Wednesday, 8 August 2012

Planting on banks and steep slopes: Part 1

Banks are always a problem, when gardening: rain erodes the soil, while failing to actually water the plants, and it can be really hard to get a good coverage of plants going.

In my experience, if terracing is not an option, it's best to get the shrubs in first, weeding around them until their roots are strongly established: then it's easier to get the understorey planted, once the shrubs can protect the smaller plants from rain.

But I like a challenge... and I have one garden which regularly presents me with a specific gardening challenge, that being how to establish new plants on what is basically a one-in-one slope.

It contains a lake (yes, I'm lucky enough to work in a garden with a lake) with steep banks virtually all the way round, as the lake is set in a deep valley. These banks are very steep, in places being more than one-in-one, which means that gardening on them is a bit tricky - I slip and scramble around on them like a mad thing, and I have been known to tie a rope to the barriers up above, in order to have something to hang on to. Not quite abseiling, but the same principle.

Over the last year we have had two rather different problems with the banks: today I'll focus on the Road Bank.

Back in March, we decided to tackle the problem of the north-facing bank, known as the Road Bank: there is a road up above, where people used to stop to admire the lake. I say "used to" as it has become very overgrown in the last couple of years, and the mature cherry tree suddenly sent up dozens of suckers. These have become hefty young trees, giving the brambles something to wind around and forming an impenetrable mass.

Here's a snap taken back in March, from a precarious perch towards the top of the slope.

As you can see, not a lot of planting remains, just a mad tangle of brambles, and some uninspiring Lamium.

Part of the problem is that the bottom of the slope used to have a two-foot high wooden edging to it, marking the end of the slope and the beginning of the lake path. Three years ago, this wooden edging was rotting away to the point where I could no longer climb up over it safely in order to get up the bank to weed it.  Well, two years later, the edging was pretty much gone, and the brambles had well and truly taken over the bank.

Here is the bottom of the bank, and the line of Hellebores - photo taken in March of this year - showing how the original bottom terrace edging has crumbled away to nothing, so the bank now slopes untidily down onto the path.

The path is about a yard wide, then it slopes down again into the water.

Not the best place to fall down!

So I was sent up there with a machete to clear off the brambles, chop down the cherry suckers, and then to dig out as many of the bramble crowns as possible.

You might remember that I wrote about Bramble Removal back in March, and this is the large area to which I was referring in that post.

Here is a section of that bank after bramble removal: first stage, chop off the mile-long razor-sharp top growth. Second stage, carefully dig out every bramble root that I can find.  This reveals the bare bank, and the number of cherry suckers. I left these until last, so that I had something to cling to and lean on while I was de-brambling, in case you are wondering.

Once I'd reached this stage, I chopped off the cherries, leaving their roots intact to hold the bank together, and in some cases leaving a short stump to assist with scrambling about on the bank to weed it - I have been up the bank several times to weed it, this summer, and it really helps having odd anchor points.. It's been massively frustrating having so much rain, as the bank has been slippery: and yes, I did tumble down it at one point, doing an impressive version of the splits en route. I still feel it in that leg muscle, to this day...

In May the client and I agreed it was time to get on with replanting, so we bought in what seemed like a lot of plants, until I started planting them, when they all disappeared against the scale of this bank. But we saved a lot of money by taking sections from other plants in the garden wherever possible, and several of my other clients kindly contributed off-cuts or thinnings of their plants.

That's one of the things I love about my clients, they are all so willing to donate plant material to each other!

We planted all the things that we knew would do well:  anything that had survived, anything already growing in the garden, and anything we could get for free. This included a lot of Cotoneaster (species unknown) seedlings, weeded out from another garden. They are very good at binding a slope together, and provide a light canopy which helps to suppress weeds, while also having berries, and often good autumn colour.

We scrounged as many Hellebores as we could from everyone in the village, along with bought-in plants such as Asarum europeum for ground cover, lovely glossy kidney-shaped leaves pretty much all year round:  Liriope spicata "Alba", again a good ground-coverer, with pretty white flowers early in the year,  and some Luzula sylvatica "Aurea" which is a golden woodrush, it has bright acid-green to yellow foliage pretty much all year round, and is excellent for planting as a "river" through a mixed herbaceous border. Up on the bank, I hope that it will spread quite rapidly, as it gives a bright glow even in the depths of winter, and doesn't require any maintenance at all. Part of my cunning plan to reduce the amount of time I spend scrambling around up there!

By summer, the brambles were growing back so I went a-scrambling again, this time armed with glyphosate weedkiller, so we'll see how well that worked: most of the plants were settling in well, and the client and I were amazed at how well the ferns were doing: being covered in brambles, we hadn't realised quite how many ferns had survived the neglect, and when I checked it last week, they were huge! Presumably they have enjoyed the wet winter and spring, combined with considerably more light than in the last few years.

