Grevillea robusta
Australian silky-oak · Silkoak · Silky Oak · Silver oak · Southern silky-oak
Description
Source: leafsnapGrevillea robusta, commonly known as the silk oak or Australian silver oak, is a fast-growing evergreen tree native to eastern Australia. It can reach heights of up to 30 meters and has a broad canopy of silver-gray, fern-like leaves. The tree produces clusters of bright orange-red flowers that attract birds and other pollinators. Grevillea robusta is often used as an ornamental tree in parks and gardens because of its attractive foliage and striking flowers. Additionally, its wood is valued for timber production due to its strength, durability, and resistance to termites. The plant thrives in well-drained soils with full sun exposure but can tolerate some shade. It requires regular watering during its first few years of growth but becomes drought-tolerant once established. Although Grevillea robusta has become naturalized in some regions outside of Australia, such as California, it can also be considered an invasive species because of its ability to outcompete native vegetation if not properly managed.
🌳 Silky oak offers a wide range of unexpected uses beyond its decorative role. Its timber, prized for being easy to work and having an attractive finish, is sought after for fine cabinetry and veneer production. Its biomass can be converted into bioenergy, and the tree acts as a biological indicator of soil with high gold content. Its adaptability and aesthetic appeal make it valuable for restoration ecology and urban landscaping.
🎭 Security, Wellness, Finances
Care Guide
💧 Water Every 7 days
Silky oak thrives in temperate climates with well-drained soil and moderate moisture. For best results, water the plant every 1 to 2 weeks, allowing the soil to partially dry out between waterings. Being an evergreen, it requires consistent moisture to support its year-round foliage growth while also adjusting to natural changes in precipitation.
How should I water my Silky oak?
Your Silky oak is not picky about how you water it, so you can use any common watering tool. This includes watering cans, hoses, or even cups. It's best to water the soil directly and make sure all areas are equally moist. Using filtered water is a good idea to avoid harmful particles in tap water. It's also better to use water at or slightly above room temperature, as very cold or hot water can shock the plant. However, the Silky oak generally responds well to any kind of water.
What should I do if I give my Silky oak tree too much or too little water?
Outdoor plants, especially newly planted ones or seedlings, are prone to lack of watering. It is important to remember to water them enough for the first few months, especially when the tree is small or just planted. Once the roots are established, Silky oak can rely on rainfall most of the time. If your Silky oak is planted in pots, overwatering is more likely. If you accidentally overwater your Silky oak, you should take immediate action to remedy the situation. First, stop watering the plant right away to minimize the impact of overwatering. Then, remove the Silky oak from its pot to check its roots. If no root rot is found, you can return the plant to its container. However, if there are signs of root rot, trim away the affected roots and consider applying a fungicide to prevent further damage. Finally, repot the Silky oak in well-draining soil. In the case of underwatering, simply water your Silky oak more frequently. Underwatering is usually an easy fix, as the plant's leaves will droop, dry out, and fall off, but they will quickly return to fullness after sufficient watering. Make sure to adjust your watering frequency as soon as underwatering occurs.
How frequently should I water my Silky oak?
Most outdoor plants can grow normally with rainfall. However, if your area lacks rainfall, you should water your plants every 2 weeks in the spring and fall. In the summer, you will need to water them more frequently. During the winter, when growth is slower, you can water them less often or not at all. If your Silky oak is young or newly planted, you should water it more frequently to help it establish and grow. For potted plants, there are two main ways to determine how often to water your Silky oak. The first is to follow a set schedule, either once a week or once every other week. However, this may not always work since it doesn't consider the specific conditions of your plant's environment. The second option is to check the soil moisture. Wait until the top two to four inches of soil have dried out completely before watering again. This method allows you to adjust the watering frequency based on the season, as the plant's water needs are highest during summer.
How much water does my Silky oak tree need?
When watering your Silky oak, it's important to note that it doesn't require a lot of water. If only a few inches of soil have dried since the last watering, you can provide about five to ten ounces of water each time you water to promote healthy growth. You can also determine the amount of water based on the moisture level of the soil. Keep track of how many inches of soil have dried out between waterings. To ensure the Silky oak receives enough moisture, water enough to dampen all the soil layers that have dried out since the last watering. If over half of the soil is dry, consider giving more water than usual. In such cases, continue watering until you see excess water draining from the pot's drainage holes. If you have planted the Silky oak in an area that receives sufficient rain, it may not require additional watering. When the Silky oak is young or newly planted, ensure it receives 1-2 inches of rain per week. As it grows and establishes itself, it can rely solely on rainwater unless there is a prolonged period of hot weather without any rainfall for 2-3 weeks. In such situations, consider giving the Silky oak a thorough watering to prevent stress.
