Why is Drought Bad for Plants?

Have you ever wondered how a prolonged dry spell might be silently affecting your cherished garden?

In this article, we delve into the detrimental impact of drought on plants, exploring both the physiological and ecological repercussions. We will also shed light on how to mitigate these effects is crucial for maintaining healthy and vibrant gardens and landscapes.

Of course, while all plants require some level of moisture, some plants are more susceptible to drought than others. Towards the end of the article, we’ll provide a palette of 6 native, and 3 exotic, plants which require very little water once established to add to your drought-tolerant palette.

The Science Behind Drought Stress in Plants

Understanding Plant Physiology and Water

Plants are remarkable organisms that rely on a constant supply of water to thrive. Water is essential for various physiological processes, including nutrient uptake, photosynthesis, and transpiration.

The journey of water from the soil through the plant’s vascular system, to its eventual release into the atmosphere via the stomata (tiny openings on the leaves), is a delicate balance that is easily disrupted by drought.

Moisture is lost more readily in free-draining substrates, such as sandy soils, and is held more tightly in water-retentive substrates, such as clayey soils. A mixture of sand, silt and clay as well as organic matter is called a “loam,” which is stereotypically the best soil type for most plants.

While it’s important to provide moisture for plants, too much of a good thing can kill them – so over-watering your plants is not a good way to prevent them drying out.

How Drought Affects Plant Processes

Reduced Water Availability and Photosynthesis: Photosynthesis, the process by which plants convert light energy into chemical energy, is heavily dependent on water. During drought, the reduced availability of water leads to a decrease in photosynthetic activity, hampering growth and reducing yield.

Osmotic Stress: Drought conditions cause osmotic stress in plants by creating a high solute concentration outside the plant cells. This imbalance makes it difficult for plants to absorb water, leading to dehydration and cellular damage.

Both of these stresses can lead to other problems, such as an inability to produce flowers or even becoming a target for pests and diseases.

Visible Signs of Drought Stress in Plants

Early Warning Signs

The initial signs of drought stress in plants include wilting, leaf curling, and slowed growth rates. These symptoms are plants’ first line of defence, reducing water loss by minimising surface area exposed to the sun and air.

Advanced Symptoms

As drought stress intensifies, more severe symptoms emerge, such as leaf scorch, defoliation, and branch dieback. Leaf scorch, characterised by brown or yellow edges on leaves, indicates severe dehydration, while defoliation and dieback represent the plant’s attempt to survive by reducing its overall metabolic demand.

Long-Term Consequences of Drought for Plants

Impaired Growth and Reproduction

Prolonged exposure to drought conditions can lead to stunted growth and reduced reproductive success. Flowers and fruits are often the first to be sacrificed as the plant diverts its limited resources towards survival.

Increased Vulnerability

Drought-stressed plants exhibit increased susceptibility to diseases, pests, and other environmental stresses. Weakened by the lack of water, plants are less able to fend off attacks, leading to further decline in health and vitality.

Mitigating Drought Stress: Choosing the Right Plants

Understanding Plant Resilience

Drought-tolerant plants are those that have adapted to survive in conditions with little water, whether through evolution or selective breeding. Xeriscaping refers to a landscaping method designed specifically for arid and semi-arid climates, utilising drought-resistant plants and water-saving techniques to create sustainable, low-maintenance gardens.

Selecting Drought-Resistant Varieties

Advice on Choosing Plants

When selecting plants for your garden, prioritising species that are naturally drought-resistant can significantly reduce water usage and maintenance needs.

These plants have typically evolved in arid environments and possess characteristics such as deep root systems, waxy or hairy leaves, and reduced leaf area, which help them minimise water loss and maximise water uptake efficiency.

Later in this article, we will explore some of the most drought-resilient and beautiful plants to have ever been bred in Australia.

