Q&A: Why do some native plants die young?

Why do some native plants die youngEach month we receive questions from our readers, which are answered by one of our experts. Here’s one about the life expectancy of native plants.

Q I love growing natives in my garden, even wattles, grevilleas and other bushes that tend to turn their heels up after 10 years or so – I don’t mind, it gives me an excuse to try something else – but it makes me wonder, why do some natives have such short lives?

A ANGUS STEWART SAYS Every plant species has a natural life span and it’s true that Australian plants, like some of their exotic counterparts, can be short-lived in the garden. There are several reasons why it happens, and the good news is that we can use this trait to our advantage.

Wattles are a great example. Most wattle species are programmed to germinate quickly after a bushfire and colonise the burnt areas. They grow rapidly and often die out within a few years to a decade, making way for slower-growing, long-term tree species that replace them. As the fast-growing wattles die and decompose, they also provide valuable nutrition for the plants that follow. We can use such plants as fast-growing ‘nurse plants’ while waiting for slower-growing plants to mature. If you want to prolong the life span of these plants by a few years, give them an annual prune behind the spent flowers. The trimmings can be used as organic mulch around slower-growing plants.

Other native plants can be short-lived when they are out of their natural climatic and soil conditions. The classic example is the flora of south-western Australia, where many species, such as dwarf kangaroo paws, grow in very well-drained gravelly soils and thrive on the hot, dry summers. When we try to grow these species in the heavier soils and more humid climates of many areas in the eastern states, they tend to be much shorter lived. Growing these plants in pots or well-drained rockery or mounded beds can prolong their life considerably.

The bottom line? Do your homework on each species so you have realistic expectations. You can also plan your garden in such a way that you can renew it every few years with different native plants so you enjoy a variety of blossoms.

For more problem-solving gardening questions and answers, including what’s causing foam to appear on a tibouchina, pick up a copy of the December issue.