COLOUR­FUL CHAR­AC­TERS

THERE ARE OP­TIONS OTHER THAN THE MORE OB­VI­OUS DE­CID­U­OUS TREES TO HELP ECHO THOSE LOVELY AUTUMNAL TONES AT HOME

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

For gar­den­ers with a long­ing for the au­tumn gar­dens of cooler cli­mates, it’s time to head west to Tam­borine Moun­tain, Ten­ter­field or Toowoomba.

Some lo­ca­tions in the Gold Coast hin­ter­land val­leys are also cold enough to in­duce the changes needed to bring au­tumn colour.

As the air and soil tem­per­a­ture drops it trig­gers chem­i­cal reactions that in­duce colour changes in fo­liage. Cells in leaf at­tach­ments break down and fo­liage starts to fall, leav­ing the dra­matic skele­ton of trunk and branches un­til spring.

Colour changes start with the read­sorp­tion of green pig­ment chloro­phyll mol­e­cules. Th­ese are stored ready to ac­ti­vate buds and restart the pho­to­syn­the­sis process re­quired to man­u­fac­ture food for the plant through spring and sum­mer.

When chloro­phyll is drained away, the re­main­ing colour pig­ments xan­tho­phyll and carotene are re­vealed. Th­ese are re­spon­si­ble for the bright golden shades, giv­ing leaves their bril­liant gold, yel­low, or­ange and rust colours. But­ter­cup yel­low leaves of gingko, the golden poplars and ash, and the rust and gold of oaks.

As chloro­phyll is lost from the leaf an­other chem­i­cal re­ac­tion cre­ates an­tho­cyanin, the pig­ment re­spon­si­ble for the vivid reds, scar­lets and pur­ples of some species. The bril­liant bur­gundy of claret ash and the deep crim­son of Ja­panese maples, or­na­men­tal cher­ries and some pis­ta­chios are the re­ward­ing out­come.

Mixed to­gether in many plants, in­clud­ing per­sim­mon (pic­tured), all three pig­ments may re­sult in a kalei­do­scope of leaf colour.

Liq­uidamber will colour rea­son­ably well in milder cli­mates, but is too in­va­sive for any­thing but the largest gar­dens. Once their au­tumn colours would have been a lot­tery, but plant se­lec­tion and de­vel­op­ment of cul­ti­vars means colour is a sure thing.

Swamp cy­press, a large-spread­ing conifer, is typ­i­cally de­cid­u­ous but some stub­bornly refuse to shed leaves. It is also a lucky dip when it comes to au­tumn colour.

Also only suit­able for large gar­dens, the au­tumn colours of trop­i­cal birch will vary from yel­low to a dull brown as it sheds its leaves to re­veal a de­light­ful trunk and branches through win­ter and bring the ben­e­fits of a de­cid­u­ous tree.

Although Gold Coast­ers can’t rely on colour from the tra­di­tional cold-cli­mate au­tumn trees, they can achieve a won­der­ful re­sult from crepe myr­tles, which are suit­able for most gar­dens.

Many new cul­ti­vars of crepe myr­tle ex­pe­ri­ence a mild colour change be­fore shed­ding leaves. Their bark ex­fo­li­ates as an ex­tra bonus, re­veal­ing pale and dark shades and tak­ing on a glis­ten­ing shine when wet.

There is splen­dour in a bare-trunked tree with its de­tailed sil­hou­ette of leaf­less branches. There are also ben­e­fits as well as beauty. A bare tree al­lows sun­light to fil­ter to the ground be­low, warm­ing the ground in early spring for flow­er­ing bulbs.

De­cid­u­ous trees also let sun­light reach through win­dows to brighten and warm build­ings. Fallen leaves are a rich sup­ply of nu­tri­ents as they break down and are a great ad­di­tion to the com­post heap.

If you’re not sure which de­cid­u­ous trees will grow lo­cally and are ap­pro­pri­ate in size and ap­pear­ance for your gar­den, check out the stun­ning but large swamp cy­press, crepe myr­tles and grove of trop­i­cal birch at the Gold Coast Re­gional Botanic Gar­dens.

Kate Hef­fer­nan is a hor­ti­cul­tur­ist, 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. De­tails at kate­hef­fer­nan.com.au

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