I am a little disingenuous when I include marestail in the title. Your real threat is almost certainly horsetail. The names are frequently confused and I regularly do so myself! Your weed will be horsetail which is an ancient spore bearing primitive plants that would be at home with the dinosaurs. It is very difficult to control in the garden. ‘Real’ marestail (latin name Hippurus) is a weed of ponds and bogland. Hippurus is merely a vigorous small flowered aquatic plant.
Now by ‘common usage’ you can legitimately call equisetum either horsetail or marestail!
|Hippurus vulgaris, the ‘genuine’ marestail to me is a harmless aquatic. You might not agree|
In one sense equisetum is a weed that has been created by man. In nature it rarely achieves the ascendancy it does in gardens. Equisetum is an extreme survivor in disturbed habitats where in the absence of natural competition it can build up a seven foot deep root system with huge carbohydrate reserves and vast vegetative reproductive capacity. Once established it is extremely difficult to eliminate. Give yourself three years and unless you are extremely diligent you will fail. Beware hysterical adverts for chemicals that claim to eliminate it in five minutes. Such products might have a place in your armoury but do not succumb to their hype.
|The herbicide of the spray train at Howden station has removed all competition and the equisetum has had many years to build up huge life prolonging resources|
There are several methods which will eventually get rid of equisetum. They are not always compatible and often cannot be used in parallel. All share the need to keep ‘on top’ and not let strong new green leaves consolidate the weed’s grip.
The herbicide glyphosate is the weedkiller that is most likely to lead to success.
I would never be persuaded to use sodium chlorate because of the extreme damage it will cause to trees and all desirable vegetation when it kills your neighbour’s garden as well as your own!
Glyphosate is a translocated weedkiller and reaches the roots via the leaves. Contrary to my earlier comment you must allow the weed to make a strong green top before you start. Such leaves will drink up your weedkiller. It is no good zapping young equisetum shoots as soon as they appear, there will be virtually zero uptake. It is no good either chopping out pieces: you will only create irregular shoot emergence which will interfere with later efficient spraying.
There will be some skill in deciding when to repeat spray. There is little value in spraying yellowing dying leaves nor very young shoots. Perhaps from emergence new green shoots should optimally have two to four weeks before you respray. If you get your first spray right it might be several months or even next season before new shoots appear.
Case study 1: a client’s garden
When I used to have clients and considered myself an ‘up market’ jobbing gardener I had a customer with about twenty square meters of horsetail at the edge of a gravel path and at the base of a hedge. I made irregular visits, perhaps in Summer every five weeks. It was quite a small garden and did not need my knapsack sprayer. I took along a most unsophisticated one pint hand sprayer made up with glyphosate at about twice normal strength. A useful feature of many hand sprayers is that they give a fine spray and each visit I gave a light spray short of ‘run off’. It took all of five minutes. Should I have been treating the lawn with herbicide on my visit I would have used that instead! After three complete Summers it was effectively gone. A total of three man-hours but over three years.
Case study 2: my new garden at Seaton Ross
When we moved in there was a small ten square meter clump in the front garden and under the brick wall a further twenty square meters on the edge of the farm field. It was necessary to kill both sides to avoid future invasion. It was late May and the equisetum was in perfect condition to spray. It was lush and luxuriant and the previous occupant who was not a gardener had (fortunately) not touched it and the roots were intact to receive their poisonous translocation. Horsetail with its siliceous surfaces is notoriously difficult to wet. I sprayed it with a fine spray, short of run off, twice that day. For extra efficaciousness the second spray was MCPA or was it - I forget - Grazon 90? My glyphosate spray was a strong one. It was a one in thirty of commercial strength 360 g/l glyphosate to water. Recently when I told the story to a visiting party I heard someone mutter, “no wonder it died”.
I did not expect anywhere near complete control so it was a nice surprise it did not reappear that season.
As expected early the next Summer there was sparse and erratic horsetail emergence. Just as well it was seriously weakened because I had already done some temporary planting using expendable plants. To avoid damaging my plants I made up my one in twenty dilution (it might have even been stronger) and used a paintbrush to thoroughly wet the horsetail leaves. If the pressure on my ‘back board’ caused slight abrasion all the better. I made two further applications that year as new shoots emerged. That’s all really!
