Hi everyone,
I thought I'd start a thread on this as it was a theme running through the marvellous Landscape Conference last week. Claudia West and others challenged us to plant up the ground layer rather than using mulch under our perennials to bring in additional biodiversity, cool the soil and to avoid the mulch making the soil too rich (resulting in some plants taking over and diversity being lost). I have had the excellent book Claudia wrote with Thomas Rainer (Planting in a Post-Wild World) for a while - so I've been experimenting with this and it's challnging to find suiitable ground layer plants. They must be enough of a competitor to cover the ground (but not smother the emerging perennials, grasses and bulbs; deal with a the full light range (full sun in winter and early spring followed by full shade in late spring and summer when the perennials and grasses overwhelm) and must in my case also be dry tolerant (or dormant in summer).
So here are some initial thoughts (I am in Oakleigh East in Mebourne - approx 600mm annual rainfall, wet winters, dry summers when I only water 3-4 times deeply, about 3 frosts per year, soil is sandy loam to sandy clay loam on a yelow clay base)......
Ajuga reptans - may work for some, but I find the dry kills most of it off in summer
Banksia Blechnifolia - I'm keen to try this - you can see it at Burnley gardens coping with pretty much complete light range - and the architectural foliage is a bonus if you like it - as long as it's repeated enough it should look OK -has anyone tried it under perennials / grasses?
Bergenia cordifolia - good for the edges - would it surve full shade further back in the border? I'm not sure- does anyone know?
Campanula poscharskyana - this one does well for me but it's never as lush as I'd like for the green mulch purpose - it survives being swamped by the perennials and grasses though.
Clivia minata - we all know this one and once established it provides a good dense ground cover and survives being overshadowed - the issue for me is that it is so good at smothering that it can't be planted enmass with perennials as it out competes them - so only really good in clumps or under subshrubs and shrubs in my view - but maybe others have had different experiences.
Cyclamen hederifolium - this does well for me - dormant in summer and pops up nicely to flowerr provided I cut down the perennials over it early enough (thats the problem - sometimes I can't bring myself to do it that early).
Dichondra repens - this is a good doer as we all know - I confess I have not used it as I thought it might not be sufficenienty dry tolerant (I'm probably wrong?) - what about 'Silver Falls' fully imersed in the border as Michael was wondering in the conference workshop? Does it survive?
Epimedium grandiflorum 'Rubrum' - this is one I'm keen to try - Andrew Laidlaw has it planted at the Bot gardens and it is making a dense ground cover with that lovely burgundy tinged foliage - it shoud theoretically cope with a wide light range - has anyone tried it?
Helliborus - what's not to like here - glossy green architecturasl foliage, winter flowers and a summer dormancy - these do well under perennials for me
Lamium galebdolon - this one is a winner for me - the silverly leaves are a bonus and it will grown in the dark pretty much. Be careful though - it's pretty weedy - so you have to be prepared for it to spread and root everywhere or to contain it...
Viola hederacea - This does well for me (too well actually) in any area that is always in semi shade to full shade (it will grown in the dark) - but if it gets the sun on it at he front of the border when it is dry in summer it burns and looks awful. Where it does well it is such an excellent competitor that it will smother a lot of perennials. I find Anemone x hybrida does well with it in a semi shades spot and I ad diversity with shurbs and bulbs...
Michael suggested at the conference that some other violets may be suitable for the ground plane - what have people had success with?
And what about smaller grasses - there must be some that would work?
Thanks in advance to all those I hope will respond.
Cheers!
Kath.
Here are a couple that work for me - I'd love it if others would add to the list what works in your experience (and if you could indicate your location and climate please).
The Tricky Ground Layer - What Plants Do Well?
Discussion
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Thanks Kath for this question. It’s exactly the kind of thing we started the forum for.
As you’ve already discussed above, I’m convinced that Viola odorata would work OK in these situations. It does well for me here in places with summer shade and zero irrigation (though admittedly, there may be a little residual moisture in the place where it persists despite the constant discouragement of being dug up by me (in the process of moving the surrounding plants) and every plumber that sets foot on our place).
The huge challenge for plants in this ‘layer’ is, of course, being in total shade for much of the growing season, a little more light throughout winter, and then full sun, briefly, in late winter/early spring (if under herbaceous perennials, which is what I’ve assumed from the start). Not only that, the density of planting over the top of these plants in summer would result (unless you’re constantly water, and I never do!) in them being dry over summer as well. The plants most commonly used for this layer in plantings by, say, James Hitchmough, are things that like at least a little moisture over summer.
So plants that might be useful in this layer will depend on
– the height and density of surrounding planting (so that this layer in my clients perennial garden at Stone Hill would be completely different to the plants for this layer in the quarry garden at Stone Hill, where light gets to the ground throughout the season)
– the watering regime
– the seasonality of the surrounding planting ie the variation in density throughout the seasons.