How can I know if I am giving enough water to my Silky oak?
The Silky oak often suffers from overwatering, which can be easily identified by a few signs. Look out for yellowing leaves and leaf loss, as well as a shriveled plant structure and possible root rot. Similarly, an underwatered Silky oak will show signs of wilting, with brown or brittle leaves. In either case, it's important to take action and restore the health of your Silky oak.
☀️ Light Full sun
Silky oak grows best with plenty of light throughout the day, though it can moderately tolerate locations with filtered light. Originating from environments rich in light, it is ideally suited to strong sunlight. Being too sheltered from the sun can cause weak growth, while excessive sunlight can result in leaf damage.
What are the sunlight requirements for plants?
Plants have different sunlight requirements to thrive. 'Full sun' means a plant requires above 6 hours of sunlight, while 'partial sun' refers to about 3-6 hours of sunlight. It's important to observe how sunlight moves through your garden, choosing spots that offer a balanced light-shade mix to ensure your plants' happiness.
How does silky oak respond to sunlight?
Silky oak does best with plenty of light during the day but can also tolerate filtered light moderately. Originating from light-rich environments, it ideally needs substantial sunlight to thrive. However, too much protection from sunlight may result in weak growth, and overexposure can cause leaf damage.
What artificial lighting requirements do indoor plants have?
Indoor plants require adequate lighting for optimal growth, especially when natural sunlight is lacking. Artificial lights, like LED, are beneficial as they can be adjusted to provide specific light wavelengths needed by plants. Full sun plants need 30-50W/sq ft of artificial light, partial sun plants 20-30W/sq ft, and full shade plants 10-20W/sq ft. Place the light source 12-36 inches above the plant, ensuring it receives 8-12 hours of artificial light daily to mimic natural daylight hours.
What symptoms indicate light deficiency in silky oak?
Symptoms of light deficiency in silky oak include smaller new leaves, leggy or sparse growth, faster leaf drop, slower or no new growth, lighter-colored new leaves, chlorosis, sunscald, leaf curling, wilting, and leaf scorching. These symptoms suggest that the plant is not receiving optimal light, affecting its photosynthesis and overall health.
How can you improve light conditions for indoor and outdoor plants?
To enhance light conditions, gradually move plants to sunnier locations to ensure they get at least 6 hours of direct sunlight daily. Use south-facing windows and keep curtains open. If moving the plant is not feasible, consider using artificial light, keeping lamps on for at least 8 hours daily or investing in professional grow lights. For outdoor plants, avoid sudden changes in light intensity to prevent sunburn. If sunlight is blocked, consider pruning obstructing trees or transplanting smaller plants during their dormant period to sunnier spots with good drainage. Remember, parts of the plant damaged by insufficient light might not recover, but new growth should be healthy with improved light exposure.
🌡️ Temperature 20–37.8°C
In its native environment, silky oak prefers temperatures between 20 and 38 ℃ (68 to 100.4 ℉). In winter, measures may be required to protect the plant from temperatures below 10 ℃ (50 ℉).
What is the preferred temperature range for Silky Oak in its natural habitat?
Silky Oak thrives in its native growth environment with a preferred temperature range of 20 to 38°C (68 to 100.4°F). It is an extremely heat-loving plant, and the winter months often require adjustments to protect it from temperatures dropping below 10°C (50°F). During colder conditions, it is advisable to bring Silky Oak plants grown outdoors indoors and place them near a bright window, albeit at a safe distance from heaters to maintain beneficial growth temperatures above the minimum suitable growth temperature. It's essential to avoid temperatures that approach the minimum tolerable growth temperature as these can cause harm to the plant.
How does low temperature affect Silky Oak and what are the solutions?
Silky Oak is not tolerant of low temperatures and shows a preference for warmer conditions, thriving best when the temperature remains above the minimum suitable growth temperature. During winter, keeping the plant above the minimum tolerable growing temperature is crucial. Exposure to temperatures below the limit growth temperature can lead to lightening of the leaves' color, which gradually turns brown or black due to frost damage, followed by symptoms like wilting and drooping. To mitigate frost damage, it's recommended to trim off the affected parts and move the plant indoors to a warm location, preferably near a south-facing window for adequate sunlight, while being cautious not to place it near heaters or air conditioning vents to avoid excessive dryness.
How does high temperature affect Silky Oak and what are the remedial measures?
