Plec­tran­thus

Strik­ing flower and fo­liage colours, mul­ti­ple forms and an easy-care habit put plec­tran­thus in the pic­ture, writes DERYN THORPE

Gardening Australia - - CONTENTS -

Grown for its colour­ful, vel­vety leaves and mass flower spikes, plec­tran­thus is an un­fussy, beau­ti­ful col­lec­tion of plants for gar­dens and con­tain­ers. Th­ese plants are a favourite at my place be­cause of their ver­sa­til­ity, and I es­pe­cially ap­pre­ci­ate those that thrive in dry shade, as well as the coloured-leafed coleus and hy­brids with flower plumes, which pro­vide the wow fac­tor in pots and beds in au­tumn.

Coleus ( Plec­tran­thus scutel­lar­i­oides) has been grown since Vic­to­rian times for its vel­vety, coloured leaves. It has the most spec­tac­u­lar fo­liage of the genus, but oth­ers have var­ie­gated cream leaf mar­gins, which brighten shady parts of the gar­den.

There are about 350 species of plec­tran­thus, which is in the mint fam­ily (Lami­aceae). Plants orig­i­nate in trop­i­cal and tem­per­ate ar­eas, in­clud­ing Africa, Asia and the Pa­cific is­lands, and about 22 species are from east­ern Aus­tralia.

Plants dif­fer in form, and can be shrubs or peren­ni­als, some with glossy, fleshy fo­liage, oth­ers with soft hairs on aro­matic leaves and stems. While they are renowned for do­ing well in shade, some va­ri­eties pre­fer to grow in full sun. All forms like free-drain­ing soil and re­sent frost. Most flower in au­tumn, though you can get flow­ers through much of the year, ex­cept in win­ter.

care & cut­ting tips

Plec­tran­thus pre­fer well-com­posted soils and ad­e­quate mois­ture, but they cope with a dry spell or root com­pe­ti­tion, es­pe­cially species that store wa­ter in their suc­cu­lent stems. Since they orig­i­nate from ar­eas that re­ceive sum­mer rain, they ap­pre­ci­ate mois­ture dur­ing the warm­est months.

Tip cut­tings, taken with at least two nodes (where leaves grow from the stem), strike eas­ily in moist pot­ting mix, and the trop­i­cal va­ri­eties will root in a glass of wa­ter. Trans­fer

to pot­ting mix when roots are about 4cm long. Take cut­tings of glossy va­ri­eties at any time, ex­cept dur­ing win­ter in cold cli­mates. Th­ese grow quickly and can fill a 25cm pot in a few months. The hairy-leafed va­ri­eties are best struck in au­tumn and spring.

The plants need an an­nual prun­ing af­ter flow­er­ing to keep them dense. Stem tips of the trail­ing forms should be reg­u­larly trimmed to en­sure they retain their com­pact shape, and to en­cour­age branch­ing.

Although plec­tran­thus are rel­a­tively un­de­mand­ing and pest-free plants, they ap­pre­ci­ate an ap­pli­ca­tion of a com­plete fer­tiliser once a year in spring. Give them a dress­ing of com­post, over the root zone, too, topped with bark or cane mulch.

Coleus, es­pe­cially those that are over­win­tered in green­houses, can suf­fer from downy mildew, so it’s best to wa­ter from be­low and keep air cir­cu­lat­ing.

all shapes and sizes

There is a wide range of ground­cov­ers to choose from. P. oer­tendahlii is an African va­ri­ety loved for its slightly suc­cu­lent, var­ie­gated leaves with sil­ver mark­ings and deep red un­der­sides, and the bonus of mauve or pink flow­ers from late sum­mer to win­ter. It reaches about 30cm tall, and can be grown as a ground­cover in the gar­den, or a trail­ing pot plant in a bright spot in­doors.

The one I find the most use­ful is P. am­biguus, which gets to about 40cm tall and cre­ates a dense car­pet as it scram­bles through dry shade be­neath trees, where stems put down roots any­where it touches the ground. It at­tracts lit­tle com­ment most of the year, then in au­tumn sends up strik­ing spires of pur­ple flow­ers that make it a high­light. I team this with the na­tive sil­ver plec­tran­thus ( P. ar­gen­ta­tus), which adds height and fo­liage con­trast. Also from south­ern Africa and sim­i­lar in growth habit is the oddly named Swedish ivy ( P. ver­ti­cil­la­tus).

Of­ten used in hanging bas­kets, it has scal­loped leaves and a lacy froth of white flow­ers, mostly in au­tumn. Th­ese creep­ing plants and sim­i­lar fleshy va­ri­eties of plec­tran­thus seed and root very eas­ily, so they are po­ten­tially weedy in ar­eas with warm, wet sum­mers.

Cuban oregano ( P. am­boini­cus), also known as four sea­sons herb, is a ground­cover that grows to about 50cm tall. Its ed­i­ble fo­liage, which is good in meat dishes, is said to taste like a strong blend of thyme and oregano. It is also used medic­i­nally in some coun­tries. I grow a var­ie­gated form in part shade.

Pun­gent leaves are a fea­ture of plec­tran­thus, and few are as smelly as dog­bane ( P. can­i­nus). The un­pleas­ant smell of its crushed fo­liage re­put­edly re­pels dogs and cats. It flow­ers best in full sun, grows about 30cm tall and 1m wide, and is al­most in­de­struc­tible. Its pretty, pur­ple flow­ers look like laven­der spikes, and ap­pear on short stems, mostly in au­tumn. But their odour will not en­cour­age you to pick a flower posy!

Shrub forms are mostly grown for their massed dis­play of small, tubu­lar flow­ers. Some have pur­ple un­der­sides to the leaves. Named hy­brids, mostly crosses be­tween P. sac­ca­tus and P. hilliar­diae, are com­pact shrubs that make ex­cel­lent con­tainer plants.

One of the taller forms is P. eck­lonii, which grows up to 3m tall and about 90cm wide in semi-shade, and pro­duces masses of pur­ple, pink or white flower spikes in late sum­mer and au­tumn. I have one that grows be­side a frangi­pani, with clivea and pur­ple trades­cantia at its feet, but it also teams beau­ti­fully with Ja­panese wind­flow­ers ( Anemone x hy­brida) and cane be­go­nias, which flower at the same time.

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