The Gold Coast Bulletin - Gold Coast Eye - - EYE GARDEN - WORDS AND PHOTO: KATE HE F FERN AN

The nec­tar-rich flow­ers of gre­vil­leas at­tract honey-eat­ing birds to the gar­den. Gre­vil­leas range from low-grow­ing ground cov­ers to rounded shrubs, small bushy trees and even large trees like gre­vil­lea ro­busta.

They are gen­er­ally fast grow­ing and ben­e­fit from prun­ing, but many gar­den­ers seem un­sure of the tim­ing and amount to re­move.

There are three ma­jor types of gre­vil­leas – and many hun­dreds of species.

Gre­vil­leas in­ter­breed freely and com­monly pro­duce “ac­ci­den­tal” cul­ti­vars, or they are some­times hy­bridised by hu­man in­ter­ven­tion.

Plant breed­ers then in­tro­duce them into nurs­ery cul­ti­va­tion for gar­den use. Many new cul­ti­vars are reg­is­tered with the Aus­tralian Cul­ti­var Reg­is­tra­tion Au­thor­ity, and those reg­is­tered un­der a na­tional Plant Breed­ers Rights Scheme are pro­tected by a type of plant copy­right.

Limited to com­mer­cial prop­a­ga­tion and sale by se­lected grow­ers, home gar­den­ers will know these gre­vil­leas by a small sym­bol rep­re­sent­ing the let­ters PBR on the plant la­bel.

Like all mem­bers of the Proteaceae fam­ily, gre­vil­leas have evolved on soils de­fi­cient in the nu­tri­ent phos­pho­rus and ap­ply­ing fer­tilis­ers with more than very min­i­mal ra­tios of phos­pho­rus will ei­ther kill them or set their growth back se­ri­ously.

Gre­vil­leas from Western Aus­tralia or in­land are some­times grafted onto a tough root­stock such as gre­vil­lea ro­busta to pro­vide the ex­tra vigour nec­es­sary to grow in the dif­fer­ent en­vi­ron­men­tal con­di­tions of the eastern states.

A wa­ter­borne soil fun­gus called phy­topthera cin­namomi is also an un­for­tu­nate risk to gre­vil­leas, es­pe­cially where drainage is poor.

This should not de­ter those keen to en­joy stun­ning flow­ers and the visit­ing birds.

Most gre­vil­leas have their main flow­er­ing in late win­ter, spring and early sum­mer. Prun­ing is best done at the end of the ma­jor flower flush, af­ter rain or ir­ri­ga­tion to en­sure rapid re­growth. Prun­ing should be stag­gered to en­sure birds don’t starve. Also prune off spent flow­ers from time to time to main­tain a tidy habit. It is also im­por­tant to main­tain den­sity and keep an even fo­liage weight dis­tri­bu­tion to pre­vent fast grow­ing gre­vil­leas from be­com­ing top heavy and blow­ing over. Dif­fer­ent forms re­quire dif­fer­ent prun­ing meth­ods.

Gre­vil­leas with nee­dle like or prickly fo­liage and spi­der flow­ers make ex­cel­lent hide­outs for small birds but re­sent heavy prun­ing.

Main­tain den­sity by re­mov­ing no more than 10 to 15 per cent of the growth at any time and cut­ting off spent flow­ers through­out the flow­er­ing time. Some gre­vil­lea flow­ers are one sided like a tooth­brush, and should only be pruned up to a third if nec­es­sary to re­me­di­ate their shape, but it’s prefer­able to trim about 10 to 20 per cent reg­u­larly.

Large brush-like gre­vil­leas are grown for their spec­tac­u­lar flow­ers, some­times lit­er­ally drip­ping in nec­tar and a feast for birds.

Trim these af­ter flow­er­ing, but avoid trim­ming prior to the late win­ter or early spring flush or the best of the flow­er­ing will be lost.

These gre­vil­leas can be hard pruned, but it’s only nec­es­sary if they have be­come too large or mis­shapen, or fol­low­ing storm dam­age.

Some in­di­vid­u­als are sen­si­tive to gre­vil­leas, so as a pre­cau­tion gloves and long sleeves are rec­om­mended when prun­ing.

Gre­vil­leas should have a place in every gar­den for their colour­ful flow­ers and the birds they at­tract. Reg­u­lar care and sen­si­ble prun­ing will make their dis­plays even more spec­tac­u­lar. Kate Hef­fer­nan is a hor­ti­cul­tur­al­ist, ed­u­ca­tor and hon­orary life mem­ber of Friends of the Gold Coast Re­gional Botanic Gar­dens. You can lis­ten to her ra­dio show Gar­den Talk­back on ABC 91.7FM every Satur­day from 9am. She has de­signed a tour for gar­den lovers in Septem­ber 2018, in­clud­ing a cruise along the vine-clad rivers of Por­tu­gal and the South of France, stop­ping at his­toric vil­lages and visit­ing gar­dens. De­tails at kate­hef­fer­

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