May 10, 2016

How To Make A Real Alpine Trough Garden

As you grow with plants, sooner or later you will confront - -  the trough garden. Stone, hypertufa or slate sinks or troughs filled with exquisite alpines. Buns, mats and hummocks so tight that ever Janet Jackson would be jealous.

Often misunderstood, or maligned because they can sometimes look 'less-than-pretty' or even awkward (in a 1970's concrete-planter-sort-of-way), let me assure you, the trough garden has some serious historical heft to it.  Their roots go back to an era where the greatest of British plant explorers (Farrer)  who collected these rare plants during the Victorian era triggered a craze in Europe which continues today to a lesser extent - a deep admiration and appreciation for high elevation alpines.

But, should you care?

Yeah. You should, but who am I to say?

As you consider making a trough garden ( and I include directions further down in this post) , think first about these three things:

1. Alpine plants need you to care about them as much as you care about the use of Glycophosphate.  There are plenty of you already who daily raise the flag on the merits of permaculture, sustainability, getting rid of lawns, GMO's -- you name the cause - but why are so few of you rallying behind the preservation of endangered climactic zones or endangered plant species?

14,000 Ft in the Swiss Alps a few years ago. Androsace helvetica plants above the clouds.

Save the high-elevation flora! (cue the Edelweiss song).  You can have a bit if Saint Moritz right on your deck.. Better yet,  you can have Edelweiss and rare gentians bloom for you this summer, and then save THAT seed rather than the seed of some dumb ol' black tomato. What the Ptarmigan are you thinking about!

2. Alpine plants matter. Sure, they both tough, and fragile, but their future is more fragile today than ever before. Climate change and over population by humans, even the realities that ski resorts are moving their slopes higher means that recreational skiing impacts them as well as hikers who are unaware. All this is impact, which to a painfully slow growing plant spells a quick death by Vibram soles and walking sticks.

 You know those 'Stay on the trail - don't step on the alpine plants' signs? If you hike, then you've seen those signs, usually on the mountain tops or any trail which extends above treeline. What a great way to send the message that not only do you care, but you are cultivating a rare species and then sharing the seed with informed gardeners around the planet.

3. Nothing says that you are smart and that you care more than alpine plants in a trough. (So, remind me one more time - what goes best with black petunias? Purple Sweet Potato Vine or Lime Green Sweet Potato vine?) Right.
 I don't care if you've even moved beyond Whole Foods and that you ride your bike to the farmers market, I'll bet anything that you still swoon over Cafe au Lait (the Dahlia) but find little else exciting at your Home Depot, Lowes or Tesco. Admit it, you're bored with the selection at the garden store. Hell, we all are. Alpines are the cure for boredom. But proceed carefully, they can be addictive.

If alpine troughs confuse you, thing of them in this way: In many ways,  growing plants is like keeping tropical fish. Some of use settle for guppies and goldfish while others like the challenge of a salt water tank populated with rare species of wild reef fish.


The good news is, an Eritrichium nanum costs a lot less than a Liopropoma carmabi. But you probably already know that.

So if you want to get a little more serious about your gardening, planting a 'proper' alpine trough may be just what you need.  I say 'proper' only because many garden writers, nurseries and media like blogs dumb down troughs, showing them planted with single-season succulents or even annuals - which is fffffine, (but to use the aquarium analogy again)...it's a bit like populating an expensive reef tank with clown fish. I think its time I share with you something really challenging - how to make a real and authentic high-alpine trough garden. Are you ready?

One of my troughs this weekend with phlox species, which are different than the Mountain Phlox we see in everyones garden this time of year. There are many species of alpine phlox too, which I believe are nicer.

Alpine through simplified, is essentially recreating a micro-habitat from a mountain peak, complete with crevices or even a scree (where rocks fall down into a valley creating a deep, rocky soil. Some alpine troughs are planted with plants from the Steppe or desert (remember how high Colorado  or South Africa is?), or even sand plants. Like aquariums, the pH and soil conditions will depend on what plant environment you are creating. Will your trough only show plants from a particular mountain in the French Alps where you hiked once? Or will it be a mixed collection, with plant from all over the world?  Most will mix plants as they learn what grows well for them, but that is how we all learn.

