Weeds: Marestail

The weed referred to as ‘Marestail’ is also called common horsetail (Equisetum arvense). It is an invasive and deep rooted plant that grows via fast-growing rhizomes (underground stems). Marestail is a very primitive plant that was around before the dinosaurs. It reproduces by producing spores that are airborne and travel on the wind as well as by underground stems (modified roots called rhizosomes). This means it can be a tricky ‘weed’ to control.

Marestail’s Extensive root system—black string-like network of underground stems or rhizomes.

Marestail has separate non-reproductive and fertile spore-bearing stems. The fertile stems are produced in early spring and are usually brown in colour. These initial stems die back and the non-reproductive green stems start to grow throughout spring, summer and until the first autumn frosts. On an allotment, this plant tends to appear where little competition exists. It can be especially annoying when you take the time to clear your plot of other perennial weeds for marestail to show up in abundance.

Non-fertile green stems appear like mini Christmas trees

How to control Marestail

Repeated removal of the green sterile stems will deplete the plant’s energy reserves. Eventually this will exhaust the rhizosome and the plant will slow down it’s growth. Marestail has a flush of growth in early spring and at this time it also produces reproductive stems. Remove reproductive and non reproductive stem as they appear.

Option 1: Dig out the green stems throughout the growing season –repeatedly! It can take years and dedication. Ensure you remove as much of the underground structure as you can. This can go very deep (like 7ft!) so it isn’t always possible to get it all out, but try and follow the black rhizomes and get them out as thoroughly as you can. If using this method you need to be very thorough. If you disturb roots by digging, but leave sections of roots they will continue to grow. If roots have been chopped up the problem can be made worse. Also, under no circumstances, rotavate the ground where there is evidence of this plant. If you do this, every tiny bit created will produce a new plant and you will increase the in-festation drastically.

Option 2: Reduce disturbing the soil structure by ‘No Dig’ and use a trowel or pull stems as they appear. This has been very successful for us! Again, this requires some persistence, but our experience has shown that the less you disturb the soil structure and the more you continue to pull Marestail out it can signficantly reduce over just a few years.

Option 3: Try chemical control if you are happy to do so. The weedkiller glyphosphate, the active ingredient in Roundup, will kill marestail if you can create the right conditions for the plant to absorb the chemical. Due to the small surface area of the stem and the waxy cuticle on the outside of its leaves, the plant is well adapted to prevent it’s uptake. If you bruise the leaf by rolling it before application this can help. Other ideas include using a weed burner to slightly damage the leaves before application or mixing the weedkiller with wallpaper paste and us-ing this more viscous solution to help penetration. The weedkiller, Kurtail, which is based on the chemical glufosinate-ammonium, is claimed to be very effective against marestail. This chemical is licensed for professional use only.

The positive side is that, although marestail is annoying, you can still grow crops. It doesn’t smother plants like vine-growing weeds like bindweed. Many allotment plots have this weed –you can to learn to live with it and try and keep it in check. Marestail can also be used to make a liquid feed which is said be an effective natural repellent for whitefly and blackfly which is a hidden bonus!