How Does Salinity Affect Plant Growth and What Can Be Done?
By Anthea Hudson
Salinity is becoming an increasing problem along waterways, on irrigated land, deserts and other areas, worldwide. Lack of flowing fresh water to flush our rivers, salts and other minerals etc in our water supply, along with other problems, all contribute to this. The plants that grow naturally, and those we plant, can be affected by changes to the natural salinity of their environment, usually in a detrimental way, especially to more sensitive plants.
This informative video goes into the causes of ground salinity and looks at some of the solutions. Well worth watching to gain a better understanding of what is actually going on.
Soil Salinity in Australia
EFFECTS OF SALINITY ON PLANTS
Plants obtain most of their water from the soil, and when that water increases in salinity it takes the plant more energy to draw it up through its roots and the plant can sometimes dehydrate even when there is water available, because it cannot keep up with the effort required to replenish its water supply.
Salt build-up within the plant itself also has effect. This shows more so in older leaves which have had longer exposure to salt excess.
Some of the signs you may see (though not always) that might indicate the salinity is too high for that particular plant are:
- Slow, stunted growth compared to an identical plant in a low salinity area
- Small stunted fruits
- Increased succulence of the leaves
- Leaves may be a darker green, or in some plants, take on a bluish green cast
- Leaves then yellowing, mottling, browning and dropping off
Kids (or even big kids!) might like to see our activity 'How Does Salinity Affect Plant Growth? A Hands-on Activity' to experiment and see for themselves what effect salinity can have on how a plant grows... or even if it does!
SOLUTIONS FOR HIGH SALINITY AREAS
So, what are some of the ways we can tackle salinity problems in our gardens?
- One of the best ways to deal with a soil salinity problem, especially if you are just starting out, or redesigning your garden, is to plant salt tolerant plants. Not only are they equipped to deal with the salt, but often actually flourish in it, and being ideally suited to the conditions, are often lower maintenance than those that are not. They are also often drought tolerant.
- There are many salt tolerant plants, depending on just how much salinity you have to deal with, but to get an idea of what might grow well in your area, go for a wander and see what is growing happily and abundantly. Also, look at what the council has planted in the way of street trees and on roundabouts and median strips... assuming they are growing well. If you live near the beach, have a look at what is growing along the foreshore. Simple observation can often give you the best information.
- Many plants are more sensitive to excess salinity in their formative stages, while germinating and initial growth. With a bit of help to reduce salinity at this stage, such as keeping well watered to dilute the salinity, some plants can tolerate more salinity once they have developed more. You can also give your newly planted seeds or plants a surrounding bed of potting mix or other low salinity soil, to ease their way while they become stronger.
- Raised garden beds, raised walled planter areas, or pots, using brought in soil, can be useful in areas you want to plant more sensitive varieties.
How to Build a Raised Bed Garden Using Pallets
- If you live close to a salt water source, or have highly saline soils, it may be advisable to put a barrier between your raised bed or walled planter area that will lessen the seeping of saltier water into your new soil. This might be a waterproof layer, or something that creates a separate segment, such as some railway sleepers on the bottom. Make sure, however, that you allow adequate drainage for your raised bed.
- Sometimes, if you live right by the ocean, salt water spray directly off the water can be damaging to your plants, so putting up a tall fence, erecting a barrier of some kind can reduce this. Winds are also often a big problem close to the sea, causing branch breakage, defoliation, bending and stunting of growth, so a barrier can also act as a wind block.
- You should also try to be aware of the salinity of the water you use on your garden, especially when using groundwater sources such as bores or wells. Greywater should also be analysed as it can contain potentially damaging excesses, or lacks, of all kinds of things. If your plants, especially low salt tolerant plants, are being affected by your water, you may need to switch to another water source, such as catching rainwater.
- If you live in an area which has snow and ice, the salt used in street de-icing can also have a severe effect on plants planted in the vicinity of its use, so planning what you plant near roadways and footpaths, to take this into account, is common sense.
The video below goes into salinity issues on a global scale, as well as more in depth looks at certain areas, and also discusses some of the potential solutions that are being trialled on farms etc.
Salt of the Earth
SALT TOLERANT PLANT LIST
Here is a list of salt tolerant plants, the majority of them Australian natives. However, as stated above, use your observations of what other people in your area are growing successfully to help make your decisions. Many factors come into play with how well a plant will grow in your location, so some plants that are salt tolerant, may not tolerate other aspects of your locale well.
For those of you who think Australian natives are boring or lacking in variety and colour... this video shows what an abundance of diversity, beauty and colour can be had from a native garden.