Now I just have to remember to keep on top of the weeding, and keep on top of the brambles.


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  1. Very interesting. I have a similar project on my lake but a lot more severe. Trying to find an answer but not having much luck. My banks are almost vertical. Tried covering in turf which looked good until resident swans decided to pull it all off. Considering willow piling but can't quite decide. Prefer plants but they will not stay in place. Oh well will keep looking!

    1. Hi Barry,

      I imagine that even if the swans had not pulled off the turf, it would have been challenging to keep it mown!

      We've tried willow piling at this garden - that's the "edging that has rotted away to nothing" that I mentioned. I don't know what went wrong when it was installed - before my time - because in my experience, it's almost impossible to kill willow. But there were very few of the original stems still growing when I started working there. I used to encourage the new growth sideways, and would try to "fedge" it for strength, but it just didn't grow. If I were asked to replace it, I would put the willow wands in at an angle of 45degrees, rather than hammering them in vertically - I think you get better growth that way.

      For your situation, the best plants will be those that will spread copiously, and will cling and root themselves wherever they go. The obvious candidates are (*takes deep breath, can't believe I am actually going to suggest this*) Vinca major/minor, and variegated ivies. Both of these are unmitigated thugs, and will stabilise and carpet the banks, as long as you don't mind having to look at them. *laughs*

      I would suggest planting a staggered line of small plants at the top of the slope, and allowing them to find their own way down. You could also try planting a couple of ground cover clematis (just google that phrase for lots of suggestions) at the top, where you can protect them from swans/rabbits, and water them if necessary, and allow them to tumble down. They don't root themselves as well as the Vinca and Ivy, but on such a steep slope they will make an interesting "curtain" effect. In winter, it's less attractive: I did this in one garden with a short but steep bank, and each winter I would go along the top and cut off all the old black growth. One year I didn't get time, and it simply sat there all winter (not to my taste, but the client didn't seem to mind!) and grew on the following year.

      Hope this helps!

  2. A very informative post. I have a north facing slope in South West France which is solid, and I mean cement- solid clay. It has been scraped of all vegetation and I now need to plant it up with something. Are there plants you would recommend for this terrible situation? Thanks

  3. James, as per the comment about, the nearest thing to a sure-fire solution is the Vinca-and-ivy route. Both of those will cling just about anywhere, especially if you plant them in staggered lines at the top of the slope, and let them find their own way downwards.

    If you need to get some of them started mid-slope, then chip out small, deep holes which are slanted backwards into the slope, such that any water (rain, dew etc) falling on the slope will tend to collect inside the lip of the hole, thus auto-watering the plants.

    Again, as per the above comment, some climbers are prepared to fall downwards rather than scramble upwards, notably ground-cover clematis, even honeysuckle, if you get them started at the top of the slope.

  4. Hi Rachel, We have a garden 'amphitheatre' (less terracing) with banks internally and externally, set halfway bewtwen to towo levele of garden, so the outer rear slope is steep and long. We were planning on having sculpted mown grass inspired by Charles Jencks, but dont think thats going to work, as we'd like easy maintenance and ideally some colour. We were also thinking on wildflower grasses, but not sure about it looking messy for most of the year. The flat internal circle is approx 6 metres diameter and we're planning on using hard landscaping (flagstones) with a possible rocky edging between the flat and slope.

    1. Hi Philippe, it sounds lovely! As far as wildflowers go, keep an eye on the blog as I will writing about that subject shortly.

  5. How lovely to find a blog about planting on slopes. I have quite a few in my garden and have a couple of methods of gardening on them that might be handy. The big slope at the top of my garden is supposed to be wildflowers, naturalised bulbs and some grass - it looks lovely in the spring, then goes a bit tatty, like a country verge - anyway, I get to that from a couple of ladders that are more or less permanently leaning on the slope. That way I can get up and down without adding to the erosion to do any cutting, planting etc. I move them about if I need to but the rest of the time the vegetation just grows up round them.
    Nearer the house I have a couple more banks where I have set some paving slabs as "stepping stones" by hacking out a bit of hill horizontally with my pickaxe and then putting the slab in so that it is about half buried and back-filling. They are really solid and it's so nice to have a horizontal surface under your feet!

    1. Hi Sally, I like the ladders idea! I guess it only works when the slope is flat and regular, but I shall start hoarding old ladders immediately.

      As for the stepping stones, what a great idea - I've often chipped out a small place to put a foot while planting, but I hadn't considered making them official by using slabs. I'm guessing that they quickly become covered by foliage, so they wouldn't be visible, so if I'm careful, the garden owner need never know!


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