– the time of year you’re willing to cut back ie whether you want to leave all the dead winter top-growth until the last minute in late winter/early spring, or whether you’re prepared to cut it back earlier for the sake of the underplanting. The early cut-back is necessary for a complex spring-bulb show, which is why I’ve rarely managed to achieve this. I’m just not willing to cut back the dead winter stems that early…
Yesterday I was weeding fat hen from a large area of recently disturbed soil at our place and was interested to see two really vigorous ground covers getting established of their own volition. Both might work in the setting you’ve discussed.
-Phyla nodiflora. Gardening Australia got in trouble a few years back for recommending this. It has clear weed potential, but as far as I can see isn’t declared as a noxious weed anywhere in Aus. It forms a tangled mat of wiry stems. Might be too competitive. But it looks to me like it’d run under stuff, probably thin in its foliage as a consequence of shade, but then leaf up as soon as there was some light. It’s here anyway, so I don’t feel badly about letting it go
– Geranium solanderi – the Austral cranesbill. This is a really annoying weed here, in my steppe garden particularly, as it has a massive turnip-like taproot. But it’s annual growth doesn’t seem to root down aggressively, and it dies back to the taproot each year, so while it’s a weed, it may be manageable, and useful under other stuff.
– Geranium sanguineum in a small form that was given me years ago by PGA. It doesn’t look like they do it any more. It was ‘Tiny Ted’ or something else equally unappealing. I’ve never been able to bring myself to chuck it out, but neither have I ever enjoyed it. It forms a very dense mat of growth in early spring, and flowers best then, but doesn’t do much from then on. I’m thinking it might cope with being overgrown by other stuff. Must try
Thanks Katha for starting this conversation! I have really enjoyed reading this information. I shall be watching this conversation with interest!
We live on a sheep farm on Kangaroo Island and faced huge bushfire threat last summer…. we were lucky and not burnt out like lots of others but we have become even more bushfire conscious! We have always used lots of broken up straw for mulch as we have it readily available from harvested crops. …. but this can be a fire hazard when it’s dry so we are looking at trying to cover bare soil with plants instead of always using mulch. (I know, I should be composting and using that!) Never enough time for everything on a farm with a large garden! So I am keen to plant more hardy groundcover plants amongst our perennials and shrubs.
Re your question…. I have tried Dichondra “silver falls” on a sunny bank…. looks stunning in summer BUT it tends to be almost dormant over winter and lets the weeds grow through it! If it was a thick cascading mat all year round I would plant more but after finding it dies back to almost dormant and becomes weed infested over winter I won’t be plant large amounts of this!
We are a coastal temperate climate with very few frosts here.
Thanks very much Michael for running this blog and website …. I am a new subscriber after discovering your work in the first Dreamscapes book! I am loving your work! I have gone to buy the second book “Australian Dreamscapes” and love that it lists the plants in the back of this book.
This was my thought about the Dichondra. Dormant just when you don’t want it to be.
As for the fire danger, I think that your plan to move towards planting is much better than the plan for compost. Any kind of dry organic layer is going to be a fire hazard.
I have been building a garden in Clunes for the last 13 years, part time with no micro climate. I thought I had a green thumb down in Oakleigh where there is no frost, wind, reactive clay, wallabies, (so cute and so naughty) rabbits and the occasional sheep getting in. oh, and like you Michael not much rain. So we have invested heavily in wire and stakes, and we do water through out summer until our trees can cope on their own. One ground cover plant that tolerates all this is Cerastium tomentosum, Snow in Summer. Not sure how it would go in shade, but can stand all of the above and is completely ignored until the flowers need to be cut back. Love the gardenist, thanks for all the reading when I’m not able to garden.
Yes, it’s that summer shade that is the killer, and that makes this layer so tricky.
Thanks for the affirmation re: The Gardenist. It’s hard to know if it’s hitting the spot, so I appreciate your comments
Hi Michael, Rosalie and Julia – thanks so much for your help!
Michael – you’ve solved a mystery for me re Phyla nodiflora – I have a photo of this on my phone (dense carpet under shrubs on a traffic island in Clifton Hill and flowering where the light penetrated) – have been meaning to get it identified. I’ll definitely try it. The geraniums are also a really good idea – thank you!
Rosalie – re the Dichondra ‘Silver Falls’ – my question is whether it would survive full shade under perennials over late spring and summer (I don’t care if it dies back significantly then) and then bounce back once the perennials are cut down in winter / spring – seems like where you are it would be dormant in winter at the very time when I need it to be covering the ground (and looking up Kangaroo Island your winters are much milder than mine – so it would theoretically do worse here) – I have some in tubes to experiment with – so I’ll still give it a go without holding out too much hope.
