Bindweed is actually a group of weeds, but the most common form you are likely to find on your plot is Hedge Bindweed (Calystegia sepium).
It is a vine plant that can quickly infest uncultivated areas.
Growing from underground stems and rhizomes means that bindweed forms a network of roots under the ground.
The roots are thick (they can be 4-6mm in diameter), a white/cream colour and are quite brittle.
Annoyingly, this means they are easily snapped and each small part of root can form a new plant.
Root systems can grow deeply within the soil. Depths of up to 20ft have been reported, but luckily most of the roots do tend to accumulate in the first two feet so are accessible.
Covering to exclude light (e.g. over winter) can stimulate roots to seek the light and grow nearer the surface.
One way to try and control the weed is to dig out the roots as thoroughly as you can. Try to ‘follow’ the root to remove as much as possible. Use a fork, rather than a spade to try and keep the roots intact. With this method you can remove the majority of the weed by the roots but with a bad infestation it may not be possible to reach deeper roots and over time these may return.
Other methods for control including using a glyphosphate-based weedkiller which must be applied to an actively growing vine. If you are happy to use this method spring is a good time to try this. Allowing new shoots to grow up a cane before applying weedkiller is effective. Remember, even if you do use weedkiller, it is unlikely to kill all of the root and other methods are likely to be required. Covering the weed for long periods can be effective, but for this you must exclude ALL light, which can be difficult in any allotment setting. Bindweed tends to spread under paths and patios meaning it can be an ongoing process to control this weed.
It is important to try and control bindweed as it has a tendency to smother your crops and severely affect plant health, quality and yield. The positive is that you can dig this plant out—it’s hard work, but do-able!