Planting a Trough


Alpines and rock garden plants look particularly attractive when grown in troughs and sinks, and this containerised method is a great idea for gardeners with limited space or time. Whilst stone sinks and animal troughs may be the most traditional materials, these now tend to be expensive and hard to find. These days, large terracotta pots and tubs, troughs made from reconstituted stone or glazed sinks coated in hypertufa are more commonly used. Whatever material you choose - make sure that it is frost-proof and has enough drainage holes to ensure a free flow of water through the compost.

Positioning the Container

Take some time to consider where you want to position your container - once filled, they are difficult to move. Most plants prefer an open site that receives sun for at least part of the day, but protected from winds. You may also find it useful to place them as near to a tap or hosepipe as possible.

Containers should be raised off the ground by about 45 cm (18 in) to allow water to drain away easily and the plants to be seen comfortably. This may be achieved by placing brick or stone pillars at the corners. If your sink or trough contains just one drainage hole, make sure that you angle it slightly with small slivers of stone so that the hole is at the lowest point.

Filling the Container

  1. Place a layer of fine-mesh netting over the base of the container, and then add in some crocks to cover the drainage holes.
  2. Add a 7 -10 cm (3-4 in) layer of coarse grit or stone chippings.
  3. Add a layer of fibrous peat substitute (or peat) or inverted, thinly cut turf.
  4. Mix in some slow-release fertilizer to the correct soil medium for your plants; most prefer a mixture of 2 parts standard potting compost to 1 part stone chippings. Take a look at the following soil recipes for moisture-sensitive, acid-loving or specialist alpines.
  5. Partially fill the trough with compost and firm gently.

Adding the Rocks

Rocks may be placed in the container to give height and allow a greater depth of compost. Crevices and niches in the rocks may also be used to support plants, especially if hard tufa is used. Roots will spread into the porous rock, which retains water and is well aerated.

  1. If you intend to grow your plants in tufa, make holes (using a hammer and chisel or a drill) 2.5 cm (1 in) in diameter, 5-7 cm (2-3 in) deep and no less than 10-12 cm (4-5 in) apart. They should be drilled vertically downwards on horizontal surfaces and angled at 30-45° on vertical or sloping faces. Soak the tufa in water overnight before positioning in trough.
  2. Position your rocks in the container, burying about a third to a half their height in the compost to ensure they remain stable.
  3. Place the rocks so that they form niches and crevices and provide both sunny and shaded faces to suit different plants.
  4. Continue to fill the trough with the compost mix, levelling it around the rocks. Finish about 5 cm below the top of the trough to allow you enough room to add a top layer of gravel.
  5. Insert a little sharp sand into each tufa hole and add some compost.
  6. Water the container thoroughly and leave to drain completely before planting.

Planting up the Trough

It's a good idea to choose compact plants with similar growth rates.

  1. Set out plants in their pots on the compost to check the arrangement and spacing.
  2. Gently slide the plants out of their pots and loosen the root balls.
  3. Carefully dig small holes of a sufficient depth to ensure that the plants are planted at their original level.
  4. Position the plants in the holes, fill in and firm well.
  5. Water the compost thoroughly, using a rose attachment on your watering can.
  6. Top-dress the trough with a 2.5-5 cm (1-2 in) layer of coarse gravel or stone chippings.

Planting in Tufa

  1. Remove the bulk of the compost around roots of the plants by washing them in water.
  2. Gently ease them into the planting holes, using a small dibber or flat bladed knife.
  3. Sprinkle compost into the holes around the plant.
  4. Make sure that the neck of the plant is firmly bedded in and is not protruding from the hole.
  5. Firm the compost and wedge small pieces of rock around the plants to hold them in place.
  6. Water thoroughly.
  7. Keep the tufa moist until the plants are established. You will need to soak the tufa regularly in hot, dry weather.