Australian oak (Grevillea robusta)

La Robusta grevillea It is a magnificent tree that, although it grows a lot in height, having a rather thin trunk and a columnar bearing, it is an interesting species to grow in medium to large gardens. In addition, it can be kept in a pot for several years, as long as it is transplanted to an ever larger one from time to time.

Its leaves are very elegant, reminiscent of those of ferns, for example; but they are not the ones that possess all the ornamental value of this plant, but rather its flowers are some of the most beautiful of the genus.

Origin and characteristics

Our protagonist is an evergreen tree native to the east coast of Australia. It is popularly known as Australian oak, silver oak, fire tree or golden pine, and its growth rate is quite fast. It reaches a height of between 18 and 35 meters, with dark green bipinnate leaves and 15 to 30cm long.

The flowers are 8 to 15cm long, golden-orange in color and bloom in spring. The seeds are produced in velvety dark brown dehiscent fruits, and are flat winged about 2cm long.

What are their cares?

If you want to have a specimen of Australian oak, we recommend giving it the following care:

Location

It is a tree that it has to be outside, either in full sun or in semi-shade. Ideally, as a youngster it should be in a bright area but without direct sunlight, and that little by little as it grows older it will expose itself to the sun.

Earth

• Garden: grows in soils without lime, fertile and with good drainage.
• Flower pot: use substrate for acidic plants (for sale here). However, it is not a plant that can be grown in a container for its entire life.

Irrigation

During the summer you will have to water very often, especially if it is a very hot and dry season, since it does not tolerate drought. The rest of the year the irrigation will be more moderate to scarce, with about two a week.

In any case, it is important to control the risks, and not go to extremes. Watering too little is as bad as watering too much. For this reason, and to avoid problems, we recommend checking the humidity of the soil before doing anything, for example with a thin wooden stick or with a digital humidity meter (for sale No products found.).

Use rainwater or lime-free.

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From early spring to late summer must be paid with Organic fertilizers, like guano (for sale here liquid and by here in granules), mulch, compost or the like.

You just have to keep in mind that if you grow it in a pot it is advisable to use liquid fertilizers following the instructions specified on the container so that the drainage continues to be good.

Pruning

After flowering It can be pruned by removing dry, broken, weak or diseased branches. It is also interesting to remove the lower ones, especially if you have other plants growing under its shade.

Multiplication

La Robusta grevillea multiplies by seeds in fall / winter and cuttings in spring. Let's see how to proceed in each case:

Seeds

1. First, you have to fill a seedling tray (like this one they sell here) with substrate for acidic plants.
2. Then, water thoroughly, moistening the entire substrate well.
3. Next, place a maximum of two seeds in each socket, and sprinkle a little copper on top. This will prevent fungi from spoiling them.
4. Then cover them with a thin layer of substrate.
5. Finally, water again, this time with a sprayer, and place the seedbed outside, in semi-shade.

They will germinate in spring.

Cuttings

To multiply it by cuttings you must cut a piece of about 30-35cm long, impregnate the base with liquid rooting hormones (for sale here) or with homemade rooting agents, and finally plant them in individual pots with vermiculite.

Keeping the pot outside, in semi-shade, and the substrate moist, they should root after about three weeks.

Plagues and diseases

It is quite resistant, but if it is watered in excess it will be attacked by mushrooms, which will rot their roots. To avoid this, you have to control the risks, and if you want to do preventive treatments with copper (for sale here) once a month.

Rusticity

Resists up to -8ºC, but only if during the day the temperature rises above 0º. It is not a plant that can be grown - at least, not outside in winter - in cold climates.

What uses is it given?

Ornamental

La Robusta grevillea it is a tree that is widely used as a garden plant, usually as an isolated specimen although there is nothing bad in alignments either. It is also sometimes worked as bonsai.

Wood

Its wood is used in cabinetmaking and cooperage.

What did you think of this tree?