Rho­dos are MADE FOR THE SHADE

A com­bi­na­tion of rel­a­tively cool con­di­tions and fairly acidic soils mean that Tas­ma­nia is an ideal place for highly-or­na­men­tal rhodo­den­drons to thrive, ac­cord­ing to gardening guru

Sunday Tasmanian - Tassie Living - - GARDENING -

PE­TER CUN­DALL

The health­i­est and most spec­tac­u­lar rhodo­den­dron dis­plays I’ve ever seen were in Tas­ma­nia. It’s the com­bi­na­tion of rel­a­tively cool con­di­tions and a fairly acidic soil that ap­pears to do the trick. Around Queen­stown, Rose­bery and north-western Tas­ma­nia, most rhodo­den­drons not only look fan­tas­tic at any time of the year, but ap­pear to be re­sis­tant to most pests and dis­eases.

This is cer­tainly due to re­li­able, year­round rain­falls re­ceived in these dis­tricts.

These highly-or­na­men­tal plants cer­tainly thrive where tem­per­a­tures re­main fairly low.

I re­mem­ber visit­ing sev­eral out­stand­ing rhodo­den­dron gar­dens high above Ho­bart at Fern Tree and was as­ton­ished to dis­cover a sur­pris­ing num­ber of very at­trac­tive chance seedlings that had ger­mi­nated in the acidic, fairly im­pov­er­ished but well-drained soil, com­mon to high-rain­fall ar­eas.

Un­for­tu­nately these seedlings also in­cluded

Rhodo­den­drons can be grown to per­fec­tion in all parts of Tas­ma­nia, although they strug­gle in al­ka­line or coastal soils

a wor­ry­ing num­ber of pur­ple-flow­ered R. pon­ticum, a no­to­ri­ously ag­gres­sive weed species now caus­ing night­mare prob­lems in parts of Bri­tain.

Luck­ily, rhodo­den­drons can be grown to per­fec­tion in all parts of Tas­ma­nia, although they strug­gle in al­ka­line or coastal soils. That’s be­cause these lovely or­na­men­tal plants are not very good at ex­tract­ing iron from the soil and al­ka­lin­ity tends to lock it up.

It is why ap­ply­ing lime – or even wood ashes – around rhodo­den­drons is a big blun­der. The dis­or­der – lime-in­duced chloro­sis – causes the youngest leaves to turn al­most white and weak­ens growth. This prob­lem can be cor­rected by sup­ply­ing iron chelates, a form which can by­pass al­ka­lin­ity.

Most rho­dos flower in mid-spring and right now is an ideal time to make a pur­chase. Early-flow­er­ing va­ri­eties in­clude

the beau­ti­ful, deep rose-red Un­known War­rior which can come into bloom in late win­ter in some dis­tricts.

We can tell if plants will flower this spring by look­ing at buds now formed at the tips of branches. Flower buds are big, fat, clearly de­fined and eas­ily iden­ti­fi­able.

Some­times, when the plants have been kept in heavy shade for too long, flower buds fail to form and are re­placed by nar­row, pointed, leaf-en­closed growth buds.

Most va­ri­eties de­mand light, dap­pled shade, prefer­ably with plenty of bright morn­ing sun while oth­ers grow strongly in full sun­light. It’s fairly easy to se­lect the right plant for the best po­si­tion by leaf­size. Gen­er­ally, plants with small leaves tol­er­ate full sun­light, while those with large leaves grow best in shade. Some de­velop enor­mous, hand­some leaves. Those of R. macabeanum are a dark, glossy green and al­most a third of a me­tre in length. They look mag­nif­i­cent fram­ing the huge, pale yel­low flower trusses.

All rho­dos have tight, com­pact root balls al­low­ing very large plants to be planted or trans­planted vir­tu­ally at any time of the year, sum­mer or win­ter in Tas­ma­nia. Even so, late win­ter is al­ways best be­cause soils will re­main moist for many weeks.

All rhodo­den­drons de­test clay so when plant­ing, ei­ther se­lect a spot where the soil is deep and fri­able or cre­ate low mounds of good pot­ting soil well above any clay. Never make the mis­take of plant­ing too deeply be­cause this may bury lower stems, risk­ing the loss of valu­able plants through col­lar rot.

Rhodo­den­drons rarely need prun­ing, but re­spond with strong new growth if leggy branches are cut back. The best prun­ing time is im­me­di­ately af­ter flow­er­ing – usu­ally in late Novem­ber.

Feed­ing rhodo­den­drons is best car­ried out just once a year, prefer­ably in late win­ter. Sheep or cow ma­nure is ideal when spread gen­er­ously over the sur­face around plants. Fresh sta­ble ma­nure is best avoided – it can kill young plants – but well-weath­ered horse ma­nure col­lected from pad­docks and fully rot­ted is ex­cel­lent. Just make sure all ma­nures or mulching ma­te­ri­als are kept well away from main stems.

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