New allotment with lots of thistles

[Colin]

Hi everyone,
We have recently taken on a very overgrown plot about 60% of which is thistles the remainder seems to be couch grass.
After serious consideration we decided against our principles (organic , chemical free) to use a weedkiller as a one-off to get us started.
The 'Round up' was duly applied and it slowly killed the weeds but the thistles seemed to thrive on it. So we have resigned ourselves to a)cover the worst part with carpet or anything we can get hold of or b)dig up every thistle on the plot, and there must be hundreds of them.
Reading books on the subject suggests that every atom of the plants must be removed from the soil to prevent an epidemic of unwanted growth next year (in a full time job this is not easy) so I suppose we must go for option a) and just use the couch infested area for the next growing season as the round up seems to have done the job on it.
If anyone has been in a similar situation or has some advice then please let me know.
Thanks.

[Allan]

There is no reason that a glyphosate treatment should fail to clear your thistle problem as it cleared ours, with the particular advantage that it will kill the creeping root system. You do not say which formulation of Roundup you use, if it was RTU in a spray gun I think there could be a problem inasmuch as it is not pure glyphosate but has added to it some fast acting ingredients which appear to give a quick fix but possibly could be killing the leaves before the glyphosate has reached the roots. I have had more success lately with the Bayer formulation (previously marketed as a PBI product)which takes some two weeks to act in the summer, possibly longer at other times but gave 100% results on all the weeds. You are asking at an unfortunate time of year as the thistle tops are dying off and so the roots will not be affected. My recommendation therefore is to lay in whatever you decide to use and have it ready for spot treatment next spring as the thistles emerge. If you use a plastic tube of some sort or a bottomless bucket you should with care be able to apply the weedkiller quite close to crops, but you will have to avoid any misting spray. Another way of doing this is aplplication by contact but not easy to do thoroughly. Do keep strictly to the instructions, too strong a solution could kill the tops prematurely and leave the roots.
Allan

[Johnboy]

Hi Colin,
I sprayed several patches of Thistles three weeks ago and it is only just apparent in the last few days that they are on their way out so do not despair. I do not use the made up sprays to which Allan refers because I find them far too expensive.
I am glad to hear that common sense has prevailed on you to give yourself a clean start and then go Organic. The other way round can give you years of work when you could be better employed tending your crops. Generally speaking you only have to treat once and on odd occasions twice with Glyphosate.
What is sad about this is that chemicals are all look upon as bad and just to confuse everybody new to gardening they are all referred to as 'pesticides' which of course is not the truth.
I adopt a 'Pragmatic' approach to gardening rather than Organic which means that I take every precaution I can but if they fail I am prepared to use a chemical treatment as a last resort.
This season I am happy to say that I have not used any pesticides whatsoever but I do use Herbicides but not normally on productive land. If a gardener does his/her job properly there should be no need for the use of weed killers on his land after first starting with a clean sheet. I use Peat and will use a man made fertilizer if I feel that it is necessary.
This puts me rather at odds with 'pure organics' which to my mind doesn't really work.
JB.

[Chantal]

One of my plots was inherited with a field of thistles over at least half the area. Being a newbie at this time, loathe to use chemicals and also without the benefit of all the advice on this forum, I dug them all out. I spent weeks clearing the ground of every tiny little piece of root. When a load grew back I did the same thing again and by the end of the year had it all under control. Only one or two thistles poke their head through my soil now and are rapidly dealt with.

However, now that I know about Glyphosate (I use the farmer's variety Glyphogen) I wouldn't hesitate to blast the wretched things if they came back in quantity. As JB says, they do take longer than other weeds to die and I sometimes find that although they look OKish on the top, the roots are starting to rot.

Stick with it and you'll soon be rid of the hateful things. Oh, and whatever you do, don't compost any of the roots that have any life left in them.

[Johnboy]

Hi Chantal,
Once Thistles get a hold the roots go way way deeper than any cultivation and to dig them out is not exactly a waste of time but they are likely to reappear maybe a couple or more years later on.
The ones I have treated are in what was a Barley Crop and suspect that the Barley seed was full of Thistle seeds as they have sprung up this year all over an 18 acre field which erstwhile had none.
JB.

[John]

Hello Colin
I know that it is very tempting when you have just taken over a new patch to blitz everything as soon as you can and get on with the growing but I think you need to take things a bit steady.
Glyphosate works by being translocated to the growing points of the plant where it then does its deadly work. At this time of year movement through the plant will be slow and so glyphosate wont be very effective. It works best on strong new active growth and this means springtime. There will also be an enormous amount of dormant weed seeds there and a spring application will catch these as well.
I would go over the plot from now on and dig out the worst of the perennial weeds then strim/brushcut it or use a rotary mower to knock everything right down. Work a section by hand through the winter so that you can use this next year for some cropping but with the rest of the plot regard it as a cleaning and clearing year. A second application of glyphosate may well be needed to deal with any regrowth. I know all this sounds a bit too long term but by this time next year though all the soil should be in excellent condition for years of weed-free growing!!!

