Frequently Asked Questions About Grevillea Plants
Grevilleas have captured the attention of American gardeners seeking drought-tolerant, wildlife-friendly plants with unique visual appeal. As these Australian natives become more widely available through specialty nurseries and online retailers, questions about their cultivation, characteristics, and performance in various climates naturally arise. The following answers draw from decades of horticultural experience, university research, and observations from successful growers across the United States.
Understanding the specific requirements of grevillea plants helps gardeners avoid common mistakes that lead to poor performance or plant loss. These species evolved under conditions quite different from typical American garden environments, making knowledge of their native ecology valuable for cultivation success. From soil chemistry to pruning techniques, each aspect of grevillea care contributes to creating landscapes that showcase these remarkable plants at their best.
What is a grevillea plant?
Grevillea is a genus of evergreen shrubs and trees native to Australia, known for their distinctive spider-like flowers and needle-shaped leaves. These plants are popular in landscaping for their colorful blooms and ability to attract birds and pollinators. The genus contains over 360 species ranging from prostrate groundcovers under 1 foot tall to trees exceeding 100 feet in their native habitat. Cultivated varieties typically fall between 2 and 10 feet in height, making them suitable for residential landscapes. The flowers consist of modified styles that curve outward, creating the characteristic spider or toothbrush appearance in shades of red, pink, orange, yellow, and white. Most species bloom for extended periods, with some varieties flowering nearly year-round in mild climates.
How do you care for grevillea plants?
Grevilleas prefer well-draining soil, full sun to partial shade, and minimal watering once established. They are drought-tolerant plants that benefit from occasional pruning after flowering to maintain shape. Soil pH should remain between 5.5 and 6.5, and phosphorus levels must stay low to prevent nutrient toxicity. Amend heavy clay soils with 50% coarse sand or decomposed granite before planting. Water deeply every 2-3 weeks during the first growing season to establish roots, then reduce frequency to monthly or less depending on rainfall. Apply a 2-3 inch layer of mulch around plants, keeping it several inches away from stems to prevent collar rot. Fertilize sparingly if at all, using only low-phosphorus formulations designed for native plants. Prune lightly after main bloom periods to encourage bushier growth and remove any dead or damaged branches as needed.
When do grevilleas flower?
Most grevillea varieties bloom from late winter through spring, though some species can flower year-round in mild climates. Peak flowering typically occurs between August and November in their native habitat, which translates to February through May in the Northern Hemisphere. However, many cultivated varieties have been selected for extended or repeat blooming. Grevillea 'Moonlight' produces flowers throughout the year in USDA zones 9-11, with heaviest bloom from late winter through early summer. Grevillea 'Penola' concentrates its display from December through April in California gardens. Cooler temperatures and shorter day lengths trigger flower bud formation in many species, explaining why bloom intensity often increases during winter months in Mediterranean climates. Individual flowers last 2-4 weeks, but plants continually produce new blooms over extended periods.
Are grevilleas frost tolerant?
Many grevillea species are moderately frost tolerant once established, withstanding temperatures down to about 20-25°F (-4 to -7°C). However, young plants and tender varieties may need protection from hard frosts. Cold hardiness varies significantly among species and cultivars. Grevillea 'Mt Tamboritha' tolerates temperatures as low as 15°F when properly hardened off, making it suitable for USDA zone 7 in protected locations. Grevillea rosmarinifolia and its hybrids generally handle brief freezes to 20-22°F without significant damage. Tropical species like Grevillea banksii suffer injury below 30°F and are restricted to frost-free areas. Factors affecting cold tolerance include plant age, soil moisture, exposure to wind, and duration of freezing temperatures. Provide frost protection for the first 2-3 winters after planting by covering plants with frost cloth when temperatures below 25°F are forecast.
Do grevilleas attract hummingbirds?
Yes, grevilleas are excellent for attracting hummingbirds due to their nectar-rich, tubular flowers. The bright red, pink, and orange blooms are particularly appealing to these birds and other pollinators. Anna's hummingbirds in California visit grevillea flowers throughout winter when few other nectar sources are available, as documented in USDA Forest Service information on hummingbird-pollinated plants. Each flower produces 0.3 to 0.5 milliliters of nectar with sugar concentrations between 18-25%, ideal for hummingbird nutrition. The tubular flower structure fits perfectly with hummingbird bill morphology while excluding many competing insects. Red-flowered varieties like Grevillea 'Crimson Villea' and Grevillea 'Poorinda Constance' receive the most hummingbird visits, though birds also feed from pink and orange forms. Beyond hummingbirds, grevilleas attract honeybees, native bees, butterflies, and in some regions, orioles and other nectar-feeding birds. Planting multiple varieties with staggered bloom times provides consistent food sources throughout the year.
