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Editor's note: This article is based on a lecture presented to the Regional Meeting of the Society for Growing Australian Plants on 18 November, 1983. The lecture was transcribed by Philip Strong.
I am grateful to Rodger for reviewing the transcript and updating the information.
The Myrtle family (Myrtaceae) contains many familiar large plants such as the eucalypts, angophoras, lilly-pillys and turpentines. In addition to these there are many small shrubby members of the family, a number of which are ideal garden subjects.
Before looking in detail at specific plants, however, I'd like to give you a brief introduction to the botany of the Myrtle family.
Botanists place plants into various genera based on certain characteristics. One of the most important plants features used in classifying plants is the ovary, where the seeds develop. In the myrtle family, plants are divided on the basis of whether the ovary is one-celled or more than one-celled. If you cut off a small flower of (say) a Beaufortia and then cut off behind the flower so that you get a cross-section of the area where the seeds are starting to form, you will see several little hollows or cells.
In one group of plants in the myrtle family, however, you will find there is only one cell (Fig.1). This is the Chamelaucium alliance which contains plants such as Actinodium, Darwinia, Chamelaucium, Verticordia, Thryptomene, Micromyrtus, Pileanthus, Calytrix and Wehlia.
The second group is the sub-family Leptospermoideae, in which there is more than one cell in the ovary. This is a much larger group (Fig.2).
The Leptospermoideae is subdivided further on the basis of the structure of the stamens; one subgroup has free stamens, the other has united stamens (Fig.3). But the botanists go even further by looking at the anthers which are the pollen bearing parts on the ends of the stamens.
In some cases the anthers are versatile (Fig.4) which means they tend to move around on the tip of the stamens (you probably need a magnifying glass to see this). In this group we have Kunzea, Callistemon, Melaleuca, Lamarchea and Conothamnus. Other members of the family have anthers which are basifixed. Plants in this group include Beaufortia, Phymatocarpus, Regelia, Eremaea, Calothamnus and Eucalyptus.
One of the most common questions that I'm asked is "What's the difference between a Callistemon and a Melaleuca?" Well, the basic difference is in the arrangement of the stamens. In a Callistemon (and also in a Kunzea), the stamens are free... they go right down to the base of the petals. In a Melaleuca, the stamens are united in five separate clusters, as shown in Fig.3.
Current botanical studies are pointing to including Callistemon with Melaleuca as some botanists believe that the above differences are not substantial enough to separate genera.
Myrtles With A One-celled Ovary
When people see this plant with daisy-like flower heads, they just can't believe that it belongs to the same family that contains Eucalyptus, Melaleuca, etc. There are two species, both from Western Australia. Actinodium cunninghamii, is called the "Albany Swamp Daisy" but it's difficult to maintain in cultivation and is often best grown as a container plant...grafting may be the answer to more reliable garden performance.
There are about 30 different species, mostly confined to Western Australia, but there are some in New South Wales, Victoria and South Australia. There are many with horticultural potential.
D.macrostegia, one of the Stirling Bells, is found in western regions of the Stirling Range and in the Porongurup Range in south Western Australia. It is one of several species which have large, petal-like bracts which are usually red with white blotches. There may be perhaps 7 to 9 small flowers within the bracts.
D.glaucophylla is a species from around Gosford on the central coast of New South Wales. It's a beautiful prostrate plant with attractive foliage. The only drawback (and this refers to some other darwinias and some Homoranthus as well) is that when in flower it has an off-putting odour; a bit like tomcats! It's one of the few darwinias that self-layers.
There are about 15 species and they're only found in Western Australia. One of the ways to distinguish Chamelaucium from Baeckea is to look at the coverings (bracteoles) over the buds. With Chamelaucium they are waxy and brown and they usually fall off. Also Chamelaucium can be distinguished from Darwinia by the style being shorter than the floral tube...with Darwinia the style protrudes beyond the tube. The foliage of most Chamelaucium has a sweet aroma when crushed.