Joe and I photograph Androsace and saxifrages on Piz Gloria in Mürren, Switzerland above 14,000 feet. This scree held many species which bloom just at snowmelt. Recreating this habitat in a trough is not easy, but one can get close, and even a few blooms on a seed-raised plant is cause for celebration.

I really started to understand alpine plants once I hiked the higher elevations of the Alps in both Europe and Japan. In that thin air above the clouds, one quickly learns that these tiny plants are not a tender as one may think. In fact, the plants that grow this high have very deep roots, and are often some of the toughest and longest lived species, but removing them by digging is illegal of course, so seeds from either wild collected seed or from garden grown plants is used, and altgouh regular garden conditions can transform the habit of many of these plants, but growing them in rocky troughs, the plant enthusiast can get close to something more in habit. The best part is, we plant geeks can also get physically close to these plants, without the heart-pounding hikes above the clouds near glaciers.

Saxifrages blooming above 14,000 feet in Switzerland. By studying these plants in the wild, we can recreate similar situations in our home alpine gardens.

All are amazing, which you have success, or frustratingly addictive when they fail, and you try again to master their environment. Start easy, and work your way up, from sempervivums and ice plants, to one day mastering Eritrichium nanum. We all need goals no matter how unrealistic they are!).

If you find the mountain phlox at your big box nursery beautiful right now, why not consider some of the many 'real' mountain phlox species like this

Before I start, I should probably brief you on what trough gardens actually are, since I have discovered that not everyone really knows what a trough is. If you're like most gardeners, you probably already have a rough idea of what a trough garden is - seeing one maybe in a gardening magazine, on Martha Stewart or at a botanic garden - or maybe you've seen something like a trough garden at your local nursery, planted with small, charming plants and you felt - "hmm, those look rather interesting, but I still don't know where to start and those bold, Proven Winners are just over there on that next table. And oh look, Hellebores!

I've wanted to write a post on 'how to make a trough garden' for years now, but I usually get distracted, either by limited plant material, or things like "I need to find a trough". For whatever reason, I have everything I need right now, and spring is one of the best times to begin one (and  autumn is the second best time).

This weekends' trough project ended up looking like this.

In true Growing With Plants tradition, I want to cover this topic in as 'real' and as 'authentic' a way as I can, given that such things are very interpretive and subjective. I'll admit, there are some learning curves to overcome, and some hurdles (like, finding really fine alpine plants), but I will provide sources for those, and troughs are something you will need to find on your own. For this post, I am going to use a polyform slate container from the nursery. I like the modernity of the cube.

Look for deep trough-like containers, since troughs, back in the 1800's were originally repurposed sinks and horse troughs. Today, you will need to improvise, but always find containers which are deep, with thick freeze-proof walls and preferably straight sides.

First, a trough building basics.

1. What is a trough garden? Troughs originally were stone sinks or stone farm troughs, often found in England and Europe where the idea of trough gardening began back in the Victorian era. You can find more history on this practice on-line, but basically, stone troughs allows those at low elevations grow many of the rare, alpine plants, particularly those found at high elevations in the Alps (saxifrages, primula, androsace, those hard-bun plants which grow in open conditions often above tree line. Today, all of this has evolved to troughs meaning most any container (rarely stone, simply due to cost, weight and cost) to special concrete mixes, often called Hypertufa.

If you are creative, many containers can be turned into an alpine trough - this galvanized horse trough shows off alpine plants perfectly in the garden of an Ann Arbor Michigan NARGS member Don LaFond. I love this look, rustic and practical.

2. What should I use for a container and where should I put it? Any deep, frost-proof container will do, preferable with thick, straight sides. before you start, you should think about weight, (once filled, moving your trough will be difficult), drainage ( aside from holes in the bottom, your trough should be set up on stones or brick so that it will drain properly, and site will be important as well. Full sun is generally ideal for most alpines - after all, they live at 14,000 feet, but some grow on the shady side of rocky peaks ( saxifrages) or an Eastern exposure. I keep our troughs either on the eastern side of the house where the house casts a shadow after about 2:00 PM or in partial shade. The rest, get full sun all day long.

Real tufa rock  is created by a complex geological method involving calcified wetland plant deposits and organic fossils. It's a fluvial deposit with lots of channels and porosity which allows alpine plants to root directly into the rock.

