Cit­rus pro­duc­tive and or­na­men­tal

Whanganui Midweek - - NEWS - With Gareth Carter

Cit­rus in­cludes well known lemons, man­darins, or­anges, tan­gelo, grape­fruit, limes, le­mon­ade and some lesser known fruits in­clud­ing lime­quat and tan­gor (cross be­tween a man­darin and an or­ange).

These pop­u­lar trees are both highly pro­duc­tive and or­na­men­tal. They can grow well in the gar­den or as con­tainer spec­i­mens with sweet smelling white flow­ers dur­ing spring and sum­mer and the fruit’s dec­o­ra­tive ap­pear­ance dur­ing the au­tumn and win­ter months.

Here in Whanganui we have a cli­mate that gen­er­ally grows good cit­rus. Most cit­rus trees are sub­trop­i­cal or trop­i­cal and will tol­er­ate tem­per­a­tures to around -2C. Trees are fairly slow grow­ing with a ma­ture spec­i­men tak­ing 15-20 years to reach 4-5 me­tres. Where the lo­ca­tion is shel­tered from wind and warmer the trees will grow faster.

Cit­rus va­ri­eties orig­i­nate from the warmer re­gions of In­doChina and the Mid­dle-East, how­ever the kumquat, sat­suma man­darin and meyer le­mon are rel­a­tively cold hardy. Sat­suma man­darin (and its se­lec­tions such as Sil­ver Hill, Miho and Miya­gawa Wase), navel or­ange and Tahi­tian lime all pro­duce seed­less fruit.

Cit­rus trees will gen­er­ally try and pro­duce fruit from the first year, but at this stage the tree’s abil­ity to bring fruit to ma­tu­rity is of­ten ques­tion­able. A good prac­tice is to re­move flow­ers and fruit for 2-3 years to al­low a strong branch frame­work to es­tab­lish. In sub­se­quent years if the tree is still pro­duc­ing larger crops than it can sus­tain the re­moval of about a third of the crop will en­sure the tree does not get into a pat­tern of bi­en­nial bear­ing. This is where the tree switches be­tween a year of heavy fruit pro­duc­tion and a year of min­i­mal crop­ping.

To be grown suc­cess­fully most cit­rus trees are grafted on to a root­stock. The main root­stock used in New Zealand is tri­fo­li­ata; it is vig­or­ous al­low­ing the tree to grow to 4 or 5 me­tres. It is also tol­er­ant of heavy and wet­ter soils and cre­ates in­creased frost har­di­ness. By trim­ming or grow­ing in a pot cit­rus plants can be kept at 1.5-2.5m.

Meyer lemons and Tahi­tian limes can be suc­cess­fully grown on their own roots. These are par­tic­u­larly suited to pots and small gar­dens as the plant vigour is less than that of a grafted tree of the same type with trees reach­ing 1.5m if left untrimmed. They still fruit pro­lif­i­cally from a young age; the plants just don’t grow as big.

Cit­rus are gross feed­ers and thrive in good soil with reg­u­lar feed­ing of a spe­cialised cit­rus fer­tiliser. Plants which are show­ing yel­low­ing of the fo­liage should in ad­di­tion be given a top up of mag­ne­sium. Yates Liq­uid Mag­ne­sium Che­late is highly rec­om­mended as a prod­uct that makes nu­tri­ent read­ily avail­able to the plant. Where soils are lighter and sandy, par­tic­u­larly in parts of Spring­vale, Gonville and Castle­cliff, an ex­tra dose of ep­som salts is rec­om­mended on a more fre­quent ba­sis. In lighter soils par­tic­u­larly, an ap­pli­ca­tion of mulch around the base of the tree at the start of each sum­mer will also be of ben­e­fit.

Prun­ing is only re­quired for shap­ing and plants are bet­ter left untrimmed from a fruit yield per­spec­tive. Prun­ing is best com­pleted in early spring be­fore Oc­to­ber when the borer beetle starts to lay its eggs. Any shoots from the root­stock should be re­moved as this will re­duce vigour from the tree and sub­se­quent fruit­ing po­ten­tial.

