Rain gardens are a relatively new approach on how to deal with water in the environment. In the last 10-15 years, there has been a big rise in the use of SUDS (sustainable urban drainage systems), the practice of delaying the entry of rainwater into the drainage system by the use of swales, ditches and ponds. However, this is generally the domain of engineers who are mostly concerned with their pipework; rain gardens, on the other hand, do the same thing, but are equally concerned with aesthetics and ecology – and so are far more exciting. Easily applied to the domestic situation, but the concept works just as well in urban and commercial design. In fact, WSUD – Water Sensative Urban Design – looks set to take on this wider role in the municipal environment, possibly replacing SUDS.
Having built many water gardens in my life, I decided (in 2010) it was time to build a rain garden in my own home, where I could enjoy it and also monitor its performance. These pictures show the just-completed garden, only a few months old; it also rained right on cue and appeared to be working well!
So what is the “philosophy” of a rain garden: why build one? Well, flood prevention is one answer; if you have ever experienced floods in your area, you have directly or indirectly contributed to them. If the rain didn’t fall on your actual roof, it fell on part of the urban fabric that has been built to support you. Another answer is to re-charge ground water supplies; many urban areas have groundwater levels that are dropping due to the fact that rain cannot permeate the land where it falls (95% of urban land is impermeable). Water tables are also dropping because we are abstracting water far more quickly than it is being replenished.
Rain gardens are a great way to re-connect with nature, opening you up to the experience of natural rhythms and process. It will sit there quietly in hot weather, dry, yet still a micro climate for flora and fauna that like a little extra moisture, in the lowest parts, providing free drainage to the drier areas. When it rains, though, the garden comes to life; water from the roof of your house, instead of disappearing down the drain, starts running into the areas of dips and dry ponds you have created, perhaps having topped up your rainwater butts first. Gradually pools start appearing and maybe in a heavy downpour, water starts running between them. How long it then takes to dissipate will depend upon your soil type; I’m on an alluvial soil, so it is very free draining; on heavy clay it might take days for the water to disperse, and this might mostly be from evaporation. This is good too as it helps re-charge the local hydrological cycle, which is also severly lacking sufficient moisture content, and may well be a significant but overlooked driver of climate change. If you have limited space or can’t allow water to rise beyond a certain level (after all, you don’t want to move the flood potential from somewhere further away, to your own home!), then you might need an overflow which puts any surplus water back to drain, or perhaps (and preferably) to another part of the garden. You will have still considerably delayed the timing of water going to drain, as well as the volume.
In my garden, I have disconnected one of the main roof downpipes (which it turned out was blocked) and used an old steel channel I found when they demolished the adjacent dairy. We have old cast-iron downpipes so I bought a 90° bend and fitted that to direct the water into the chute. I then dug a channel and partly lined the bottom with plastic, because our ground is very free draining and I wanted to connect this to an existing small water feature, so that this was topped up by rainfall. Surplus water is then dispersed to the sides, through the planting. If I were designing this from scratch, I would put the pond before the raingarden, so this was topped up first. Having said that, this section of the garden has always been incredibly dry and I’m hoping that the ground will, over time, recharge itself and things will grow better. This dryness is evidenced by the fact that we have a young fig growing well, right by the downpipe.
In periods of heavy and prolonged downpours, it may be that the pond will overflow; this will happen at the back and will disperse out away from the house under the bushes. With our soil, I don’t see the need for any further overflow drainage.
The roof section that feeds this downpipe is about 50m2, south facing. We get on average 50cm rain per year, so this should capture 25m3/year. This morning in light/medium rainfall, the chute was delivering 3 litres/minute (nowhere near the rate of a hosepipe). The rain garden is about four metres long and I’m not sure how to measure the drainage rate of soil, apart from having the plasticity index measured in a lab but over time I will use these figures to try and calculate how much water is passing through the system; in theory 25m3/year.
