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On a Chalk Hillside October 2021

Bindweed and Ground Elder 

As this month ends in Halloween, I thought I would get you in the mood with a couple of my scary garden monsters!
First though, I will start with a beautiful plant combination from the beginning of July this year:-

I think you will agree that the Valarian (Centranthus ruber var. coccineus) and Geranium (Geranium × oxonianum f. thurstonianum) are beautifully set off by the white lacy umbel surrounding them.  If it were Orlaya grandiflora, or Ammi Majus, or Ammi visnaga for example you would be agreeing with me wholeheartedly.  Fashionable, on trend umbels.  If  I told you it is in fact Anthriscus sylvestris (Cow parsley) you would be surprised it was flowering that late, but not too troubled, but what if I tell you it is in fact Aegopodium podagraria, a plant introduced by the Romans.  In the Middle Ages it was grown in gardens as a vegetable, the leaves can be cooked like spinach with an unusual tangy taste.  It was grown in the gardens of roadside inns and monasteries as a quick palliative for travellers’ gout and therefore called Herbe Gerard after St Gerard the patron saint of the gouty.  Can you tell what we call it nowadays yet? – yes, Ground Elder.  Also a misnomer, not an elder, though the leaves do look a bit like those of the Elder bush, it is indeed a member of the carrot family.    Even when it was grown as a useful pot herb John Gerard wrote complainingly about it in his Herbal of 1597 ‘Herbe Gerard growth of itselfe in gardens, without setting or sowing and it is so fruitfull in his increase that where it hath once taken roote, it will hardy be gotten out again, spoiling and getting every yeere more ground, to the annoying of better herbes.’
You may recall when we arrived here the huge rectangular rose bed was completely covered in a green mat of ground elder, and I had to dig out the top six inches of completely dense matted roots like a carpet – as you can see from this picture from mid April 2005:-

You might have thought that this level of clearing would suffice, but not only does the rootstock snap at the least provocation and grow back from the tiniest bit of root left in the ground, every so often (maybe every 12” or so) the plant throws out a deep root that you don’t notice when you hoover the matted roots all off below soil level.  Then it regrows.  If you take your eye off it for a season (and by a season I really do mean every 3 months you need to thoroughly dig and weed the bed as well as spot weed throughout) it will regrow dramatically.  You relax over winter as it vanishes completely below ground, (being a true hardy herbaceous perennial),  which is a mistake (it is also the best time to try and dig the roots out as the ground is wetter then and you have less snapping of roots as they come out.)  Here is the same spot in early June after a period of neglect:-

If you look closely you can see that it is smothering the two lavender bushes – who are hanging on grimly as they have deeper roots than the ground elder.  It is also trying to strangle the Centaurea montana.  If you dig the cornflower up to try and move it elsewhere you will discover the questing roots of the ground elder have run through, round and back again meaning that the only way to be sure you have removed all the ground elder roots is to wash the cornflower’s roots completely clean of soil and forensically examine each root at the junction with the next to be sure.  You can imagine that this is absolutely impossible to do with the sort of rootstock that hardy geraniums have – here is a rootstock of a hardy geranium I dug up last winter to show you what I mean:-

This rootstock occupies the same part of the soil (ie the top 6”) as the ground elder, and is far too dense to remove the ground elder roots successfully as you snap the ground elder roots into smaller and smaller pieces whilst stressing the geranium by mangling its roots more and more.  Roses and lavender having deeper more open roots can compete to a degree with the ground elder for nutrients and moisture.   However as you can see here from early June, the ground elder leaves can completely cover the plants it is aggressively growing its roots through too – here swamping a Geranium endressii AND a Geranium molle:-

Not only can the Ground Elder spread aggressively by its roots, as you can see from this photo only a month later in early July, it sets a lot of seeds:-

As with all families, there is usually one member that is the black sheep.  If you take the Convolvulus family, there is the lovely Morning Glory I cultivate up a pergola – here in Blue from as long ago as September 13:-

