Garden School:

Garden School:
Teaching this week: Rose pruning (as always!) and water management

Monday, 27 August 2012

Planting on banks and steep slopes: Part 3

I wrote recently about establishing shrubs on slopes, with the throwaway comment that if terracing is not an option, establishing shrubs first is the easiest way to get started.

Of course, that generated the question "How, exactly, do you establish a shrub on a steep slope when the soil keeps getting washed away by the rain?"

Oh dear, slap on the wrist for me: this is exactly what I hate most about gardening columns, and gardening books: they blithely tell you what to do, without telling you exactly HOW to do it. Rather like that Mrs Beeton cookery book, whose recipe for Hare soup begins "First, catch your hare"  which makes the assumption that we all know how to catch hares. Or would want to.

OK, the answer is in two parts: you either plant very small plants, whose above-ground growth is so small that it won't catch the wind, or the rain, and be knocked over or washed out.

Or, you plant much bigger specimens, and make special planting holes for them.

Obviously, when planting on a slope you can't dig a hole straight down, as you do in a normal garden - you have to slope it backwards diagonally into the slope. How to describe it? Dig a hole that is at right angles to the surface of your slope. So that when you slot in the plant, in its pot, it sticks out at a silly angle but sits flush with the surface.  Then dig a little deeper, and increase the angle of your hole a little, so that the plant is more nearly upright, but you must make sure that all of the rootball is tucked within the planting hole, otherwise the soil will wash away and expose the roots, and the plant will die.

Here's my solution to the problem: I make miniature terraces, for individual shrubs.

Just take a short length of wood - planking, half-round timbers, leftovers from DIY projects - , and two stakes - stout canes, metal rods, old broom handles, tree stakes or whatever you can find - and use the  stakes to support the wood, just below the plant.

Remember the impressive terracing of the Grand Bank?  I found some leftovers on the bonfire pile and liberated them to make a mini-terrace for a Photinia that we planted even higher up that bank, and which was struggling due to soil erosion.

Not terribly elegant, but considering I was clinging onto bare, slippery soil about ten feet above the impressively high Grand Bank, I think I did reasonably well.... the two wooden stakes were hammered about 18" in to the hillside, and the short length of half-round post is simply held there by gravity, and soil.

After installing it, I scraped down some loose soil from above, and captured some of the loose soil that had already washed down, and rammed it all against the half-round wood. This ensures that the Photinia doesn't get washed away, and helps to catch any rainfall, allowing it to soak into the captive soil, rather than just rushing off down the hillside.

We planted two Photinia and one Buddleia (which you can just see, to the right) to give a splash of colour to this newly opened area, and it will be interesting to see how long they take to get established up there. In particular, I will be interested to see if this Photinia does better than the other one, which doesn't (as yet) have a mini-terrace all of its own.

Although I intend to keep scrambling up there to clear away the smothering ivy, I'm not worrying too much about the Glechoma muralis as it helps to reduce soil erosion, and will help to retain moisture around the planting hole.

Diversion about Latin names: this is why it's so important to learn the "proper" names of plants - Glechoma is variously known (according to wikipedia) as Creeping Charlie (never heard it called that), Ground Ivy (ah yes, that's what it's called in Oxfordshire) and gill-over-the-ground, a name that I have never heard before. By using the "proper" name, you know that you are talking about the same plant. If you hate latin names, and struggle to work with them, I'd be very happy to come along to your gardening group or social club to convince you!

Back to planting on a slope: I have also had some success using lengths of landscaping fabric to make a sort of bag, or sling, that can be used in place of the wood, with a couple of stakes. It's less obtrusive, and seems to last long enough for the plants to get their roots well established.

A final word about planting on a slope: when you've done it, and are watering the plants, water them very, very slowly.  If you sloosh the water around too quickly, it just runs off the surface, adding to the soil erosion problem.  Use a fine rose on the watering can or hosepipe, and run it gently for just a couple of seconds, then wait until the water has soaked in, then another couple of seconds, wait, and repeat.

It takes time, but you should only need to do it for a couple of weeks, unless you are planting in the middle of a really hot summer... and let's face it, I can't remember what a hot summer feels like, can you?

1 comment:

  1. Wonderfully practical advice, Rachel! The mini-terraces are just brilliant: thank you for sharing x


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