C.uncinatum, 'Geraldton Wax', is an extremely variable plant in terms of flower colour and flower size. Flowers can be white, purple and various shades of pink and some forms have flowers larger than a 20 cent piece. It's grown a lot for its value as a cut flower and the industry is now growing a number of different forms and exporting them overseas to places like Germany Japan, Holland and the USA. There were some problems, however, with flowers falling off during transportation. This has now been overcome by the correct post-harvest treatment.
Chamelaucium 'Walpole' is an unnamed species which has wrongly been called C.axillare. There is a hybrid of this and C.uncinatum which arose as a chance seedling in a garden in Mildura. It's an excellent cut flower. It produces a mass of pale pink flowers. Other hybrids of the same parents have also become available, notably 'Lady Stephanie'.
These can be quite a problem for many people to grow. Many of them come from areas where growing conditions are fairly specialised. Usually they like good drainage, plenty of sun and they generally don't like other plants growing in close proximity to them. Almost all of the 97 species occur in Western Australia with 3 species in the Northern Territory.
One of the simplest ways to identify a Verticordia is to look behind the petals at the calyx which has hairs all around it...this is why they are called "feather flowers".
V.plumosa is probably the most reliable species. The plants usually reach about a metre high by a metre and a half wide. Flowers are pink to purple and it's an excellent cut flower.
There are about 76 Calytrix species spread right across Australia. One species, C.tetragona, occurs in all states including the Northern Territory but many of the others are quite restricted in distribution. Most Calytrix have long hairs or awns on the tips of the calyx and the flowers nearly always occur in terminal clusters at the ends of the branches. Lhotskya is now included in Calytrix.
A feature of Calytrix is that many of them flower over the summer months.
C.glutinosa has quite a wide distribution in Western Australia and it's fairly reliable in cultivation in Victoria. It's very showy and the flower colour can be variable, from pale to deep pink.
C.flavescens, like most of the yellow-flowered species has a beaut, spicy scent which I like but which some others think is dreadful. It's also excellent for attracting butterflies, although some people might not like the end product of butterflies...caterpillars, but they don't usually do too much damage. They're nature's pruners!
There is not a wide range of thryptomenes in cultivation. Of the approximately 40 different species in Australia, only 4 or 5 are generally found in gardens. Most of them are good for long-lasting flowering, even when picked. T.calycina, the Grampians Thryptomene, is renowned for this characteristic and is used widely in the florist trade.
This genus is closely related to Thryptomene and there are about 12 species. The best known is M.ciliata. This occurs in a myriad of forms....prostrate, upright, column-like and there's one from western Victoria which looks like a miniature conifer. In some forms the flowers start off white and deepen to quite a deep red.
Myrtles With More Than One Cell In The Ovary
Now for some of the plants in the 2-5 celled ovary group....
There are three genera here (Astartea, Babingtonia and Baeckea) that cause some confusion in identification. With Astartea, the stamens are in clusters and they're almost always opposite the gaps in the petals. Baeckea, on the other hand, have stamens which are scattered...they're opposite the petals as well as in the gaps. Babingtonia, recently reinstated as distinct from Baeckea, have flowers with stamens opposite the petals.
Astartea fasicularis is a very adaptable garden plant; it flowers for ages and ages and it has white or pale pink flowers. There is a tendency for some people to steer clear of white flowers and I think that is a pity. White is a very useful colour on dull days to lighten up a garden and it's also good for shady spots. White-flowered shrubs are also good to plant among other coloured plants. There has been some confusion between A.fasicularis and A.heteranthera. In the latter, the flowers are on stalks which are longer than the leaves and it is very uncommon in cultivation.
This is is the "Native Pomegranate". There are only two species, both from Western Australia.
B.pulcherrimum often grows in fairly sheltered conditions in nature but we find in southern Victoria that we need to give it as much sun as we can. The stems and leaves are very subject to attack by grey mould.