Whereas the white form of this flower, we are NOT pleased to see in this garden:-

Insects love it though:-

As I am sure you all know, there are two sorts of bindweed – what is now called Hedge bindweed – Calystegia sepium – and a smaller version with slightly more glaucous leaves and a smaller pinkier flower – field bind weed or Convolvulus arvensis).   Hedge bindweed (the pictures above are from this sort,) is the predominant type in this garden unfortunately.   You may remember I said last month that after a very dry spring we had sudden rain/hot weather/rain causing a lot of sappy growth – this is what I meant – from the 11 June this year – bindweed “suddenly” overwhelming a Phygelius capensis and a rose on the right of the picture:-

When we moved here from our London garden I was (unfortunately) familiar with bindweed, so had tried very hard to screen every plant that we dug up and brought with us for bindweed roots in its rootstock.  My husband thought I was being obsessive about it, but I didn’t want to bring the problem with us.  We moved in in November, and in the December my step Mum (the original Hardy Plant Member in our family) was visiting and helped us heel in plants we had brought with us into the big square bed outside the sunroom at the back which had some gaps in it.  Ha ha she said (or some less repeatable phrase) you didn’t need to worry about bringing bindweed with you – you have it here already.  The roots were running along the edge of the concrete path that adjoined the bed (and indeed ran right under the bed and popped up in the one the other side of the path too, it transpired.)  
You are probably all familiar with the fat white roots of bindweed – another questing rootstock that snaps at the slightest provocation and can regrow from the tiniest fragment left behind.  Here Is an example of the rootstock in a soil pile I was digging out:-

You can see the finer grass roots, and the thicker white bindweed roots.  Here is a closer look at the bindweed roots:-

If you look closely you can see lots of straight ends to the roots denoting that I have snapped these off – bearing in mind this is a soil pile that I created on top of horticultural fleece that had been there only for about 9 months…….This is not the only clever thing the bind weed roots can do – if you were to put the horticultural fleece over the top of them – say to cover a bed or border to exclude light as a means of clearing the soil from weeds, the bindweed roots would laugh in your face (well, you know what I mean!)  They simply carry on growing through the soil for meters across the ground until they find light eventually.  I do mean meters – we have previously covered an area the size of 3m square with light excluding products to no effect.  Here is a couple of shots of what we found when we lifted a 3m x 1.5m galvanised steel corrugated sheet from the ground (the sort of thing that you clad roofs of barns with:-

Hopefully you can see that its bone dry under there – the slow worms love it, and the bindweed goes along the long length of the galvanised sheet.  The roots of both bindweed and ground elder (and indeed the slow worms) are not deterred by weight either – here was what we found under a 1 tonne dumpy bag of builders sand we emptied when we were laying a patio this February:-

The **!**! Ground Elder is even starting to sprout!!!
Before you ask, unless you are prepared to spray there is very little you can do apart from digging the roots out, weeding, weeding, weeding.  If you do want to spray, you need to do it when the ground elder or bindweed is in full growth – so that the herbicide goes down into the roots quickly from the leaves.  If you leave it til this time of year when the hardy herbaceous perennials are slowing their growth and beginning to die back it will not have any effect.  I felt slightly better about having bindweed when I visited RHS Wisley for the first time in 2019 as they had a whole border empty near their lake/greenhouse with a sign saying this had been emptied so they could get rid of the Hedge bindweed.  We haven’t been back until this year, and by then THAT border had been replanted, but a border in their Cottage Garden had been cleared and had a sign that it was empty because they were trying to get rid of the Hedge Bindweed.  We saw the same thing at Iford Manor when we went in July this year – so it is possible that that is a viable option if your border gets too overwhelmed with bindweed to cope with “just” weeding it.  You would need either a lot of space to put the plants you remove, or very deep pockets to bin them all and start again with new stock that you KNOW doesn’t have any bindweed roots hidden in them.
Are you suitably spooked for Halloween now?  

Next time I shall give you an update on my mixed native hedge in the orchard.

Sheila May

Posted by Sheila May

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