Select and Cultivate Appropriate Varieties of Grevilleas
Grevilleas are a wide group of plants, all but seven species coming from Australia. They are widespread across Australia, occurring in both cool temperate, and hot tropical climates.
There are around 250 species. About half of these are native to the south west corner of Australia.
Known commonly as “Spider Flowers”; the Grevillea flower is more like a brush than a traditional flower. It has obscure petals, but is none the less very colourful. Flower colour varies greatly; and most hold their flowers for a long period.
Grevilleas include both small to very large plants (from prostrate ground covers, through small and medium shrubs up to large trees).
Their hardiness is variable according to species. The foliage is also variable ranging from small, entire leaves to lobed or pinnate leaves. All are arranged alternately on the stems and some have hairy under surfaces. Most have a medium to fast growth rate.
There are 8 lessons in this course:
Review of the system of plant identification, general characteristics of Grevilleas, information contacts (ie: nurseries, seed, clubs etc.)
Planting, staking, mulching, watering, pest and disease, feeding, pruning, protection from wind, salt air, etc.
Methods of propagating Grevilleas. Propagation of selected varieties.
The Most Commonly Grown Varieties.
Other Important Groups.
Other Grevillea Varieties.
Making The Best Use of Grevilleas.
In containers, in the ground, growing for profit etc. (to sell the plants) etc.
Special Assignment. On one selected plant or group.
Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.
Identify a range of different Grevilleas.
Explain the culture of different types of Grevilleas.
Propagate different Grevilleas
Discuss different uses for Grevilleas
Compare identifiable characteristics and cultural preferences of a range of Grevilleas.
Discuss a range of Grevillea hybrids and cultivars
Identify and compare a range of commonly cultivated Grevilleas.
Discuss one Grevillea species, cultivar or type in depth.
Diversity in Grevilleas
Grevilleas come in all shapes and sizes, from low ground covers to tall trees.
Commonly called spider flowers, there are around 250 species of Grevillea. Most are hardy, both to frost and drought, and area easily grown, flowering in some cases for months. They prefer full sun and good drainage; most are happiest in a slightly acid soil. Like many of the Proteaceae, they are sensitive to excess phosphorus and too much lime in the soil. As well as the species, there are now many attractive hybrids to choose from and the following is only a partial list.
Ground Cover Grevilleas
A large range of grevilleas can be grown as ground covers. Some hug the ground, and others are spreading but may grow up a little. Here are some of those that are more commonly cultivated as ground covers.
Grevillea aquifolium (Prickly Grevillea)
Growth: 4 wide x 1.5m high
Grevillea aquifolium is a dwarf to medium shrub with a prostrate habit. Flowers are green red and sometimes yellow. Flowering is usually scattered but occasionally profuse; a reliable plant which is popular in temperate regions. It is frost and dry tolerant. It occurs naturally in heath or woodland areas in well drained sandy or gravel soils. Generally grows in acidic soils, however is also tolerant of alkaline soils.
Growth: 0.1-2.5m x 1.5-3m.
Grevillea australis is a dwarf to medium shrub with spreading ascending branches. It naturally inhabits subalpine and alpine areas of South Eastern Australia. Flowers are cream, sometimes profuse, and inconspicuous with a sweet scent. The plant is hardy, frost and snow tolerant.
Grevillea confertifolia (Grampians Grevillea) There are three forms occurring naturally, occur naturally on moist sandstone soils, woodlands or open forests, in temperate south east Australia.
Habit - usually low growing spreading plants; but can also occur as small shrubs to 1.5m tall.
Leaves are needle like to 3 cm long, Low growing ground cover habit, growth tips can tend to be covered with fine hairs.
Flowers - either wine red or rosy pink, short toothbrush type to 1cm.
Conditions - tolerates frost and light snow.
Problems - humidity can be a problem (better in drier climates), Pests may include: scale, leaf miners, caterpillars (causing webbing).
Grevillea x gaudichaudii
A very popular spreading grevillea; grown extensively in temperate regions throughout the world. Originate from the upper Blue Mountains in NSW, where it grows in sandstone.
Habit – there are two forms; A dense low groundcover with prostrate branches and reddish new growth 0.3m x 5m. The second is a more scrambling form without the reddish growth. Leaves -11 x 7.5cm stalked ovate, divided green to reddish.
Flowers - are on racemes approx 8 cm long, they are pinkish red about 2.5 cm. Attractive to nectar feeding birds.
Conditions - tolerates wet periods and heavier soils, but they need to drain freely. Prefer shade but tolerate open sunny aspects; grows well on banks.
Problems - it is difficult to grow in subtropical areas; prone to leaf Spotting Fungi.
Propagated - from cuttings.
Most grevilleas are shrubs, of varying sizes, but a few do grow into tall trees; including the following.
Grevillea baileyana (Findlay’s Silky Oak)
It is a small to medium sized, handsome tree with a bushy crown. It is common to Queensland and New Guinea subtropical and tropical rainforests. The profuse flowers are fragrant, white and crowded in racemes 6 -15 cm long. They contrast nicely with the dark foliage attract nectar feeding birds. The wood has been harvested and prized by furniture manufacturers.
The tree requires free draining soils, and protection from hot dry conditions when being established. They will tolerate light frosts.
Grevillea robusta (Silky Oak)
Grevillea robusta is a very popular ornamental tree. It is endemic to Queensland and New South Wales and grows in rainforests. It is a small to medium sized tree with either a spreading or an elongated crown (to 30 meters).
The flowers are brilliant orange and in racemes and rich in nectar, which attract nectar feeding birds. The wood is harvested and prized by furniture manufacturers.
The tree is grown widely in many countries around the world. It is hardy and adaptable; it will tolerate numerous climates and soil types.
Habit – a small to medium slow growing tree with a narrow crown. Leaves - 10-50cm long and 0.3-1cm wide. Narrow at base, linear, and often curved.
Flowers - are cream and fragrant and crowded on racemes which are 7-13 cm long. Attractive to nectar feeding birds.
Conditions - originates from watercourse of inland Australia. Drought and frost tolerant.
Propagate – from seed.
How You Might Use What You Learn
As a nurseryman
- As a plant breeder
- As a cut flower grower
- As a landscaper
- As a garden writer or consultant
- As a plant collector or passionate amateur gardener.
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