How to improve your soil for borders that thrive

How to improve your soil for borders that thrive

By improving the soil around trees and shrubs, they will repay you with strong, healthy growth and long life. A failsafe guide by our partners, Amateur Gardening.
It's amazing that established mixed borders planted with trees and shrubs thrive as well as they do in gardens around the UK. Most people snip bits off these large plants when they overhang paths or generally get too big, but never think that they need feeding and watering in the same way as bedding, or plants in pots. Planted fairly densely, they’re awkward to get to, and anyway, they generally get by.

But to get the best from your garden borders, all plants need feeding and the soil improving. Border plantings can be in place for decades, and big plants suck the goodness out of the soil. Putting it back is quite a straightforward job. It should be done each year, any time between late autumn and late March, as long as the soil is not frozen or waterlogged.

Rake and weed 

First, rake out loose fallen leaves and debris from under all plants. Next, identify and mark positions (usually around the edges of the border) where bulbs and deciduous perennials are nestling under the soil. If you spot any perennial weeds such as dandelions, dig them out, root and all.

Add fertiliser 

Once you know where everything is, spread a generous amount of bonemeal fertiliser around the root area of all plants (pictured). Bonemeal is high in phosphates, which promote strong root growth. It’s OK to apply this type of feed in winter as it does not promote tender top growth or flowers that would be damaged by frost. 

Apply two to four good handfuls over the root area of bigger shrubs, and a good sprinkling around the crowns of perennials. This usually means covering the whole soil area of the bed. 

Hoe the soil

Now use a Dutch hoe or a long-handled cultivator and tickle up the top surface of the soil so it’s loose and fluffy. Work around bulb plantings and the crowns of perennials. Don't dig deeply, as many shrubs are shallow rooted and could be damaged. Hoeing does three things: it removes any small weeds; helps to incorporate the bonemeal into the soil; and opens up the surface to help water penetrate.

In the highly unlikely situation that the soil is very dry, water well after hoeing. It's probable at this time of year that rain will have penetrated deeply, so watering should be unnecessary.

Add mulch

Finally, apply a mulch of home-made garden compost, well-rotted horse manure (available bagged from garden centres) or similar humus-rich material such as bark chippings (pictured) over the surface of the soil, 1in to 2in (2.5-5cm) deep. Don’t cover the crowns of dormant perennials or bulbs, and keep the mulch an inch or two away from trunks and stems of trees and shrubs, as direct contact may cause damage.

The mulch suppresses weeds and locks moisture into the soil. In time it will be drawn into the soil by worms, improving its structure and adding nutrients.