Suitable plants


Many drought tolerant plants have silver or grey-green leaves, their light leaf colour reflecting the harsh rays of the sun. Some have a coating of fine hairs on their leaves or stems, helping to trap moisture around the plant tissues. Below is a selection of plants with good drought-tolerant properties.


Trees


Acacia dealbata (mimosa) AGM: Height 15-30m (50-100ft); spread 15m (50ft)


Cercis siliquastrum (Judas tree) AGM: Height and spread 10m (30ft) Koelreuteria paniculata (golden rain tree) AGM: Height and spread 10m (30ft)


Ptelea trifoliata ‘Aurea’ (hop tree) AGM: Height: 5m (15ft) Conifers


Chamaecyparis lawsoniana (Lawson cypress): Height and spread variable according to cultivar


Cupressus arizonica var. glabra: 10-15m x 4-5m (30-50ft x 12-15ft) Juniperus: Height and spread variable according to species and cultivar Pinus: Height and spread variable according to species and cultivar


Palms


Cordyline australis AGM: 3-10m x 1-4m (10-30ft x 3-13ft) Trachycarpus fortunei AGM: (20m x 2.5m (70ft x 8ft)


Small shrubs


Artemisia ‘Powis Castle’ AGM: 60cm x 90cm (24 x 36in) Halimium: Height and spread variable according to cultivar Hebe: Height and spread variable according to cultivar Lavandula (lavender): Height and spread variable according to cultivar Nandina domestica (sacred bamboo) AGM: 2m x 1.5m (6ft x 5ft) Ozothamnus ledifolius AGM: 1m x 1m (3ft x 3ft) Perovskia atriplicifolia ‘Blue Spire’ AGM: 1.2m x 1m (4ft x 3ft) Santolina chamaecyparissus AGM: 50cm x 50cm (20in x 3ft)


Making a gravel garden A


Medium-large shrubs Abelia × grandiflora AGM: 3m x 4m (10ft x 12ft) Arbutus unedo AGM: 8m x 8m (25ft x 25ft) Callistemon citrinus: Height and spread variable according to cultivar Elaeagnus angustifolia AGM: 6m x 6m (20ft x 20ft) Olearia macrodonta AGM: 6m x 5m (20ft x 15ft) Ozothamnus rosmarinifolius ‘Silver Jubilee’ AGM: 2-3m x 1.5m (6-10ft x 5ft)


Vitex agnus-castus: 2-8m x 2-8m (6-25ft x 6-25ft)


Climbers Campsis: 10m (30ft)


Eccremocarpus scaber AGM: 3-5m (10-15ft) Jasminum officinale: 12m (40ft)


Passiflora caerulea (e.g. ‘Constance Elliott’ AGM): 10m (30ft) Solanum crispum: 6m (20ft)


Herbaceous perennials Baptisia australis AGM: 1.5m x 60cm (5ft x 24in) Euphorbia: Height and spread variable according to cultivar Eryngium: Height and spread variable according to cultivar Echinops: Height and spread variable according to cultivar Osteospermum jucundum AGM: Height 10-50cm (4-20in) Spread 50-90cm (20-36in)


Verbena including V. rigida AGM and V. bonariensis AGM: Height and spread variable according to cultivar


Grasses


Cortaderia selloana: 2.5 -3m x 1.5m (8-10ft x 5ft) Panicum virgatum: 1m x 75cm (3ft x 30in) Pennisetum alopecuroides: 0.6-1.5 x 0.6-1.2m (2-5ft x 2-4ft) Stipa gigantea: AGM 2.5m x 1.2m (8ft x 4ft)


Suitable plants


gravel garden is a great option for a low maintenance garden. It also lends itself to Mediterranean-style drought-tolerant planting so things like lavender, euphorbias, Cistus, Santolina and Phlomis are ideal and provide plenty of nectar and pollen for visiting insects.


Any area is suitable for a gravel garden, although a sunny, well-drained spot is best for most Mediterranean plants.


While it is possible to make a gravel garden on any soil type, a predominantly sandy or gravelly soil naturally lends itself to this type of style.


How to make a gravel garden • Gravel garden plants thrive in unimproved sandy soil with relatively low fertility. If your soil is clay based, then incorporation of plenty of organic matter into the soil may help to alter its character a little.


• If you do not require plants to self-seed, lay landscape fabric over the soil before planting and cut crosses just large enough to insert each rootball.


• Different-sized gravel is available: fine grades are 10mm or less, chunkier types are 20mm or more. Medium-grade gravels, particularly if angular in shape, are easier to walk on than smaller grades, rounded pea shingle or large cobbles. If cats frequent the garden, larger grades will deter unwanted activities.


• Avoid using limestone chippings if growing acid-loving plants. • A 25kg (50lb) bag of gravel will cover 0.6sq m (0.6sq yd) to a depth of 5cm (2in). Gravel can also be bought in bulk, delivered by truck, usually in bags holding about 1 cubic metre, which should cover around 20sq m (about 18sq yd).


• Gravel can be bought in a wide range of colours. Try to match the colour with other paved or stone structures in the garden. Local gravels are usually cheapest.


• Top up gravel levels can as and when required. • Weeding is most intensive in the first few years of establishment. After this time, the plants are generally large enough to suppress weeds. Removal of surplus self-seeded ornamentals may be required.


• Remove spent flower stalks in the autumn or, if left over winter for architectural effect, in early spring.


Source: RHS Press Office


Bulbs • Allium • Colchicum • Crinum x powellii • Nerine bowdenii


Shrubs • Ceanothus • Cistus • Cordyline • Cytisus • Hebe • Hypericum • Juniperus • Lavandula • Rosmarinus • Salvia • Santolina


• Thymus • Yucca


Herbaceous perennials • Achillea • Bergenia • Crambe • Crepis incana • Echinops • Eryngium • Euphorbia • Iris unguicularis • Kniphofia • Nepeta • Oenothera • Osteospermum • Papaver


• Phlomis • Sedum • Verbascum


Grasses • Miscanthus • Pennisetum • Stipa


Bedding • Cosmos • Gazania • Portulaca


Climbers • Campsis • Trachelospermum


Small plants can become swamped by gravel. Plant them on a low mound so that that they are raised slightly above the level of the gravel. Where landscape fabric is not used, weeds and self-seeding plants may become problematic, popping up where not wanted. However, allowing self-seeding can give the garden a more natural look even if some weeding is required.


If your soil type is heavy, clay-based, damp, or has a high water table, then gravel garden plants may not thrive. You may be better off going for a different style of garden and selecting planting to suit the conditions. You may decide to do without a lawn in your drought-friendly garden, but if you cannot do without this feature in your garden, then you may be pleased to know that lawns are surprisingly drought tolerant, and usually recover well in the autumn rains, even if they have been brown and parched most of the summer. Lawn irrigation should rarely be required, if at all, to keep the grass healthy.


GCU AUGUST/SEPTEMBER 2011 15


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