Rock Garden Soil FAQs

What type of soil do I need for rock-garden plants?

Most rock-garden plants growing in sunny positions require well-drained soil. For those growing in wetter conditions I recommend equal parts by bulk of peat, sterilised loam, and grit (not sand) and half a part of shingle; the grit should have grains 3-13 mm (1/8 – ½ in) in diameter, and the shingle approximately 6 mm (¼ in). For drier sites omit the shingle in the mixture. As long as this goes into the top 150-250 mm (6-10 in) of soil, the remainder can be the garden soil you already have. For shadier-area plants, you should either double the peat content or, better, use leaf mould instead of peat.

I have inherited a rock garden which has been sadly neglected. How should I set about improving it?

The first task is to propagate any of the plants which you want to keep, then remove and dispose of all but the best of the dwarf conifers, which can be retained to good affect and, hopefully, last a further 15 to 20 years. If there are any perennial weeds, remove them carefully by hand or with a weedkiller. Lastly, remove the stones to a pile well away from the site and re-build. If you try short cuts in this process, such as patching up the itructure, I am sure you will be disappointed with the results.

Do I need to prune any of my rock-garden plants?

Yes, you should remove dead and decayed wood from shrubs and old flower-heads from cushion plants; cut all herbaceous plants hard back in late winter or early spring; and pull off dried bulb foliage (but only when it comes away easily). Use a pair of shears on the stronger growers—trailing plants such as aubrietas and helianthemums—so as to keep them compact and encourage them to produce the maximum amount of flowers next time.

How often do I need to water my rock-garden plants?

Frequency will obviously depend on the weather, but never water more than once every five days. However, when you do water, give the plants a good soaking, until the soil is wet to a depth of at least 150 mm (6 in).

I am told that rock-garden plants are prone to ‘rotting off. How can I prevent this happening?

This problem affects grey-foliaged and cushion plants, which can retain water in their compact leaves or hairs, and more especially plants producing rosettes. Putting extra grit below the area of planting will help, and in the late autumn I like to put a cover of glass over these plants. This cover must be removed in the spring, when the sun has become warm enough for growth to begin.

How do I get rid of perennial weeds?

In a rock garden in otherwise good condition, use a brush to paint the leaves of perennial weeds A/ith a suitable weedkiller when :hey are in full growth in June. If :he weeds persist repeat the dose n July, provided that the ground is -noist and the weeds are pulled away from any plants.

Then leave the site for 12 months before starting from scratch.

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