Soils & soil analysis

Soils at Wisley

The soil at Wisley plays a significant role in determining the range and quality of the plants grown in the outdoor displays. It is not surprising therefore that much time and effort is put into managing this valuable resource effectively to get the very best from the plants on show.

Intensive use of some parts of the garden has meant that soil structure and fertility have developed over the years as a result of regular cultivation, fertiliser application and organic matter amendment. In contrast, the soil in less frequented areas such as the Pinetum and Arboretum remains relatively unchanged from its natural state. The native soil in the Wisley area is predominantly sandy and free-draining with an acid reaction. To the North of the garden, closest to the River Wey, there are seams of clay mixed with the sand making it less well drained. It is no accident that this low-lying area is where the lake and ponds are to be found. Further away from the River Wey towards the South the land rises to form Battleston Hill which is composed of layers of acid sand and gravel. This steeper, well-drained area is home to a large number of rhododendrons and camellias.

The light sandy texture of the soil means it is quick to warm in the spring and easy to cultivate, but it does lose nutrients and moisture rapidly, and is prone to 'capping' or crusting following heavy rain which can inhibit seedling emergence, and if machinery is used for cultivation, 'pans' or compacted layers can form below the soil surface which resist root penetration.

To help overcome these problems, there is widespread use of well-rotted organic matter both incorporated as a soil conditioner before planting and applied to the soil surface as a mulch. A range of materials are used for these purposes. The main soil conditioners are composted horse manure and wood shavings, home composted garden waste materials and leaf mould. For mulching, shredded conifer bark, double chopped mushroom compost, shredded wood waste and polo stable manure are widely employed. Soil conditioners add nutrients to the soil and improve retention of nutrients and moisture by improving soil structure. Mulches supply some nutrients as they rot down, but their main functions are to suppress annual weed growth, protect the surface structure of the soil and reduce evaporation. This last function is very important because a great deal of water is needed to sustain plant growth on sandy soils during the dry summer months and it is important to make irrigation as efficient as possible.

To be able to grow the widest range of plants, some areas of the garden have been limed to reduce soil acidity and raise pH to between 6.5-7.5. Where this has been achieved, and organic matter and fertiliser have also been applied, the resulting soil proves to be very fertile and excellent growth in a huge range of plants is achieved. Some parts however are not limed. The natural acidity of these areas, combined with the free draining soil make them ideal for acid loving plants such as rhododendrons, camellias, and heathers, and it is not surprising therefore that Wisley is renowned for stunning displays of these and other calcifuge (lime-hating) plants.

For information on current work at Wisley on soils click here

Soil analysis service

Analysis of soil samples from your garden is just one of the services available to RHS members.
For further information on the Soil Analysis Service click here.

Links

Soils organistations

Sustainable horticultural practices , including soil management issues

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