As climates change, landscapers need to consider which plants best suit the climate and environment in their clients’ gardens. In this article, horticulture expert Jon Muller takes us through the science and shares his top picks
I’ve recently returned to Wellington from a holiday in the winterless north, which made me consider which plants are best able to withstand harsh environments.
As a result, I thought ‘what are the main elements plants (and humans) must deal with?’ In my mind, they are:
1. Water and drainage.
2. Temperature, including frost.
3. Wind, including coastal.
4. Sunshine – light and shade.
Plants have adapted to a mixture of these elements in each of the zones they come from.
Broad Varieties
There are three main plant types:
1. Xerophytes (‘dry plants’) that prefer dry hot conditions. These have adapted to dry conditions in various ways. They can have fleshy leaves with stored water, like succulents; rolled-up or spiny leaves to reduce transpiration, like grasses; or leaves with furry undersides or glossy tops to reduce water loss, such as pohutukawa.
2. Mesophytes (‘middle plants’) that prefer the middle range of conditions.
3. Hydrophytes (‘water plants’) with modified roots that prefer wet conditions.
All these types have adapted to these different conditions. The trick is to match the plants with the area they originate from. Either you match the plant to its original environment or modify the environment if you want a different type of plant.
For example, if you have a Mediterranean plant, which likes hot, dry conditions, such as lavender, and you have a poor draining soil, you could build a raised garden to improve drainage. However, if your site is shady and you want to plant a sun-loving plant like lavender, it won’t work.
Environment matters
Additionally, there are a number of environmental factors you need to consider before deciding on what plant to use and their hardiness:
1. Aspect: does your garden area face south, so it’s shady; or north, so it’s sunny?
2. Topography: is your site flat or on a slope? If flat, does it get flooded easily? If steep, does it drain readily?
3. Soil: is your soil heavy clay, draining poorly; or sandy, draining easily?
Plants have adapted to these various elements and environments in different ways. I have just read about the devastating fires in California. One promising plant to make the environment more resilient is the agave plant. Their skin is very resistant to heat and they have a high water content, making them less likely to catch fire. They also have deep roots, which allow them to survive fires that can destroy other vegetation.
Top picks
If you work in an area that is prone to fires, you should consider using fire-resistant plants and keep growth away from buildings.
Some examples of fire-retardant plants are:
• Agave
• Aloe
• Coprosma
• Disphyma
• Phormium
• Yucca
Nature can teach us a lot about how plants adapt to their environment. Matching the correct plant to a specific environment is crucial as weather becomes more extreme.
Below are some examples of plant combinations that tolerate dry conditions:
1. A mixture of Aeonium Schwarzkopf and Senecio serpens, chalksticks.
2. Phormium cookianum planted behind Carex testacea and Astelia chathamica.
3. Xeronema callistemon.
4. Coprosma kirkii in front, planted behind the Aeonium.
Jon Muller has owned Wellington Gardens Ltd for 24 years. He practices landscape design and
construction, with an emphasis on planting design. He has taught at polytechnics and university, mostly in soft landscape subjects. He has written six gardening books, including Wellington Gardens, and enjoys helping clients find landscape solutions. He also helps students and workers studying for their landscape qualifications.