All the ones Iv'e mentioned are the best spreaders. The yellow form being the best in my soil but could vary. Yes 20 inches of soil is generous and will ensure success, I think what I am trying to say is can you get into the soil to plant not just in one area but in various parts where roots may be thicker. In some gardens trying to plant in such a difficult area can be impossible. The only alternative being a thick bark mulch.
I have worked as a Gardener for 24 years. My latest garden is a new build garden on heavy clay.
I popped back on to give you the link to Plant delights but you found it already so good.
Rubrum which Punkdoc mentioned we grow too, near the same area. It is a cracking little thing that spreads well and nothing to not like about it. All the ones mentioned so far are all easy the Asiatic ones are much more challenging to grow well and often grow along or near water.
It is really down to your personal choice of colours. You said the pots you can get are 9 cm. If they are full well grown plants that fill the pots I would if your budget allows buy a couple of groups of three. It depends on how willing you are to weed until they establish. Planting these about a foot/12 inches or 30cms apart. It is a bit hard to say as you won't know how big or full they are until you get them. Sounds like you are buying online? You may need to buy more if they are dinky, but depends on your patience versus costs.
It will be a couple of years until they really cover the ground with their lovely thick rhizomes/ roots.
Cyclamen are nice be it coum or hederifolium, under trees. But bear in mind the leaves will die down so you won't get groundcover as such, although where ours grow we get very little in the way of weeds. Also the anemone you mentioned are nice for a splash of colour, but by the time late spring/early summer comes the leaves disappear completely.
Another thing that might grow well there is the Ophiopogon, there are green with white flowers or a sumptuous black with little lilac ones. They have a fleshy root that stores water and does well in shade. And do not die down.
As a side issue, @Pink678 , when we were first digging over our garden, we were left with lots of large areas of bare soil and were bothered, like you, of cats using it. We had taken down a large Buddleia and we cut the main trunk up ( previous owners had let it grow like a tree) and laid bits of logs all over the soil.( at odd angles) This seemed to keep a neighbouring cat out. Perhaps if you've any logs or old pots or the such like, you could dot them about until you are ready for planting. Might look a bit unsightly but that doesn't matter if it does the job.
I have E. rubrum, which I've found to be a slow spreader, and E. Frohnleiten, a lovely yellow that is rather more vigorous....I've split and spread it around in shady spots under shrubs where it grows very happily. Another possibility is Geranium nodosum, which is happy in dry shade and comes in several varieties (I have Silverwood and Whiteleaf as well as the basic one)....it makes about 30cm in height, spreads without becoming thuggish and flowers from spring till...well, still flowering now! Personally, I found G. macrorrhizum smelled like cat pee (so has been banished)!
@GardenerSuze, that's a good point about the various parts of the soil where some will have thicker roots, I will bear that in mind.
I'm going to be well aware that this is a difficult area to grow in and I might have limited success.
@Rubytoo I just love the look of Rubrum flowers so glad to hear it spreads nicely.
I would be buying online so it's a bit hard to know how much the 9cm ones will fill the pots.
I am also considering 2 litre pots to get a better root system.
About how far apart would I plant the 2 litre ones?
@Songbird-2 thanks for that suggestion! I just scooped 3 lots of cat poop this morning. They didn't even bother to cover them up. I removed loose soil, sprayed a lot with citronella/eucalyptus (helps marginally), then after your suggestion I found a small pile of branches and laid them over the area though it doesn't cover all of it.
I wish there was some kind of bark chippings material that cats hated. It would be expensive to buy a bag but worth it to me as the time really adds up if I am clearing up after these cats daily.
@KayJ thanks for that tip that the Frohnleiten is more of a vigorous spreader than the rubrum, I want to get it and the yellow flowers against the reddish green leaves look pretty.
Overall now I am thinking of going with epimedium rubrum, epimedium frohnleiten, and the two types of ferns. I was going to get 9cm pot size ferns but don't know if they will be ridiculously small and slow growing.