This is another very showy genus. It is fairly easy to separate from other genera mainly because of the flowers which are in groups of two at the base of the opposite leaves. There are about 13 different species, all from the west.
H.angustifolium is fairly common in cultivation and there are quite a few different selections. It has masses of flowers which often start off with pink buds, open to white and then deepen to a deep pink.
H.robustum is quite a difficult one to keep going unless grown in well-drained, light soils. It's extremely showy with large deep pink petals and it can reach 2 to 2.5 metres in height. Grafting of H.robustum onto Darwinia citriodora has been successful.
H.robustum and some of the other hypocalymmas have a very beautiful, spicy scent.
These have flowers which are in very tight bundles and which can be at the ends of short branchlets or in the leaf axils. There are about 11 species and they're confined to Western Australia. The most familiar one is the small tree, A.flexuosa, sometimes called the "Willow Peppermint" or "Willow Myrtle". Its flowers are somewhat like those of Leptospermum.
A.parviceps is a small species which has become popular because it produces masses of flowers which last for a long time when cut. They develop a soft cream colour when dry and they don't drop their petals. This species is commonly used by florists.
The leptospermums (tea trees) are familiar to most; they're a very showy group of plants. They have suffered a bit because of comparison with the hybrid tea trees which have been widely sold and which are very prone to scale and borer attack. There are over 75 different species, mainly in eastern Australia.
Leptospermum rotundifolium is a magnificent species. The flowers are often the size of a 20 cent piece and there's wide scope for selection of colour forms. Down around Jervis Bay and on the Nerriga-Nowra road there are some beautiful forms.
With these we are starting to get to the plants with showy stamens, rather than those where the petals are the prominent feature. There are about 40 different kunzeas, mainly Western Australian but there are a few eastern species. The flower heads can be globular, a bit like some of the melaleucas, or they can be in spikes. If you're not sure if a plant is a Melaleuca or a Kunzea, look at the stamens...with Kunzea the stamens are free (Fig.3). Also, with Kunzea the seed is shed as soon as it's ripe rather than being retained within the woody seed capsules for many years.
K.pulchella occurs on granite outcrops in Western Australia. It's a beautiful species with intense red/pink flowers. It can reach 3 to 4 metres in height by a similar width. It's not usually dense unless you prune it to promote lateral branching. Normally it's quite a graceful, slightly open plant.
K.pomifera, or "Muntries" is an excellent groundcover with white flowers. Its stems often self-layer. Sometimes it doesn't flower regularly; you might get a burst of flowers one year and none for the next couple. It's found naturally in western Victoria and in south-eastern South Australia. The small fruit are edible and were commonly collected by early settlers to be included in desserts.
K.parvifolia is a small plant which is similar to K.capitata from New South Wales. It produces masses of pink flowers and is usually less than about a metre in height. There is also a dwarf form which is very dense and less than 1 metre in height.
This genus is very common in cultivation. Sometimes people get confused between these and the "brush-type" kunzeas. Basically, kunzeas have much shorter brushes and they shed their seeds when they are ripe.
C.viridiflorus is a species from Tasmania which grows well on the mainland. As the name indicates, the brushes are green or, more truly, lemon-green. It grows about 2 to 3 metres in height and doesn't mind growing in waterlogged ground.
C.salignus is one that I hope people grow a lot. Foliage is an important characteristic in gardens and this species has beautiful reddish new growth. Flowers can be cream, pink or rarely purplish or red.
Callistemon "Reeves Pink" is one of many, many cultivars. It usually grows to about 2 metres, but can get a bit taller.
C.sieberi (previously known as C.paludosus) is usually an upright, fairly straggly bush. There is, however, a selected, weeping form with soft pink brushes and foliage which weeps almost to ground level.
To have lots of flowers on your callistemons, cut them back after flowering to promote plenty of new side shoots which will bear flowers next year.
This is another very familiar, large genus. Flowers have the stamens in five separate bundles.
M.fulgens is a Western Australian species which usually has red flowers, but there's a salmon coloured form which is very attractive and unusual. What we have known as M.steedmanii is now M.fulgens ssp. steedmanii.
