Planting a garden on a slope!
Oh my goodness, what do you do with a really steep slope of untamed grass and a desire to have something nice to look at! This week is all about how you go about planting a garden on a slope.
What are the problems!
Before starting the potential problems need looking at and thinking through before you don crampons, attach ropes and climb the garden armed with a spade! What could go wrong, what will go wrong and how do you stop that happening. Sloping gardens create their own unique set of problems, so what are they?
- Access and maintenance
- Drainage and run off
- Differing light levels
Access and Maintenance:
How much is the garden going to be used? The design the garden takes needs to really reflect how much use it will have as opposed to how much use you think it will have. For example, at the top of the garden there is a lovely view, but access to it is awkward. The standard design model would create a seating area at the top of the garden to maximise the view.. The question though, is whether installing a patio will mean everyone makes the effort to climb to the top to use it. Are you really going to traipse to the top with a cup of tea each time you want to sit outside for just a few minutes?
Maintaining a garden on a slope is tricky, let’s face it weeding can be a real chore at the best of times, but add to that the added ‘faff’ factor of climbing up a slope as well, and one’s enthusiasm for a gorgeous manicured haven of flowers could be harden to achieve! There are some basic rules of thumb though that designs can follow: Create one flat space to sit out in, that holds a table and chairs AND is simple to access from the house.
Terracing the garden will allow more of it to be usable BUT it is expensive to install. Ensure the flat bits are created where the nicest parts of the garden to sit in are. Terraces don’t need to be evenly spaced or identical heights
Accept that maintenance is more difficult on a slope, so choose plants that won’t grow too quickly!
Drainage and Runoff:
Now this is blindingly obvious, but sadly often not considered properly. Rainfall will run down the slope, no surprise there; but what this means is those plants at the top of the slope need to be able to suck up the moisture quickly before the water drains away AND what happens at the bottom of the slope! The slope will channel the water downhill, so what is at the bottom, your patio, a retaining wall… the back door?
Over-compensate for water run off. The climate crisis means more intense rainfall, factor that in when designing the drainage channels at the bottom of the slope
Plants at the top of the slope need to be more drought tolerant, those at the bottom need to be better at sucking up rainfall
Gravity is a problem on a slope; all the forces point to the bottom of the slope. Everything will fall downhill unless there is a force holding it in place. Taking the example of this sloping garden, currently it is grassed over, the knitted root system is the force holding everything in place. The roots bind the soil in place, remove the grass and the soil will look to slide to the bottom.
So what does this mean, well, you need to create new forces to hold the soil on the slope. Creating a terrace adds the retaining force back in. If the slope is not going to be terrraced, then the plants will have to hold the soil in place. The best plants to choose then are those plants that spread via underground roots. These root systems will gradually weave together and help prevent soil eroson. Plants such as Persicaria, Lysimachia, Mint or Pachysandra which in a normal garden might be too vigourous, on a sloping space will quickly fill bare patches and help knit the soil together.
Ensure 80% of the plants have good root systems to help keep the soil on the slope.
It may not seem to be that important, but there is less light at the bottom of a slope, purely because is falls into shade sooner than at the top of the slope – this is more pronounced on north facing slopes. If taller plants are placed at the top of the slope, their shadows drop light levels even further. It is not a massive problem, just one you need to consider before you plant.
Sloping ground changes the perspective of the garden, Up slopes have the effect of shortening the length of the garden, whereas downslopes extend the length of the garden.
Because you are viewing the garden from lower down and looking upwards, the slope prevents you from seeing all of the plant – you only see the top of it. Use plants that are roughly similar in height, then all the plants will be seen up the slope. Its a bit like being in the cinema, everyone gets cheesed off if a 6ft tall person sits in front of you; you can’t see the screen properly. Planting up a slope uses exactly the same principle but in reverse.
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