A long hot sum­mer when trees are well wa­tered will re­sult in bet­ter fruit pro­duc­tion, fol­lowed by the cooler months which pro­motes the change in skin colour of the fruit from green to yel­low. When the sum­mer is cooler the crop yield, size or qual­ity tend to suf­fer.

When grow­ing cit­rus in pots and con­tain­ers it is im­por­tant to use a “pre­mium” pot­ting mix such as Tui Pot Power, and fer­tilise monthly or bi-monthly us­ing a spe­cial­ist cit­rus fer­tiliser that is suit­able for pots and con­tain­ers such as os­mo­cote for cit­rus. The ad­di­tion of sat­u­raid re-wet­ting gran­ules to cit­rus grow­ing in con­tain­ers is highly rec­om­mended. This prod­uct should be ap­plied an­nu­ally, it chan­nels wa­ter to the root zone where it is needed most. It pro­motes even wa­ter dis­tri­bu­tion so there is less wa­ter run off and dry spots in pot­ting mix and soils. It makes wa­ter­ing, rain­fall and fer­tilis­ers more ef­fec­tive. It can also be used in the gar­den even in sandy, clay or com­pacted soils.

The most com­mon prob­lem with cit­rus is usu­ally sooty mould, a black sticky sub­stance on the leaves and stems. This is ac­tu­ally a sec­ondary prob­lem caused by the pres­ence of scale and aphids which, while suck­ing the good­ness from the tree, se­crete a sug­ary sub­stance upon which the mould grows. The sug­ary sub­stance is also at­trac­tive to ants. The good news is this is eas­ily con­trolled with a spray of a suit­able in­sec­ti­cide such as Growsafe En­spray 99, this is an or­gan­i­cally cer­ti­fied spray­ing oil.

As men­tioned above, avoid any prun­ing be­tween the early spring to mid­sum­mer pe­riod to re­duce the risk of at­tack from borer beetle. If you do prune be sure to seal cuts with prun­ing paste. The tell­tale sign of a borer at­tack is saw­dust piles on and around the plant from holes in the stems/trunk where the bee­tles are ac­tive. This can be con­trolled with the use of No Borer Spray In­jec­tor into the holes. They can be dif­fi­cult to con­trol so pre­ven­tion is bet­ter than try­ing to fix later.

Here are some good va­ri­eties to grow here in Whanganui;

■ Man­darin Sat­suma Va­ri­eties: Do you love those big seed­less, man­darins with the soft puffy easy to peel skin? Then plant a man­darin sat­suma va­ri­ety — good ones in­clude; Sil­ver­hill, Kawano and Miya­gawa. They have easy peel, sweet juicy fruit with seg­ments that eas­ily sep­a­rate.

■ Le­mon Le­mon­ade: A very juicy, le­mon-like fruit with a mild, re­fresh­ing grape­fruit-like flavour. Fruit can be eaten fresh or juiced. Fruit has a very strong scent. A heavy crop­per.

■ Lime Bearss: A hardier se­lec­tion of Tahi­tian lime with small, thin skinned, deep green seed­less fruit which turns lime yel­low at ma­tu­rity. Pro­tect from frost. Tree habit is vig­or­ous and spread­ing.

■ Or­ange Navelina: Our favourite early ripen­ing navel or­ange which is also heav­ier crop­ping and more vig­or­ous than par­ent Navel. Deep or­ange rind, slightly oval shaped, sweet juicy fruit. Ripens from late win­ter. Pro­tect from hard frosts. 2.5 x 2m.

■ Tan­gor Kiy­omi: For some­thing dif­fer­ent try this hy­brid cit­rus fruit — it’s a cross be­tween a man­darin and or­ange. It has large fruit like an or­ange, with the easy peel of a man­darin. It’s very juicy, thick skinned and seed­less when self pol­li­nated.

■ Gareth Carter is gen­eral man­ager of Spring­vale Gar­den Cen­tre

Sweet NZ grape­fruit grows well in the North Is­land and is a Whanganui favourite.

Rodger Fox

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