Large-flowered grevilleas

Large-flowered grevilleas are in flower most of the year, so it’s a no-brainer to include at least one in your garden! These shrubs to small trees have deeply toothed leaves, and display their exquisite flowers on the tips of branches so that you – and every honeyeater around – can’t help but rush to appreciate them.

It was a chance crossing in the late ’60s between the Western Australian Grevillea bipinnatifida and the subtropical G. banksii var. forsteri that produced ‘Robyn Gordon’, and started all the fuss. Nowadays, we’re spoilt for choice, with an array of cultivars being developed by clever breeders who are always striving for even more and bigger look-at-me flowers.

Popular varieties

Taller varieties, such as ‘Honey Gem’, ‘Moonlight’, ‘Misty Pink’, ’Jester’ and ‘Sylvia’, make excellent screening plants.

There’s plenty of choice in the useful 1.5–3m range, too, which can be used to create an informal hedge or to separate zones. If you’re crazy for colour, go for ‘Bush Lemons’, ‘Blood Orange’, ‘Lana Maree’ or ‘Lollypops!’, but if your garden palette is more restrained, consider ‘Ivory Whip’, ‘White Socks’ or ‘Silvereye Cream’. Also in this category are the renowned ‘Peaches and Cream’ and ‘Superb’ – both of which can reach 2–3m wide, so make sure they have enough space to shine.

There are also small-growing, wide forms, such as ‘Loopy Lou’, ‘Orange Wow’ and ‘Billy Bonkers’, which make colourful, dense groundcovers that double as lizard habitat. Compact growers, such as ‘Robyn Gordon’, can be used as pretty structural plants in a bed of mixed natives, and also as a gorgeous feature in pots.

Growing grevilleas

Preparing the soil
A soil pH of 5.5–6.5 is ideal for all these grevilleas. If it’s too low or high, nutrient issues can occur. Amend pH problems at least a couple of months before planting. To reduce a high pH, apply iron sulfate at the rate recommended on the packet instructions. Mulching can also help to lower pH over time. To increase soil pH, apply agricultural lime or dolomite.

It’s important to plant into well-drained soil – especially in temperate climates, where soil is often wet and cold in winter. It’s worth taking the time to conduct a percolation (drainage) test. Simply dig a hole 20–25cm wide and deep, and fill it with water. If the water drains away in 15 minutes or less, you’re good to go! If it takes longer, it’s best to plant into a mound 20cm or more high. To do this, turn over the soil in the position you’re planting, break up large clods, and add extra of the same soil from elsewhere in the garden so there’s enough soil to create the mound. Add gypsum to the hole, which improves the soil’s drainage in the long term.

If your soil is heavy, it’s worth looking out for grafted forms. Although they’re more expensive, they’re more resistant to root rotting diseases caused by wet soils.

Planting
When you’re ready to plant, don’t add any fertiliser to the hole or mound. And after removing the plant from its pot, resist teasing the roots. If roots have formed a mat at the bottom of the pot, snip them off with secateurs. Also remove any larger roots that have hit the side of the pot and headed down, to encourage a stable, well-structured root system. Position the plant and backfill, then water it in with seaweed solution and, if the plant is lanky and unstable, remove the top half so it’s less prone to blowing over. It’s best to remove the flowers so the plant can put its energy into growing roots and settling in.

Watering
To ensure your new plant doesn’t dry out, water it daily until new growth appears. Use only enough water to dampen the potting mix that the plant came in. When there’s new growth, reduce watering to every second day for about a week. Then water weekly for a month. Feed in spring with a pelletised native fertiliser, and once a season with a fish-based liquid fertiliser.

Pruning
Most large-flowered grevilleas respond well to hard pruning every one to three years. Prune to a minimum of 1–1.5m from the ground in order to encourage epicormic buds to shoot – you’ll be rewarded with healthy foliage and flowers where you can enjoy them!

Pests
There are a couple of pests to look out for. Grevillea psyllid damages flower buds, causing them to drop prematurely; use a pyrethrum or soap-based spray. Grevillea leafminer feeds between the leaf surfaces, skeletonising the leaves; horticultural oil can work, but it must cover all parts of the foliage, which can be hard to do. Annual pruning can help control this pest.

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