Aussie Garden Beauties - Tribute to Australian Native Plants
Cynodon dactylon (Couch Grass)
Pennisetum clandestinum (Kikuyu)
Trifolium fragiferum (Strawberry Clover)
Carpobrotus glaucescens (Pigface)
Coprosma repens ‘Kirkii’
Correa decumbens (Spreading Correa)
Eremophila biserrata, (Prostrate Eremophila)
Eremophila glabra (Emu Bush)
Erigeron glaucus (Seaside Daisy)
Dianella revoluta (Flax Lily)
Ficinia nodosa (Knobby Club-rush)
Hibbertia scandens (Climbing Guinea Flower)
Juniperus conferta prostrate (Shore Juniper)
Kunzea pomifera (Muntries)
Lantana montevidensis syn L. sellowiana (Trailing Lantana)
Leuocophyta brownii (Cushion Bush)
Myoporum parvifolium (Creeping Boobialla)
Orthrosanthos laxus (Morning Iris)
Parthenium argentatum (Gray Guayule)
Phyla nodiflora (Lippia)
Rhagodia spinescens (Spiny Saltbush)
Scaevola aemula (Fairy Fan Flower)
Top 10 Coastal Plants for Salt-Laden Windy Situations
Shrubs and Trees
Acacia acuminata (Raspberry Jam Wattle)
Acacia ampliceps (Salt Wattle)
Acacia cyclops (Coastal Wattle)
Acacia iteaphylla (Flinders Ranges Wattle)
Acacia longifolia (Sallow Wattle)
Acacia pendula (Myall or Boree)
Acacia pycnantha (Golden Wattle)
Acacia retinodes (Wirilda)
Acacia salicina (Coobah, Native Willow)
Acacia saligna (Golden Wreath Wattle)
Acacia sophorae (Coastal Wattle)
Acacia stenophylla (River Cooba)
Agonis flexuosa (Willow Myrtle)
Albizia julibrissin (Silk Tree)
Albizia lophantha (Cape Wattle, Swamp Wattle)
Allocasuarina verticillata (Drooping Sheoak)
Alyogyne hakeifolia (Red-Centred Hibiscus)
Araucaria heterophylla (Norfolk Island Pine)
Atriplex cinerea (Coast Saltbush)
Banksia ericifolia (Heath Banksia)
Banksia grandis (Bull Banksia)
Banksia integrifolia (Coast Banksia)
Coast Banksia (Banksia integrifolia)
Banksia marginata, inland form. (Silver Banksia)
Banksia media (Golden Stalk Banksia)
Banksia speciosa (Showy Banksia)
Callistemon citrinus (Lemon-Scented Bottlebrush)
Callistemon rugulosus (Scarlet Bottlebrush)
Callistemon salignus (Willow Bottlebrush, Pink Tips)
Callistemon teretifolius (Needle Bottlebush or Flinders Ranges Bottlebrush)
Callistemon viminalis ‘Hannah Ray’
Weeping Bottlebrush (Callistemon viminalis)
Casuarina glauca (Grey Buloke)
Casuarina littoralis (Black Sheoak)
Casuarina obesa (Salt Sheoak)
Ceratonia siliqua (Carob Tree)
Correa alba (White Correa)
Correa backhousiana (Velvet Correa)
Correa reflexa (Native Fuschia)
Enchylaena tomentosa (Ruby Saltbush)
Eremophila bignoniiflora (Eurah)
Eremophila calorhabdov (Red Rod, Spiked Eremophila)
Eucalyptus campaspe (Silver-Topped Gimlet)
Eucalyptus eremophila (Tall Sand Mallee)
Eucalyptus erythronema (Red-Flowered Mallee)
Eucalyptus kruseana (Bookleaf Mallee)
Eucalyptus leucoxylon ssp. megalocarpa syn. E. leucoxylon 'Rosea'(Large-Fruited Yellow Gum)
Eucalyptus macrandra (Long-Flowered Marlock)
Eucalyptus spathulata (Swamp Mallet)
Eucalyptus torquata (Coral Gum)
Hakea cycloptera (Elm Seed Hakea)
Hakea drupacea (Sweet-scented Hakea)
Halosarcia spp. (Samphire)
Hebe sp. (Hebe or Veronica) especially ‘La Seduisante’, ‘Blue Gem’, H. buxifolia and H. andersonii.
Lagunaria patersonii (Pyramid Tree)
Melaleuca armillaris (Bracelet Honey Myrtle)
Bracelet Honey Myrtle (Melaleuca armillaris)
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Melaleuca decussata (Cross-Leaved Honey Myrtle)
Melaleuca ericifolia (Swamp Paperbark)
Melaleuca halmaturorum (Swamp Paperbark) - Extremely salt tolerant
Melaleuca huegelii (Chenille Honeymyrtle)
Melaleuca hypericifolia ‘Ulladulla Beacon’
Melaleuca lanceolata (Moonah)
Melaleuca linariifolia (Snow-in-Summer)
Melaleuca nesophila (Showy Honey Myrtle)
Melaleuca quinquenervia (Broad Leaved Paperbark)
Broad-leaved Paperbark (Melaleuca quinquenervia)
Melaleuca stypheloides (Prickly Paperbark)
Prickly-leaved Paperbark (Melaleuca styphelioides)
Myoporum acuminatum (Waterbush)
Myoporum insulare (Boobialla)
Myoporum viscosum (Sticky Boobialla)
Nerium oleander (Oleander)
Old Man Saltbush (Atriplex nummularia) Will tolerate extreme salinity
This video is a fascinating look at how salt bush is being used to help solve salinity on a remote property experiencing salinity problems.
Salt Bush Project
Olearia axillaris (Coast Daisy Bush)
Olearia glutinosa (Sticky Daisy Bush)
Pittosporum angustifolium (Butterbush)
Prosopis pubescens (Screwbean Mesquite)
Rhagodia candolleana (Seaberry Saltbush)
Ricinocarpus pinifolius (Wedding Bush)
Sarcocornia spp. S quinqueflora (Glasswort, Samphire)
Scaevola crassifolia (Thick-leaved Fan Flower)
Senna artemisioides (Silver Cassia)
Templetonia retusa (Coral Bush)
Westringea fruticosa (Coastal Rosemary)
Westringia Flat and Fruity
Westringia Flat and Fruity
And finally, if you would like to create a native garden which will better survive not only salinity but other Australian conditions as well, this greta video goes into setting up and caring for an Australian native garden, specifically in a coastal area, which naturally has quite a high salinity.
How to look after your native garden with Sabrina Hahn