When placing tufa rocks in your trough, it's nice to get some height. I like to look at the entire scheme from the side, to create my little Zermat or Montreux. Pay attention when you are in the mountains, and try to recreate the same conditions in your container. You know, like scaping an aquarium.

3. I hear about Tufa rocks but I don't know what they are, and what is Hypertufa? Tufa is a natural occuring porous rock, but Hypertufa is a concrete mix (remember, tufa is expensive, and concrete is basically limestone too), so thanks to some good recipes,  which gardeners use to make hypertufa, a decent subsitute was creates which uses concrete, peat, vermiculite and sometimes other material like fiberglass fibers, to cast 'stone', or faux-tufa  trough-like containers.  Some look crappy, others, amazing. You will need to judge. Again - plenty of recipes for hypertufa on-line, (I recommend this book on Garden Troughs which has a great recipe by Rex Murfitt and Joyce Fingerut). You may opt to just forego the mess, and buy a nice container instead but they can be costly. Remember, bigger is always better than small containers for the plants. (Again, just like an aquarium).

My Betsy Knapp troughs, both planted and un-planted near the greenhouse.

Good  hypertufa containers are expensive, and bad ones are just half as expensive. Buy what you like, and move on from there. My favorite are made by Betsy Knapp from upstate New York, but I am not sure if she is making them anymore. Join your local NARGS to see where they get theirs, or you can try to make one.

Tufa Rock is actually real rock, not concrete, but it is terribly rare. Created by either fluvial or lacustrine systems involving stromatolites or encodes - um, never mind. Read about it here.  Basically, all you need to know is that tufa is very special, usually expensive and its hard to come by. Not much help, am I? It's a very weird and specific rock which is razor sharp, porous, made from limestone and sometimes includes sea shells fossils. Found where there was once ancient oceans or salt lakes in places which are too few around the world.  Much does come from North America, but most sources are kept secret.

Again, I would say that you join NARGS  or an alpine society, surely someone will connect you with a dealer (tufa is indeed the drug of choice amongst alpine gardeners but few will reveal their dealers). I went to an auction last year in Michigan, but when pieces reached $200 per piece, I backed off.  Don't let this discourage you.  You can certainly create an authentic rock garden without tufa rock, but if you can get some, magical things can happen as plants can grow IN IT, which is very cool. Since alpine plants can root through the open pores of this limestone rock, it allows the alpinist to raise alpines which look more dense and tight, like those found at high elevations.

One good tip from me - if you order saxifrages from Wrightman Alpines, most will come already planted in Tufa rock ( at $15 each, that is a bargain). You will find Harvey Wightman online and at Trade Secrets this weekend in Connecticut. I'll be there too.

4. What should I use for soil in a trough? Will regular potting soil work? It really depends on what you are growing, and once again, just like raising tropical fish, you will learn that certain plants require acidic conditions, while other will require alkaline. Most alpines love lime, and so alkaline is preferred, which here in New England makes trough culture very practical. Tufa rock is pure limestone, and it is one reason why lime encrusted plants such as the bun and mats of saxifrages do so well when planted in it.

Many of the choicest alpine plants for hard mat's like this. This will take some expertise, but given the right conditions, this would be the ideal to achieve.

I use a mixture that works for me, but you will see on-line that there are dozens of recipes for the perfect soil for troughs, ranging from mud-like clay, to pure sand. I use this formula for most of my troughs, but augment it with adjustments based on what I am planting.

My wheel barrow full of ingredients for a nice, trough alpine soil mix.

Matt's Trough Soil

2 parts loam (freshly dug from under the lawn where grass was growing (less weed seeds, and I don't like sterilizing it).
1 part sharp sand
1 part pumice (looks like perlite, but this won't decay - ask for it at your marijuana growing store)
1 part organic material such as rotted wood mulch, leaves, coir, or sterilized peat-based potting mix

I also add 1/2 part small gravel.

Obviously, this is a mix which is loam based and although very fast draining it isn't as lean as most alpine growers often suggest. Iv'e found that in many mountain areas above treeline, there are rocky scree areas where the soil is often many feet deep with shards of rock, but under that, the soil is rich. in snow melt areas, where gentians and primula grow, the soil is often wetter and more clay-like than one imagines. I pair this with what I've learned from other alpinists - that sometimes richer soil (Kris Henderson's primula, for example), or Josef Halda's clay mixtures which contain more nutrients than most lean mixes do quite well.

