October 1, 2009

A Trough Building Workshop

The next three posts will show what we did last weekend. IT started with a Trough building workshop hosted by the Berkshire Chapter of the NARGS ( North American Rock Garden Society and Wrightman Alpines) and was held at the home of Berkshire NARGS chapter member Robin Magowan in Litchfield, CT. We then moved on to tour the gardens of another NARGS member, Elisabeth Zander in nearby Goshen, CT. So these three events and gardens deserve three distinct postings, the workshop by Harvey and Irene Wrightman, Robin's garden, and Elisabeth's amazing garden. First, the workshop.

Last Saturday was about a perfect, an autumn day can be in New England, and Litchfield County, Connecticut wasn’t too shabby, either. Joe and I we're fortunate enough to be invited to participate in a trough building workshop arranged by various members of the National Rock Garden Society's Berkshire chapter, and alpine plant nurseryman, Harvey Wrightman, of Wrightman Alpines in Ontario (they ship to the US, thankfully!).

The workshop featured a demonstration on a new way to grow alpines in troughs, which was introduced to Harvey by plantsman and explorer Josef Halda, who is friends with Harvey, and who toured the US and Canada earlier this year while on the NARGS national speakers tour. Halda also stayed with us while in New England in May, but we only discussed this new method, which seemed rather unbelievable, but the results we are seeing are quite impressive.
Saturday's workshop/Demo showed how clay can be used as a growing material for some high elevation alpines when sandwiched between sheets of split tufa (limestone) rock, which is porous.

About 15 of us watched Harvey's wife Irene demonstrate how to wash the soil off of young, potted alpines, or from rooted cuttings, and then focus on how she smeared with a trowel, a slab of rock with the muddy mixture, not unlike making a sandwich. The plants roots are pressed gently into the clay, and the top, growing crown is left emerging. Finally, another rock is pressed on top, sometimes with a bit more clay (mayo) and voila, you are done.

We all enjoyed making these alpine sandwiches, and then placing the assemblages into sand and gravel, which filled our troughs that we brought. Then, smaller plants, some rooted into pure tufa rock, are places around the structures we made, and finally top dressed with gravel.

Trough are a traditional English method of cultivating certain more challenging high alpine plants which prefer particular conditions such as scree, crevice or tight rock cracks, where they often grow and mature into tight, hard, bun-like structures, or, simply remain small. Although these plants demand exacting conditions, often a complex combination of fast drainage, constant moisture and frigid winters with no thaw, fast snow melt, permafrost, etc, alpine plants are becoming more popular with people who are concerned about the environment, for they are more endangered than ever, with threats of global warming, and ski areas being relocated higher in the alps and world wide, the declining phenomenon of permafrost in Alaska, and other environmental threats from the encroachment of humans into fragile habitat, if you are looking for a true 'green' statement that really means something, an alpine trough garden may be something to consider. These are not easy plants to get, or to grow, but once established, are rather care free, which is surprising, even to me. A perfectly planted trough can remain untouched for years if sited well.

This workshop introduced many of us to a new method of growing these fussy plants. The method is just about the exact opposite of how the world of rock gardeners have traditionally cultivated these plants, so sit tight, and listed. These hard, limestone encrusted Saxifrages and alpine gentians and primula which typically would be grown in a gravelly, mix of perlite, rock chips and soil, are instead, planted in wet clay. That's right, wet, sloppy, clay. This is the odd part of this method, - the clay, since it seems counter-productive to what one normally uses to pot alpines in, mainly, and alpine mix which is fast draining, with a little organic material. But when one thinks about the science of it a bit more, you can see the logic. Many alpines grow best, to character, dense and tight buns, when grown in pure tufa or limestone rock. Their tiny hair-like roots can move between the channels in the rock, and the plant grows hard and dense. Clay, when surrounding the roots, is mostly limestone elements and particles, with enough grog and chip to still move water through, but only when not fired (think clay pot, when wet), It is both porous and solid. I assume the clay soil once dry, never becomes mud again, but simply sponges water in a capillary action. And since the volume of clay is small, the mass never really exposes its surface to large amounts of water, since the clay is basically filling a crevice, and not a pot. Gravity and capillary action drays water up and down, and in this 1/4 -1/2 inch sheet of dry clay sandwiched between to porous slabs of rock, the perfect temperature and moisture levels are maintained.

Of course, we still need to see results, so stay tuned. But the pieces I have of pure tufa, in which silver saxifrages and Primula allioni are growing in, are 2 years old, and in perfect, hard, character, as if growing on top of the Alps. And, they are in full sun, in troughs, which I rarely water, if at all in the summer, and are exposed to all the winter snows and cold a New England winter can toss at them.

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