Ideas for Troughs & Tufa

One of the best "trends" to hit mainstream gardening is container planting - trough gardening for most of us. Adaptable and accessible to most any situation, troughs can be used as accents to an alpine garden or perennial garden; or, they can be the sole feature with a varied number of sub-themes. Each container represents its own particular ecological/horticultural expression. Using the Czech style of narrow clay crevices, it is possible to provide a better growing environment for both the easy alpines and those that we know less about their specific cultural needs.

Containers - Almost any sort of container will do for a first effort. Hyper-tufa troughs are readily available and will last ~ 10 years or more. For more permanent troughs, look for ones that have a good customer rating.

Some recommendations:

Betsy Knapp - sleek, modern looking, these troughs are light and very, very durable. Also, Betsy can make shapes and sizes not normally seen. Here are some examples from Matt Mattus' garden blog.

Wrightman Alpines - a variety of natural stone troughs in sandstone, limestone and tufa. The tufa troughs are lighter in weight (~40%) than other stone. Tufa has an earthiness that helps to create the mountain atmosphere of the planting.

HaddonStone - manufactured stone; but, very well sculpted troughs. They are heavy and permanent. Only 2 styles listed on the website.

Soil - We use Spanish River Carbonatite(SRC) in most of our container mixes. The carbonatites are particularly good sources of minerals in a form that feeds at a steady rate and does not over-stimulate growth. A reasonable substitute would be "greensand", which may be easier to source.

For troughs I use:

-a coarse sand as a base material, ~ 65%

- SRC ~20%

- composted pine bark or some other organic material ~15%

This is a physically heavy mix, but it provides long-lasting, stable structure and nutrition for the plants. Mixes that use a lot of organic material tend to negatively change in a short time. One could add pumice (Pumice Distributor (Dry Stall)) or Perlite to lighten the mix.

Planting- Now comes the part where you must ditch all the poisonous cultural teaching of agrarian-derived societies; i.e., the rock formation that you will create will be elevated and not appear to be stable. I find it easier to deal with pre-school children. They instinctively "get it." For the chasmophytic plants, what they desire is a place without the competition of those horridly aggressive flatland grasses and forbs _ the basis of agricultural crops. When you think about it, the narrow crevices where the special ones grow will have thin veins of soil that have been brought in by wind and water. The soils that will stick are mainly the smaller particles of silt and clay which also provide more nutrition for the plants though the actual volume may not be very much at all.

So, for the basic formation in a trough, you can use any type of stone that has flat surfaces that you then align to form a narrow crevice. It may be vertical or tilted. There may be 1 or 2 parallel lines in the formation for the trough. Don't make it too complicated or you will be lost in the details. This crevice line presents a significant space for a good number of plants to grow. One side of the crevice is plastered with a sticky clay. The plants, rooted cuttings or seedlings (minus most of their potting mix) are laid out on the clay with their roots suitably spread out. You can see now the advantages:

1. a greater choice of plants as larger, potted specimens can be used
2. immediate contact with a growing medium (clay), and less damage to the roots.
3. "perfect drainage"- I love those words used to describe the right site for a plant, -rich soil, moist, but well-drained." _ how is that possible after a huge rain and the air turns steamy??? An elevated position means the crevice will provide a more constant moisture level and allow the area around the crown to dry quickly. The crown is where most disease problems occur.
4. The drama of vertical plantings, cascades falling over a cliff are obvious and appealing. This is the best way to improve the beauty of a planting. Although the technique is simple, I am always amazed at the variety of compositions that I see in the workshops we run.
5. It is important to keep the crevice to less than1/2" wide. Capillary movement of water is better in a narrow column. Also, some erosion of clay will occur until the plants cover the line. This is less of a problem in a thinner line. You can always dress-up the line with more. Adding some small gravel bits helps too.
6. Almost any plant in our catalogue can be used. The decision then lies in what the combinations will be. Ever wonder how confusing that can be. The great thing about this method is it intuitively directs you to place things. To make the verticals work, you need small mat-formers such as arenaria tetetraqutra, androsace villosa, draba bryoides, silene acaulis, gypsophila aretioides, asperula spp. and the ultimate plugger sempervivum cvs. of the tiny sort. These plants spread quickly enough to stop erosion. They are small enough that other, showier plants can grow through the mats. Semp's which are so easy to establish are especially good. Once they outgrow their usefulness, they can be removed with little disruption. The mats provide a good foil to set off the choicer plants _ these are myriad in number, tight growing androsace spp., kabschia's and tiny campanula like c. zoysii.

Bread for the crevice sandwhich.

Clay (butter...) smeared on both sides of the rock

Remove soil and gently press the roots onto one side of the clay smeared rock.

Bring the rocks together and with force press hard to get any air bubbles out of the clay.

Plants will fill and trail down the crevice as they grow. Touch up with extra clay where needed.

The method used does take a little nerve and daring, but that's why you're here, right! It helps to actually see it done. I'm sure as more people employ the technique and the results are seen, that it will become a valuable tool. 

Just think, the Czechs were doing this 25 years ago.

(June 2010)