Sink and trough gardening

Create a miniature alpine landscape with year-round interest. Planting into sinks and troughs raised off ground level lets you admire these often brightly coloured jewels close at hand.

Planted up crevice trough

Quick facts

Suitable for Sinks and troughs
Timing Create fake stonework when cool but not frosty; Plant up in spring
Difficulty Moderate

Suitable for...

Planting alpines and rock plants into sinks and troughs is a perfect way to provide the well-drained soil conditions and open sunny position they need to thrive. You have the opportunity to enjoy flower and foliage throughout the year.

Stone sinks are traditional for planting into, but it is quite acceptable to ‘make’ the stonework yourself and apply it to any rigid container such as an old glazed sink or even a polystyrene fish box.

How to do prepare a sink for planting

Positioning the sink

Choose a sunny, open spot, away from the drip of trees. Mount it on supports that are not obviously visible and ensure these are not too high, to avoid giving a 'perched' effect. A height of approximately 45-50cm (18-20in) from the ground to the top of the trough will give the right sort of scale, except on a paved area where only a few inches high will give a better effect overall. Make sure the trough is level.

Drainage and compost

Cover drainage holes with squares cut from a piece of old shade netting, piece of terracotta pot or stones. Prepare compost by mixing equal parts of John Innes No.2 and coarse grit (use John Innes Ericaceous instead of No.2 for acid-loving plants).

It is unnecessary to put a layer of pebbles or grit in the bottom of the s ink. This can hinder drainage.

Planting a sink

  • Fill the trough with the compost, leaving a gap of 2cm (¾in) to accommodate a grit dressing after planting
  • Arrange a few 'architectural' rocks to suit the scale and eye
  • Plant your selection a little high when planting leave space for the 2cm (¾in) deep collar of sharp grit or other decorative aggregate. This helps to conserve moisture, prevents heavy rain splashing soil on flowers, and reduces risk of stem rots. The grit will reduce weed growth and may help reduce the compost slumping too quickly
  • Using a watering can with a sprinkler rose, give a really good soaking until water is seen appearing from the drainage hole

See gallery step-by-step for planting  a crevice trough.

Ongoing maintenance

  • Do not allow troughs to dry out, especially during the first growing season
  • During the plants' resting time no additional watering will be necessary in normal winter conditions, but watch out for the drying action of frost, especially as some alpines start root growth in very early spring
  • A carefully planted trough will need the minimum of attention
  • Deadhead as necessary and cut back herbaceous types
  • Scatter a dressing of Vitax Q4 slow-release fertiliser, or similar, in early spring
  • Check for vine weevils and slugs which love tender alpine growth

Creating a crevice trough STEP 1: Insert slates or stones in a layered fashion to mimic rock strata
Creating a crevice trough STEP 2: Fill the container with equal parts John Innes Compost No.2 compost and coarse grit
Creating a crevice trough STEP 3: Work more gritty compost between the crevice layers
Creating a crevice trough STEP 4: Carefully plant small alpines into the crevices, working the roots down with a dibber or pencil
Creating a crevice trough STEP 5: Top off with more grit, water in and stand in an open sunny position
An alpine trough with perspex to keep the crowns dry in winter
    Creating a crevice trough STEP 1: Insert slates or stones in a layered fashion to mimic rock strata Creating a crevice trough STEP 2: Fill the container with equal parts John Innes Compost No.2 compost and coarse grit Creating a crevice trough STEP 3: Work more gritty compost between the crevice layers Creating a crevice trough STEP 4: Carefully plant small alpines into the crevices, working the roots down with a dibber or pencil Creating a crevice trough STEP 5: Top off with more grit, water in and stand in an open sunny position An alpine trough with perspex to keep the crowns dry in winter

    Fake stone and hypertufa troughs

    Preparing glazed sinks to make ‘fake’ stonework (hypertufa)

    Heavy sinks are best mounted on stones or old bricks, approximately 15-25cm (6-9in) high, and prepared in situ.  Smaller ones can be prepared where convenient and moved to a permanent site when dry. Drying usually takes about three weeks, after which sinks can be planted.

