I recently attended a workshop on grasses and other monocotyledons, held by the Friends of RBG Cranbourne. We were ably led by experts through the details of classification of grasses (Graeme Lorimer), then other monocots (Neville Walsh). However, I am certainly not going to write about taxonomy. Two other speakers in particular touched on aspects more related to garden design and I have added further thoughts of my own.
One speaker, Brian Bainbridge, talked mainly about cultivating grasses, though his talk is generally applicable to all monocotyledons. He structured his talk under four Rs – repetition, reference, rejuvenation and residence.
His first advice was to use repetition of as many plants of a single species as possible in an area, to achieve different rhythms and patterns with the different foliage, flower and seed-head types. In his photos, some patterns were soft and curved, some stiff and straight; some dense, some more sparse, with different colours, different types of flower or seed-head – no two patterns looked exactly the same.
Any area of a single species of grass makes a wonderful matrix or background for any colourful forbs, whether in nature or a planted garden – Brian said like a chorus behind soloists. Grasses look fantastic with dew or frost, and their movement in the slightest breeze adds another dimension to a garden.
Using references is obviously important, to choose reliable species to suit the growing conditions. References can be books, knowledgeable people, or reference sites. In a wetland area, for example, just a few inches difference in height means different species will prosper.
Of course some species are fussier than others. However, one grass species mentioned that was tolerant of a variety of conditions was Rytidosperma duttonianum or Brown-back Wallaby-grass.
Rejuvenation is essential for grasses, for biomass reduction – “they were made to be eaten”. The growing point of a grass is near its base but may migrate up through dead leaves if no rejuvenation occurs. Two natural methods are rarely available. Fire is ideal but normally inappropriate. Grazing animals such as kangaroos are seldom a possibility. Most of us have to rely on cutting back or mowing at a suitable height, at a suitable time of year. An annual mow might be carried out after flowering and seeding, or mowing done once every three (maximum five) years.
The last R is the importance of grasses as a residence for a myriad of residents – mainly insects, also spiders and seed-eating birds such as finches. Butterflies are frequent visitors. Grasses are the basis of a whole fascinating ecosystem. When revegetating a natural area, the ground flora including grasses would ideally be the first plants put in, with trees planted last.
Another ‘R’ could be added here, for re-creating natural grasslands. These once covered one third of Victoria but now, sadly, only tiny areas remain.
As they grew on rich volcanic soils, almost all were replaced quite rapidly by pastures for livestock. Sue Murphy and colleagues at Burnley College have done a lot of work on trying to re-create natural grasslands, with their forbs. They have found it very difficult. Grasses grew well – often too well – but common forbs such as daisies, orchids, lilies and pea-plants were more difficult to maintain. (Some natural grasslands are more ‘grassy’, others more ‘forby’.)
For both natural and created grasslands, burning is a good management tool. It can be timed to remove annual weeds and it kills tree seedlings to keep the area open for grasses. It also kills unwanted soil seed banks. A single annual weed species can be eliminated in one year by removal of all flower stems before seeding occurs. However, in areas over-run by a variety of weeds it’s too difficult to remove them selectively.
One extreme solution is to ‘scalp’ the upper layers of soil in that area, removing the soil complete with all its seeds, and start again with the seed mix of the wanted grasses and forbs – extremely difficult and a lot of work! Mycorrhizal fungi, bacteria and other microorganisms in the soil are also removed with scalping. These all play a part in the ecosystem underground and research on this is limited. Almost all Australian plants (not only orchids) depend on mycorrhizal fungi, the Proteaceae Family being the exception.
If you want to create a grassland, how realistic and authentic do you want it to be? Do you want a predominance of colourful forbs, which can look stunning – but probably for a relatively short time each year? You need to balance authenticity and aesthetics. Managing a large grassland area in a garden over many years is a challenge, especially with weedy grass invasion.
For those of us with smaller gardens, where closer maintenance and specific weed removal is possible, trying a small patch of a grass with a few selected forbs can give a lot of pleasure. We did this with just a small area of a local Rytidosperma racemosum (Wallaby-grass). Wallaby-grass can also be used to form a lawn, as can Microlaena stipoides (Weeping Grass). These two can be combined in a lawn.