In the future I'll think about other geraniums like geranium nodosum, or some of my geranium from the other spot in the garden. And hopefully some bluebells and snowdrops in the green next spring for either side to the path.
I know only too well @Pink678 how you feel about your visiting cats causing problems, Most of us on here have experienced that deep joy( not!) and very little works. You could try a Scarecrow squirter / Cat Deterrent that squirts water at them as the unit is motion activated, I think. ( I've never used one) as they seem to work. Sorry I don't know the name of it.( others on here will probably tell you if you needed to know). Its a bit of a thankless task, we tried covering the soil with green garden wire.....they did it on top of it.....they did it on grass, on gravel, everywhere and never covered it up. There are Discussion Threads on this forum and from what I can glean, the Scarecrow things do work. My only tip would be to cover as much of the soil as possible, with odds and ends from around the garden, then get the plants in and ,once established, that should solve the problem...less soil, less space for them to use as a toilet. We put some logs under our Griselinia , three years ago, they are still there but the cats have kept well away. The space in between the logs isn't enough for them to get in between them to the soil.
By the way this is a weed that has overtaken under the leylandii further along to the left which is not in the photos, an area I didn't clear as it didn't look as bad.
I'm wondering if anyone knows what this weed is? It is happy there at the moment so if it's not too invasive I will leave it for a bit.
If the suppliers does not have the height and spread of whichever plants you choose then I would use the RHS site which usually has the expected height and spread of trees shrubs and plants. Anything you care to put into the search will give some details. And the estimate of time until the plant reaches the stated proportions.
Thanks Rubytoo, the 2 litre epimeidums I am looking at say 0.5m - 1m for the frohnleiten and 0.1 - 0.5m for the rubrum. So I might get more of the frohnleiten for the bigger spread.
Good to know JennyJ - I don't mind that weed really, at least the leaves are quite attractive.
Posts
Rubrum which Punkdoc mentioned we grow too, near the same area. It is a cracking little thing that spreads well and nothing to not like about it.
All the ones mentioned so far are all easy the Asiatic ones are much more challenging to grow well and often grow along or near water.
It is really down to your personal choice of colours.
You said the pots you can get are 9 cm.
If they are full well grown plants that fill the pots I would if your budget allows buy a couple of groups of three. It depends on how willing you are to weed until they establish.
Planting these about a foot/12 inches or 30cms apart.
It is a bit hard to say as you won't know how big or full they are until you get them.
Sounds like you are buying online?
You may need to buy more if they are dinky, but depends on your patience versus costs.
It will be a couple of years until they really cover the ground with their lovely thick rhizomes/ roots.
Cyclamen are nice be it coum or hederifolium, under trees. But bear in mind the leaves will die down so you won't get groundcover as such, although where ours grow we get very little in the way of weeds.
Also the anemone you mentioned are nice for a splash of colour, but by the time late spring/early summer comes the leaves disappear completely.
Another thing that might grow well there is the Ophiopogon, there are green with white flowers or a sumptuous black with little lilac ones.
They have a fleshy root that stores water and does well in shade. And do not die down.
Its a bit of a thankless task, we tried covering the soil with green garden wire.....they did it on top of it.....they did it on grass, on gravel, everywhere and never covered it up.
There are Discussion Threads on this forum and from what I can glean, the Scarecrow things do work.
My only tip would be to cover as much of the soil as possible, with odds and ends from around the garden, then get the plants in and ,once established, that should solve the problem...less soil, less space for them to use as a toilet. We put some logs under our Griselinia , three years ago, they are still there but the cats have kept well away. The space in between the logs isn't enough for them to get in between them to the soil.
And the estimate of time until the plant reaches the stated proportions.
For example Epimedium rubrum, on the left a few lines beneath the photos:
https://www.rhs.org.uk/plants/93397/epimedium-rubrum/details