Can grevilleas grow in pots and containers?
Dwarf and compact grevillea varieties thrive in containers when provided with excellent drainage and appropriate potting media. Use containers at least 15-20 gallons for most cultivars, with multiple drainage holes to prevent waterlogging. Create specialized potting mix using 40% pine bark, 40% pumice or perlite, and 20% compost to replicate the fast-draining conditions grevilleas require. Avoid standard potting soils that retain excessive moisture. Grevillea lanigera, Grevillea 'Mt Tamboritha', and other naturally compact forms work particularly well in containers. Place pots in locations receiving 6-8 hours of sunlight daily and water when the top 2-3 inches of soil feel dry. Container plants require more frequent watering than in-ground specimens but should never sit in saucers of water. Fertilize container grevilleas 2-3 times annually with low-phosphorus liquid fertilizer at half strength. Container cultivation allows gardeners in unsuitable climates to grow grevilleas, moving them to protected areas during extreme weather.
Why are my grevillea leaves turning yellow?
Yellowing grevillea leaves typically indicate iron chlorosis caused by excessive phosphorus, improper pH, or overwatering. Grevilleas evolved in phosphorus-poor soils and cannot properly regulate uptake when levels exceed 10 parts per million, leading to iron deficiency symptoms. Test soil to determine phosphorus levels and pH; if phosphorus is high, leach the soil with deep watering and avoid any fertilizers containing this element. If pH exceeds 6.5, apply soil sulfur to gradually lower it to the preferred 5.5-6.5 range. Overwatering causes root damage that prevents nutrient uptake, producing similar yellowing symptoms. Allow soil to dry between waterings and ensure drainage is adequate. Apply chelated iron as a temporary treatment for severe chlorosis, but address underlying causes for long-term resolution. Yellowing of older leaves while new growth remains green is normal as plants shed aged foliage. However, if yellowing progresses to new growth, investigate cultural conditions immediately.
How fast do grevillea plants grow?
Growth rates vary considerably among grevillea species, ranging from 6-12 inches annually for dwarf varieties to 2-4 feet per year for vigorous cultivars. Grevillea 'Moonlight' typically adds 18-24 inches of growth each year under optimal conditions, reaching mature size of 8-10 feet in 4-5 years. Groundcover types like Grevillea lanigera spread 12-18 inches annually, covering assigned spaces within 2-3 years. Grevillea 'Penola' grows more slowly at 8-12 inches per year, taking 3-4 years to reach mature dimensions. Growth rates depend heavily on climate, soil conditions, water availability, and plant age. Young plants grow faster than mature specimens, and growth accelerates significantly during the second and third years after establishment. In ideal conditions with adequate water, some species grow twice as fast as in stressed environments. Most grevilleas reach 70-80% of their mature size within 3-4 years, then slow considerably. For more details on selecting appropriate varieties for your timeline and space, visit our main page covering different grevillea species and their characteristics.
Troubleshooting Common Grevillea Problems
| Problem | Likely Cause | Solution | Prevention |
|---|---|---|---|
| Yellow leaves | Phosphorus toxicity or iron deficiency | Apply chelated iron, test soil pH | Use low-phosphorus fertilizers only |
| Leaf drop | Overwatering or root rot | Reduce watering, improve drainage | Plant in well-draining soil, water deeply but infrequently |
| Poor flowering | Insufficient light or over-fertilization | Ensure 6+ hours sun, reduce fertilizer | Site in full sun, fertilize minimally |
| Leggy growth | Lack of pruning | Prune after flowering to shape | Tip prune regularly to encourage density |
| Spider mites | Hot, dry conditions | Spray with water or horticultural oil | Maintain adequate moisture during heat |
| Wilting despite moist soil | Phytophthora root rot | Usually fatal; remove plant | Never overwater, ensure excellent drainage |
Additional Resources
For more information on watering practices, the University of Arizona Cooperative Extension recommends applying 1 to 1.5 inches of water per irrigation event, allowing soil to dry between applications.
Grevilleas belong to the Proteaceae family, which includes numerous genera adapted to nutrient-poor soils with specialized root structures.
Learn more about grevilleas by visiting our home page or exploring our about us section.