile.

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  • You are likely to get an answer by posting on the L

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  • Flowers are the critical thing when identifyng plants - if you are an RHS meber send a

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  • Sounds like your best bet is to replace with new trees planted elsewhere.

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  • Send a pic with your membership number to the See conversation

  • Check for red spider mites under the leaves of course, but if these are absent we must

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  • Our wisdom on this can be found above: 

    • Cut back fruited canes to gro

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  • I think you may have to be a little more forthcoing about what you suspect is not worki

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  • I think you might get more responses if you were to post this  on the

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  • Matter of taste we would say, I think.We find See conversation

  • Burnt ideally, but otherwise compost but don't use the resulting compost on the veg plo

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  • Good point, thanks for bringing this to our attention. We will amend but in the meantim

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  • Consider posting this on our lavender page ideally w

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  • Follow this link to citrus problems

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  • This is usually a sign of stress.  Is your red acer actually a Japanese acer? Cons

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  • This is usually a sign of stress.  Is your red acer actually a Japanese acer? Cons

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  • Newly plants are vulnerable to the usual establishment proble

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  • Thanks for this - climbers of all sorts are very valuable as shelter for wildlife

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  • Lillies will do much better outdoors but a short stay inside while they are flowering m

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  • Deadhead, but not obligatory.

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  • Acers must never be waterlogged and never dry so thay are a tricky but by no means impo

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  • It all dep[ends where and how many leaves, but as this plant resents pruning aim to rem

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  • Temperature differences between day and night commonly cause leaf curling at this seaso

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  • For peach leaf curl what you see above is all you have got, but your plums will I think

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  • Thanks for your input.  Sad to say that some rabbits, especially young ones, or hu

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  • It sounds as if the graft (generally a seedling wisteria with the paler flowers of the

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  • Posting this on our apple scab page might get more replies: 

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  • You would probably do better to post this on our box page: 

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  • Sadly pictures cannot be shown - if RHS member email picture to us: gardeningadvice@rhs

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  • Thanks for this useful comment. As a gardening charity we only claim full competance in

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  • I have sent you an email that I hope helps.

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  • Although peas and broad beans fix all the nitrogen they need, runner and French beans f

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  • After flowering, grow the bulb on and apply a balanced liquid fertiliser weekly, but if

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  • After flowering, grow the bulb on and apply a balanced liquid fertiliser weekly, but if

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  • After flowering, grow the bulb on and apply a balanced liquid fertiliser weekly, but if

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  • Depends how many leaves, whether old or young leaves, if any insects are present and if

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  • Rye is slow to get going and is best sown early, althouhg it will pick up in spring&nbs

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  • Although we cannot completely rule out success the disease is likely to be present in a

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  • This sounds consistent with leaf scorch

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  • There are a number of causes of bleeding in birches and these may be innocuous, but sus

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  • Do the marks rub off?  Re they surrounded by a pale halo?  If yes disease mig

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  • Consider if your conservatory is unheated, when cold and/or over watering should be con

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  • The question is why did the hawthorn hedge die and become colonised by ivy? You would b

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  • A good tip indeed, prhaps one for our fuchsia ...

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  • The question is whether the bulbs persist or die away - it is worth looking at the rema

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  • To know what is going on here you need to cast your mind back.  Consider if moss p

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  • Thanks for your intersting comments - we wonder if other people have found this too?

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  • Find out where snails originating and act accordingly - for more options send details i

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  • OK to compost if well buried in other gunk.  Contact us with your membership numbe

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  • Sure sign of mice - replant with spring cultivar at end of Feb, and set mouse traps as

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  • Without seeing them it is hard to say - consider sending a sample or picture ...

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  • Without seeing them it is hard to say - consider sending a sample or picture ...

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  • Leatherjackets tend to die down of their own accord in well-tended veg gardens and are

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  • Yes, hard pruned trees will do this, including apples, and it is not a good thing - con

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  • Does our canna page help: https://www.rhs.org.uk/advice/profile?p

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  • Choose a relevant profile and add your question to the comments - s

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  • Check for verticillium wilt as per our web pages: ...

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  • We are not so sure soil minerals and properties have that much in

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  • Yes, perfectly safe - new soil must have had spores, how disappointin

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  • Although ponds are not improved by shade or by leaves and you sho

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  • As you can tell by the prevalence of slugs (and snails) in garden

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  • It is up to you - many people like the spent heads in the winte

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  • Note above: Hosta foliage dies down in winter and is then consigned

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  • Small plants are always vulnerable - traditionally a cold frame would

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  • We don't recommend the use of coffee to control slugs: ...

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  • Sales of slug killing nematodes boomed this summer - details from main manufacturer: ...

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  • With recent rains slugs will be on the move again now - be ready to protect young plants b

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  • Yes, trees can get signs of stress especially if newly planted or suffering form water str

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  • Yes, trees can get signs of stress especially if newly planted or suffering form water str

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  • It depends on what the veg is and the identity of the insect, but if you are an RHS member

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  • Consider our web page on this: https://www.rhs.org.uk/advice/profile?pid=517

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  • It is the aphids that do the warping - treat before leaf distortion occurs.

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  • Controlling aphids is more satisfactory solution!

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  • Good move - should work, but worth treating aphids to reduce numbers and therefore problem

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  • It is honey fungus season again - remember that it is the white material under the bark th

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  • It sounds as if another root disease or an environmental problem has done for your hedge.

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  • You can do as you wish on your own land, but it might be difficult to offer them for sale

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  • Whoops sorry - link: http://www.barenbrug.co.uk/documentLibraryDownload.asp?documentID=122

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  • If your friend is an RHS member she can ask our advice team (gardeningadvice@rhs.org.uk) d

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  • Yes, a three year old tree should shift easily enough - after leaf fall of course - from N

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  • Many apologies for tardy reply - we needed to update web software before staff could use i

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  • Privet is very susceptible to honey fungus indeed, so I would be surprised if there was an

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  • Tricky this as it hard to know if LJs are present at the optimum treatment time in early a

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  • Your suggestion of shrubs is sound - it is in the nature of climbers to head off up into t

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  • Many apologies for the delay in replying - I don't think it possible to post pictures here

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  • Many apologies for the delay in answering - our web software needed to be updated before s

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  • Link stakes are easy: http://www.harrodhorticultural.com/the-original-link-stakes-plant-su

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  • Your inclinations are sound - cut back or if you want to collect seeds or to enjoy seedhe

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