Citrus so­lu­tions: your ques­tions an­swered

Aussies love grow­ing citrus, and ques­tions about lemons, limes and other juicy de­lights dom­i­nate the air­waves on gar­den­ing talk­back. Here’s a se­lec­tion of reader queries. If your prob­lem isn’t cov­ered, send it in!

Gardening Australia - - CONTENTS -

We have lots of fruit on our 15-year-old man­darin tree but it’s all very dry and woody, and it was the same last year. The tree has a good wa­ter sup­ply. Do you have any sug­ges­tions?

Don and Hazel Bar­rett, Wodonga, Vic

Phil Dud­man says There are a num­ber of fac­tors that can cause dry pulp in citrus fruit, in­clud­ing hot, dry con­di­tions while fruit are form­ing. Although your tree has good wa­ter, when con­di­tions are warm to hot, and there is no rain, be sure to give it a deep soak­ing ev­ery 7–10 days. This is bet­ter than reg­u­lar light wa­ter­ing. Even if it’s done daily, light wa­ter­ing barely pen­e­trates the soil. At the other end of the scale is frost. Ex­tremely cold tem­per­a­tures can freeze the juice, rup­tur­ing the tiny vesi­cles in­side. The juice is drawn to the rind, where it evap­o­rates, re­sult­ing in dry pulp. Leav­ing ripened citrus on the tree too long can also cause wood­i­ness at the stem end. Citrus are greedy plants and of­ten bear dry fruit when un­der­nour­ished, so re­mem­ber to feed them with citrus food ev­ery three months or so. Also, the spined citrus bug feeds on fruit, caus­ing dry brown stain­ing of the pulp. Pick off or spray with pyrethrum.

One of the fruits on our es­paliered Va­len­cia or­ange looks rather un­usual (be­low). I guess we could call it a lemor­ange. Is this a com­mon oc­cur­rence? I won­der what it will taste like. Gisela McMichael, Up­per Sturt, SA

Ian Tol­ley says The odd-shaped Va­len­cia mu­ta­tion is an ef­fect of ul­tra­vi­o­let light on one flower bud at the time of set­ting. Ran­dom mu­ta­tions like this are rel­a­tively com­mon but they are usu­ally var­ied in shape, size and colour. The fruit is quite ed­i­ble, and you will find that it has nor­mal fruit char­ac­ter­is­tics in­ter­nally.

We have had a pot­ted lime tree for about five years. Each sea­son, it has plenty of flow­ers but most don’t pro­duce fruit, and those that do ap­pear don’t grow big­ger than 1cm and are too small to use. Michelle Weir, Mar­rickville, NSW

El­iz­a­beth Swane says Af­ter five years in the same pot, it’s time to re-pot the tree into fresh pre­mium pot­ting mix. Make sure it is in full sun, and wa­ter and feed it reg­u­larly with small amounts of an or­gan­i­cally based fer­tiliser for flow­ers and fruit.

I’d like to try my hand at es­palier. Which type of citrus tree would you rec­om­mend?

Joy Soren­son, via email

Phil Dud­man says All citrus are suit­able for es­palier, but I find man­darins are the best. They are gen­er­ally com­pact in their growth and are also pro­lific bear­ers. A man­darin tree trained in a fan shape over a wall space 2.5m wide and high should pro­duce all the fruit you need. Limes are an­other good choice.

My neigh­bour’s lemon tree, which has a cou­ple of branches on my side of the fence, is in­fected with citrus gall wasp. I’ve found four gall-wasp sites on my four-year-old Eureka lemon, which is 1.5m tall and about 20m from the fence. I bought in­sect traps from a gar­den cen­tre, and they told me to put them on my tree at the end of Au­gust. My gar­dener sug­gested I re­place them in Fe­bru­ary or March, and an­nu­ally at the end of Au­gust. I un­der­stand there’s no spray for citrus gall wasps. Can you please en­lighten me? Jan Killen, Mitcham, SA

El­iz­a­beth Swane says If not man­aged, citrus gall wasps will stunt your tree’s de­vel­op­ment. They are a ma­jor pest of the citrus in­dus­try, so it is im­por­tant that gar­den­ers do their bit to man­age pop­u­la­tions. Cur­rently, the best treat­ment is to prune off the gall and de­stroy it (see Jane Ed­man­son’s trou­bleshooter on page 46).

