COASTAL GARDENS

You're on holidays at the beach house, or you live in a coastal town, and you're having problems growing plants in the garden. Maybe your plants are yellowing, burnt or stunted, or possibly you can't even get them established in the first place. If this sounds familiar, we'll give you some ideas on how to overcome common problems in growing plants by the coast.

Firstly, you may need to change your expectations. You can't grow the same range of plants that flourish a few kilometres inland - many plants simply can't tolerate the salt levels, dry sandy soil and wind exposure of the coast. If your ideal garden is a lush green lawn surrounded by roses and azaleas, forget it - you'll always be struggling against the natural conditions and it's unlikely that you'll ever achieve a really healthy and attractive garden. It's better to choose plants adapted to seaside growing and modify the site to encourage these to grow to the best of their ability.

Depending on how close you are to the sea, and how exposed your garden is, there are several problems which you will need to deal with; the most severe being high salt levels both in the soil, and carried in wind and water sprays, and physical damage from strong winds.

Dealing with Salt
Salt is carried by wind and is deposited on the plants and onto the soil. It can cause severe leaf burn and defoliation; over time the plants become stunted and fail to thrive, especially those growing on the seaward side. The problem is compounded as salt accumulates in the soil.

Choosing salt-hardy plants and blocking the passage of salt-laden wind are the best strategies. The plant lists below will help you to select appropriate plant species.

Creating Wind Breaks
Coastal winds damage plants in several ways:

  • causing physical damage to limbs, especially in storms
  • causing stunting (shortened limbs and small leaves), as a result of long-term exposure
  • carrying salt deposits that accumulate on foliage
  • carrying sand that abrades leaf tissues, resulting in leaf drop and shoot dieback (often called wind pruning)
  • carrying salt deposits that accumulate in the soil

A barrier that prevents or slows down the prevailing wind, therefore, is paramount in a coastal garden. A good windbreak greatly enhances the variety of plants that can be grown in the garden.

Solid fences and walls are useful because they can be erected quickly. These include brick walls and timber or brush fences. A drawback is that they can create turbulence as the wind is forced up and over the fence. A permeable fence (ie. a fence that wind can move through) is a better choice as it will filter the wind and reduce its speed. Shade cloth, lattice, hessian (as a temporary measure) are good choices.

Growing hardy salt tolerant plants as frontline protection against wind is the best long-term windbreak. A mixture of shrubs and trees that filter the wind is better than using a solid line of one species. Plants also have the advantage that they bind the soil, reducing soil erosion. Some of the hardiest plants to use are those that are indigenous to the area (they are native to the area and are accustomed to the local conditions).

Other Strategies for Growing Coastal Plants

Tree guards
Plastic tree guards or shadecloth supported by stakes will help protect newly planted trees and shrubs.
Growing in containers
Salt sensitive plants can be grown in pots. Use a good quality potting mix and preferably place the pot in a sheltered spot, away from salt laden winds.
Conserving moisture
Even if your garden receives regular amounts of rain, the plants can still suffer from water shortage. Sandy soils are very free draining, so adding organic materials and using surface mulches is important. Seaweed is the most obvious choice for a mulching material - it's free and is usually plentiful, but it needs to have any surface salt washed off before you use it. Many soils consisting of high levels of fine sand commonly are water repelling, particularly when they have been allowed to dry out. Water from irrigation or rain will sit on the surface in puddles, or run away down slope without much infiltrating into the soil. They are said to be hydrophobic. This problem can be overcome by the addition of wetting agents such as Saturaid or Wettasoil.
Installation of a drip irrigation system will also help plants establish and grow.
Fertilisers
Coastal soils are generally impoverished and have limited capacity to retain applied nutrients. Organic materials are useful; also apply slow release fertilisers (eg. blood and bone or Osmocote) to promote growth.

Hardy Seaside Plants

Trees

  • Acacia longifolia var. sophorae (Coast Wattle)
  • Agonis flexuosa (Willow Myrtle)
  • Allocasuarina littoralis, A. torulosa, A. verticillata (Drooping She Oak)
  • Araucaria bidwilli (Bunya Bunya Pine), A. cunninghamii (Hoop Pine), A. heterophylla (Norfolk Island Pine)
  • Arbutus unedo (Irish Strawberry Tree)
  • Banksia integrifolia (Coastal Banksia), B. serrata
  • Callistemon viminalis (Weeping Bottlebrush)
  • Callitris columellaris (Coast Cypress Pine)
  • Casuarina cunninghamiana, C. equisetifolia subsp. Incana
  • Cocos nucifera (Coconut Palm)
  • Cupressus macrocarpa (Monterey Cypress)
  • Eucalyptus ficifolia (Red Flowering Gum), E. botryoides, E. calophylla 'Rosea' (Pink-flowered Marri), E. lehmannii (Bushy Yates)
  • Melaleuca armillaris, M. elliptica, M. nesophila, M. squarrosa
  • Metrosideros excelsa (NZ Christmas Tree)
  • Olea europea (Olive)
  • Phoenix canariensis (Date Palm)
  • Pinus nigra maritima (Corsican Pine)
  • Tamarix parvifolia (Tamarisk)
  • Tristania laurina

Shrubs

  • Acacia saligna
  • Agave attenuata
  • Banksia ericifolia (Heath Banksia)
  • Banksia marginata
  • Brachysema lanceolata (Swan River Pea)
  • Callistemon citrinus, C. rigidus
  • Coprosma repens (Mirror Plant)
  • Cordyline australis
  • Correa alba, C. reflexa
  • Dodonea viscosa (Hop Bush)
  • Echium candicans (Pride of Madeira)
  • Escallonia macrantha
  • Feijoa (Pineapple guava)
  • Hakea laurina (Pincushion Hakea), H. sauveolens
  • Hebe cultivars
  • Kunzea ambigua
  • Leptospermum laevigatum (Coast Tea Tree)
  • Leptospermum petersonii (Lemon-scented Tea Tree)
  • Leucophyta brownii (Cusion Bush)
  • Melaleuca fulgens, M. hypericifolia, M. laterita
  • Murraya exotica (Mock Orange)
  • Myoporum insulare (Boobialla)
  • Nerium oleander (Oleander)
  • Olearia sp. (Daisy Bush)
  • Polygala sp.
  • Raphiolepis species and cultivars (Indian Hawthorn)
  • Rosmarinus officinalis (Rosemary)
  • Vitex spp.
  • Westringia fruticosa (Coastal Rosemary)

Groundcovers/Small Shrubs

  • Alyssum maritimum (Sweet Alice)
  • Arctotis (Aurora Daisy)
  • Carprobrotus glaucescens (Pig Face)
  • Cerastium tomentosum (Snow in Summer)
  • Hemerocallis (Day Lily)
  • Hibiscus scandens (Snake Vine)
  • Gazania (Gazania)
  • Lantana montevidensis (Lantana)
  • Mesembryanthemum sp. (Pigface)
  • Myoporum acuminatum (Boobialla)
  • Osteospermum cultivars (African Daisy)
  • Pelargonium australe
  • Sedum spp.
  • Scaevola aemula
  • Stachys byzantina (Lamb's Ears)

Climbers

  • Bougainvillea
  • Ficus pumila (Climbing Fig)
  • Hedera helix (Ivy)
  • Hibbertia scandens (Guinea Gold Vine)
  • Petrea volubilis (Purple wreath)
  • Pyrostegia venusta (Orange Trumpet Vine)
  • Solandra guttata (Cup of Gold)
  • Tecomanthe hillii
Suggested Reading
Read this ebook written by our principal, John Mason  (click for details)