Troughs for alpines – how to cover a belfast sink

Stone troughs are a perfect foil for tough but beautiful little alpine plants.  Rock chicks of the mountains, these plants are best displayed with stones and gravel and need good drainage. Alpines are great plants to grow, suit a small garden, roof terrace or balcony and have something to offer the beginner gardener or alpine expert.

Of course you can grow alpines in wooden boxes, terracotta pans, or indeed any container where good drainage can be supplied – but I think the traditional stone trough, aged with moss and lichen, can be hard to beat aesthetically.  They provide the perfect show stage for rock chick plants.

Real stone or fake?

Real stone troughs can be very expensive to buy, particularly antique ones carved from whole pieces of limestone or sandstone.  You can expect to pay in excess of £1000 for a large one and even a small good quality one measuring 50cm x 40cm will set you back several hundred pounds.  Solid stone troughs are also extremely heavy and expensive to ship or transport.

Bargains can be found on ebay and other online auction sites but courier prices can be large unless you can can find a seller nearby.

The alternative is to make a trough that looks like stone, but isn’t and will cost you a fraction of the price. Unlike fake grass or plastic plants, this is one hack that really works and not only is it cheap and easy to do but the resulting troughs can be hard to distinguish from real stone, particularly after a season or two of weathering.

Look-alike stone in hypertufa

I am not practical when it comes to DIY but making a mix called hypertufa to cover an old sink was unbelievably easy and fun to do.  I’m doing nothing new here. The wonderful Alpine Garden Society has a fantastic downloadable PDF on their website which describes how to do this, as well as how to cover polystyrene fish boxes or to fashion a trough by sandwiching hypertufa between two cardboard boxes.

I remember the cardboard box technique being demonstrated by the late great Geoff Hamilton who presented Gardener’s World when I first fell in love with gardening.  I remember marvelling at the hypertufa hack back then.  20 years later I finally gave it a try.

My chosen method was to give an old enamelled belfast sink a facelift using hypertufa, as I happened to have an old chipped one from a kitchen refurbishment.  If you haven’t got one then look at online auction sites or in architectural salvage yards. Good quality ones can cost tens of pounds but you only need a chipped poor quality one and these you can get for under £20.

What is hypertufa?

Hypertufa is a cement based mix named after tufa rock, a natural stone traditionally mined in Wales.

The three ingredients of hypertufa are:

1. Cement
2. Sharp sand
3. Coir or other compost

That’s it.

I happen to be doing building works at the moment so all the ingredients were on hand but a large bag of each ingredient would cost you no more than £4 from a DIY store.  £12 for all the ingredients and you’ll have plenty to spare.

Preparing your sink

Put your sink up on a couple of planks or a pile of bricks so that you can work on it easily.  If you can, move it to its final position as they are heavy to move, even heavier once the hypertufa is applied.

Usually made of white enamel, the sides of a belfast sink are shiny and therefore difficult to stick anything to.  Preparation is therefore important.  First, clean your sink as best you can with soapy water then dry thoroughly with a tea-towel.

The next step is to create a ridged non shiny surface. I used white craft glue, otherwise known as PVA glue, for this purpose.  Apply it with a paintbrush and run the brush repeatedly backwards and forwards horizontally.  This will create tiny ridges which will help to create the perfect surface for the mix to stick to.  You could also try mixing some sand into the glue before applying to create an even better surface for the mix to stick to.

Cover the insides too but only to just beyond where you want you final soil level to be (say 5-7cm down).

Go and have a cup of tea and wait until the glue is drying but still a bit tacky.  In hot dry weather this will take less time but on a damp, cold bank holiday weekend in England I waited an hour and a half.

Mix your Hypertufa

Admission time – to cover this sink I made the mixture in my builder’s cement mixer and did a bulk job that covered the whole sink.

However, it is very easy to do in smaller batches on a board, or in a bucket.  There are various recipes out there and the Alpine Garden Society has mixtures that are supposed to look like various different stones.

I kept it simple and went for one part cement, one part sharp sand, one part coco (coir) compost.  In my case I used a builder’s shovel – so one shovel cement, one shovel sand, one shovel of compost were my proportions.

Add enough water to make the mixture wet but not sloppy.  A sloppy mix will slide off, along with the smile from your face.  Think the kind of consistency of a good mud pie from childhood and you’ll have the perfect mix – malleable enough to shape – and to hold its shape.  I used 5 shovels of each ingredient to cover my whole sink (90cm X 60cm).

Applying the hypertufa

I’ve read various methods which say start at the bottom, or start at the top but I just went for it and started randomly in the middle.  I started with a trowel but I admit I found it easier to put it on with my hands.  If you do this, wear rubber gloves as cement is corrosive.

Gently press the mix onto the sides of the sink, over the rim at the top and down the insides of the sink. Using both hands it’s easy to mould the hypertufa over the sides, over the top and under the base to make sure that all the white enamel is covered. I covered the whole sink, with the help of my father-in-law in just under an hour.

You don’t want perfectly even coverage as very few natural stone troughs are uniform.  I chose to create a stipple effect with my fingers as I went along. This achieves the hewn look that chisels make and will create the environment for mosses to take hold.

Drying and finishing

Depending on the weather, the trough should have set fully within two days.  Check it after a few hours to see how it’s doing as you can still shape it a bit and improve the finish by rubbing it with a bit of damp hessian, or a brush. You can choose to add a stippled finish at this point too or you could add diagonal lines to look like a stonemason’s chisel marks.

I moved my trough into its position by my new greenhouse in May 2018 and planted it up with some easy to grow alpines in June.  If you want to read about how to plant up a trough and what plants I chose click here.