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Building Troughs
by Kay Lancaster
November 13, 1999

The Bulletin of the American Rock Garden Society had a special issue on hypertufa and growing plants therein, now collected as their Handbook on Troughs. The information contained in those 70+ pages is wonderful, and I can't begin to summarize it here. But Here's some of the recipes from Michael Slater's article:

(All measurements are by volume of dry ingredient)

Standard US hypertufa:

•2 parts portland cement

•3 parts sieved peat moss

•3 parts perlite

•Enough water to moisten (to about drop cookie dough consistency)

Don't add more cement to the mixture above, it actually makes it more fragile. Equal parts of all ingredients work, too. If you're looking for a "how many bags of what to buy", 30 lbs of portland cement, 1 cu ft compressed peat moss, and 1.5 cu ft of perlite are about right.

Tougher hypertufa

To the regular mix above, add 1-2 c "permanent acrylic bonding agent" like Acryl 60 or Embond. Also add 1/10 oz Hi-Tech fibers per gallon of mixed hypertufa. Sprinkle fibers slowly over the surface as you mix, or you get "fur balls".

Let troughs cure thoroughly... they're usually ready to unmold in 36-48 hours, but need a month wrapped in plastic to cure completely at room temp. At cooler temps, the curing is slower. The trough has to be kept moist at all times to cure properly.

The cured concrete will be quite alkaline, and needs to be treated with vinegar or dilute acid for most plants.

Wayne Kittredge's hypertufa rocks:

•4 parts portland cement

•16 parts peatmoss

•1 part diatomaceous earth

•1 part play sand

•1 part expanded clay

•1 part vermiculite

•1 part perlite

•1 part long-fiber sphagnum peat

•1 part grass clippings

•1 part "serendipitous ingredient of your own choosing"

Remember, these troughs are heavy... an 8x12x12" trough, planted, can be moved by one person, though it'll take a minimum of two for 12 x 24 x 12". These should have walls about 1.5" thick. Larger troughs require 2" thick walls.

Someone on the alpines list, a fellow member of the bad back brigade, mentioned that he's given up on growing in hypertufa altogether, and makes fake hypertufa by pinning together slabs of 2" thick insulation styrofoam, and coating the whole with grey acrylic cement patching goo. Much lighter and easier to move, if less aesthetic.

Kay Lancaster

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