Raised beds idea.

Hi,

I'm new to the forum, hello from the Midlands!

I have a problem, and I'm trying to think of a solution.

We bought a new build 5 years ago, and the soil is heavy clay. The back garden is particularly damp and the lawn gets very squishy over the winter. About a quarter of the grass died over winter, so I'm currently over seeding with a wet suitable grass seed.

The problem I have is that the border plants (which were mainly herbaceous perennials have died, I assume from being too wet.

The things that are doing okay are 3 roses, a young apple tree, an acer, a honeysuckle and some ferns.

I'm considering putting in 4 sections of raised beds about 25cms deep around the borders, with no bottoms, and filling them with good quality topsoil.

Will this provide better getting conditions for perennials?

Will I have to water then in the summer, or will the plants roots draw up water from under the topsoil?

Have I had a good idea or a stupid one?

Thanks in advance!

 

The short answer is - yes it will make life much easier.

The ideal method of dealing with heavy clay is to add loads and loads of organic matter - ie rotted manure, compost , leaf mould etc. The biggest problem with that is that it can take a bit of time to get a good mix. I've never gardened on anything but clay - and often with gardens that have had little to no cultivation, so I usually do both methods, depending on what I want to grow.
If you want lots of perennials which like sharper drainage, then yes- make some raised beds, but fill them with a good mix of soil, manure, compost and even some pea gravel or similar. Allow it to settle - you'll have to be patient, as the level will gradually drop over time.
It also depends on what you make them with, and where you site them as to how well any plants will grow, but that happens with a standard border at ground level too.
Your climate is a huge factor - we have very high rainfall here, so most perennials I grow are in the raised beds, but if you also have shrubs in there as well, that helps to take up excess moisture too. Perennials on their own can mean empty ground over winter, as many are deciduous, so the ground can then become very wet, and not ideal for any emerging plants.
My raised beds vary in height - from around 8 or 9 inches, to a couple of feet, and the lengths are up to several metres.

 

Amazing, thank you for such a quick response!

 

While raising the beds will definately help , consider the possibilities of drainage across the entire garden. It depends of course on whether there is anywhere that water can go, its not illegal to let it on to a neighbours plot but it will not make friends. Often new builds are stripped of topsoil (they sell it !) and clay subsoil lifted from foundations and smeared / puddled by machinery to landscape before turf.
Initially dig a hole say 350mm square and500mm deep. Examine the strata/layers revealed, this may show more porous material below. Leave it overnight and examine in the morning, assuming no rain has fallen, Has it filled with water ?
Then fill it level with water and record the levels over the next day. This may indicate whether it can drain away. Further info on request.

 

Will I have to water the raised beds for the first year (or when longer?) until the roots of the plants get down to the wetter clay?

I'm looking at getting 25cm deep raised beds, so around 20cm (8") of soil, and I'm going to plant a mix of evergreen plants like rhododendrons or similar, and perennials.

Thanks!

 

Hi, Leicester here I have large 35cm high raised beds and grow shrubs, perennials, annuals and fruit trees in mine all with no problem. All I use is Wickes topsoil and a few chicken manure pellets round the green gage/plums in the spring. Be warned though, raised beds will need topping up annually as the soil level drops. It's a PITA but it's only once a year so isn't a major inconvenience.

And yes, you will need to water!

 

I have raised beds, 18" deep. Yes, you will have to water as they dry out more quickly than the ground. Also, as has been mentioned, the soil will settle, so allow time for that to happen before planting. I have found shrubs manage better than perennials in my raised beds.

 

If you're aiming to grow rhododendrons, you'll need to fill the raised beds with an ericaceous mix and water with rainwater. Then, you'll need to choose perennials that like acid soil.

 

Rhodos are shallow rooting @Owen Fell , so that means you have to be vigilant re watering. I'd be inclined to have them separate from other perennials if rain isn't sufficiently consistent, rather than mixing them all together, but it depends on your climate. I rarely have to water anything in a raised bed here, for the reasons I gave initially.
They really don't need particularly acidic soil, neutral to acidic is fine, but compost alone is no use for long term planting, epsecially anything woody. It needs to be a soil based medium, and with good drainage in the bed, ie with grit or gravel added, or plenty of organic matter. Open to the underlying ground is always better, and yes, you'll need to ensure the soil level is adequate in them year on year.
If you're only having the beds at that sort of height, you may need to amend that underlying soil first. For example, a solid layer of clay below a small amount of better soil isn't ideal, and can still become waterlogged, which rhodos won't appreciate.

 

@ViewAhead That the soil might settle never entered my head when I set my beds up, I just went ahead and planted straight away. By the time the next spring rolled around, the soil level had probably dropped by about half. The problem I have now is that because it settles less and less each year, I've vastly overestimated how much topsoil I'll need. I've accumulated about 20 25l bags of topsoil which are taking up space I want to use.

 

My commiserations, @Februarysgirl. I got it badly wrong too. In my defence, I was a complete novice and had never grown anything in the ground before. I reckon mine has settled by 4-6" overall. It is tricky to top it up without burying shrubs deeper than their growth points, and a further problem was I added a gravel topping.

You live and learn! And that's part of the joy of gardening. Though finding storage for 20 spare bags of topsoil is quite a challenge, I'm sure.

 

@ViewAhead The only plants I had before the raised beds were at the end of the garden in the shade. They were just ferns and perennials so didn't need any attention other than pruning in the spring. The first year with the raised beds, I had three trees and perennials but I realised I had the planting all wrong so needed to lift the perennials anyway. Topping up around the trees was a bit awkward but the graft point is a decent height from the soil level. I have bark chippings topping mine.

The bags of topsoil have just been stacked against the side of the raised bed that can't be seen unless you go round there This year I finally have a use for the excess though. I'm putting planters all around the edges of the beds and planting vinca minor "Atropurpurea". The way through the beds is all gravel and I want to make it narrower with cascading foliage. Thing is though that I'm gussying up the planters to look like stone and I'm terrified of getting it wrong!

 

for your project, @Februarysgirl.