The Grevillea rosmarinifolia is an evergreen shrub native to Australia; about two hundred evergreen species belong to the genus grevillea. The foliage, as the Latin name says, is similar to that of rosemary, the leaves are small, linear, needle-like, pointed, dark green, shiny and leathery; the shrub has a compact and densely branched development, overall it resembles a small conifer.
Between the end of winter and the beginning of spring at the apex of the branches particular flowers bloom, gathered in racemes, they are red or pink, often with cream-colored spots; they have no petals, and consist of a single elongated calyx. The adult specimens reach 150-200 cm in height, but the growth is not very rapid; pruning in general is not necessary, sometimes intervening to remove the branches damaged by the weather, or to give shape to the crown of the shrub, which is often used to give rise to rounded or cone-shaped forms. Grevillee were introduced to Europe in the nineteenth century, but in recent years they have been enjoying renewed success, due to the fairly easy cultivation and the very particular flowering.
The cultivation of the grevillea it is not difficult: we must only keep in mind that, depending on our climate, it may need even a few years before starting and giving us great satisfaction.
Origins and history
All the plants belonging to the genus Grevillea come from the southern hemisphere and in particular from Australia, islands of Oceania and Southeast Asia (Indonesia, New Guinea, New Caledonia). Some smaller populations originate instead of southern Africa. This genus is part of the Proteaceae family and has about 250 species of trees and shrubs, all of which are evergreen. Their natural habitat is wooded: they are found in humid and luminous forests or at the edge of clearings. In the right conditions they are very robust and are among the first to establish themselves in a territory after fires or other natural events that leave the bare ground: in some areas, due to this characteristic, they are considered invasive.
The genus is incredibly polymorphic: it includes trees that can reach 30 m in height, but also shrubs that do not exceed 30 cm. Also the habit is incredibly variable: from erect to a ground cover and a climber. There are notable differences in terms of foliage and flower coloring. These have particularly attracted the attention of horticulturists: they are available in yellow, red, orange and pink. They do not have petals, but look like cylindrical inflorescences similar to toothbrushes. Their production is very prolonged: some species carry them from the beginning of winter to the end of spring, being among the first plants to attract pollinating insects such as bees and butterflies.
THE GREVILLEA IN BRIEF
Family, genus, species
Proteaceae, gen. grevillea, more than 250 species
|Type of plant||Tree or shrub|
|Origin||Southeast Asia, Oceania, Southern Africa|
|Habit||From erect to falling back to ground cover|
|Use||Hedges, tree, isolated specimen, in groups, rock garden, vase|
|Height at maturity||From 50 cm to more than 2 meters depending on the species|
|Growth rate||From medium to fast|
|Maintenance||Low and simple|
|Water needs||normal; land always fresh in the early years|
|Minimum temperature||Not very rustic. The most resistant -8 ° C for short periods in sheltered conditions|
|Ground||Light, draining, poor|
|Fertilizer||Every 15 days (liquid) every 3 months (granular); initially more phosphorus|
|soil pH||Subacid or neutral|
|Soil moisture||Always fresh, no puddles|
|Propagation||Cutting, sowing (difficult)|
Grevillea rosmarinifolia plants are planted in a sunny, or partially shady place; in general they can withstand winter temperatures close to -7 / -5 ° C, although it is advisable to place the shrubs in a place sheltered from the wind.
In areas with very cold winters it is advisable to cultivate in pots, or it is possible to cover the shrubs with non-woven fabric during the winter months and with mulching material to protect the root system.
Over the years these plants tend to become stronger and more resistant to cold weather.
As we have said, grevillee particularly love light and heat. They should therefore be positioned throughout Italy in full sun: insertion in a slightly shaded area may be suitable only in the extreme south.
These plants are also particularly sensitive to the wind, especially at the beginning of spring: to avoid this we choose to place them near a wall facing south or near other plants that can act as windbreaks, without however removing light.
Gravillea watering and irrigation
The shrubs of Grevillea rosmarinifolia endure without problems even prolonged periods of drought; to obtain healthy and vigorous shrubs it is advisable to water the soil during the spring and summer months, always waiting for it to dry perfectly between one watering and another. In winter the watering should be reduced. Check and avoid water stagnation.
In autumn we bury a good quantity of mature manure at the foot of the shrub, or a handful of slow-release granular fertilizer.
Grevillee do not fear drought and are therefore very suitable for Mediterranean gardens without access to sources
THE GREVILLEA CALENDAR
Vegetative rest October-January
Vegetative growth June-October
Cleaning / pruning Late flowering (summer)
of water; it is necessary, however, to pay particular attention during the first few years from the plant because young plants are much more prone to drying, especially at high temperatures. We therefore advise, for the first 2-3 years, to irrigate quite frequently from June to September, checking that the soil is always slightly damp below the surface (but we carefully avoid stagnation, a frequent cause of radical pathologies). We use the most possible rainwater or a little limestone to avoid an excessive increase in salinity that would lead to the onset of physiopathies.
In pot. Potted plants are very easy to care for from this point of view: the substrate must always be fresh. We check by inserting your finger about 1 cm deep. Even more important is the use of demineralized water, given the limited space and greater risk of accumulation. We absolutely avoid the use of saucers. During the winter the irrigations can be very delayed (especially if we move the plants in a warm greenhouse). We only check that the ground bread never gets completely dry.