A saxifraga or Saxifrage (kabsciha type, which means this.) Not all saxifrages are the same. Learning about them will require some fun reading time, but I imagine that you will like that part.

The goal here is not to mimic those exact conditions found in alpine areas though, but to keep ones growing in 'character' as best as one can, since you may be raising them at low elevation. The environment above the clouds or at 10,000 ft is quite different than that found at 1500 above sealable Strong ultraviolet light (it's why many alpines have fuzzy leaves, to protect themselves from the sun or to capture moisture from clouds), many require long, cold winters which are dry, since the snow melts only once, and when it does, rather quickly, (which is why many people cover their troughs with roofs during the winter, for it's not the cold that can kill these plants, but thaws and wet, icy snow).

Dense buns like this, are what you want this summer!

I say, experiment with soil mixes, but generally speaking, first know nutritionally what your species will need (pH and chemical needs), and work from there, knowing that the fact that you are raising your plants in a container and not in an open alpine garden makes a big difference as well. The roots on many alpines are almost as thin as human hair, but can be as long as 4 feet, as they need to meander through layers of rocks to reach soil. Plants that are planted in tufa rock will root through the rock, and will help one achieve the desired look as the plants mature.

Androsace blossoms are very small. This relative of the primrose, is makes a terrific trough plant.

As you can see, alpines are not easy, but I will say that they can be rather carefree, at least most of the year. I rarely water my troughs all summer, and aside from covering them in the winter, or replacing dead plants, I fuss very little with them, once established. That said, I've killed hundreds of plants getting to those handful which have lived with me for more than 15 years.

A trough in early summer, at Wave Hill. Troughs like this once established can live for many years, as long as they get some winter protection from wet weather. As for cold? Bring it on!

My haul from last week's plant sale at Tower Hill Botanic Garden where there were a few sellers of alpine plants.

What should I buy for plants, and what are 'true alpines"? I group 'true alpines' as plants which grow not only at high elevations, but those which grow in wild areas which remain small. The purists may say that these plants are saxatile or dense, growing mats and bun plants, but this isn't always the case. Still, you will want plants which will remain small for  along time, and the finest ones are the real rarities like alpine gentians and hard, crusty saxifrages, trough gardeners often include small plants which might be native to dryland areas, or snowy plants, woodland and prairie plants, even seaside plants which appreciate nooks and crannies or which grow in crevices.

These rooted cuttings of a choice alpine Saxifrage, purchased from Wrightman Alpines don't look like much, but I knew what they were for when I spotted them at the Primrose Society meeting last weekend - 

Few of you will be able to grow alpines well, (heck, even I struggle, but I like a challenge, and maybe you do too.), I say start with the easier alpines - sempervivums, and personally, I like to add the silver saxifrages in here (I highly recommend those already grown in tufa rock cubes, such as those sold by Harvey Wrightman Alpines, they work very well, and I can't think of anyone else who grows these plants in this way).

The small saxifrage rooted cuttings can be easily manipulated into small crevices that I made, or into holes drilled into the tufa rock.

These rooted cuttings are not being grown in tufa rock, because they are intended to be set into tufa by the grower - you (or me, as in this case).  Small, tiny rooted saxifrage rosettes like this can be carefully poked into holes which are filled with a sandy mud created by hammering some tufa and mixing it with water, combined with little soil.

 Once watered in, the small cuttings will grow ever so slowly. Eventually becoming like the rock they grow on, themselves. The dense, buns are really somewhat hard (the foliage actually has limestone in it!). 

How you curate your plants for your trough is up to you. Some folks like to recreate a special hike or trip (all of the plants found a Mountain in Crete, or in Switzerland), but generally, you will be limited to what you can find via mail order, or at your nursery.

Some nurseries will carry saxifrages already growing in tufa blocks, like this one from Harvey Wightman Alpines. Carefully unspotted, this block will be set directly into a prepared trough. I find these Harvey Wightman plants very sturdy and a great way to get an established alpine into your garden.

