Send in the goats: Alastair tackles Japanese knotweed

Sixteen members joined us this Friday, with 12 referrals passed and £10,300 of business generated from past referrals. Another strong week for the group.

This week’s 10 minutes came from Alastair of Butler Procter, who told us everything we never knew we needed to know about Japanese knotweed.

It arrived in the 19th century, brought from Japan by Philipp von Siebold and taken to Kew Gardens. The Victorians thought it was beautiful and planted it everywhere. We’ve been living with the consequences ever since.

The real trouble is underground. In a good summer the plant can grow up to 10cm a day, while its roots can go three metres down and spread seven metres across. It won’t grow through solid concrete, but it will find the smallest crack and make the most of it.

That matters for property. Alastair explained that RICS guidance suggests knotweed can take 5 to 20 per cent off a property’s value, and that he works to 30 to 50 per cent where it’s well established. If it spreads next door, there can be legal liability too.

So how do you get rid of it? Herbicide treatment works, but typically takes three to five years. Digging it out is quicker but very expensive, and the tiniest piece of root left behind will reshoot. Whatever you do, don’t cut it, pull it or compost it.

Then came the surprise third option: goats. Given time, a goat will happily eat knotweed into submission. Alastair told us about a mill owner who penned off an affected plot, put a billy goat in, and now has no knotweed at all.

He finished with a warning about two garden favourites. Buddleia roots may do more structural damage than knotweed, and bamboo belongs in pots, never in the ground.

Thanks to Alastair for a talk that was as entertaining as it was useful.

Ingroup meets every Friday from 8am to 9am in Kendal. If you’d like to come along as a guest, get in touch.