What is the impact of salt upon plants?
The presence of a low-level of salinity in soils is unlikely to adversely affect plant health or growth, further both two constituent elements within salt, sodium and chloride are beneficial to plant growth within appropriate levels. However, there are numerous conditions and locations where plants may be harmed by excessive salt, either through sea spray or the absorption of salts from the soil through osmosis.
Sea spray involves sea salt aerosols being carried from the ocean into the atmosphere by winds and deposited onto land. This deposition of sea salt can be of serious impact, with the well-known desiccating (drying or removing of moisture) effect of salt impacting the leaves, twigs and buds of plants. Once desiccated, the outer or effect layers of plants are removed, leading to the death of tender new growth and exposing tender, inner tissues in old growth.
Soil salinity has a slightly more complex impact on plant health and growth. Salt in the soil dissolves in rainfall into separate sodium and chloride ions, which are absorbed into plants through osmosis (the same process through which other crucial nutrients are absorbed). In high concentrations, sodium and chloride ions can displace other critical nutrients, such as potassium, nitrogen, and phosphorus, hindering their uptake. Once inside the plant, chloride ions interfere with photosynthesis and chlorophyll production, ultimately leading to dieback when large amounts accumulate. High sodium concentrations impede water uptake and dehydrate plants, causing them to cease transpiration to retain water. However, this cessation also halts the uptake of carbon dioxide and photosynthesis additionally hampering the movement of nutrients and water throughout the plant. Elevated sodium levels can also result in soil compaction, reducing drainage and soil aeration—both vital components for healthy plant growth.
How can I manage saline soils or salt spray?
Salt spray and saline soils may pose challenges for many gardens, but they need not be insurmountable issues. Numerous plants exhibit tolerance to moderately saline soils, as detailed in the ‘Salt Tolerant Coastals‘ category, experiencing minimal problems. Additionally, gardeners can sidestep soil salinity concerns by cultivating plants in containers or raised garden beds, enabling the creation and control of the soil medium.
Salt Spray can be effectively managed through the establishment of protective hedges or rows using salt-tolerant species such as Sea Grapes, Cocoplums, Natal Plums or Pigeon Plums. These plants, aside from being productive in themselves, will also create a sheltered area shielded from salt-spray, allowing for more sensitive plants to be grown. Similar protective effects can also be achieved using structures or buildings.
How can I enhance my plants’ resilience to wind and protect them?
Encouraging strong root systems is a crucial aspect to maximising wind tolerance. This can be achieved through providing conditions optimal for health root growth, such as a well-draining, moist soil such as loam. Sandy soils, prone to heavy leaching, can be weak, while dense clay soils pose challenges for root expansion and drain poorly during heavy rainfall, leading to waterlogging and root rot. A fertile soil with a complete range of, amendable through fertilisers, is also critical with Potassium particularly fostering healthier root growth and thicker cell walls.
Deep-watering is highly advantageous in cultivating deep root systems that not only stabilize the plant but also enable it to access nutrients and water from a broader range. Regular shallow watering, while important, promotes surface-level root growth which lacks the stabilizing effect of deeper roots.
Staking is a critical process that can impact a plant’s wind tolerance. If staking is necessary for newly planted trees due to strong winds or awkward forms (such as being excessively leggy or spindly), it should still allow plants to move in the breeze and stimulate anchorage root development. Once plants are established, staking can be removed, and plants can rely on their own strength to tolerate winds.
In addition to strengthening individual plants, gardeners can also establish natural structurals such as hedges or tree rows, or artificial structures such as walls or fences which can provide protection from strong winds. Refer to the ‘Hedging Plants‘ page for suitable choices.
Which plants are resistant to salt and wind, and which ones are susceptible?
Refer to the ‘Salt Tolerant Coastals‘ page for plants with medium-high salt tolerance, in addition to wind tolerance. Refer also to the ‘Wind Tolerant Trees‘ page.
Specific salt and wind tolerance will vary greatly amongst plants and are noted on specific pages, however, there are some more general observations that can be noted. Firstly, both marcot and cutting grown trees do not develop taproots, a crucial factor in plant stability and as a result are intolerant of strong winds. By comparison, both seedling and grafted plants will develop taproots. Low-lying bushes and shrubs are generally more wind tolerant due to their form.
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