My normal routine weed control is accurate spraying with a much weaker directed knapsack spray. In year three there was some very weak equisetum emergence but only at the beginning of the season. Perhaps even in year four there was the very occasional shoot. Even now I sometimes pass the time of day to a lone delicate fine frond.
Case study 3: Bolton Percy Cemetery Garden
When I took on Bolton Percy cemetery forty years ago it was completely overgrown with weeds such as nettles, brambles, couch grass and horseradish. The latter had roots thicker than your arm reaching two spits down. I had other ‘fish to fry’ and was unconcerned about fairly substantial colonies of horsetail. I had no intention to make a garden and my scorched earth policy was to blanket spray the overgrown acre. Glyphosate was very expensive at that time and as a ‘tight’ Yorkshireman no doubt I diluted ‘commercial product’ at one in a hundred. As the dead weeds gave way to a thatchy mulch and eventually rich dark soil, I started popping in plants and changed to accurately spot spraying. The garden ‘happened by accident’ and ten years later the always open cemetery was ‘opened’ for the ‘yellow book scheme’.
I never consciously made any special effort to control marestail but my maintenance spraying that continues to this day has for all practical purposes eliminated it. There are places where my ornamental plants are so dense that I am unable to spray. Sometimes in one little corner I spot a few fronds of equisetum. Deprived long ago of its substantial deep carbohydrate reserves, amongst competing healthy vegetation it is no problem at all.
Case study 4: blackout.
A cultural control for weed is to smother the ground completely with black polythene. It takes a long time for horsetail to die. The principle is that if horsetail is deprived of the ability to photosythesise it will eventually exhaust its reserves. More organically inclined gardeners use cardboard and newspaper. It must be constantly replenished because in no circumstance should equisetum push through.
I have no idea how many years it takes to eliminate equisetum by this method. I have turned to the experience of blog correspondent Sarah Stu and below quote her verbatim.
Unfortunately I haven't been at all scientific with the horsetail battle. As well as the cardboard I've used glyphosate, ammonium sulphamate, lime, wood ash, plastic sheet, upturned plant pots and root removal. The cardboard has become my preferred option, as it doesn't require a daily check, it's not as ugly as plastic, and it is improving the soil. In terms of success, again it's hard to say. Apart from not having counted the shoots, I've got rid of lawn and paving where it could hide, and we've had some very wet seasons that seem to have encouraged it to pop up in new places. It was never a dense infestation, but it was spread over a big area, so counting would be the only way to check progress. So although I'd love to say I'm making a difference, I think it's going to take a bit longer before I know!
Sarah, like me, makes it up as she goes along! I know that she will keep us up to date with her progress. It has been two years so far. I have suggested to Sarah that if she stands container grown plants on top of the plastic mulch they might look rather nice.
I must add a disclaimer that feeding the horsetail with potash and lime will be no help whatsoever.
I know that Sarah will confirm that in no way should plants be planted through the polythene or cardboard. The horsetail will escape! Many allotments are graveyards of old carpets matted with copious ground elder, couch and marestail. Testament to innocence.
Case study 5: exhaustion by repeated hoeing
My only actual experience of eliminating a difficult perennial weed by this method is couch grass when I was home as a lad sixty years ago. The previous occupant of our new home had a peculiar method of ‘controlling’ his weed. He rotavated his garden once a year! What a wonderful way to propagate couch. The garden was a vigorous monoculture!
I gained my love of the soil as a result of the intimate relationship I developed when forking it out!
Forking half the garden was enough for me and I read I could eliminate couch by repeated hoeing! Not only can you exhaust it’s carbohydrate reserves if you are sufficiently diligent it also runs out of axillary buds! In the case of this particular weed, hoeing quite deeply to chop part of the rhizome helps. The key to my success was being pathetically and pathologically motivated to not let a single blade of couch remain above ground for more than a week. It still took over a year to completely eliminate the couch.
I once told a former schoolfriend about this method. I saw him again after a gap of twenty years. “Remember when you said I could ‘get rid’ by hoeing, I am still hoeing and it’s still there!”.
Many York allotments are invaded by horsetail. Even if you do get rid of it, it comes back from a neighbour.