Rock gardeners are serious plant people, and often raise many of their plants from seed, not the easiest thing to do, but if you join your local rock garden society, most hold an annual seedling or plant sale in the spring or autumn, and this alone, if often the only and best way to obtain really choice alpines. It's how I started.

I like to combine both established saxifrages into my troughs, along with rooted cuttings. It's always best to try and keep like plants together, all high elevation bun type plants work well together, with no thugs or fast growing types. Troughs like this can last for many years with little maintenance aside from covering with a plexi panel in the winter to keep the snow and rain off of the planter.

Edelwiess, alpine poppies, saxifrages and more allows me to have a bit of the Alps right on my deck.

So are you interesting in making a trough this spring? If you are undecided, then here are a few more reasons why you might want to try making one:

A collection of alpines in troughs  at Wave Hill in mid-summer.

So, you might be thinking - all this, and for what? I'd much rather have a pot of petunias in bloom for all of the ease, low cost and color. But I challenge you with - how exciting is that? And, what does that pot of petunias say about you?


For plants,:

Wrightman Alpines in Canada (he ships to the US)
Arrowhead Alpines

For Hypertufa Troughs:

Betsy Knapp Troughs

For more information, consider joining:

The North American Rock Garden Society (NARGS)
The Alpine Garden Society (UK)
The Scottish Rock Garden Club

All three of these societies have terrific color journals, and website with lots of pictures and information about alpine plant culture. I encourage you to join them all, if you are interested in learning about alpines, but remember that all of these groups cover plants beyond alpine plants as well, including wild flowers, native plants, trees and shrubs, dryland and desert plants, and bulbs. The best part about joining any of these societies, will be the relationships with other people who will be more than helpful in getting you started whatever your interests are. It's how I got started on my path, with shared seed, invitations to meetings, cuttings and plant sales, advice and friendships with continues today.

Full disclosure, I am currently the President of the North American Rock Garden Society.


  1. Great post! I'm a member of the Potomac Valley NARGS chapter. We made a bunch of troughs last fall, planted them this spring, and had them for sale at the US Nat'l Arboretum Plant sale about 10 days ago. We sold all the planted troughs we brought, including a few empties. So quite successful! I love them and they are great for people with little room, such as apartment dwellers. It is a sustainable way to garden; as you mention they don't require a lot of water, though I do have to water mine regularly down her in northern VA in the summer, and not a lot of maintenance. See you in Steamboat!

    1. You are right - troughs are so great for apartments - and in New York City, there are so many terrific rooftop gardens and terraces - just like mountain peaks!

  2. What a great and comprehensive post. The only addition I would suggest is a cement mixer for mixing soil alpine soil. It's a great investment for the long term. If not using it right away I store it in those plastic bags that the sand or potting mix comes in.

    Oh, and by the way, the cost-effective approach to that wonderful tufa last year in Michigan was to buy a whole pallet for $300. It was a terrific bargain, though certainly a load for my pickup truck.

    1. Great idea for the cement mixer, but honestly, that sounds a little serious as an investment - I think I'd rather spend that money on Tufa! I think a palette of Tufa in New England might be more, as much of it comes from Ohio, not far from you in Michigan.

  3. john in cranston9:59 PM

    I can't vouch for the rarity or authenticity of the plants, but The Farmer's Daughter in Wakefield RI has a huge collection....

    1. Thanks for reminding me - I really need to go check that place out. Many people have mentioned it to me.

  4. thanks, Matt, for an excellent primer on trough culture. I especially like the aquarium analogy. I saw the troughs at Wave Hill in the late 90s and became 'infected'. As a sculptor and a gardener, troughs are my sweet spot. I've given up a good portion of my suburban driveway to my own recreation of Wave Hill, with 40+ troughs. Nobody really needs a three-car driveway anyway, right?

    I'm looking forward to meeting you this fall when you speak at our NARGS chapter here in north NJ. I make and sell lots of hypertufa troughs every year and will bring a few empties to show.

  5. Such a detailed information on a real alpine trough garden. Very soon I will work on this. Loads of thanks Matt for taking out time for this lovely project.

  6. What an excellent post, thank you so much Matt, it contains everything I try to convey to customers & students. We have a couple of hypertufa classes coming up, could I share images (especially of the soil components in wheelbarrow)? Thanks from Oregon & I am bookmarking this blog!

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