The usual form of Themeda triandra (Kangaroo Grass) has wonderful rusty seed-heads and there are other forms, such as tall ‘True Blue’ (quite elegant) and low, spreading ‘Mingo’. Both have attractive, lilac-blue-grey tones in their foliage. Then there are species of Austrostipa (Spear-grass), such as Austrostipa elegantissima – its seed-heads are exquisite when backlit. There are many hundreds of Australian grass species!
It’s interesting that, in the plant family tree, grasses are the most ‘developed’ of all monocots, whereas orchids are now considered very ‘primitive’! Of course, being wind-pollinated, grasses have a significant potential as weeds. They have spread world-wide and colonised wherever conditions suited them. We should still be very careful about introducing foreign grasses into our own area. (But then, how foreign is foreign? How long is a piece of string?)
We have a great range of monocotyledons in Australia and they add a very distinctive element in our gardens. They occur in most of our ecosystems as an important part of the natural environment, so a garden of shrubs without monocots looks ‘unnatural’ to me.
Tufted or strap-leaved Australian monocotyledons of different sizes can be used individually in a garden, in proportion to the size of the garden – large monocots for a large garden, smaller for small. They can be massed for repetition of a single species but they could also be used to create formal patterns.
An amazing number of species have now entered the nursery trade, many with sub-species, forms or cultivars. They provide great variation in colour and texture, from those with fine grass-like foliage to substantial broad-leaved lilies. We can use these variations to have fun with patterns and a touch of formality in an informal garden can be a focus.
A pattern could involve plants in parallel lines grading upwards in height, arranged in straight or curved rows, of even circles. Picturing just three rows of plants in the design – tall, medium and short – ‘tall’ plants would have foliage to a metre or more, ‘short’ would be less than 50 cm, and ‘medium’ in between. Flower stems often rise above foliage.
Among the tallest monocotyledons are the magnificent Doryanthes excelsa (Gymea Lily) and D. palmeri (Spear Lily). For either, the eagerly awaited plume of red flowers is stunning. An alternative would be a Grass-tree such as Xanthorrhoea australis, with its exquisite fine foliage and tall creamy-white flower spike. Tall Lomandra hystrix is substantial and impressive.
Of medium height, there are many dianellas (Flax-lilies) to chose from, with dark-, mid-, or blue-green leaves, or even variegated, often with blue flowers and purple fruit. An alternative is beautiful Libertia paniculata (Branching Grass-flag), with dainty white flowers.
Grass-like lomandras offer a full spectrum of sizes, including L. longifolia (there are beautiful fine-leaf forms as well as the ubiquitous one with broader foliage) and many reliable forms of L. confertifolia and L. filiformis. Colourful Anigozanthos species and cultivars (Kangaroo Paws) really deserve a whole article.
Short plants in the front row could form a border. Two Snow-grasses, once both called Poa australis, are rather similar – Poa fawcettiae is a beautiful, silvery blue tuft and P. costiniana slightly more greenish or purplish. They will eventually spread to a width greater than their height. A colourful choice would be low Conostylis species, displaying masses of upheld yellow flowers in spring and summer.
All the monocotyledons above can tolerate drier conditions but others need more moisture. These include tall Dianella tasmanica (Tasman Flax-lily) and Helmholtzia glaberrima (Stream Lily), looking particularly splendid near water.
Of medium height are four lovely plants with blue flowers: Orthrosanthus multiflorus (Morning Flag), Stypandra glauca (Nodding Blue-lily) and, slightly shorter, Thelionema caespitosum (Tufted Lily) and Orthrosanthus laxus (Morning Iris). Patersonias (Purple-flags) range from medium to short.
Little plants for the front row might be dwarf Morning Iris (Orthrosanthus laxus) or dainty Thelionema umbellatum with delicate white flowers.
Marvellous monocotyledons, including grasses, have something to offer every garden.
[All photos by Diana Snape]
For more information about growing Australian plants including Native Plant Guides, visit Australian Native Plant Society (Australia).