I was sent this picture (right) of a rain garden I designed for a client around the same time that I made mine. What a great picture, it gets right to the heart for so many issues about life, play, learning, experience, the elements. We tend to over-design our environments for safety, yet end up sanitizing them to the point where life becomes uneventful and we loose the richness and diversity that being connected to nature gives us. On a rainy day most kids are sat in front of the TV; I think this as a much better option…
The soil in this raingarden is a heavy clay and so holds the water for longer. It is bigger than mine and would need to be to increase the percolation area. You can also see that mine is more planted and this is again a condition of its function – theirs was designed to be a play space for the children (which is why I’m so pleased that it is successful). When they have grown up, it can be planted more intensely. It also created a feature in an otherwise rather awkward, narrow, North-facing space.
Rainwater management isn’t just for large commercial or public-realm sites, it can be done in your own garden too, with multiple benefits to environment, garden, wildlife and of course, you.
The emergence of the idea of resilient planting is a response to a number of different pressures which all have one underlying cause – climate change. Whatever the cause – and I’ll get on to that later – I see it as the most exciting change to the way we design our gardens and landscapes.
Last year we had one of the hottest summers ever recorded and it serves to heighten awareness of the vulnerability of some plants and garden styles to the increasingly erratic climate we are dealing with in the UK. We seem to swing from one extreme to the other, and this is only likely to get worse. I’ve witnessed a number of stressed plants in my own garden but feel relieved that most have thrived throughout the heat, without any watering on my part. this is down to soil, drainage, micro-climate and above all, plant choice.
Ballota pseudodictamnus, a Mediterranean sub-shrub with grey, felted leaves, loved by bees.
We garden on an alluvial coastal plain, and are fortunate to have a very free-draining soil overlying a clay substrate. It gives us fertile soil, great drainage and a moist sub-strata within the reach of most plants (many areas around us are of much heavier clay). A large section of our front area used to be a paddock with a rubble driveway and this now forms the basis of much of my dry garden. Some rubble was removed and topsoil added, but a lot of areas are still rubble-strewn, not unlike some rocky soils. The down side of all this is super-fertility and a soil filled with weed seeds, bindweed and couch. To be honest, I’d have preferred a poorer soil.
When thinking of resilient planting, we have to match our plant type to the environment; we also have to think, long-term, of how our environment might change in the coming years. This is not so important when dealing with short-lived plants such as herbs, sub-shrubs and perennials, but is super important when dealing with long-term structures, especially trees. This is doubly true when we look at the potentially disastrous effects of imported pests and diseases that we are having to content with. Climate change, especially milder winters, mean that exotic pests are happily making a home here and wreaking an unintentional devastation to trees such as our native ash and even oak.
Phlomis russeliana, after flowering. The stem leaves have since dropped, leaving a brown, architectural structure.
No-one can say exactly which way our climate will go as the world hots up; we know we (in the UK) will always be maritime, because that can’t change, but as the Jet stream (wind currents) varies and the Gulf stream (water currents) weakens, we don’t really know what kind of climate we’ll end up with. We can only plan for extremes, and select our planting choices with that in mind. In this respect, the “new perennial” or “naturalistic” planting isn’t necessarily going to be the toughest choice as they come from a continental climate which generally have hot summers and very cold winters. Prairie plants tend to get out-competed here with our mild winters and grasses and forbs that can grow all year round, given mild conditions. The aforementioned fertility (at least in my garden’s case) also doesn’t help as wildflower meadows/prairies tend to have poor soil which helps keep the grasses from assuming dominance. During the heat-stressed weeks, I noticed that where I have perennials like Echinacea and Veronicastrum (in moister areas than the dry garden), they suffered from the lack of water. which resulted in the Veronacastrum flower spikes looking stunted. for more moisture-demanding planting, sub-surface irrigation using harvested rainwater might become a necessity.
To my mind though, if you need irrigation you’re working with the wrong plant-types, trying to grow plants that can’t naturally cope with the conditions that predominate. Save your water for the newly planted and the vegetable plot and for this, consider rainwater harvesting, rather than mains. When selecting plants, see what grows well, both of native and non-native origins and build adaptive micro-ecologies. Our climate is changing faster than the current ecosystems and ecologies can cope with and we need to do whatever we can to build new planting that is of maximum benefit to local wildlife, as well as ourselves.