John

PS Don't do what I did and rotovate it - I'm still digging out thistles after nearly half a lifetime of digging and delving.

[richard p]

another approach recognises that deep rooted weeds such as thistles have a role in bringing minerals up from deep in the subsoil and the growing and rotting roots help to open up the soil structure, to this end the weeds are allowed to grow then strimmed or hoed before seeding and allowed to rot in place. it can be viewed as turning a problem into a managed resource.

[Colin]

Thank you all for your sound advice.
I was so encouraged I went and did some digging. It wasn't easy cutting through the spaghetti-like grass roots but it was good excercise on a fine day. From your comments I now know where I went wrong with the Roundup.
After cutting down the 2-3ft high thistles with a brush-cutter, the resulting stubble did not have enough leaves to absorb the weedkiller so now they are laughing at me
So I will be patient and get the buggers in the spring!
In the meantime I'm going to cultivate the spaghetti and hope that it turns into something more useful!
Thanks again,
Colin

[Allan]

Glyphosate is also useful on other perennials, dock, dandelion, both sorts of convolvulus, buttercup, cinquefoil, equisetium using special technique, brambles. The RTU form is very handy for spot treatment but it is expensive on large areas.
I have been refilling those handsprays for economy, it keeps better when diluted than they tell you but false economy to keep more than a month or so.
I now have 4 Bayer 5-litre battery powered sprayers which were bought for reasons of arthritis, two are very useful just on clean water.
Allan

[bottomleypots]

Hi,
I was brought up on hill farm in yorkshire and my grandad used to tell us;
"Cut a thistle in May and a 1000 will come to its funeral day,
Cut a thistle in June,is far too soon
but cut a thistle in July and they'll all die!!"
It seemed to work on the grass land -might work on the allotment who knows??

[Allan]

Grandad hadn't heard of glyphosate.
If you are going to cut them at all the nearer you can get to the flowering time the better as the plant's resources have gone into the seeds,but it is very critical as it is no good doing it once the seeds are set if the top is to be left on the ground, even a day could make all the difference and you will still get viable seeds on the ground. Our farmer keeps missing the right time by a few days, so the grazing still has new thistle seeds each year. Of course if you could take the tops away and burn them that would be different.
One disadvantage of glyphosate is that it isn't very nice having to dispose of dried dead thistle plants, they are very prickly so I favour spraying them as soon as they are any size, even if an extra squirt of weedkiller is necessary later on, there is then little to dispose of. This is where the 750 ml sprayer is useful as you can keep one at hand while you work. Even a fiver on a RTU sprayer isn't all that bad for the year, it is less if you buy other, not fast, formulation.
Allan

[vivie veg]

This year having struggled for an afternoon to clear a 10 foot by 20 foot plot of thistles and nettles by digging them up and still had about 10 times more to go at, I gave up organic aspirations and bought some Glyphosate and sprayed away. After about 2 weeks they showed signs of dying, but before I got around to planting, more thistles were coming up, so I repeated the spray, then a fortnight later the thistles and nettles died off, but came up again so a third spray went on.

Eventually I planted my squashes and marrows, as I could not wait any longer for the weeds to be killed and managed to squeeze in a few sweetcorn plants, thinking that they would grow taller than the thistles anyway. I managed to get a good crop of marrows and squashes but have to dodge the nettles and thistles. I have one area that I did not plant up as I could not get rid of the thistles.

BUT the area that I dug over, pulling up the roots has remained nettle and thistle free. I did give it a dig over with the rotavator in April Approx a month after digging up the nettles and thistles.

I also had areas covered in black and white polythene. This had been down for a year and not only were the weeds suppressed but the ground was lovely to rotavate. I think I will stick to this method for future weed eradication.

[Allan]

Well done, VV, persistence pays. If you had waited until all the thistles had emerged you might have managed with fewer sprays but as long as you cleared them that's what counts.Next year watch out for any new ones that you often get from thistledown that blows around in the summer, it is possible to dig these out while they are really small.
Allan

[vivie veg]

Allan,

The point is I DID NOT clear the thistles, after 3 sprays approximately 3 weeks apart I gave up as I needed to plant the squashes and sweetcorn!

The only thing that worked was the manual digging up of the roots in late march followed by rotavating mid April and black plastic!

[Allan]

The point there is that of course you cannot kill any thistles until they emerge and that will not have finished for all by late March. Only sodium chlorate will kill roots with no tops but then you cannot plant for at least 6 months. Even so it is perfectly feasible to kill the late emergers among your wanted plants if you apply glyphosate by contact e.g. by daubing, or the way I do it is with a cut-of drinks bottle over the weed and spray inside that.On big weeds I have a red bucket with the bottom removed to confine the weedkiller to the weed. You have to be reasonably careful, no wind if outside and use droplets or jet but I have yet to see any unwanted damage.