M.wilsonii is another very showy plant with bright reddish pink flowers. It has a massed flower arrangement but has a relatively short flowering period. A low growing selection is very attractive.
M.thymifolia is very adaptable; it will grow in waterlogged conditions and it also doesn't seem to mind if it dries out. It flowers right through summer and even autumn. There are different flower colours...it's usually mauve but there are deep purple, white and pink selections available.
There are about 20 different species in this genus, all confined to Western Australia. Many are excellent for attracting honey-eating birds. One way to tell if a plant is a Beaufortia is to look at the stamens; they tend to be unequal in length and branched. Except for B.sparsa, they all have leaves which are opposite each other on the stems.
B.purpurea is one that I used to think was only a small plant but it can reach nearly 2 metres high and wide. The purple flowers appear right through summer. In fact most of the beaufortias flower during that period.
B.orbifolia is probably one of the most adaptable ones for cultivation in eastern states. It usually grows on shallow sand overlying fairly heavy clay, although in some areas you can see it growing in very deep, pure ironstone gravel. When the flowers open they're quite green in the centre so, as they mature, you get a combination of green and red. A marvellous plant!
B.decussata is one of those useful plants for extremely narrow areas. The bush tends to grow upright to about 2 to 3 metres high but may be less than half a metre wide. Pruning the top growth will promote lateral growth. It has deep red flowers.
Finally, a small genus...Phymatocarpus. There are only two species and they're not very commonly grown.
P.maxwellii varies in colour a bit. It's usually pink but it can sometimes be deeper in colour, tending to purple. It's very similar to some of the melaleucas and has small, oval leaves. To tell the difference, you've really got to get out the magnifying glass and examine the anthers that are erect and attached to the stamens at the base.
A good way of growing many of the plants described here is by using the "bog method". It's very simple and just about foolproof, which is great if you're just starting to become interested in plant propagation.
First you get an ice cream container or something similar and pour some water into the bottom. You then fill your seed-raising container (a punnet or even a margarine container with holes cut in the bottom) with a suitable seed propagating mix and sprinkle the seed very, very finely on the top. Then just "plonk" it gently into the water in the ice cream container and maintain the water level about half way up the seedling container. The capillary action will draw the water up into the mix. This will keep the seed moist.
Once the seed has germinated and gets to about 5 to 10 millimetres high, you can remove the container and then water with a very fine spray...not a heavy spray as that can damage the seedlings.
The advantage of this method is that if you go away for up to a week the seed wont dry out provided, of course, there is enough water in the larger container.
People are often a bit loathe to try propagation from cuttings; they think it's a bit difficult. Well, some plants are difficult to grow from cuttings but many are quite easy.
Conditions will vary from one plant propagation unit (or glasshouse or poly-house to another) but, as a general rule, the best type of material to use as cuttings is young growth which is just beginning to become firm but which is still supple....the type that springs back when you bend it and doesn't break. Getting the right type of material is very, very important. Sometimes it makes the difference between getting roots onto plants or not having success.
The use of a hormone rooting powder or liquid that is suitable for semi-hardwood growth can be beneficial in promoting root production and growth. A cutting propagation medium which drains very well but is still moisture retentive should help you have success.
Rather than go into depth here, there are a myriad of books and articles which cover propagation in detail and should enable you to get onto the right track if you are not a regular propagation practitioner. It is certainly a wonderful thrill to have success in propagating plants so...go to it!!!
Rodger Elliot is well known to most Australian native plants enthusiasts through his long involvement in the propagation and cultivation of Australian plants, as well as through his writing and lecturing on our native flora.
His major project in recent years has been as co-author, with David Jones, of the "Encyclopaedia of Australian Plants", of which 7 volumes plus supplements have been published. He is also the author of numerous other books on Australian plants and writes for several magazines and journals.
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Australian Plants online - December 1999
Association of Societies for Growing Australian Plants