Tufa and Alpine Garden Display
Use a piece of Tufa to create a rocky outcrop for a collection of delicate alpines. The crumbly, porous rock offers the ideal growing conditions for many of these tiny plants.
A collection of tiny alpines will provide a fascinating and compact display for the patio. Many require an extremely free-draining medium to survive and will thrive if grown on a piece of tufa (porous rock), with their roots pushing down into the rock itself. Tufa looks most effective when partially covered with carpet-forming Stonecrops and Raoulia, with a few tiny flowering Primulas or Saxifrages to add colour.
Tufa is available from some of the larger garden centres, but it is a good idea to phone around first to check on availability. Large pieces look most effective when free-standing on the rock garden or patio, but they are generally quite expensive. Small pieces can be made to be more of a feature, when they are used in the top of a cement trough to form a rocky outcrop.
Protect from heavy rain
After planting the alpines, place the trough in sun or light shade, preferably in a sheltered spot where it will be protected from heavy rain. In warm weather, water the display regularly, using a watering can fitted with a fine rose.
PICK AND PLANT
A wide choice – There are many alpine plants that are suitable for planting in a trough or in tufa; most garden centres offer a large range, sold cheaply, especially in the Spring. The tiny plants will look most in proportion in a small trough.
Stonecrops (Sedum species) – these carpet-forming, fleshy perennials are ideal; try S. lydium with its bright lime green and scarlet colouring, or S. oreganum, which has thick leaves suffused with bronze. S. spathulifolium is very attractive, with unusual silver and red markings.
Primulas – most of the alpine Primulas are suitable for growing in tufa, but choice may be limited by availability. Look for cultivars of P. allionii, which form little neat rosettes and produce tiny, pale purple blooms in the Spring; also P. frondosa, the leaves of which are covered in a fine white dust (farina), and which has lovely pinkon tall stems.
Raoulia – these evergreen, carpet-forming plants have tiny, silver leaves – try R. australis or the larger-leaved R. hookeri.
Saxifrages – many are suitable; choose from the countless, compact, cushion-forming types, like Saxifraga ‘Gloriosa’.
Houseleeks (Sempervivum species) – most of the rosette-formers will thrive in these conditions, but choose one of the smaller- growing types that will not look out of proportion in the small trough.
Preparing the Trough
Place a good handful ofmaterial in the bottom of the trough, making sure that you cover the drainage holes to prevent compost from leaching out during watering.
Pieces of broken flower pot or some spare pieces of slate or stone are all suitable as crocks.
The alpines will require a free-draining compost to grow well, as these types of plant dislike moisture around their crowns. Mix up a suitable compost by adding about a third by volume of horticultural grit to a proprietary compost and combining well.
Fill the trough with the free-draining compost mixture, making sure you do not displace the crocks in the bottom. Firming as you go, make sure the trough is filled to the top so that the plants will be level with the rim and the mat-forming specimens can spill down the sides.
If the piece of tufa is small, stand it right on the top of the compost to make the most of it. If the rock is large, sink it into the compost a little to make it look more like a natural rocky outcrop. You may need to remove some of the compost from the trough to do this.
Planting the Trough
It is necessary to make holes in the tufa in which to plant the alpines.
Using a screwdriver, work away at the crumbly rock to form a hole about 5cm (2in) deep and about 2.5cm (1in) wide. Make holes for the other plants in the same way, spacing them evenly over the rock.
Remove the plants from their pots and tease the compost carefully from between the roots of each to leave a small rootball, which will fit in its hole in the rock. Arrange the roots in the holes and fill around them with a little compost. Water and mist the plants thoroughly.
Plant the remaining alpines in the compost in the trough around the tufa, to the same depth that they were in their original pots, and space the plants to allow room for them to spread. Try to group together plants of the same species for a more natural look.
Finally, cover the entire surface of the compost with a 1cm (l/2in) layer of horticultural grit. This will not only provide an attractive surface, but also serve to keep the crowns of these damp-hating plants away from the moist compost underneath so that they won’t rot.