Rhodo­den­dron a cool cus­tomer

The Leader (Nelson) - - OUT & ABOUT - STEPHEN MCCARTHY

Rhodo­den­drons are a very di­verse genus of over 800 species of ev­er­green and some de­cid­u­ous shrubs widely distributed across the tem­per­ate to cool re­gions of the North­ern Hemi­sphere. The genus takes in plants not only known as rhodo­den­drons but also ev­er­green and de­cid­u­ous aza­leas, the Vireya sec­tion from trop­i­cal south­east Asia as far south as north­ern Aus­tralia, with New Guinea be­ing home to more than 200 species.

The head­quar­ters of the rhodo­den­dron is China which has by far the most species.

Rhodo­den­drons are very vari­able in stature with some be­ing ground hug­ging dwarfs adapted to ex­posed moun­tain­ous con­di­tions, while oth­ers could cor­rectly be clas­si­fied as small trees usu­ally as part of the un­der­story in moun­tain­ous forests.

Some grow on the ground but quite a few grow on rocks or even as epi­phytes in trees where they send their roots into the moss and de­tri­tus which col­lects on the branches or crotches of trees. The com­mon fac­tor in their habi­tat is mois­ture com­bined with ex­cel­lent drainage.

Rhodo­den­drons will never sur­vive a poorly-drained soggy soil and get­ting the soil right is a key to suc­cess in their cul­ti­va­tion. They all pre­fer a soil with an acidic re­ac­tion be­tween pH 4.5 to 6, high in or­ganic mat­ter for wa­ter re­ten­tion.

A cool root run is also es­sen­tial for most rhodo­den­drons and this is best achieved by or­ganic mulches which have the ef­fect of con­serv­ing mois­ture and do­ing away with cul­ti­va­tion around the plants which could dam­age their del­i­cate root sys­tem which is usu­ally near the soil sur­face.

Pine nee­dles make an ex­cel­lent acidic mulch for rhodo­den­drons which lets the wa­ter through read­ily. A light dress­ing of ar­ti­fi­cial fer­tiliser for acidic lov­ing plants is ben­e­fi­cial to give plants a boost - I suc­cess­fully used a light dress­ing of one part of sul­phate of am­mo­nia to two of su­per­phos­phate, as rec­om­mended by Peter Cox, the fa­mous Bri­tish rhodo­den­dron breeder.

Many rhodo­den­drons are ideally suited to plant­ing un­der de­cid­u­ous trees which give them light in the win­ter months and shade in sum­mer. In gen­eral the larger the leaves the more shade the plant will tol­er­ate and re­mem­ber that too much shade will also de­crease the num­ber of flow­ers on many rho­dos. Many of he newer hy­brids have been bred to with- stand open gar­den con­di­tions so there is lit­er­ally a rhodo­den­dron for all sit­u­a­tions. While most pre­fer a shel­tered site away from strong winds and frosts, many will also stand these con­di­tions.

To get the best out of your rhodo­den­dron’s flow­er­ing, dead­head­ing of the spent flow­ers be­fore they de­velop seed cap­sules is ben­e­fi­cial. You will find you get more ter­mi­nal shoots if these are re­moved, re­sult­ing in many more flow­ers next sea­son.

PHOTO: IMO­GEN MCCARTHY

An epi­phytic Vireya rhodo­den­dron on Mt Kin­a­balu, Bor­neo.

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