Julia – I’ve tried the Cerastium and while it will grown in a spot where it gets filtered light all day (near the trunk of my Chinese Elm) it does not survive full shade for me – simply disappears never to be seen again. So it’s a good one for the edges / areas where the perennials are not so thick and tolerates my sparse summer watering regime provided it’s not in full sun where it shrivels and looks awful (and eventually dies).
I also thought of Myoporum parvifolium after I wrote the first post – have not tried it – but theoretically it could work – it would probably need to get a decent foothold before it was overshaddowed though. And this brings me to another theory – perhaps the ground cover needs to have a chance to get established before the so called ‘seasonal theme layer’ is added – maybe the ground layer is more difficult to add when perennials are large and cover the fledgling plants quickly in spring / summer- if I was starting from scratch I’d probably try establishing the ground layer for a season before adding the perennials – has anyone tried that?
Cheers!
Kath
The trouble is that none of these are any more than just ideas. There’s all sorts of good reasons why they may not work, but all are worth a try.
I’m totally with you re: the Cerastium being good for the edges. It’d be the same with ‘Silver Falls'(though, as you point out, this would fail at the very time in the year when you need it most, ie late winter/early spring). Which then highlights the difference between plants that could do this job where the main planting was thin (a la Bettina Jaugstetter’s ABB planting, in which planting is chosen that will allow light to the ground level all year) compared with plants that would cope with summer deep shade, then progressively more light at the winter wears on, and then with being trodden on when we’re cutting back. What we really need are plants that are summer dormant, then appear late summer through early spring. This is why primroses are so perfect in the UK. (Having said that, I wonder if a solid blanket of grape hyacinths might do the job? My only concern is that they start into growth in late Feb, and would be seriously shaded by the time the perennials were cut back. And having said that, perhaps they wouldn’t really mind, and would recover once the light kicked in. They’d probably look a bit etiolated, but might still work). The little daffs like Jetfire and Tete e tete would flower OK in this setting, but wouldn’t really provide any weed suppression, and would not like to be walked on once they’ve emerged.
I’m interested in your Myoporum idea. It might just work given that the tips remain quite soft and green. They’d look absolutely terrible immediately after the cut-back of the perennials, but might recover quite quickly.
I can’t imagine virtually any truly woody ground cover coping at all.
I’m in the Adelaide Hills and this year I’m trying a white form of Eschscholzia californica, I have the orange form, which survives without watering until it’s killed off in the height of Summer before setting seed for the next season. It can be a bit promiscuous, but it’s easy to pull out. I’m hoping the white form is a little less vigorous, but still dense enough to smother the winter weeds and allow my perennials and bulbs to poke through in Spring.
Yesterday I sprinkled some of the seed over the top of some tulips I’d just planted, as well as in the foreground of my white garden. I expect it’s more ivory than white, but I think it still works. Fingers crossed!!
Hi Tracey, I have a cream form of Eschscholzia here that I’d never considered for this kind of planting. I must give it a go. My feeling is that here, in cold, mouldy old Woodend, there wouldn’t be enough growth on it in late winter/early spring to fill in over the perennial downtime, but I’m determined, now, to take more notice of it in August/September, to see if it has any bulk
I have worked in many gardens in metro melbourne that have Stachy byzantina as a ground covering plant and have spent many hours pulling bucket loads of it out as it is a vigorous grower, I think it might be useful as a ground cover in the sort of dense summer peaking perennial gardens as I often end up cutting it back all the way to the ground as it finishes flowering in late spring, just as the summer flowering perennials are really starting to bulk up and the shading would start to become a problem. I ve definitely seen them regroup and start growing in heavy shade and provided they start getting getting more light into autumn I believe it could recover the ground over winter and provide a show in spring as well as acting as a green mulch.
I’m about to start a perennial/shrub garden in dry, clayey, rarely frosted Werribee, and am very interested in all the above comments, having just found this website. Many thanks! At my last garden I used viola odorata, the common violet, in this way. Or perhaps it might be more accurate to say that it used itself, as I simply planted one slip which took off and spread obligingly right around the garden. It coped with everything from dry full shade to dry full sun, and the most upkeep it demanded from me was pulling it out at intervals to keep it within bounds. The leaves did burn a bit in the height of summer where it was in full sun, but not to the degree that it was a major problem.
I’ve grown various of the above mentioned low growers with mixed success in Werribee’s heavy soil and lack of water (I only water about 3 times per summer) Dichondra copes with shade but doesn’t really do well for me. Erigeron works well, and flowers continuously provided I get my act together and give it the occasional trim. It tends not to grow back enthusiastically once it has been shaded though and in that situation will sometimes sulk and die after a trim.