The best time to plant the grevillea is spring, when the minimum temperatures have stabilized above 10 ° C: in fact, the plant is distinctly thermophilic and heliophilous. We dig a deep and wide hole at least twice the earth bread and create a thick draining layer with gravel on the bottom. We extract the plant from the pot (avoiding as much as possible from disturbing the roots) and insert it into the hole. We cover with suitable soil and compact well. Let us water abundantly
THE GREVILLEA CALENDAR
|Flowering||February to June|
|Vegetative rest||October to January|
|Vegetative growth||June to October|
|Cleaning / Pruning||End of flowering (summer)|
Grevillea rosmarinifolia plants love soft and very well drained soils, possibly sandy; like most of the proteaceae also the grevillee prefer slightly acid soils, therefore we add to the earth of our garden of the peat, or of the specific soil for acidophilic plants.
The grevillea needs quite poor and very draining soils, with a subacid to neutral pH. The compact and clayey ones that could cause radical rot, stunted growth and the onset of physiopathologies must absolutely be avoided.
If our soil were of that type it is advisable to create a very large hole and replace it completely or by mixing a large amount of sand, also creating a thick draining layer on the bottom. Even more effective in keeping the area isolated is the insertion of a large private vessel in the bottom of the hole.
Gravillea multiplication and propagation
The multiplication of this variety occurs by seed, in spring; to favor the penetration of water inside the seeds it is advisable to lightly scratch them with very thin sandpaper, or to engrave the rigid cuticle that encloses them. In summer it is possible to propagate these shrubs through the preparation of semi-woody cuttings.
The propagation of grevillea at home is very difficult, especially through seed.
You can try it by previously scarifying the grain or leaving it overnight in warm water. Afterwards it will be placed in a germinator maintaining a constant temperature of 15 ° C and high humidity. A strong but not direct light is of much help.
A little simpler is the success of the cutting: semi-woody segments of about 8 cm are taken. They are placed in a very light mixture (half sand or perlite and half soil) and it always remains moist, mixing a liquid rooting hormone with water. We cover with transparent plastic and keep in a shaded area, until they begin to vegetate.
Pests and diseases
Generally these plants, being rustic and resistant, are not affected by pests or diseases. If you notice the presence of some pathology it is necessary to intervene promptly with the use of specific products, so as to effectively combat the problem and keep your plant in perfect health. Numerous preparations are available on the market that are successfully used in relation to the type of problem that affects the plant.
Grevillee, if grown in the right conditions, are very resistant and are rarely attacked by pathogens. We only need to pay attention to water and water stagnation, which must be the least calcareous possible.
Climate for the Gravillea
There are more or less rustic grevillees: the more resistant ones withstand temperatures around -10 ° C, but for short periods, in well-drained soils and very well sheltered from the wind. We evaluate well the intrinsic characteristics of each species and cultivar.
It is also necessary to specify that long and hot summers make these shrubs more resistant to cold: they are able to make the new jets become more profound and more robust when the bad season arrives.
As a result, their cultivation in the open ground is to be taken into consideration only in the southern regions or in the coastal areas (but in an area sheltered from the wind). In all other areas it is largely preferable to grow them in pots so that they can be picked up in a cold greenhouse (or in a bright and slightly heated room) from the end of October.
Grow the Gravillea in a vase
Pot cultivation can be done anywhere and is quite simple. The grevillea requires a rather large and deep vase (at least 40), possibly in terracotta (to promote transpiration avoiding both overheating and root rot). On the bottom we have to prepare a thick draining layer based on gravel or expanded clay. Good compotes are those suitable for cacti or citrus fruits. If we want to prepare the substrate ourselves we will have to mix garden soil, sand and peat in equal parts.
Repotting may become necessary every year: radical development is very rapid. It should be done in mid-spring, taking care to touch the roots as little as possible.
Gravillea fertilization and pruning
Young plants should be fertilized with products with a high phosphorus content: this avoids any excessive and prolonged flowering which would be detrimental to vegetative growth. Let's administer it every 15 days if it is liquid and every 3 months if it is granular, from spring to autumn. From the third year we can instead use a balanced product or with a slight prevalence of potassium.
It is not strictly necessary: we can intervene, however, from mid-spring to early summer, to shorten the branches a little, especially for plants kept in pots. In this way they will remain more compact and tidy and the following year we will obtain a more abundant flowering.
Grevillea rosmarinifolia: Grevillea variety
FLOWERS AND LEAVES
Red, rosé or white, from February to June, but also scattered in other seasons
Red, rosé or white, from February to June, but also scattered in other seasons
Not at all rustic, it wants warm climates. Suitable for the coasts and the extreme south
|Grevillea robusta||Beautiful foliage similar to that of ferns. It rarely blooms in golden yellow|
Tree or shrub, up to 30 meters, but can be contained
Fast growth, simple seeding. It tolerates the calcareous soil more
|Grevillea rosmarinifolia||Silver foliage, red or pink flowers from February to June|
Approximately 2 m x 2 m, hanging branches
Up to -8 ° C in optimal conditions;
|Grevillea wickhamii||Orange, red, yellow or pink flowers in spring-summer|
|Grevillea juniperina||Flowers from December to July, bright pink and yellow in small bunches. Needle leaves, pungent|
About 2 m x 2 m, compact and dense posture
Very tolerant, up to -8 ° C
|Grevillea lanigera||Red-pink and cream flowers, rounded needle leaves|
Up to 50 cm high, suitable for a vase
Up to -5 ° C if protected. Ideal in rock gardens or as a ground cover