All the colours of the rainbow

Sunday Tasmanian - Tassie Living - - HOME - Peter Cundall

THE rhodo­den­dron genus is enor­mous. It in­cludes aza­leas, the sub- trop­i­cal vireya and hardy de­cid­u­ous mol­lis and Knap Hill hy­brids.

Flower colours cover al­most the com­plete spec­trum with only a true blue a rar­ity.

They can be planted or trans­planted at any time of the year. The best time to buy plants is mid- spring when most are in flower.

Some have big leaves, which means they need part shade, oth­ers with small leaves pre­fer full sun.

Most thrive in open wood­land con­di­tions. De­cid­u­ous trees with­out greedy, com­pet­i­tive roots pro­vide per­fect, dap­pled shade. Eu­ca­lypts are among the few ev­er­greens suit­able for un­der- planting with rhodo­den­drons.

Some small, com­pact rhodo­den­drons make ex­cel­lent rock gar­den plants in full sun. Their tiny leaves al­low them to blend in per­fectly with lichen- cov­ered rocks and alpine plants.

All rhodo­den­drons have com­pact root- balls so are suit­able for grow­ing in large pots, urns or tubs. Buy good qual­ity, acidic pot­ting soil.

Add pul­verised but coarse coir ( coco- peat) to in­crease bulk by 20 per cent.

The soil from fully de­cayed au­tumn leaves or rot­ted pine nee­dles are won­der­ful ad­di­tives.

Avoid ar­ti­fi­cial, chem­i­cal fer­tilis­ers. Sheep ma­nure is per­fect. Dur­ing hot weather, all pot­ted rhodo­den­drons need to be wa­tered twice daily.

When pot­ting soils start to dry out, rhodo­den­dron root- balls be­come wa­ter­re­pel­lent so at­tempts at ir­ri­ga­tion fail be­cause the wa­ter flows to waste through drainage holes. Dry­ing out is the most com­mon cause of fail­ure with rhodo­den­drons grow­ing in con­tain­ers.

Even large rhodo­den­drons can be safely moved and the only risky time is im­me­di­ately af­ter flow­er­ing when young frag­ile shoots may be snapped off.

Al­most all rhodo­den­drons are lime- haters so de­mand an acidic soil.

These plants are not par­tic­u­larly good at get­ting iron from the soil be­cause of the spe­cial way they take up nu­tri­ents.

When soil is al­ka­line or has been limed, the ef­fect is to lock up iron. Most other plants can over­come this, but not rhodo­den­drons.

The youngest leaves dis­play iron de­fi­ciency by turn­ing pale while leaf veins stand out clear and green.

This is “lime in­duced chloro­sis” and is a fa­mil­iar sight in gar­dens where builders’ rub­ble has been dumped, or near walls in which lime mor­tar has been used. Wood ash is highly al­ka­line and causes the same prob­lem as lime.

Iron chelates have been used suc­cess­fully to over­come this dis­or­der. It can be found at most gar­den cen­tres and, af­ter be­ing di­luted with wa­ter, it is sprayed over and around rhodo­den­drons dis­play­ing an iron de­fi­ciency.

Many small or thick leaved rhodo­den­drons are able to grow with few prob­lems even where strong winds blow.

It’s the thick, felt- like layer be­neath the leaves that stops them from los­ing mois­ture.

Many species and CV’s have this pro­tec­tive

layer which is a pale fawn or buff colour and is very much part of the at­trac­tion of these spe­cial plants.

R. de­gro­ni­anum is one heav­ily felted species that is much sought af­ter by col­lec­tors and ad­mir­ers.

Most pop­u­lar rhodo­den­drons have an­ces­tors that orig­i­nate from west­ern China and the Hi­malayan re­gion. Flow­ers are usu­ally in com­pact or loose trusses. Some are like clus­ters of glis­ten­ing waxy bells, as with R. Win­some which is happy grow­ing in full sun.

Other sun lovers in­clude white pearl and the spec­tac­u­lar pink pearl, both of which can grow to the size of small trees.

There are a num­ber of yel­low or cream va­ri­eties. Unique prefers part shade and al­most glows when in bloom.

R. fra­grantis­sima is so heav­ily fra­grant the cut flow­ers can dom­i­nate even a large room.

When flow­er­ing trusses wither they are best snapped off at the neck. This stops seed cap­sules from form­ing and en­sures stronger growth for an even bet­ter flow­er­ing next spring.

Rhodo­den­drons grow best with plants that like the same acidic soil and grow­ing con­di­tions. Tree ferns, lil­i­ums, daphne, Solomon’s Seal, pieris, helle­bores, Ja­panese maples and other wood­land plants all make ideal com­pan­ions.

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