Sunday, June 1, 2014

On the attack - early summer weeding

A day spent in the garden – weeding. Having been away for 2 weeks there is a lot to do at this time of year. This is the crucial period, to stop things seeding. It is also a very good time to evaluate what we're doing. And – more generally to reflect on what naturalistic planting is, and how realistic a proposition it is.

I must admit I have a slightly bipolar relationship with the gardens – sometimes revelling in its rich assortment of plantlife that very largely looks after itself (and wildlife, like the almost deafening sound of bumble bees feeding on Symphytum caucasicum), and at other times feeling almost despairing at holding the ring against an incredibly aggressive weed flora. I sometimes worry that if I don't get on top of things, grass and nettles could overrun everything in no time at all.

The planting is largely made up of robust perennials which can indeed look after themselves: some of them stay more or less the same size, others spread out to form solid clumps, some seed around and are gradually insinuating themselves themselves all over, some seem to get overwhelmed – either by stronger-growing neighbours and/or weedy spontaneous species.

The best way to keep unwanted weedy wild species at bay is to have as complete a vegetation canopy over the soil as possible. A lot of my planting is a lot more dense than most people's. Eventually, I aim and intend that it should be as dense as natural vegetation - but with a composition which is aesthetically pleasing for as long as possible. At this density, some garden plants have a different form to how they are grown more conventionally - for example many clump formers like geraniums and astrantias form long stems which wend their way through other plants. This method of growing does not suit species with ground level foliage, like asiatic primulas, which will not tolerate taller things growing above them; primrose/polyanthus/oxlips though seem ok, as their become semi-dormant in summer and don't mind being crowded and overshadowed.

We have an incredibly aggressive weed flora: pasture grasses, creeping buttercup, stinging nettle, dandelions, wood avens. My recent visit to the USA has illustrated just how successfully some of these have joined/invaded the North American flora – and yet not a single species of North American origin has become a problem alien in Britain (a few have, possibly, in mainland Europe). Weeds are a problem because if not dealt with they would quite quickly out-compete almost all garden perennials (and many natives too).

Our garden gets high rainfall, the soil hangs on to it, and we have a very high level of fertility, so if a plant likes it here, it grows incredibly vigorously. Such a situation is exploited most effectively by the species which can make the most of the resources available – which varies enormously. Those which can turn nutrients into leaf and root the fastest tend to be the most troublesome.

 But what makes a plant a weed? Such a question leads onto my idea of the hierarchy of weeds.
  • Public Enemy Number One(s)
  • Those to eliminate as much as possible, but not necessarily totally
  • Wild Plants which are not really Bad Weeds, but Which I Don't Like
  • Minor nuisances, usually tolerated
The list can be cross-referenced to the different parts of the garden, where different standards apply:

The Wild Garden where Those to eliminate as much as possible, but not necessarily totally can be given plenty of scope (because the inhabitants of the wild garden will, for the most part, keep on top of them).

The Borders – where Minor nuisances, usually tolerated, are indeed tolerated, as well as a certain number of Wild Plants which are not really Bad Weeds, but Which I Don't Like are also allowed to get away with it.

Vegetable Garden, areas for annuals and test and nursery beds – have to be kept clear of almost anything and everything.
    Public Enemy Number One(s)
There are a few (very few) species which are so effective at utilising nutrients and turning them into growth which suppresses all else that they just have to go: dug out or Rounded-upped (or otherwise herbicided). The Stinging Nettle tops the bill. This is a very worrying plant, not just because it will get the better of just about any non-woody plant but because it is capable of slowly smothering the entire British non-forest flora. L
isten to this BBC podcast . Fed by nitrogen pollution, septic tanks and over-use of fertilizer, I have seen nettles advance over more diverse floras here since we moved – in places where they must be being fed by nitrogen pollution (caused by car exhausts primarily). It was worrying to see them in the Pacific North-West recently too. Mind you, they make nice soup!
Cocks foot grass (Dactylis glomerata) is another, an aggressive tussock former which eliminates all competition.

Those to eliminate as much as possible, but not necessarily totally
 The Creeping Buttercup (Ranunculus repens) is a good example here, which flourishes on our damp soil. It makes establishing anything difficult, and can cover ground with frightening speed. However I cannot help but be charmed by its yellow flowers at this time of year, which when dotted around between and beneath other plants are undeniably part of the visual mix here. The fact is, most the stuff I grow gets bigger than it does, and so it gets out-competed, so it is simply not a major issue for the borders and certainly not the Wild Garden.

Wild Plants which are not really Bad Weeds, but Which I Don't Like
Horrible smelly Stachys sylvestris is one, can't remember its English name, runs but not a real nuisance, if it had better flowers I would have no problem with it. Ditto Wood Avens (Geum urbanum). To be honest, i can't see it out-competing most of the things I grow, as it does not spread but stays very tight, it just seeds so such, and doesn't earn its keep, but there is no way I can do much more than keep its numbers down. There is a grass too (not very good at IDing grasses), I think it is Agrostis stolonifera, which seems to get everywhere, but it is so light and it seems very uncompetitive that I can't get too overexcited about it. Trouble is, these are not problem plants, but they seed so much, and in quantity could become competitive against desired plants in spring. If the worst comes to the worst they can be hoed off in dry winter weather (on the rare occasions we have it) or Rounded-Upped if they are growing en masse at this time. Most native weedy species start into growth before non-native perennials, which is part of the problem as it gives them a competitive advantage, but it does mean you can see them and eliminate them.

Epilobiums/Willowherbs too, but they are quite easy to pull out, or hoe off the seedlings. They don't compete and as they canopy builds up they lose their habitat.

Plants that some people think are weeds but I don't (at least in perennial plantings).
Hairy Bitter Cress, little speedwelly things,

One final point, because the garden vegetation is very dense, which is one of the visual delights, plants tend to support each other - weeding or stepping into plantings can cause gaps, plants to collapse - and they can take some time to pick themselves up again and sort out their positions again. Something to think about, when we have a garden opening coming up, but then if you don't deal with those creeping buttercup plants now they'll seed and spread.

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ProfessorRoush said...

Noel, I should send you some Common Dayflower (Commelina communis)to see if we can give back some weeds from North America to the old country. Yes, I've got problems with the European nonnatives, but dayflower is more difficult to eradicate than bindweed here.

sally said...

I love your weed classifications, great article!

Met oog voor schoonheid said...

Noel, what is Stinging Nettle. Could you please use Latin names too, for f.a. Dutch readers like me?

Noel Kingsbury said...

Sorry, Stinging Nettle is Urtica dioica. ouch!!

Met oog voor schoonheid said...

Thanks. Interesting post!

Paul Steer said...

I too have an abundance of nettles, but they are easily dealt with in the borders in spring, the spreading roots can be teased out, I leave a significant amount of nettle, not just because they make great soup, but because they are an essential food plant for a great number of the caterpillars of our native butterflies, so are the other weeds you mention.

Unknown said...

Hi Noel, interesting topic on weeds. One thing is for sure, don't let them outrun you.

Roger Brook - No Dig Gardener said...

I grow a commelina that freely self seeds but I doubt if it would ever be a problem as a weed in the UK. I agree very few introductions make it into your severe category of weeds - although I am fully aware some none natives such as japanese knotweed worry some folk!
Our worst weeds are natives such as bracken and bramble.