It’s an exciting time to be a gardener, for there is no place now for the self-indulgence and nature-control-freakishness of the past. What there is a the possibility of co-creating new ecologies that adapt to changes, halt decline and make our local wildlife vibrant and healthy.
Along the way, we can create the most stunning of gardens!
In my previous post I talked about a regenerative planting methodology for urban landscapes, in which I suggested you would manage, rather than maintain your planting areas. So how exactly do you you do this? Both involve work and the difference is a subtle but important one, in both attitude and application. Think urban forester rather than garden pruner. The picture above illustrates this perfectly, so let me explain.
It shows two hazels in my garden, both planted as young bare-root trees in the winter of 07/08. The one on the left was coppiced down to the ground in the winter of 12/13, the other has been pruned to keep a structure of older wood, with all suckering growth removed annually. What is the difference? The coppiced hazel has been less work overall and has not been touched since it was coppiced, the pruned tree has been pruned annually, which was not great amount of work but this is just one tree. If there were a hundred, it would be a different matter. The main difference is that the pruned tree has catkins, the coppiced tree does not, but I think this is a difference of genetics, rather than pruning technique, as they have always been like that. The shape of the pruned tree is also wider in its spread and will become gnarled as it gets older.
So in terms of management, if you go the coppice route you do nothing much to the trees except coppice them every 4-5 years. I would suggest that 50% of the trees are coppiced so that not all structure is removed at once. Notice that the growth of the coppiced hazel is straighter, making for a productive yield of canes and poles that can be used in the local community. Other trees that can be coppiced include sweet chestnut, lime, alder, ash, willow and hornbeam. Birch and oak will coppice, but from young trees only. Willows and dogwoods grown as bushes for their winter colour can be coppiced or “copparded” (inbetween coppice and pollard) to around 300-600mm every two years to keep the winter stem colours strong.
Salix elaeagnos (foreground)
By adopting such techniques in our larger masses of urban street planting and parks, we would deliver a more biodiverse, beautiful and biophilic interaction for all concerned. It would also cost less both to establish and possibly to maintain, than traditional planting. The above willow is beautiful and graceful, yet I have seen it all too often used in municipal car-parks and reduced to a-n-other shrub that is caressed all to frequently with the indifference of a hedgetrimmer.
Time to re-wild our inner selves, and our urban landscapes. We can do so much better than the average landscape we see in our towns and cities.
Curiously, I’ve never really written about green roofs, yet they are an important part of the urban greening scene and definitely a part of my “building biomembrane” concept. Perhaps it’s because the subject is so well covered by the commercial sector and various organisations; far better than green walls but then, they have a twenty year head start.
And twenty years ago, I was putting green roofs into some of the landscapes I designed and built. Here’s one in my own garden, on a wood store: the one at the back is an 18 year old turf roof, with soil and grasses, such as was common in those days. There’s a lot of Sedums, Sempervivum, bulbs etc that have been added over the years, or found their own way there. The roof to the front is about two weeks old, consisting mostly of Sedum album, which was growing prolifically in a graveled part of my garden where I didn’t want it. I put a layer of soil and compost under it and slapped the darn stuff down!
I also have another Sedum/succulent roof over my porch, which is much more akin to a modern extensive green roof, with a mix of compost and expanded clay pellets (ie lightweight aggregate). It is much less prolific and to my mind, less successful therefore. I used to be quite adept at building hobbit-like turf-roofed garden structures from chestnut and reclaimed timber, such as this one, built for a show:
These days I like to do rustic with a contemporary feel, such as my current summerhouse, which I built last year. It doesn’t have a green roof, simply because it faces away from us so we’d never see it. It’s insulated and timber-lined inside, so stays fairly warm with a little help. The windows all came from a house up the road, so fitting my desire for recycling. Double-glazed too…
Of course, the best kind of green roofs are the ones you can use as garden or green space. I’m designing one right now which overlooks the Thames; an early concept modeled below. I’ll put more up on this as things progress…
Every morning I walk into the garden to let the chickens into their run; to do this I have to walk through a part of the garden. Today, I stopped in my tracks, in the middle of a particular section, which is my favourite part. I wasn’t thinking about the garden, or the plants, but in a rain-washed sky, they still managed to grab my attention somehow. This small area of gravelled path, herbs and perennials, just demanded my awareness.