California Poppy and Stachys byzantina are only interested in growing in full sun for me.
I am interested in the idea of epimedium rubra and cerastium tomentosum and will try these.
Perhaps one answer to the problem is to have a variety of groundcovers to cope with a variety of conditions and to grow and compete together on their own plane.
Really looking forward to continuing to get good practical help from this blog – many thanks and keep it up!!
Thanks Annie, for adding your experience. Viola odorata is clearly phenomenally adaptable and obliging, and hugely underused for this kind of role. Really looking forward to hearing how you go with the other stuff. Weird how much instinct plays a part in this – what might work and what might not. Certainly feels like just about any ground cover plant with a woody-ish stem is going to struggle (like the Cerastium), unless is roots everywhere it touches the ground (as does Phyla), and that rapidity of recovery after being released from deep shade is essential (which, to me, makes the Epimedium option unlikely, but I’d be totally delighted to find my instincts wrong on that one). Viola odorata ticks both of these boxes ie multiple rooting spots ie almost a network of rooted stems, and phenomenally rapid recovery. On that count, it’s just occurred to me – I wonder how Convolvulus sabatius would do, at least in a less frosty climate than mine? It is capable of that multiple rooting, and is fast to leaf up when exposed to sun… It wouldn’t be good for me, as the time of year when sun is likely to penetrate through to ground level would be when it’s very cold, which puts it into relative dormancy, but it might be good anywhere a little warmer. What we need, more than anything, are plants whose seasonal cycle is the reverse of normal herbaceous perennials or deciduous shrubs. That, again, is where Viola odorata gets a guernsey.
I am having some initial success covering ground permanently and ephemerally in shade in a couple of situations with new plantings. With caveats!
1. Shade/sunny shrubby underplanting beneath existing Melaleuca linariifolia (brutally dry) no irrigation.
Plectranthus suavolens? (maybe parviflorus)
Prostanthera scutellariodes prostrate form
Myoporum insulare prostrate form
Wildtech nursery in Heyfield have a great range of selected, garden worthy natives, many in prostrate form. Some you didn’t even know could be prostrate. The Plectranthus looks promising and awesome. Similar to P.argentatus, but with a smaller leaf. Horizontal, and without the lax habit, lots of adventitious roots on the stems (typical of the genus). Plectranthus always look better I find if planted as lots of layered stems. This produces a multi-stemmed, self supporting growth habit, rather than planted as a single stemmed floppy specimen. So here’s the caveat, the plant needs to be gardened a bit to enhance the horizontal, ground hugging habit with pruning and occasional stem layering, but it will be way better for it.
The Prostanthera scutellaroides is a very tidy, quick growing prostrate shrubby groundcover but loose enough to let bulbs and other emergents through. Prostanthera genus always generally worth considering in shade/sunny hostile areas.
I’ve seen Myoporum insulare grow in the full light range from deep shade under pines to full sun coastal exposure where I live that I’ve just taken it for granted, or simply hated it. Recently looked upon it though with fresh eyes when this prostrate form appeared on a local nursery grow list (its provenance is Mornington, there is also a WA form named I think, ‘coastal carpet’). Growing between ankle and shin high in dry shade and full sun, but so many buds and responsive to clipping can be kept low as you want.
2. Second situation is perennial borders backed with evergreen loose screening (Seville orange).
I’ve let Smyrnium olusatrum, commonly called Alexanders, self-seed and then thinned to where I want it to cover ground. It’s looking good but needs to be used smartly and ruthlessly.
It’s biennial, but you get thick groundcover when a seedling population comes up through autumn and winter, and then space for summer perennials. Actually prefers shadier spots in my experience and you can pull out when it moves into flowering phase or keep and get lovely black seedheads. Not for everyone and needs ruthless direction to where you want it to grow.
Finally, I’ve seen a colony of Salvia forsskaolii hugging the ground well when not in flower in deep shade at Lambley. Grew the plant years ago in a sunny exposed location, so was surprised. Rare plant though, does anyone know if it is perennial or biennial?
Plectranthus forsteri?
I’m in inner city Melbourne and have tried:
Myoporum parvifolium – turns horribly woody in areas which get shaded after a season or two.
Dichondra repens – is burning up in areas exposed to full sun.
Viola hederacea – better then dichondra but needs water (I feel too much water) to not go limp and shabby in the summer sun.
Adjuga raptens ‘jungle beauty’ – Looks amazing until summer rolls around when the sun torches it, even in partly shaded positions (I’m watering it more then I’d like just to see if that’s a solution).
Erigeron – I’ve only had this in for a little while but it seems to be going leggy in the shade.
After reading all the above and from my own experience it seems the best way may be to allow a mixture of ground covers to compete.
Loving this blog!