    A simple technique to prepare old glazed or domestic sinks to look like stonework is as follows:

    • Remove any metal fittings
    • Clean and wash the sink thoroughly and allow to dry
    • Apply a coating of Unibond or other adhesive (obtainable from most ironmongers' stores). Allow this to become tacky while mixing the hypertufa as follows:

    Traditional mix (all parts by volume)
    1 (or 2) parts peat substitute 
    1 part sharp sand  
    1 part fresh Portland cement  

    The peat-substitute in the mixture provides the stone colouring and variations in the quantity of peat-substitute used will give corresponding variations in colour of the finished product. Too much will give a less durable finish.

    • The best time to carry out the work is during cool, but not frosty, weather as the coating mixture will then remain workable for longer than it will in warm, dry conditions
    • Wear household gloves – hypertufa and cement are corrosive
    • Avoid making the mixture too wet. A 9 litre (2 gal) bucket full of the complete mixture is approximately sufficient for coating an average-sized sink, so start with a half bucketful, treating a section at a time. Add the water gradually
    • Apply the mixture to the tacky adhesive. This should extend over the rim, 5-8cm (2-3in) down the inside, and 8-10cm (3-4in) under the base, so that on the finished sink no glazed surface is visible
    • Apply two or three coatings for greater durability and resistance to frost damage
    • To simulate stonework, mark or jab the surface with an old paintbrush or chisel as the material dries
    • To encourage moss and algae to give an appearance of age, apply liquid manure with a paintbrush

    Hypertufa troughs

    Traditional stone troughs, and even glazed sinks, are now becoming difficult to obtain, although reproductions are available. As an alternative, new troughs can now be entirely made from hypertufa.

    Prepare the mixture as for coating but add a little more water.

    1. Find two wooden boxes that will fit inside one another, with a cavity of 5-7cm (2-3ins) between them.
    2. Stand the larger box on blocks so it may be lifted easily once finished.
    3. Pour two thin layers of the hypertufa mix into the base with strong wire netting between the layers and parallel to the vertical sides.
    4. Press two 5cm lengths of thick dowels or pegs through the hypertufa to make drainage holes.
    5. Fit the smaller box inside the larger, with wire netting between the two, and fill the space with the mix, tamping it down to remove air pockets. For a single trough strong cardboard boxes can be used as a mould.
    6. When the cavity is full, cover the trough with a sheet of plastic for at least a week while the mix sets and protect the trough from frost, if necessary. 
    7. When the mix has set hard, remove the boxes and dowels. If the boxes do not slide off easily, ease them off carefully with a fine chisel and a small hammer.
    8. Roughen the surface of the trough with a wire brush and paint on a coat of liquid manure to encourage algal growth.

    You can use a fish box to create a lighter trough;

    • Work on a large sheet of polythene
    • Make two drainage holes of 2cm (¾in) in the base
    • Wrap the whole box with small gauge chicken wire
    • Start by covering the base, ensuring the hypertufa mxture is well packed through the wire
    • Make the layer no less than 2cm (¾in) thick
    • Carefully turn the box right side up and work on covering the sides and down 5-8cm inside the rim

    Choice of plants

    You may like to choose a mixture of plants that flower (or have attractive foliage) at different times of the year.  Alternatively, you can plant one type of plant en masse, such as sedums or for a shady spot in the garden, ramondas.

    A trough full of silver-leaved saxifrages can be extremely attractive all the year round. Choose plants carefully to avoid rampant growers that will smother the rocks and slower-growing neighbours.

    Please see our web profile on plant selections for sinks and troughs.

    Problems

    If the temperature is high (over 20°C) and the hypertufa dries too quickly, it can crack. Wrap the sink in damp hessian to allow the covering to dry gradually.

    Advertise here

    Gardeners' calendar

    Advice from the RHS

    Find out what to do this month with our gardeners' calendar

    Advice from the RHS

    Did you find the advice you needed?

    RHS members can get exclusive individual advice from the RHS Gardening Advice team.

    Join the RHS now

    Discuss this

    for the site or to share your experiences on this topic and seek advice from our community of gardeners.