Stupid questions about building a rock garden

[Rockgardens]

I’ll preface this post by saying I know NOTHING about gardening but am keen to learn.

Our garden is built on a slope. We’ve dug out tonnes of earth and built a level patio with a retaining wall. The remainder of the garden is not quite steeply sloped, it’s not a massive area, maybe 3 metres deep.

The soil is awful full of rubble / tipped out cement thanks to the builders who did our extension. We need a relatively cheap solution.

I was wondering about building a rockery but don’t know how feasible this is on a steep slope.

Also I don’t understand whether if a rockery is feasible how the planting is done. Would we need to make the existing shit soil good, no idea how we’d do that, or do you just chuck compost between the rocks and plant into that?

No idea where the “not” came from, my fat fingers. The rest of the garden is very definitely steeply sloped

what Is the sun like on the area ? Full sun. Partial shade etc. This will determine what plants u can use even if u make the soil better.

Lavender is really good in rubbish soil. But u need to have fun sun. The garden centre have plants made for rockery’s. So maybe start looking there. But u need to figure out ur sun amounts

The garden is west facing and the area is in full sun in the summer from about 11 in the morning until 6pm ish

Rock plants like poor drainage ( brick and rubble is ideal ) with some gritty / sandy soil on top. And they grow on steep slopes but they like full sun. And they tend to be very small so they won’t hide a fence or wall behind.

Would that work for you?

How stable is the slope at present? Is soil/ rubble rolling down or being washed down in heavy rain?

The plants don’t need to be particularly big.

I just can’t get my ahead around the basics at the moment. So do I need to put topsoil over the crap soil I have? Clear….as best I can….the rubble and crap off the surface of the existing soil? I really don’t get it.

The existing surface is pretty stable, not much, if anything gets washed down the slope

It might be that a rockery isn’t the best solution so I’m open to ideas, they just need to be very cheap ones 😂

If I were you I'd plant plants suitable for rock or gravel gardens, into the existing soil, and then cover the whole lot with a layer of gravel. It will look lovely, I love gravel and rock gardens.

That was my first thought @HamFrancisco but I was worried the gravel would just end up slipping down the slope, it really is quite steep. That’s when I wondered whether larger rocks would have more chance of not slipping down

Hmm, you can get that stabilising grid stuff.

I might reconsider the gravel option then as that seems simpler.

Would you attempt to sort the soil out at all beforehand? Or just plant rockery type plants and hope for the best?

I'm not an expert but I gather lots of gravel plants grow happily enough in poor soil, have a look at Beth Chatto's gravel garden, it's built on a carpark.

Erigeron karvinskianus is your friend. Find a space for it, shove it in, and it will spread. Others that will work include Aubretia, Saxifrages, thrift, Campanulas, Sedum. You’ll have to water regularly for the first couple of years but once established they’re very resilient and love a site like that.

So from this thread I think I’ve gathered, don’t worry about clearing or improving the soil just choose rockery plants. Put down grid stuff for gravel, plant, cover with gravel and done?

One more question, would you put weed control matting down under the gravel?

Weed control matting is the devils work. Don’t use it. It decays after a few years leaving you with a border full of shredded plastic, all tangled up with your plant roots.

The chief difficulty with steep slopes is that weeding is such a challenge to reach and hard work.

I would aim for a combination of:
robust compact shrubs with deeper roots that don’t need much care- and don’t spread too widely (so need very little pruning) and will provide a good visual structure.
Intersperse with groundcover low spreading plants that will suppress weeds.

Larger shrubs that cope very well on a slope -Weigela Florida Variegata will survive almost anywhere and is slow growing. Of course buddleia is very adept on a slope as is Amelanchier Canadensis. Berberis thunbergii 'Crimson Pygmy' a dwarf easycare shrub with eye catching leaf colour. Cornus alba aurea - dogwood is a tough variety.
If you wanted something with winter interest cotoneaster lacteus is a large shrub with arching branches. It’s many small flowers are very attractive to bees and other insects and it berries heavily in winter providing food for birds. It can be restricted to a single trunk to create more of a tree than a shrub.

On a steep slope, larger shrubs do provide stable points for holding onto when you’re climbing up..

In between the shrubs I would echo what @VenusClapTrap advises.
Low level plants with spreading roots to keep everything in place and suppress weeds. Once the plants have some anchorage and spread, they will limit any movement of gravel and larger rocks, so add those at a later stage into the gaps.

I have found ivy is particularly useful in slope coverage and management and the more attractive variegated types are more visually appealing and less likely to be rampant.
Cotoneaster humifusa is recommended for slopes - a prostrate spreading everygreen with winter berries, and also cotoneaster adpressus.
Geraniums also thrive and spread well, as does Alchemilla mollis, and Bergenia. Erica carnea will flower long into winter.

I’ve just seen your latest post about grid and weed control matting. I would advise against using either. It’s a quick fix but shrubs and ground cover planting will be more effective and much less work over time. Also will look much more attractive.

Weeds will eventually find their way through a gravel grid probably after 2 or 3 years. Climbing up over a gravel grid on a steep slope to sort them out is tricky without larger stabilising shrubs. Shrubs also act as a safety backup to limit your slippage and potential fall whilst working on a slope.

If you fancied a cheap tree (or several), I found hawthorn whips grew very well on a steep sunny slope with poor soil - limiting them to just one main stem to grow on a single trunk as a specimen tree, not as a hedge.
Great for wildlife and has year round interest. You can buy them individually for a few pounds online.

I love building a rockery! A photo or diagram of your space would be handy, but I get why you might not want to post a photo on an internet forum.
Concrete in rubble will be fine for acid loving plants but not ideal anything which prefers a neutral or alkaline ph.
I always start with getting my rocks in first, depending on the size I generally start at the bottom by making my first 'line' of rocks or bricks, leave a gap and lay the next line down. I start adding layers on top top of my rock layer. Basically you are making miniature gardens using rocks as a border for each mini garden.
If I've layered the rocks, and my plants are small I'll add in additional compost. If I'm planting a shrub I tend to dig out a hole.
The beauty is there isn't a right or wrong, plenty of colour and it will look awesome, no matter how wonky your rock work i(in fact the wonkier the better, as it will look more natural!).