Available in sizes ranging from evergreen shrubs to trees, Grevilleas are known for their delicate foliage and stunningly showy flowers. Grevilleas are native to Australia and thrive in warmer climates. They grow quickly, survive well, and are partial to well-drained soil. Grevilleas come in an astounding number of varieties, offering something for virtually every yard, garden, or park. Here’s what you need to know about choosing, planting, and taking care of your Grevillea.
Choosing the Right Grevillea
Grevillea is an entire genus of plants, which includes nearly 300 species. It’s no wonder. While Grevilleas are native to Australia, it has proliferated on a global scale. Since there are so many species and cultivars, choosing the right Grevillea can become quite the task!
First, there’s size. Grevilleas can come in a modestly small shrub or an extremely large tree. There’s also the flowers. Flowers can be small and large, come in different shapes, and in different colours. The flowers of the Grevillea are extremely noticeable, with flowers that are tube-like and come with long tendrils. Finally, there’s the foliage. Even the leaves of the Grevillea can differ, with some looking more needle-like like pine, and others looking more like ferns.
Common Types of Grevillea
- Long John. Up to ten inches tall, Long John has bright, coral flowers that attract both birds and hummingbirds. Hardy in zones 9 to 10 and best in full sun, Long John is a small shrub that can be easily maintained and shaped.
- Peaches and Cream. Adorned with multi-coloured flowers, Peaches and Cream can grow in partial sun, and grows from 4 to 6 feet in height. A smaller Grevillea, this is ideal for pots and garden accents.
- Silky Oak. Up to 70 feet in height, this Grevillea is a full evergreen tree that produces bright, orange flowers. It’s hardy in zones 10 to 12 and can become semi-deciduous in colder climates.
If you’re in a climate that can occasionally be colder, you will want a frost-hardy species of Grevillea. Some are less frost hardy than others and will not be able to overwinter well.
Planting Your Grevillea
Grevillea thrive in hot, dry weather, with well-drained soil. They should be placed in a sunny location, full sun if possible. To plant a Grevillea, dig a hole that is twice as wide and just as deep as the root ball. Separate the roots and place the plant in, backfilling firmly but not packing in the dirt. Soak the entire area completely with water, and cover in mulch.
Continue to water the Grevillea twice a week for the first few months as it establishes itself. Water deeply so that the roots will continue to grow; shallow watering can cause roots to grow only along the surface, which ultimately weakens the plant.
Taking Care of Your Grevillea
When fertilising, avoid fertilisers that are high in phosphorous. Too much phosphorous can cause poisoning in a Grevillea and cause it to die. Worse yet, phosphorous poisoning can take up to a year to show in plants, so it’s possible to over-fertilise and not see the results of that over-fertilisation for many months.
Exact care for the Grevillea depends on the type of Grevillea, given that the genus comes in a variety of sizes and types. Shrub Grevilleas can sometimes be shaped, and otherwise should only be lightly pruned. Larger Grevillea trees may also need regular pruning for health and shape. Grevilleas will not need to be watered extensively, but you will need to make sure it drains properly when watered.
Common Problems With Grevilleas
Though the Grevillea species is generally hardy, any plants can experience issues from time to time. Since Grevilleas are such a broad type of plant and tree, the exact issues that are encountered will depend on the exact species and cultivar. Nevertheless, there are some problems that are more common among Grevilleas.
- Root rot. If you begin to see white fungus at the base of your Grevillea, it’s likely that the roots have begun to rot. This is why it’s so important to keep your Grevillea well-drained because any moisture that lingers will promote fungus growth. Once root rot has completely taken hold, the plant cannot be salvaged, and instead will need to be pulled up and replaced. The soil around root rot may still have fungus spores in it for some time. It is possible to fight root rot if caught early, by exposing the base of the plant and the top of the roots to circulating air.
- Cinnamon fungus. Another type of rot, Cinnamon fungus will appear as yellow, wilted leaves, and orange marks along the trunk and stems. Cinnamon fungus can be fought by allowing the area to dry out between watering, and watering the soil around the plant rather than watering the plant itself. However, it mostly appears in areas that have poor drainage and can be difficult to defeat.
- Sooty mold. This black mold may start to appear across your Grevillea in humid conditions, but it is an aesthetic issue rather than a health-related one. This sooty mold can usually be removed by hand from plants if they become a nuisance and can be discouraged by keeping plants from becoming too moist.
- Brown, falling leaves. Brown leaves that are hanging or falling generally means that the Grevillea isn’t being watered enough. This can happen during droughts, or it can happen because roots are damaged and the Grevillea isn’t able to take in as much water as it should. Start watering more frequently to see if this issue may resolve, but remember that the Grevillea also needs to be allowed to dry.
- Burnt leaves. Burnt leaves generally indicate phosphorous toxicity, which is known to appear in many native Australian plants. Unfortunately, phosphorous toxicity can be fatal to a plant, and often does not show up until months after the plant has reached toxic levels. Phosphorous can cause plants to grow poorly, and the best solution is to avoid adding more phosphorous to the soil.
The showiness and diversity of the Grevillea is what makes it attractive to so many landscapers and gardeners. Coming in everything from small bushes to tall trees, the Grevillea is a beautiful accent throughout the year. As long as you ensure that it’s in well-draining soil, and avoid over-fertilising with phosphorous, it should continue to grow very quickly.