The yel­low cylin­dri­cal traps you are us­ing are a use­ful in­di­ca­tor that gall wasps are about, but there is con­cern that they also trap ben­e­fi­cial in­sects, in­clud­ing bees and but­ter­flies. Bet­ter to stick with phys­i­cal con­trols, and have a chat with your neigh­bours to en­cour­age them to man­age their gall wasps, too. Ev­ery bit you do helps re­duce the pop­u­la­tion and spread of this pest.

I have a Meyer lemon in the yard. I re­cently re­turned from a hol­i­day to find fruit fly have taken over, de­stroy­ing most of the fruit, which don’t look fully ripe. Some­one sug­gested putting my chooks un­der the tree to eat the grubs, but they don’t seem to like it there. It was also sug­gested to freeze fruit that’s not too dam­aged, as this kills the bugs in­side, leav­ing fruit that can be juiced.

Is it too late to put traps in the trees? Also, how should I dis­pose of the dam­aged fruit?

Bar­bara Golden, Lai­d­ley, Qld

Phil Dud­man says Meyer lemons have thin skin and tend to be more sus­cep­ti­ble to fruit fly dam­age than other pop­u­lar va­ri­eties for your area, such as the thicker-skinned Eureka, so you might con­sider plant­ing one of those. In the mean­time, there’s a range of strate­gies for deal­ing with your fruit-fly is­sue. The first is hy­giene. Col­lect all fruit that has been stung, both fallen and on the tree. Put th­ese into a black plas­tic bag and leave it in the hot sun for 3–4 days.

The heat will kill the lar­vae. Next, dig a deep hole and bury the dam­aged fruit. Freez­ing would in­deed kill the lar­vae, but the qual­ity of the juice would be ques­tion­able. Com­mer­cial traps, avail­able at gar­den cen­tres, are quite ef­fec­tive in at­tract­ing male and fe­male fruit flies. Two traps set up ad­ja­cent to your lemon tree should sig­nif­i­cantly re­duce dam­age. The liq­uid at­trac­tant in the trap needs to be re­plen­ished ev­ery three months or so. I would also con­sider putting ex­clu­sion bags over at least half the crop. Buy th­ese ready­made or make them from rem­nant fab­ric. Once fruit reaches about a third of its ma­ture size, slip bags over them to keep the egg-lay­ing fe­males off the fruit. Bag­ging half the crop will give you some in­di­ca­tion of how ef­fec­tive the traps are and may help you de­cide whether to bag more or less fruit in fu­ture.

My beau­ti­ful lime tree fruits pro­lif­i­cally but I’ve no­ticed some­thing has been eat­ing the bark off the branches. Any idea what it might be? Ali­son Neilly, Forster, NSW

Phil Dud­man says The cul­prits are rats. You’ll need to net or screen the tree to pre­vent the pests get­ting to it, or use rat baits in a pet-safe con­tainer.

My man­darin tree’s leaves are dis­coloured. The veins are dark green and the leaf sur­face is yel­low in-be­tween. The tree is also drop­ping the im­ma­ture fruit. What could be wrong with it? Roma Har­ris, Urunga, NSW El­iz­a­beth Swane says This con­di­tion, known as chloro­sis, is a sign of iron de­fi­ciency. Citrus trees that are grown in al­ka­line soils have an in­abil­ity to take up iron nu­tri­ents. Treat your tree with liq­uid iron chelates, which are ab­sorbed through the leaves and roots. To im­prove the soil, add a layer of com­post or mulch 50mm thick. Citrus trees are gross feed­ers, so ap­ply citrus fer­tiliser ev­ery three months or so. Once the tree is look­ing greener, it should be able to hold the im­ma­ture fruit. Reg­u­lar wa­ter­ing is a key to main­tain­ing fruit pro­duc­tion.

