Building a rock garden (or rockery) extends the range of plants you can grow by creating a specialist environment for alpine species. Alpines grow on rocky mountain slopes where the drainage is good and there is plenty of light. By using carefully placed rocks you can mimic these conditions in miniature: a large rock set at the right angle will create both north- and south-facing slopes, for example.
You may also want to consider creating an alpine scree in a flower bed, especially if you have a sloped garden.
Choose your rockery site
First you need to choose the right location for your rock garden. It should be well away from trees and shrubs so that it gets maximum light levels.
A rock garden can be as big or as small as you want. If you’re gardening on a grand scale you may need to hire earth-moving equipment to shape the land and lift in boulders; on a smaller scale you can manage with ordinary garden tools, though a crowbar can be useful to manoeuvre large rocks.
A rock garden can be built on level ground or on a slope, and is an ideal way to cope with a steep garden, front or back. To build on level ground either dig down or create a small mound.
You could also build a miniature rockery in a container such as a large pot or an old sink.
Find out about growing Alpines in troughs, sinks and containers
Rockery ideas and inspiration
Rockeries can come in all shapes and sizes, from miniature rock gardens in containers to large slopes.
For inspiration and ideas visit Pinterest to see what other gardeners are doing with their space.
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Building a rockery: what you need to know
What time of year should you build your rockery?
Although you can build a rockery at any time of year the best time to start it is in winter. This gives the rocks and soil time to settle before adding the plants in spring.
Which type of rock?
Local stone will always look most natural –, for example granite in South West England, slate in Wales and sandstone in central England. For information about rocks in your region visit the Open University’s page on UK rocks.
Reclaimed rocks from a reclamation yard are ideal, as are rocks bought directly from local quarries. You could also look online at sites such as eBay, Preloved, StreetLife and Gumtree to find available rocks in your area.
Read our guide to choosing and buying stones for a rock garden
The best compost mix for alpines
Make your own alpine compost by mixing together equal quantities of weed-free topsoil, horticultural grit and leaf mould. If you don’t make your own leaf mould buy coir instead. Use this mix to fill the planting pockets and crevices between rocks.
Alpine soil shouldn't be overly rich, so you do not need to add fertiliser or manure.
What you need
To build a rockery you will need:
- A spade and shovel for moving soil
- A trowel for planting
- A crowbar for manoeuvring heavy rocks
- Stretch of permeable landscape fabric
- Enough hard core/rubble to cover the area (broken pots, old bricks and stones are ideal)
- Rocks of all sizes – large ‘keystone’ rocks and small stones for the surface (ideally locally sourced)
- Weed-free topsoil
- Compost (see above for ideal Alpine compost)
- Alpine plants
Rockeries are ideal for sunny well-drained slopes
How to build a rockery
Mark out the area where you are building your rockery with pegs and string.
Start by clearing the soil of weeds. If you have problems with tough perennial weeds such as ground elder or bindweed you may need to use weedkiller.
Add a layer of hard core or rubble to support the rocks and to improve drainage.
Add a layer of permeable landscape fabric – this will stop the rockery soil from washing away, as well as preventing any weeds from growing up through the stones.
Set the biggest rocks or ‘keystones’ in position first – you may need to use smaller rocks or even bricks to hold them in place. Work out where north is, so that you can angle rocks to create different micro-climates within the rock garden.
Then ‘bed’ them in with a layer of weed-free topsoil – bagged topsoil will be sold as weed free, or you can sieve your own, but this won’t get rid of small weed seeds.
Fill in the site with smaller rocks, bedding in as you go with more topsoil.
Use some of the small rocks to create planting ‘pockets’ – small horseshoe shapes where the rocks will hold the compost mix in place.
Finally use small stones, grit or gravel as a mulch layer wherever you see remaining are earth.
A rockery creates a specialist environment for a wider range of plants
How and when to plant
You should plant alpines in spring, as this gives them a whole growing season to establish before winter.
Plant sun-loving alpines on the south side of large rocks, and those that like cooler conditions on the opposite side.
Water the plant while still in its pot. Then remove the pot and gently tease out some of the roots – particularly if they are wound round and round the rootball. Plant the alpine in a planting pocket or crevice between rocks, firming the compost mix round the roots. Finish with a handful of horticultural grit or gravel – this helps drainage and also acts as a weed-suppressing layer.
Read our suggestions for rockery plants
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