Grow cit­rus around Whanganui

To be grown suc­cess­fully most cit­rus trees are grafted onto a root­stock.

Whanganui Chronicle - - 48 Hours/Gardening - Gareth Carter Gareth Carter is Gen­eral Man­ager of Spring­vale Gar­den Cen­tre

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 juicy fruits that add a dec­o­ra­tive ap­pear­ance dur­ing the au­tumn and win­ter months.

Here in Wan­ganui we have a cli­mate that gen­er­ally grows good cit­rus. Most cit­rus trees are sub­trop­i­cal or trop­i­cal and will tol­er­ate tem­per­a­tures to around -2 C. 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 is warmer, the trees will grow and ma­ture faster.

Cit­rus va­ri­eties orig­i­nate from the warmer re­gions of Indo-China 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’ and ‘miho’), Navel Or­ange and Tahi­tian or Bears Lime all pro­duce seed­less fruit.

Cit­rus trees will gen­er­ally try and pro­duce fruit from the first year, but at this stage the trees 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 ap­prox­i­mately 1/3 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 onto a root­stock. The main root­stock used in New Zealand 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. 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. It is a prod­uct that makes nu­tri­ent read­ily avail­able to the plant. Where soils are lighter and sandy par­tic­u­larly in parts of Spring­vale, Gonville & 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 in con­serv­ing soil mois­ture & help­ing re­tain nu­tri­ents.

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.

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