Soil Management and Mulching Techniques

Improving soil structure can enhance water retention and reduce evaporation. Incorporating organic matter into the soil can improve its texture, fertility, and moisture-holding capacity. Applying mulch around plants acts as an insulating layer, keeping the soil cool and moist while suppressing weed growth.

Organic mulches, such as bark or straw, also gradually break down, adding nutrients back into the soil. Ground-covering plants can help to cover the soil and preserve moisture, even though they will uptake some for themselves.

Practical Tips for Gardeners and Landscape Professionals

Efficient Watering Strategies

Optimising watering schedules can dramatically increase water efficiency. Watering deeply and infrequently encourages plants to develop deeper root systems, enhancing their drought tolerance. The use of drip irrigation systems or soaker hoses can target water directly to the roots, minimising waste.

Landscape Design for Drought Prevention

Designing landscapes with drought prevention in mind involves grouping plants with similar water needs, reducing thirsty plants and capturing as much water into tanks and the soil profile (through rain gardens) as possible.

Irrigation can obviously help out in dry conditions, but many gardeners prefer to rely on the available rainfall alone – especially in xeriscaping.

Drought-Tolerant Plants: Thriving in Arid Conditions

The following resilient plant species are not only capable of thriving in water-scarce environments but also contribute to water conservation efforts while maintaining the aesthetic appeal of green spaces.

Macarthur™ Callistemon viminalis ‘LC01’ PBR

Macarthur™ Callistemon is a testament to the beauty and resilience of drought-tolerant plants. A hybrid incorporating the best traits of Callistemon ‘Little John’ and ‘Captain Cook’, it boasts a compact growth habit and an impressive display of flowers. The bushy, tidy growth and fresh green-toned foliage make it an attractive addition to any garden.

Suitable for full sun to part shade, it tolerates a wide range of soil conditions including free-draining, clay-dominant, and even wet feet, as well as frost and drought.

With minimal care requirements beyond initial watering until establishment and occasional pruning to maintain shape, Macarthur™ Callistemon is ideal for gardeners seeking a medium-sized shrub with low maintenance needs.

Ozbreed Aussie Box® Westringia hybrid ‘WES08’ PBR

Another standout for drought-tolerant plants is Ozbreed Aussie Box® Westringia. This native box-style hedge plant is celebrated for its dense growth habit and mauve flowers, which add a splash of colour to drought-resistant landscapes.

Its ability to thrive in full sun and withstand dry conditions, including coastal locations with salt spray, makes it a versatile choice for a variety of settings.

Ozbreed Aussie Box® requires little water once established and responds well to pruning, allowing it to be shaped as desired for hedges or standalone specimens. Its resilience and decorative appeal make it a favoured choice among home gardeners and landscape professionals alike.

Crimson Villea™ Grevillea rosmarinifolia ‘H16’ PBR

Crimson Villea™ Grevillea is a vibrant addition to any drought-tolerant garden. Characterised by its striking red flowers that bloom throughout most of the year, especially winter, this plant not only adds visual interest but also attracts pollinators such as birds and bees.

It thrives in full sun, requiring minimal water once established and is tolerant of frost, making it suitable for a wide range of climates. Crimson Villea™ Grevillea’s compact and rounded growth habit makes it an excellent choice for small gardens, borders, or as a feature plant. Its resilience and continuous flowering make it a valuable asset in creating colourful, water-wise gardens.

Tanika® Lomandra longifolia ‘LM300’ PBR

Tanika® Lomandra has established itself as a staple in Australian landscapes due to its robustness and aesthetic appeal. This evergreen plant boasts a compact, fine-leaf form that remains vibrant throughout the year.

From April to October, it produces small yellow flowers, adding a subtle splash of colour to gardens. Notably soft to the touch, it’s a plant that children will enjoy encountering, and is perfect for playground soft fall.

Ideal for slopes and dryland areas, Tanika® Lomandra requires minimal care once established, thriving in full sun to moderate shade, and tolerating frost and drought conditions well.

