Troughs and sinks should be treated like miniature gardens. They make ideal homes for many small slow-growing alpines, and each one should be regarded as an individual specimen with its own particular characteristics. Above all, however, troughs and sinks are fun to make, and hours of pleasure can be had in their creation and in the selection of suitable plants. The surface can be enhanced with pieces of rock, placed to provide various niches for the plants, and making it resemble a miniature rock garden.
A container brimful with colourful little alpines can be a real focal point in the garden. Placed on a patio or on the edge of a terrace or lawn, a well-planted container can add interest for many months of the year.
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Choosing the right container for Alpines
Containers come in all sorts of shapes and sizes, but for alpines the best by far are stone sinks and troughs. Old sinks are scarce today and therefore very expensive, but new ones are being made out of stone and also other materials, including terracotta and cement, and these are often readily available at garden centres and nurseries.
When you select a trough or other container for alpines, make sure that they have adequate drainage holes at the base. If not, additional holes will need to be drilled.
Always place the container in its final position before filling it – it will become heavy and far more difficult to move once it is full of compost (soil mix). At the same time, raise the container off the ground and stand it on bricks or blocks, which not only enhances the appearance but will allow excess water to drain away quickly. Raising the container in this way also prevents worms from getting into the trough or container from the ground below.
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Using a hypertufa mix
Alternatively, troughs can be constructed at home relatively cheaply using a hypertufa mix. Hypertufa, which simulates natural rock, can be very effective. It is made from one part per volume of coarse sand or fine grit, one part cement, and two parts sphagnum peat, which is mixed into a stiff paste.
Old glazed sinks can be coated with hypertufa mix to make them look like a stone trough. The same mix can be applied over the surface to a depth of about 2cm(3⁄4in).
In order for the hypertufa to stick properly to the sink, roughen the surface with a scourer, such as a glass-cutter, and coat the surface to be covered with a bonding agent, such as epoxy resin.
Properly constructed, hypertufa will last for many years, and after a while it will become embellished with mosses and lichens, as real rock does, to make it look authentic.
How to make a hypertufa trough
Use two cardboard boxes for the inner and outer moulds, allowing for walls 5–7.5cm (2–3in) thick. Coat the inside of the outer mould and the outside of the inner mould with oil to prevent the hypertufa from adhering to them.
The base and sides of the trough should be reinforced with fine-mesh wire netting, which can be worked into a trough shape that will fit midway between the outer and inner moulds.
Making a hypertufa trough steps 1 and 2.
Place about 2.5cm (1in) of hypertufa mix in the base of the outer mould, firm down and level carefully, then place in the wire mesh. Add a further 2.5cm (1in) of hypertufa. Push through several base-depth pieces of broom handle to create drainage holes. These can be left until the hypertufa has set firmly.
Put the inner mould inside the outer one, and fill the space between the sides with more hypertufa mix. Firm down well and evenly to eliminate all air pockets.
Making a hypertufa trough steps 3-4
Once it is firmly set, remove the moulds and carefully knock out the drainage plugs. Roughen the outer surface of the trough with a stiff wire brush, and round off the edges to give the trough a more natural look.
Compact alpines such as Antennaria dioica ‘Minima’ are ideal for planting in troughs. For added contrast and variety, try introducing a few small conifers or miniature shrubs as well.
Making a hypertufa trough steps 5-6.
Planning your mini rockery
Troughs are miniature gardens. Each is an individual creation that can be enhanced with small rocky outcrops, slow-growing dwarf shrubs (especially conifers and daphnes) and a variety of exciting little alpines.
They can be fascinating to create, and little niches and pockets can be made to accommodate the different plants.
Crevices between adjacent rocks are particularly valuable for alpines such as saxifrages. Troughs can be filled with standard alpine compost (soil mix) or with different compost to suit different types of alpines.
For instance, a humus-based mixture will be suitable for small ferns, ramondas and dwarf willows, while a trough filled with an acid growing medium will be ideal for ericaceous plants such as dwarf rhododendrons, cassiopes and autumn gentians.
It can also be fun to plant a trough with a single group of plants – one filled with different kinds of Sempervivum (houseleek) or encrusted saxifrages can be very appealing, and will provide lasting interest throughout the year.
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How to plant your Alpine trough
Place the trough in its final position before it is filled; otherwise, it will be too heavy to move. Troughs look best when raised off the ground by 20–30cm (10–12in), standing on bricks or concrete blocks. Make sure that they are stable and will not tip over.
Ensure that the trough is level and has adequate drainage holes. Place coarse drainage material over the drainage holes and the base of the trough to a depth of about 10cm (4in). Pieces of broken pot, brick or other rubble will suffice.
Fill the trough with a suitable alpine compost (soil mix), adding it in layers and making sure that it is firmed in adequately, especially in the corners and around the edges. Fill to 2.5cm (1in) from the top.
Decorate the surface with suitable pieces of rock. Angle the pieces into the compost, making sure that about one-third of each piece is buried. This will create mini-outcrops that will provide various pockets for planting the alpines.
Place the selected alpines in the trough, scooping out holes to take the root ball of each in turn. Firm the plants in, but avoid the temptation to over-firm. Place the larger and central plants first, finishing with those around the edges.
Finish off with a top-dressing of coarse grit or rock chippings, making sure they are pushed well under each alpine. Water the trough thoroughly.
If plants are carefully selected, a trough or sink can resemble a miniature rock garden. Add small conifers and dwarf trees to frame other plants, and miniature shrubs to provide contrasting form and colour throughout the year.
Plants suitable for sunny, alkaline troughs
Dianthus alpinus (alpine pink)
Draba aizoides (yellow whitlow grass)
Gentiana verna (spring gentian)
Juniperus communis ‘Compressa’
Linum arboreum (shrubby flax)
Polygala calcarea ‘Lillet’
Saxifraga cochlearis ‘Minor’ (and many other saxifrages)
Sempervivum arachnoideum (and many other sempervivums)
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