In botany, the term "perennial" is generally used for the category of plants that live for more than one year, in contrast to annuals which complete their life cycle and die withing a year or biennials that mature, set seed and die in a two-year cycle.
In horticulture, "perennial" is usually applied to flowers other than annuals/biennials that are not woody or only only somewhat woody (versus true trees and shrubs which are technically perennial too). Examples are salvias, chrysanthemums and gerberas. It's a loose term whch might also include bulbous plants, ornamental grasses and sub-shrubs, which are comparable in their decorative uses in the garden.
Perennials are often associated with traditional, flowery English-style or cottage gardens. Consequently, many perennials you'll see in gardening books are unsuitable for most of Queensland. Unless you live in more temperate areas like Toowoomba and Granite belt, success here starts with selection of types suitable for tropical conditions. Be sure to check suitability for your climate when ordering perennials from suppliers based in the southern states.
Some of the more flamboyant perennials can also be used in tropical garden designs.
Get Results Gardening is a newsletter-style, mini-magazine for Australians, with an emphasis on the South East Queensland. It covers easy to grow perennials and other plants suitable for this regions, plus basic gardening information, trends and design concepts that will be of interest to home owners across the country. Get a three month trial for free and without obligation with a simple email request and learn more about other plants suitable for the subtropics. More information at calyx.com.au/getresultsgardening.html.
Queensland Peony Breakthrough
Growing peonies in the subtropics was never a practical proposition before, but breakthrough research at the University of the Sunshine Coast means that peonies could soon become a valuable cut flower crop in Queensland. Biologist Krista Bogiatzis began working on the problem at USC in 2015 and has now determined the exact combination of temperature and growing conditions to get them to bloom in the subtropics. What's more, they can be timed to take advantage of high-demand and under-supplied periods in other regions. For the local market, Queensland-grown flowers avoids the risks, costs and quality issues associated with importation of live product. (September 2019)
Other perennials suitable for the subtropics
Two varieties of alstroemeria of different heights
Throw up spikes of small flowers in white, pink and purple shades. Described as an annual in some publications as they are a warm-climate plants that will not survice frost.
Dianthus and Carnation
Florist style carnations are rarely grown in Qld these days, but the smaller bedding dianthus are still grown as short-lived perennals.
Increasingly popular in Queensland. They have a cottage-garden look but are suitable for a hot climate and don't need a lot of water. Gaura featured in the 08-09-2023 edition of Get Results Gardening. When you request a free trial (go calyx.com.au/getresultsgardening.html for more information), you can ask for a copy of the 08-09-2023 edition if you want to see the Gaura article (Australian residents only).
Also known as cherry pie. Although this could be classified as a small shrub, it is more like a perennial in its look and the way you would place it n the garden.
Sold by one distributor in Australia under the name Little Boy Blue®. Sub-shrub with bright blue flowers.
Also known as lions ear or lions tail. Whorls of flowers borne on tall stems 2m or more high. The most common colour is orange but there is also a white form white might be preferable for some garden designs. Useful for a adding a strong vertical element.