Before we leave the veg garden at Tyntesfield, I thought I’d just share this bit of veg-growing geekery: just to demonstrate that it’s not only computer whizzes who get unfeasibly excited at obscure things that mean nothing to anyone else, this little patch of 1.5m high nondescript greenery had me jigging on the spot and getting quietly quite worked up while all around me were just wondering what the heck it was there for and hurrying past to have a look at the pretty orange pumpkins.

This is Tagetes minuta: aka the Mexican marigold. It’s a giant of a thing, well over head height. Unlike other tagetes, its flowers aren’t much to write home about either being small, yellow and nondescript: like ‘an impoverished pale yellow groundsel’ as Chiltern Seeds, one of the few who stock the seed, describe it.

But this in veg-gardening terms is the Hadron Collider of weed control. Totally cutting edge, and the very latest thing.

You see, it’s an allelopath: which is to say it emits powerful chemicals from its roots which inhibit the growth and indeed eventually kill any plants which dare to try and grow nearby.

Great Darwinian survival-of-the-fittest strategy: and coincidentally an effective poison against bindweed, couch grass and ground elder. I haven’t heard whether it tackles mares tail too.

Of course you can’t plant anything else while this natural weedkiller is growing: but if you have an area to clear sow it with Mexican marigold and it’s supposed to be a very effective way of doing it. Certainly better than the usual black plastic (which just makes the roots come to the surface in my experience: you still have to weed them out in the usual way and then they break and come back… you know the drill).

The reason I was getting so excited is because this is the first time I have seen it in action, properly growing in the ground. I don’t have an area in my own garden I can clear to give this a try (despite having the bindweed problem from hell) so I was delighted to find Tyntesfield’s gardeners are carrying out the experiment for me.

They won’t know results until the middle of next year: this has been growing in this patch all this summer and so we’ll have to wait till spring next year to see if the bindweed comes back. I will give them a ring in six months or so and find out how they got on. Watch this space.