I suggest that hoeing can work as long a you are as obsessively compulsive as I was with my couch! Hoeing is an enjoyable and speedy operation. I only recommend hoeing if it is done very shallowly and unless your general weed control is as pathetic as that of most people - who have a solid mass of germinating weed seeds - you only sever the weed and do not hoe the complete surface. I have seen it recommended that at the start of your mission that an initial light forking-out helps. There is no need to remove the cut shoots when you hoe, they will not survive if cut at ground level. Consider your horsetail as a green manure that mines nutrients from seven foot down.
Case study 6: use of defoliant glufosinate-ammonium
A widely promoted ‘professional’ contact weedkiller is promoted to ‘curtail’ horsetail (my pun on the chemical’s commercial name). I looked up the dictionary definition and it defined ‘impose a restriction on’. Could this be the first case in history of accuracy in a pesticide name?
Now I have no experience of glufosinate-ammonium but I do know that like diquat (Weedol) it is a defoliant that introduces no active residue into the soil. Diquat is known as ‘the chemical hoe’. It rapidly kills plant foliage thereby weakening a perennial and killing most annuals. Its effect on a weed is no more or less effective than hoeing. Like diquat, glufosinate is not translocated down and does not kill roots. I am sure glufosinate-ammonium gives a spectacular kill of the leaves..... It just might be worth trying.
Case 7: Learnt at a Party in France
Added July 2015
Ammonium sulphamate – not to be confused with ammonium sulphate.
I recently met a lovely lady at a garden party and the course of conversation moved to mares tail. She had legally purchased on the WWW a supply of ammonium sulphamate compost accelerator. She had decided to use it a little early on her living mares tail.
She did not look like a criminal to me.
Although in the past ammonium sulphamate has been used widely for weed control by large organisations in conservation projects;
and previously shown by The Henry Doubleday Association to be very effective as a translocated herbicide against mares tail - albeit not approved now for organic gardeners;
and is thought to be very environmentally friendly on account of of its almost immediate degradation into a fertiliser when it reaches the soil;
it has now lost its Common Market licence as a herbicide.
Wikipedia emphasises that the licence withdrawal is nothing to do with lack of efficacy or safety. Wiki says nothing about bureaucratic bumbling and costs to a manufacturer of obtaining a licence.
No matter, ammonium sulphamate would appear to be at least as effective as glyphosate. My new friend waxed lyrical about it. She thought so highly she had also incriminated her neighbours. No use getting rid of horsetail at home if it creeps back from over the fence.
This would appear to be a parallel situation where in the UK it is legal to use iron sulphate on your lawn as a fertilizer but it is illegal to sell it as a mosskiller! (This suits the retailers very well).
Two garden reprobates you might wish to avoid
The scouring brush horsetail, Equisetum hyemale and the dwarf horsetail Equisetum scirpoides are actually sold as a garden plant and this idiot grows them. I use glyphosate to curtail it! It’s rather invasive. By my pond it looks rather fine and the young frogs that emerge from my pond love it!
|To the right of the top pond the E. hyemale and E.scirpoides are confined by the water on one side and the lawn on the other.(Well almost)|
|Equisetum hyemale even intrudes into my giant gunnera|
|Spot the fine clump of Equisetum hyemale and look around and spot invading pieces|
More on my suggestion that in undisturbed habitats horsetail is just a wild flower
|You can’t see horsetail here in this view of Tignes in the French alps. Neither can I. It is actually not uncommon but nobody sees it|
|No, no equisetum obvious here either!|
|Where a habitat has been disturbed and weeds lack natural competition they can build up their resources|
|This disturbed ground is still a strong stand of rose bay willow herb many years after the site has been abandoned.|
|I have NEVER seen equisetum in this section of Worsbrough cemetery garden. Formally under a cover of six foot bramble for more than forty years horsetail would not have survived|
Dancing with horsetail sporesThank you Sarah Stu for this charming and hilarious tube link
This video is the most amusing thing I have ever seen.
added July 2015Several readers have expressed concern about the copious number of spores produced by their horsetail. As far as I am aware they are insignificant in spreading the weed in your garden. In nature establishment from spores is very slow and takes many years. Think how difficult it is to get fern spores to establish. Think also the number of spores that will float into your garden from elsewhere without establishing
I can't resist publishing this picture from reader Alisonc. These are the things that can come up from seven foot down
For what it's worth weedol mentioned above has changed into several new formulations and is now merely a brand name.