Keeping Down the Weeds

My allotment is not as tidy as I'd like it to be just now. Somehow my allotment energy runs rather low in August and after rushing around to keep up with all the jobs for several months I've been tending to slow down lately. Consequently, the grass is getting a bit long and the weeds are popping up behind my back!

So what of the theory that growing perennial vegetables is easy? Well I'm still subscribing to that theory! Half the work has come from sowing and planting annual vegetables and then keeping them watered in this dry summer. The other half has come from areas of the allotment where I have grass paths to cut and areas of bare earth to weed. Where I've managed to establish clover on the paths instead of grass, and a cover plant growing around the stems of the perennial vegetables and covering the bed, harvesting the crop has been practically the only work.

So that is my plan! To transform all the grass paths to clover paths - possibly keeping a central grass path - and get ground-cover in place on all the beds.

Ground-cover plants are one of the facets of a forest garden which help to make them self-maintaining. I'd love to have a forest garden but it wouldn't fit within the constraints of our allotment rules. So where the forest garden features ground-cover as one of several layers in a blended diverse mix of plants, I'm aiming for a simpler food crop + ground-cover with the latter growing at a distinctly lower level. You see I have to be careful how I garden. I've learnt the hard way that, where I see useful plants, allotment authorities may see weeds! My solution is to plant in such a way that, despite the ground-cover, a traditionally-minded onlooker will still be able to distinguish the crop and the vegetable bed neatly bounded by the path and hopefully be satisfied.

Bare soil around crops was traditionally advocated in annual vegetable gardens to avoid competition for nutrients and water. The role of organic mulches for water conservation and to save on weeding is now widely appreciated but ground-covers are still sometimes viewed with suspicion. But they can work very well in a perennial vegetable garden. Because perennial vegetables grow over several seasons they have time to put down deep roots and can co-exist quite happily with a shallow-rooting ground-cover.

Three photos illustrating different methods of weed control: hoeing potatoes, mulching and ground-cover

Courtesy of (left to right) OakleyOriginals, hardworkinghippy, fishermansdaughter

Keeping down the weeds:
hoeing potatoes, mulching potatoes, buckwheat ground-cover around Jerusalem artichokes

There is a simply enormous choice of ground-cover plants to choose from even with my personal proviso that they should be very low growing. The ones I've established to date are really an outcome of what I've managed to beg, borrow and steal or what have otherwise come my way. In the meanwhile considering what might be the perfect ground-cover for a given vegetable crop is always good fun.

Perhaps the quintessential ground-cover might have the following properties:
weed-excluding
shallow-rooting (to avoid competition with a deeper-rooting crop),
fast growing (but also easy to control)
beneficial or at least not deleterious to the adjacent food crop
suitable to the available light conditions and soil
perennial (to avoid the need for replanting - although enthusiastic annual self-seeders replant themselves and may work well around root crops where there is ground disturbance at harvest)
nitrogen-fixing (so the crop may get extra rations from the nitrogen the ground-cover fixes from the air)
edible (for extra yield - although other qualities like attracting insects to pollinate fruit plants or keep pests in check can be equally worthwhile)
evergreen (giving protection to the soil-life from the harsh elements in winter and offering some weed exclusion early in the spring)

An effective shallow-rooting ground-cover around the sea kale on the plot has been creeping Jenny (Lysimachia nummularia). It is very ground-hugging, weed excluding and attractive. It is also easy enough to control.

Creeping Jenny keeping down the weeds around sea kale

But I can't eat it! I can eat wild strawberries though which can also form a good mat. I put these around the perennial brassicas at first because they cope well with shade but then read that brassicas and strawberries are bad companions (have a deleterious effect on each other's growth). Rather than wait to discover whether this was true I moved the strawberries to the tree onion and potato onion beds earlier this year and they are beginning to send out runners.

Wild strawberries around a tree onion

I've planted Siberian purslane around the brassicas in place of the strawberries as it is another perennial edible shade-lover and spreads quickly by self-seeding.

Siberian purslane is evergreen, perennial and edible

I think that the onions will push through the strawberry mat easily enough in spring but I'm not totally confident that the same is true for another combination I'd like to try. I'm propagating silverweed (Argentina anserina) which has a shallow edible root to maybe plant around the deeply rooted asparagus. They will both appreciate the sand I've added to the clay soil and I like the idea of the two feathery foliages growing together. Silverweed sometimes forms a very dense mat though so I think I'll keep it to just one portion of the asparagus bed until I see the asparagus spears pushing through it in spring. And I'm not very sure how shallow-rooting silverweed really is - will digging around to harvest it damage the asparagus? Perhaps it might actually be better around the skirret and I could harvest both roots at the same time.

Silverweed (Argentina anserina)

I'm attempting to grow lawn chamomile (Chamaemelum nobile 'Treneague') around the Babington leeks thinking that its anti-fungal properties may ward off the leek rust which can be a serious problem on leeks and can over-winter on perennial ones. Leek rust killed off the top-growth of the Babingtons early in their first year. This year they got it but kept growing and are now 5-6 feet tall and forming their top-set bulbs. The chamomile is growing very slowly at present and doesn't like the dry conditions but I will split the clumps this autumn and distribute them evenly over the bed to help full cover develop.

Lawn chamomile (Chamaemelum nobile 'Treneague')

Other ground-covers I'm trying are bugle (Ajuga reptans), an early-flowering nectar-rich plant which is coping with the deep shade cast by the leafiness of the Daubenton kale; lamb's lettuce, an edible evergreen annual and keen self-seeder; and purple creeping thyme, which has germinated easily in a pot and being a sun-lover might be another good one for the alliums which cast very little shade.

There are other things to consider, one being how well ground-cover plants will stand up to me mulching the vegetables with compost to feed them and when would be the best time of year to do this. So plenty to do and think about before attaining the goals of a weed-free allotment and not getting tired out by August!

Ground-cover update here.

N.B. I sell a range of perennial vegetable plants on my website.