During the hotter months, it's important to ensure that the Silky Oak is kept below the maximum suitable growing temperature. Exceeding the tolerable growing temperature maximum can cause the leaves to lighten and increase the plant's susceptibility to sunburn. To address damage caused by excessive heat, it's advisable to trim away sunburned and dried-up parts and then move the plant to a location that offers protection from the midday and afternoon sun. Additionally, watering the plant in the morning and evening will help keep the soil moist, aiding in the plant's recovery and wellbeing.
💨 Humidity
🪴 Soil 6-6
🌱 Fertilizer
Fertilizing is essential for caring for the Silky oak. Regular feedings during the growing season preserve the energy required for its showy foliage and promote overall growth. Skipping fertilization can lead to unhealthy leaves, reduced ornamental value, and stunted or weak growth that is more susceptible to breaking.
Why do I have to add fertilizer to my Silky oak?
Silky oak requires regular fertilization primarily because its showy leaves demand a considerable amount of energy for their production and maintenance. Additionally, the tree needs energy to support the growth of its stems, branches, roots, and other vital structures. Neglecting fertilization can lead to two likely outcomes. Firstly, the leaves may lose their natural color and texture, resulting in an overall unhealthy appearance that diminishes the tree's ornamental appeal. Secondly, the overall growth of the Silky oak may slow down or produce weak growth that is susceptible to breakage.
When should I fertilize my Silky oak tree for the best results?
Silky oak plants benefit from occasional feedings, so you don't have to stick to a strict feeding schedule when planting them. A simple way to fertilize your Silky oak is to apply the fertilizer while watering it on occasion. It's important to give your Silky oak a good amount of water during the growing season. You can feed it once every two to three weeks, consistently throughout the period when it's producing new growth.
When is it not a good idea to put fertilizer on my Silky oak?
You can follow a regular fertilization schedule for your Silky oak throughout most of the year, specifically during the active growing season of spring, summer, and early fall. However, it's important to refrain from using fertilizer on this plant during the winter. During this season, the Silky oak enters a dormant growth phase, during which it either produces no or very little new growth. Since the plant requires less energy during this time, fertilization is not necessary.
Which kind of fertilizer does my Silky oak tree require?
For Silky oak fertilizer, an ideal blend of nutrients is needed in relatively low amounts. The N-P-K ratio of 3-1-2 is recommended. However, a general-purpose fertilizer with an even nutrient blend can also work well. Regardless of the type of fertilizer used, the ratio of each nutrient should not exceed 3. You can choose between granular or liquid fertilizer. If you opt for a liquid-based fertilizer, it is best to dilute it by half. Granular fertilizer has few drawbacks, but using liquid fertilizer, especially while watering the Silky oak, is often the most practical choice.
How can I make my Silky oak plant grow better?
To fertilize a Silky oak easily, you can feed it whenever you water it. Here's how you can do this: 1. Gather your fertilizer and a water container like a watering can. 2. Mix the fertilizer with water to dilute its strength. 3. Pour the water with the fertilizer onto the soil, ensuring it soaks down to the roots. Alternatively, you can use a granular fertilizer. Here's how: 1. Sprinkle some of the granular fertilizer on the soil where your Silky oak is. 2. Granular fertilizers are usually slow-release, so you won't need to fertilize as often as with a liquid fertilizer. Remember, it's always beneficial to water your Silky oak while you feed it.
🪴 Pot & Repot 2-3 years
When repotting Silky oak, pick a pot 1–2 inches (2.5–5.1 cm) larger that has ample drainage. Use a well-draining potting mix. Repot in spring or fall, making sure the root ball sits slightly lower than the rim of the flower pot. Water thoroughly after repotting and place it in a warm spot with indirect sunlight.
✂️ Pruning
Silky oak is characterized by its fern-like leaves and yellow flowers. To maintain its health and shape, it is best to prune from early to late winter. Begin by removing any damaged branches to improve air circulation. Light pruning will encourage dense growth and help manage the tree's size. However, avoid heavy pruning to prevent stress, ensuring healthy blooms and maintaining the tree's vitality.
🌿 Propagating
🐛 Diseases & pets
☠️ Toxicity
Characteristics
- Plant Type
- Tree
- Life Cycle
- Perennial
- Genus
- Grevillea
- Family
- Proteaceae
- Hardiness Zone
- 10-12
- Mature Height
- 4.88 m to 39.93 m
- Mature Spread
- 7.62 m to 9.14 m
- Leaf Color
- Green
- Leaf Type
- Evergreen
- Flower Color
- Yellow, Orange, Gold
- Flower Size
- 7.62 cm to 15.24 cm
- Bloom Time
- Spring, Fall, Winter
- Planting Time
- Spring, Autumn
- Harvest Time
- Early summer, Mid summer