It tolerates sandy to clay soils, avoiding wet feet to prevent issues with phytophthora, for which Shara™ and Evergreen Baby™ Lomandra offer resistant alternatives.

King Alfred® Dianella caerulea ‘JOHN316’ PBR

King Alfred® Dianella is a tall native flax lily, featuring striking blue-green foliage and producing vibrant blue and yellow flowers in spring, followed by attractive purple berries. This low-maintenance plant thrives in full sun to part shade, requiring little water once established.

Its toughness against cold, drought, and frost makes it a versatile choice for various landscape applications, including borders, mass plantings, and as a feature plant in both residential and commercial settings.

It’s one of the best erosion control plants, improving stability by 752% (source: https://www.ozbreed.com.au/best-plants-for-erosion-control/), however it needs to be pruned back to the ground every year or two for it to live longer.

Anigozanthos hybrid ‘Amber Velvet’

Amber Velvet™ Kangaroo Paw stands out with its mid-sized stature and striking amber flowers, which appear from late winter through to summer. The velvet-like texture of its flowers adds a unique tactile element to gardens, alongside its visual appeal.

This kangaroo paw variety is known for its robustness, thriving in full sun and tolerating light frosts and drought conditions once established. Suitable for soils with drainage, Amber Velvet™ kangaroo paw is perfect for adding a touch of drama to garden beds, borders, and container plantings.

Its low maintenance requirements and high disease tolerance make it an appealing choice for gardeners seeking impactful, water-wise plants.

Bingo Blue™ Agapanthus hybrid ‘ANDbin’ PBR

Bingo Blue™ Agapanthus stands out with its vibrant blue flowers that bloom en masse from October to November, with sporadic flowering throughout the year. This compact plant reaches 40cm in height and 60cm in width, with the flower spikes extending to 60-80cm. It’s known for its toughness, being both drought and frost-tolerant.

Ideal for garden beds, borders, patio pots, and planter boxes, Bingo Blue™ Agapanthus requires minimal care once established, thriving in full sun to part shade. It adapts well to most soil types, particularly flourishing in rich soil.

For optimal flowering, a slow-release fertiliser in spring is recommended, alongside regular removal of older leaves and spent flower stems.

Sea Urchin™ Aloe hybrid ‘ANDsea’ PBR

The Sea Urchin Aloe is a striking addition to any drought-resistant garden with its orange/coral-coloured flowers and vibrant green, spiky foliage. Blooming in winter, it provides a pop of colour and attracts pollinators when few other plants are in flower.

Extremely drought-tolerant, it requires minimal watering once established and thrives in full sun to part shade. The compact size makes it an excellent choice for rockeries, container gardens, or as a striking groundcover.

Its resilience to dry conditions, coupled with low maintenance needs, makes the Sea Urchin Aloe an asset for creating visually captivating, water-wise gardens.

Thin Red™ Photinia x fraseri ‘NP01’ PBR

Thin Red™ Photinia offers a columnar feature shrub (or shrubby tree) for xeriscapes that will reach 4m high x 60cm wide when unpruned. Use it as a thin screen for privacy, a feature plant, or keep it in a pot for smaller balcony gardens. It produces bright, red new growth as well as white flowers in spring.

Perfect for narrow spaces, this plant is drought-tolerant, frost-tolerant, and moderately tolerant of humidity. Prune it once or twice a year for more compact and bushy growth, or allow it to express its natural shape which is naturally very upright.

Daniel’s Wrap

After reading this article, you should understand why plants struggle in drought, and have a good plant palette of cultivars that require minimal water. If none of these plants fit the bill you’re looking for, try browsing the Ozbreed catalogue as we do have many drought-tolerant specimens, including native and exotic ground covers, grasses, shrubs and more.

By selecting the right plants and employing sustainable gardening practices, we can mitigate the effects of drought stress and cultivate resilient gardens and landscapes. Let us be proactive in our choices, applying the knowledge gained to enhance the resilience of our green spaces against the challenges of drought.

Image Attribution: 1, 2