The gravel garden with herbs and perennials
There used to be nothing here but a bit of hard-standing and grass, but two years ago I excavated some of this and created the borders; the only difference is the plants! This is what I would call the creation of an intangible element, where the essence of something is somehow holistic, giving rise to an overall, well, awareness, within a space of something greater. What I can’t quite get over, is that somehow, the plants DEMANDED my attention…
So I can’t quite define the overall feeling I’m getting from this space; if it is holistic, then the whole is, of course, greater than the sum of it’s parts. There are some great “parts” in there though, and I guess this is what makes the art of gardening. So I have some English lavenders, broad leaved sage (makes a low mound 6ft wide with no flowers), Perovskia, Verbina, Carex, Sea Lavender and Kale, Echinacia, Fennel, Rosmary Fota Blue etc, etc. All beautiful plants as individuals; collectively, they obviously add up to something else. The power of plants to make our lives feel better…
Having just written the post on Dubai, we go from the ridiculous to the sublime… my summerhouse, is of course, far more significant!
Weeks of heavy rain and flooding have proved one thing – it doesn’t leak! You haven’t seen it yet with all doors and windows, so here it is:
Needless to say, it’s not finished yet, with some painting to do to the windows, especially indoors. Internal insulation and timber cladding is yet to come, plus an electricity supply, possibly solar, although we’d like to have some heat in there for winter use. All the windows are double glazed, so it should stay reasonably warm.
This space is already in use and has greatly expanded our living environment – our old cottage gets too little natural daylight, and the summerhouse is West-facing, so a great afternoon spot, and positioned to get the last of the sun.
Of course, it would help if we could have a summer…
I’ve just posted up an article on edible landscapes, which originally appeared on my old site, thedesignodgardens.com. I want to gradually update and re-write some of my better stuff from there, so this is a start and an important one, for it shows the direct link between gardens and sustainability – that S word… you can find the article <a href=”http://www.marklaurence.com/articles/edible_landscapes.html”>here</a>.
So in one of those typically rain-drenched weeks (Jubilee week, no less), I decided to take time off and build a summerhouse. Well, you have to be an optimist, don’t you?
I had already built a deck to front it over the winter, from some oak planking I had left over from one of my very last landscape jobs, some years past. I had also salvaged some rather nice timber, double-glazed windows from a local house refurbishment that was going on in the village. So I ordered the timber, having done some back-of-an-envelope sketches, and got working. Below are the pics (as it’s raining right now) of things so far:
There’s much more to do, including making some doors from another pair of the windows, which will be a bit challenging. I also want to line the inside walls with timber and insulation and put a sedum roof on – all will help with temperature fluctuations… I’ll keep you posted on it…
Yesterday I introduced my fedge and polytunnel. Well, the first of these might be new to you; it’s a conservation term, used to describe an artificial hedge made from brushwood cuttings. I have quite a few willow in the garden which hadn’t been pollarded for a few years, so when I did them in March (before bud-break), I ended up with two problems; a massive pile of rubbish, and a rather exposed rear boundary, consisting of a section of low wall, and a high section. We know that a fox jumps up through the low section, to try his luck with our chickens (unsuccessfully so far). A fence was required.
With a bit of permacultural-style thinking,the problems solved each other; the fedge became the disposal solution for the rubbish, which meant we didn’t have to buy a fence – two expenses saved! Furthermore, it looks rather attractive with the willow-stem colours and it will become populated by ivy and the like, making a great wildlife haven. I just have to prevent the willow from rooting, if I don’t want it to…
And finally, here’s the coffee/wine section of the polytunnel. Hard work, all this veg growing…