Sinks make excellent containers for alpines or rock plants, and they form attractive features on both formal and informal patios. One can, in fact, create miniature rock gardens in these containers.
The old shallow stone sinks are worth searching for, but are not easily found these days, for they are scarce collectors’ items and demand a high price. The alternative is to convert a white glazed sink so that it resembles stone. You should be able to pick up one of these quite easily from a scrapyard or local builder for they are frequently discarded with the boom in fitted designer kitchens. Perhaps this is more practical, anyway, for a white glazed sink has a greater depth than the old-fashioned stone versions, so there is less risk of the compost drying out rapidly during warm weather.
A glazed sink is covered with hypertufa, which is a mixture of cement, sand and peat. When this has hardened and has become well weathered it looks like natural tufa rock. Before you apply a hypertufa mix the sink has to be treated with a PVA adhesive, to ensure the hypertufa sticks to the glaze. This adhesive, which is used in the building trade, is available from DIY and hardware stores. Brush it on the outside of the sink and part of the way down on the inside. When it has become tacky (before it completely dries) apply the hypertufa mix.
The hypertufa mix consists of 2 parts sphagnum peat, 1 part sand and 1 part cement – parts by volume.
Add sufficient water to make a stiff but pliable mix. Then spread it about 12 mm (Vi in) thick all over the treated parts of the sink, firmly pressing it into place with your fingers. Leave a fairly rough texture to resemble natural stone.
The hypertufa will take at least two weeks to harden thoroughly, after which the sink should be filled with a solution of permanganate of potash, and left for at least 24 hours, which will remove any harmful chemicals from the cement. Afterwards wash out the sink thoroughly.
Before filling the sink with compost decide where you want it on the patio – choose the sunniest spot -and then stand it on two rows of bricks, two courses high, to raise it slightly above ground level. The bricks can be bonded with mortar for stability. Place over the bottom of the sink a 2.5 cm (1 in) layer of crocks (broken clay flower pots) to act as drainage. Put a large piece over the drainage hole. Cover the crocks with a thin layer of coarse peat or leafmould. Then fill to within 2.5 cm (1 in) of the top with potting compost. A soil-based type is best for alpines. Add to this one-third extra of coarse horticultural sand or grit to ensure really good drainage. The sand or grit should be free from lime.
Before planting, bed a few pieces of natural rock into the compost to create a mini rock garden. Set rocks to about one-third of their depth into the compost.
Choosing plants
First plant one or two dwarf conifers to give height and contrast in form. The most suitable is the tiny Noah’s ark juniper, Junipems communis ‘Compressa’, with greyish-green prickly foliage.
For the edges of the sink use trailing alpines like Phlox douglasii, a mass of lilac flowers in the spring; and the pink, early summer flowering Aethionema armenum. The spreading, silvery-leaved Raoulia hookeri (also known as R. australis), will ‘soften’ the edges of the sink as it becomes established.
Fill in with more alpines, choosing those of restrained habit so that they do not take over the entire container. Suitable kinds include the thrift, Armeria caespitosa, a mound-forming plant studded with pink flowers in the spring; the rose-pink, early summer flowering rock pink, Dianthus neglectus; Geranium cinereum, spring flowering, pink blooms; Gypsophila caucasica, white flowers in early summer; saxifrages like the white, spring flowering S. X burseriana; and the cobweb houseleek, Sempervivum arachnoideum, whose rosettes of succulent leaves are covered with white webbing, like spiders’ webs.
When planting is completed cover the surface of the compost with a thin layer of stone chippings or pea shingle. This will create an attractive appearance and help to ensure good drainage around the plants.
Many people with small gardens like to grow some fruits and vegetables and often opt for cultivation in containers on the patio. Certainly many crops are suited to container growing and although essentially utility plants, nevertheless they can, with a little thought, be made to form attractive features in themselves or to combine pleasantly with ornamental plants.