Building up rockery on the cheap?

Shoxt3r

Hi all,
We've had our rockery now for a few years and I've been piling up compost every year but the anti-weed covering we placed underneath it all keeps getting exposed and also means that plants are uprooting.
What cheap ways can we build it back up again? I'd rather not get bags and bags of compost again...
Thanks!

Ted_Head

If the soil/compost is getting washed out then you can try and make it less leaky by using more stone. You can use ordinary garden soil or compost you've made from kitchen waste. If you use bark on top that should help with the soil getting washed out? Possibly. 
I don't really understand what's happening.

Davesnave

There are different weed barrier membranes and some are somewhat better than others on the flat, but on a steepish slope they all do badly. Whatever's piled on top of them eventually slides off, as you've found. The result isn't pretty.

Nature provides us with ground cover plants and most of those are undemanding. Stick them in ordinary soil and they grow, eventually knitting together  and being their own weed barrier. If you keep putting compost into the soil, it just becomes looser and less able to anchor plants, so they pull out easily. Planting in 'pockets' of compost is similarly doomed, because the roots then don't spread out so much as you'd want, but tend to stay in the nice friable stuff.

Get to know a bunch of good, tough ground cover plants, like Campanula poscharskyana, and ditch the membrane would be my advice.

-taff

What are you trying to grow in the rockery? If you're happy with the plants you have try and create terraced areas rather than haphazard rocks for the soil to pool in. Otherwise, do as dave says and get some good ground cover plants. I quite like lambs ears, I put two in the front garden last year, they've already colonized two foot of space from plants with three leaves originally.

[Deleted User]

Stachys 'lambs ears' would be too chunky, i'd have thought would be better in the ground - gorgeous pink flowers on them though, lovely, and great colonisers 👍
Also great slug and snail accommodation though, i removed mine for that reason, Bergenia the same 🤨

Rockeries can either be 'true', as in a rocky/stoney area with small pockets of alpines.
Or they can be rock gardens where different shrubs and prostrate trees are grown through the stone area.

In my last garden i had a rockery, full of alpines, got my inspiration from the alpine garden at RHS Wisley - used to be an annual pilgrimage for me pre covid 🙄😏 - the effect of that type of rockery is gorgeous in springtime when alpine flowers bloom but year round they're probably not as exciting as some might want.

A rock garden could be planted up to have successional blooming year round.

Davesnave

I think it depends on the level of expertise and committent to the idea of an alpine garden as to what's suitable or not. I took my cue from the OP calling this a 'rockery,' not a 'rock garden,'which they'd have done if their interest was alpines.

Similarly, alpines would not appreciate annual doses of compost, though the occasional cow pat might be tolerated!

Shoxt3r

Thanks for the feedback all - that would seem to make sense that the compost is sliding off as the rain and winds come in during the course of the year. We have a few large-ish rocks dotted around but maybe it warrants ditching the membrance and going for something more natural.
As an inexperienced gardener, I think it's also the case that when we're watering, the compost is simply compacting down so we need something with a bit more structure for the plants to grow into? We built the rockery up entirely from compost rather than soil which I think is most of the problem - thinking that this would help nurture the new plants too...

Davesnave

Shoxt3r said:

we need something with a bit more structure for the plants to grow into? We built the rockery up entirely from compost rather than soil which I think is most of the problem - thinking that this would help nurture the new plants too...

You have correctly identified the problem.

Alpines and low plants used in rock gardens don't get any fancy treatment in the wild. They grow where the soil is thin and lacking in nutrients, so in a garden the soil for them needs to be gritty, well-drained and not too humus-y.

Farway

Davesnave said:

Shoxt3r said:

we need something with a bit more structure for the plants to grow into? We built the rockery up entirely from compost rather than soil which I think is most of the problem - thinking that this would help nurture the new plants too...

You have correctly identified the problem.

Alpines and low plants used in rock gardens don't get any fancy treatment in the wild. They grow where the soil is thin and lacking in nutrients, so in a garden the soil for them needs to be gritty, well-drained and not too humus-y.

OT, Dave I know you visit Rosemoor, do they have an Alpine area?

They do at Wisley and apart from the cold greenhouses they've made an area with nearly upright vertical slates about 75 degrees from horizontal, mimicking mountain outcrops I guess.

The plants are growing in the small gaps between the slates, dry, drained and baked in summer

Davesnave

Farway said:

Davesnave said:

Shoxt3r said:

we need something with a bit more structure for the plants to grow into? We built the rockery up entirely from compost rather than soil which I think is most of the problem - thinking that this would help nurture the new plants too...

You have correctly identified the problem.

Alpines and low plants used in rock gardens don't get any fancy treatment in the wild. They grow where the soil is thin and lacking in nutrients, so in a garden the soil for them needs to be gritty, well-drained and not too humus-y.

OT, Dave I know you visit Rosemoor, do they have an Alpine area?

The position on clay in the bottom of a valley doesn't lend itself well, but of course money isn't a huge constraint and environments may be modified. I'm not aware of an alpine area, but there's a Mediterranean garden facing south with raised beds that come close to rock garden conditions and some of the planting comes close too. Looks a bit of a mess to me sometimes out of season, but that's a personal view!

Suzie_Hall

I'd start by creating some informal tiers using rocks or large stones to add stability. I see others have made good suggestions about soil etc.