We have just har­vested our first crop from our ma­jes­tic Tahi­tian lime tree. Most of the limes have a scaly mark on the peel (be­low), and the in­ner fruit is golden rather than green, which is not what we ex­pected. Are you able to pro­vide some advice? He­len Taylor, via email

Phil Dud­man says It looks like citrus scab, which is a fun­gal dis­ease that causes raised wart-like scabs on the skin, although the fruit in­side is un­af­fected. The dis­ease may also be present on the tree’s leaves and stems. Pick and prune off all the af­fected fruit, fo­liage and stems, and spray with a cop­per fungi­cide, mak­ing sure you cover all re­main­ing plant ma­te­rial, in­clud­ing the trunk. Fol­low up with an­other ap­pli­ca­tion shortly af­ter flow­er­ing, just as next sea­son’s fruit are formed. When they are picked young, Tahi­tian limes are dark green out­side and green­ish in­side. As the fruit ages on the tree, the skin and flesh be­come more yel­low. This may ex­plain the golden flesh, or you could have a Rang­pur lime, which is dis­tinctly golden in­side.

I’ve been grow­ing a fin­ger lime bush in a pot for about three years, giv­ing it the proper treat­ment, and it looks healthy and green. Last year, it was cov­ered with flow­ers, but it didn’t pro­duce any fruit. Could you please ad­vise what I should do?

Maryse Ne­morin, via email

El­iz­a­beth Swane says

There are some seed-grown and cut­ting-grown fin­ger limes avail­able for sale but, for re­li­able fruit pro­duc­tion, a grafted tree is your best op­tion, as the fruit will be true to type, and grafted trees have bet­ter vigour and reach ma­tu­rity ear­lier. The graft union will be no­tice­able at the base of the tree. Fin­ger lime trees take about 2–3 years to set­tle into their spot in the ground or a pot, of­ten putting on good growth be­fore flow­er­ing and fruit­ing. It’s a pos­i­tive sign that your tree flow­ered well last year. Flow­ers can drop if the tree is wa­ter-stressed, so make sure to wa­ter well and don’t let it dry out while in flower. Use a wet­ting agent reg­u­larly to help pot­ting soil re­tain mois­ture, and ap­ply a slow-re­lease citrus food. You should see fruit form­ing this year. As the tree grows, re-pot into a larger con­tainer, us­ing fresh pot­ting mix. Most peo­ple grow their fin­ger limes in a sunny spot, but they are ac­tu­ally an un­der­storey plant and pre­fer early-morn­ing sun or dap­pled light. Full sun in a pot might be too stress­ful. I was given this man­darin tree (above) by my boys on Mother’s Day last year. While we were look­ing af­ter my mum’s Bor­der Col­lie puppy, the top sec­tion (above the graft) was de­stroyed. With lots of TLC, the base of the tree has since taken over and seems to be do­ing well. Will the tree still fruit? Tess Doyle, via email

El­iz­a­beth Swane says

Lucky es­cape for your young man­darin tree! It ap­pears to have re­cov­ered well and the graft is un­dam­aged. There’s a small sucker com­ing from be­low the graft (the fo­liage looks smaller and stems are thorny). Re­move this by rub­bing it off or cut­ting it off flush with the trunk. The tree looks like it could do with an ap­pli­ca­tion of slow-re­lease citrus food, as the leaves are not as green as they could be.

We have a four-year-old man­darin tree, planted in granitic soil, that is wa­tered by drip­per three times a week and fer­tilised with citrus fer­tiliser. It is 2m tall and a very healthy spec­i­men, but has never flow­ered or fruited. What do we need to do?

Max and Coral Cox, Long­wood, Vic

Phil Dud­man says

Is it a grafted spec­i­men? If not, it may take seven or more years be­fore you start see­ing flow­ers. Is it get­ting plenty of sun­shine? To flower, all citrus need four or more hours of di­rect sun daily, and de­mand at least six hours a day to fruit well. Have you done any prun­ing? If so, you may have cut off flow­er­ing wood. Are you ir­ri­gat­ing in win­ter, as well? It might pay you to re­duce wa­ter­ing in win­ter. A lit­tle wa­ter stress in win­ter may help to bring on flow­ers in spring.

mis­shapen Va­len­cia or­ange af­fected by ul­tra­vi­o­let light

sucker vis­i­ble be­hind main stem

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