Allotment Growing

Vegetable, Fruit & Herb Gardening

Weeds and What to do

There is an old saying that ‘one years seeding is seven years weeding’. Unfortunately this is very true.

Most annual weeds spread thousands of seeds that lie in the ground until conditions are right then appear. Turning over the soil brings seeds from yesteryear to the surface and up they pop.

Luckily, most of these annual weeds are pretty easy to deal with. Just hoe through them, leave them to dry or collect them for the compost heap. Catching them young is most effective – better to hoe little and often .

There are other weeds that present far bigger challenges. These are perennial and live from year to year, As a general rule, hoeing them just cuts the top off and they pop back from their deep roots – it seems with more vigour as well!

For some weeds the only method (realistically) is chemical sprays but where possible I prefer non-chemical methods.

So to the tricky devils…

Nettles.

Nettles form a mass of yellowish roots, from which they happily re-grow. Now nettles tend to be full of goodness (yes you can eat young ones) both for us and the garden. Taking frequent cuts will, eventually, kill the plant off. If you have a patch of nettles in a corner, use them as a compost mine. Otherwise, dig out the roots and watch out for re-growth from the small pieces you are bound to miss.

Nettles seem to prefer an acid soil and liming to a PH above 5.5 or 6.0 seems to really slow them down.

Dock Leaves

Where there are nettles, you will find docks. They have a long tap root from which they will re-grow. You have to dig out the root and then kill it. You can either leave the root to dry out or drown them in a barrel of water to do this.

Be careful about rotovating where there are docks – the root cuttings will all leap up multiplying the problem.

Dandelions

Like docks, they have a deep root but are not quite so vigorous. Treat as docks.

And yes.. you can eat them as a salad if you're really hungry.

Bindweed

Bindweed (Convolvulus) is quite pretty with its trumpet shaped white flowers. It grows about a foot a second when your back is turned, strangling any crops you have planted. Under the soil it produces white running roots, which travel along popping up when you think you have got it.

Basically dig out the roots, even a piece an inch long is enough to start it off. Small infestations can be coped with by hand but if you have a serious amount then you probably need to go chemical.

Glyphosate or Amicide will kill it off after a couple of applications. You can either spray it or paint it directly onto the leaves. I have heard of allowing the leaves to climb up a frame and then spraying to try and maximise the amount of poison getting to the roots.

Couch or Twitch Grass

Couch grass (twitch) is another plant with creeping underground stems. Treat as bindweed.

Grows away from roots or bits of roots so rotovation is a great way to spread it.

Very susceptible to shading so you can kill it by covering with old carpet, black plastic etc.

Horse or Mares Tail

Horse or Mares Tail, Equisetum Arvense is, in my opinion, public enemy number one. It looks like it belongs in Jurassic Park and, unchecked, spreads like wildfire.

In spring, brown green shoots appear with small cones at the tips that produce spores. (Arghh – millions of ‘em) and it grows away from creeping thin brown roots that you can hardly see as they are soil coloured. Digging out these roots is not feasible – they go down into the soil for up to 1.5 metres – yes, 5 feet.

Later the ‘leaves’ or tails appear. These will die off as autumn turns to winter and the roots sit there waiting for spring. The leaves have a waxy coat, which makes the plant highly resistant to weedkillers.

Crushing the leaves to break up the coating helps weedkiller to penetrate and become absorbed but in large areas it is not so easy to crush all the leaves . However, glyphosate weed killer will have an effect and eventually kill the plant. You will probably need 5 or more applications. Knock it back, it re-grows and you repeat.

I don’t think you can clear this in less than one season.

Ammonium Sulphamate seems to be a far more effective weed killer. It can kill it in one application but may well need two. It used to be available as Amicide but now you need to look for a brushwood killer that incorporates it like Rootout or Deep Root. Just check the packet for ammonium sulphamate.

I’d recommend NOT digging where there is horsetail until it is dead for sure. Otherwise it just starts springing up from the root cuttings. Drying or drowning the roots prior to composting is a must.

I've been contacted by Mr Charles Bailey who points out that Horestail is correctly applied to the weed growing on land whereas Marestail is correctly applied to the weed growing in water.

He also puts forth an organic control method, which he says is effective.

Without resorting to chemicals you can control/irradicate horse tail by digging/forking through the soil when it is in the right condition: ie not too wet and sticky!

Once you have removed as much as possible, any that shoots is easily dealt with. Before it reaches 3 ins/7cm high, hoe off an inch below the surface.

Eventually the food supply in the root is exhausted. Let it get bigger than stated and food begins to be stored in the roots again, and round and round you go ad infinitum.

Never touch Horsetail with a mechanical cultivator. If you do you will understand why it has been around for 60 million years

Glyphosate

This herbicide seems fairly safe. It is systemic, being taken down to the roots and I understand it is deactivated by contact with the soil. It is not approved by UK organic standards but I heard some European countries allow it in organic standards. It is the main constituent in Round Up and Tumbleweed ready mixed.

Fairly cheap but don’t use that as an excuse to over use it. The dead weeds can be composted without the compost becoming toxic. Weed killers should always be treated with caution

Amicide

Amicide (Ammonium Sulphamate) was an effective weedkiller used for killing tree stumps and brushwood clearing. In effect it is crooked sulphate of ammonia (a chemical nitrogen fertiliser). The plant absorbs it, taking it to the roots and dying.

After 8 weeks or so, it reacts with the air to form sulphate of ammonia – adding a nitrogen boost to the soil. Re-planting is safe after 12 weeks. It may make the soil more acid – so check pH.

As with all chemical weed killers – read and follow the instructions very carefully. I forgot to add some detergent to the Amicide and it greatly reduced its effectiveness. I also find applying it to horsetail with a pressure sprayer, fine spray, most effective.

Unfortunately Amicide is no longer available so now you need to look for a brushwood killer that incorporates it like Rootout or Deep Root. Just check the packet for ammonium sulphamate.

Images Courtesy of Broad Leys Publishing.