What seems to be the ongoing issue around the invasion across some of the allotments. I have looked at potential options for the control and removal of this invasive weed.
Unchecked, it can and will spread like wildfire. It produces spores, spreads from the roots and even small pieces of root will grow into plants. In spring, brown, green shoots appear with small cones at the tips that produce spores.
Digging out these roots whilst an option will be a thankless task as in most cases the roots go down go down into the soil for up to 1.5 metres – yes, 5 feet. Horsetail, is a prehistoric, pernicious, spreading, perennial weed that can quickly colonise and take over large areas of the garden or allotment as we are becoming aware. It spreads through its black, creeping, perennial “roots” – underground stems or rhizomes. These grow quickly in the soil and can spread over great distances. Horsetail creates large clumps of upright stems that can smother and kill smaller plants below and surround larger plants, spoiling their appearance. The roots can grow in between those of cultivated plants, making them difficult to remove and control. After the spore producing shoots the leaves or tails appear. These will die off as autumn turns to winter and the roots sit there waiting for spring when they start the cycle again.
The main issue is that it cant be iradicated easily and will on average take up to two to three years to get on top of it, whist some manufactures of herbicides will advercate that they can get rid of it, it is only the stem that is being killed, the root system is much more likely to remain and promote more growth the following year, hence the reason that you need to keep treating it at additional expense. Putting it in to compost bins if you dig it out will only by all accounts let the root system become active again once in contact with the soil., burning it is the only sure way to stop any spread.
So can we control it with contact herbicides?
The problem is that the leaves of Horsetail have a waxy coating which makes it highly resistant to any contact 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.
Progreen have a product on the market called KURTAIL-EVO it is expensive and it is not a selective herbicide therefore it will kill anything it comes in to contact with and should be applied professionally, or at least wearing the correct PPE. https://www.progreen.co.uk
Agrigem have a product on the market called DIAMOND HORSE TAILWEED KILLER it will be effective against the following Annual Weeds, Bamboo, Bindweed, Bracken, Broad-leaved Dock, Couch Grass, Garden Weeds, General Weeds, Gorse, Horse Tail, Japenese Knotweed, Mare's Tail, Nettle, Pavement Weeds, Perennial Weeds, Ragwort, Rhododendron, Sycamore, Thistle. Again its expensive and will need to be professionally applied. https://www.agrigem.co.uk
So there are a few weed control options available, if you are to spray, then you need to spray with a systemic weedkiller, this is one that is absorbed through the leaf then moves down to the roots to hopefully kill them. As has been mentioned the leaves are thin and contain silicon making absorption difficult. To ensure the weed killer works effectively:
- Spray the plants when they’re growing actively, this is mainly from May to September/October.
- The larger the leaf area present, the greater the amount of weedkiller that can be absorbed and move down to the roots. So don’t bother spraying when the growth first emerges through the soil – wait until the stems are around 30-45cm (12-18in) high.
- Use a fine spray to thoroughly coat the leaves in small droplets.
- During the summer, spray in the evening to prevent the spray evaporating and to give maximum time for the spray to be absorbed. In spring or if overnight dew is forecast, spray earlier in the day to allow the spray to dry before dew falls.
- One application of weedkiller is unlikely to kill all the horsetail. You will need to spray once, allow the horsetail to die down, and then spray the regrowth again. Three or more applications a year, over a couple of years, may be needed to completely kill it, depending on how extensive the root system is.
- If anyone knows of or has had success in treating the weed, please let us know so we can share with others.
Allotment Garden: Vegetable, Fruit & Herb Gardening on an Allotment, General Gardening Help and Advice (allotment-garden.org)
The National Allotment Society – National Society of Allotment and Leisure Gardeners Ltd (nsalg.org.uk)
How to get rid of horsetail/marestail – Which? Gardening Helpdesk