How to grow mandarin and tangerine

Buy from a trusted or certified nursery, never a roadside seedling. A grafted tree has a sweet fruiting top (the variety you eat) joined onto a separate root variety called the rootstock — you can see the join as a knuckle-like bulge low on the stem.

Ask for a rootstock matched to your soil and drainage — this is the tree's insurance against root rot and dry spells. Tell the nursery if your soil is heavy, sandy, or lies wet in the rains.

Avoid sour-orange rootstock where citrus tristeza virus (CTV — a sap-borne virus that slowly kills trees on the wrong root) is known in your area: trees on sour orange collapse when it strikes.

Insist on clean, certified stock. Greening — also called HLB (huanglongbing) — and tristeza (CTV) have no cure; a tree that arrives infected will never come right, so you must start clean.

Pick a healthy young tree: a straight stem, deep-green leaves with no blotchy uneven yellowing, and a well-knitted graft join.

Choose the best-drained spot you have — deep soil where no water sits after rain. On a wet or heavy site, plant on a raised mound or ridge so the roots never sit in water.

Give each tree room: about five to six strides apart (≈5.5 m) in every direction, because a mandarin grows into a spreading 3–5 m tree that must not crowd its neighbours.

Dig a hole a little wider than the roots but no deeper than the root ball — dig too deep and the tree sinks as the loose soil settles, and the graft ends up buried.

Set the tree so the graft join (the knuckle low on the stem) sits about a hand-span (≈20 cm) above the soil — never bury it. A buried graft lets the trunk rot and lets the sweet top grow its own weak roots.

Firm the soil around the roots and build a low basin (a ring wall of soil) to hold water, then stake the young tree against wind so the roots are not rocked loose, and water it in well to settle the soil.

Keep a weed-free ring wider than the leaves reach around the tree, clear of grass and weeds, so nothing competes with the young roots for water and food.

In the first 2–4 years after planting, give the tree a light prune (this task comes round about every 5–7 months) — you are shaping, not cutting hard.

Pick 3–4 strong branches spread evenly around the stem to be the main arms, and remove shoots that compete with them so the middle stays open like a cup or wine glass.

Cut out any dead, crossing or inward-growing shoots and the fast, upright water shoots (thin, whippy shoots that shoot straight up and carry no fruit).

Rub or cut off any shoots growing below the graft join or from the ground — these are rootstock suckers, from the root variety, not your sweet top, and will never give good fruit.

Trim the very lowest branches (the 'skirt') off the ground so that fruit and leaves never touch the soil, where rot and black spot start.

Every 3–4 weeks, walk slowly around the tree and look closely at the new leaf flush (the soft, bright young leaves) — this is where trouble begins.

Psyllids are the sap-sucking insects that inject greening as they feed: look for insects no bigger than a rice grain, sitting tail-up at an angle (almost standing on their heads) on new shoots, with white, waxy curly threads and twisted young leaves.

Greening / HLB: look for blotchy, lopsided yellowing — patches that do not match on the two sides of the leaf's midrib (unlike hunger, which is even on both sides). Suspect trees are often stunted, with off-shaped, hard, part-green fruit.

Citrus leafminer: look for silvery, snake-like squiggly trails just under the skin of young leaves, and young leaves left curled and twisted.

Scale insects: look for small hard bumps like tiny limpets on twigs and leaves that do not move when you touch them, with sticky honeydew (the sugary droppings sap-suckers leave) and the black sooty mould that grows on it.

Foot / root rot: check the trunk base for gum oozing from the bark near the soil and a thin, yellowing canopy — a sign of wet-soil rot.

If a tree strongly looks like greening, mark it and open the greening (HLB) guide — an infected tree must be removed so it cannot feed psyllids that carry it to the rest.

Water every 1–2 weeks (more often in heat and on sandy soil), keeping the soil moist but never waterlogged — mandarins rot in standing water.

Check before you water: push a finger into the soil at the drip line (the ring under the outer edge of the leaves, where the feeder roots are) — water when the top few finger-joints (3–5 cm) are dry.

Feed little and often for frame growth — spread the fertiliser your recommendation gives in a ring around the drip line, never against the trunk.

Keep fertiliser a hand-span (≈20 cm) clear of the trunk — piled against the stem it burns the bark and feeds foot rot.

Lay a mulch ring (dry grass or leaves) around the tree but pulled back off the trunk, to hold moisture in and keep weeds down.

Every 3–4 weeks, look over the whole canopy — leaves, shoots, and later the rind of the fruit.

Citrus black spot (a fungal disease): look for small, dark, slightly sunken spots with a pale grey centre and a dark ring, on leaves and especially on the rind as the fruit colours. Fallen leaves under the tree keep the disease alive.

Citrus leafminer: look again for silvery, winding trails and curled, twisted young leaves on the new flush.

Aphids (tristeza carriers): look for clusters of small, soft insects on the soft new shoots, curling the leaf tips, with honeydew and sooty mould. Aphids spread tristeza (CTV), the sap-borne virus that slowly declines trees.

Tristeza decline: watch for a tree that is yellowing and thinning all over and cropping poorly for no clear reason — on a susceptible rootstock, that can be tristeza.

Rake up and remove fallen leaves and fruit under the tree as you go — they carry black-spot spores across to the next flush.

Prune once a year in the cool, dry season, after harvest and before the main flush — not in wet weather, when fresh cuts invite rot.

Remove the dead, diseased, crossing and inward-growing shoots and the upright water shoots, so the centre stays open like a cup and light reaches inside.

Cut off any suckers from below the graft join or from the ground — they are rootstock, not your sweet fruiting variety.

Lift the skirt: trim the lowest branches so fruit and leaves never touch the soil, where black spot and rot begin.

Keep it light — a few clean cuts. Hard pruning throws the tree into leafy regrowth and costs you next year's fruit.

Feed every 2–3 months through the growing season — several small doses, not one big one, so little washes away.

Spread the fertiliser your recommendation gives in a ring around the drip line (under the outer edge of the leaves), where the feeder roots are — never piled against the trunk.

Use a compound that carries nitrogen (N) for leaves and shoots and potassium (K) for fruit size and quality, plus the trace elements mandarins need.

Read the leaves: magnesium hunger shows as yellowing that spreads in from the leaf edges leaving a green arrow-shape at the base; zinc hunger shows as small, narrow leaves with yellow blotches between green veins. Correct either with a leaf-feed (foliar spray) of the missing element — the zinc goes on with the flowering spray.

Feed onto moist soil or water it in so the tree can take it up, and keep the fertiliser a hand-span (≈20 cm) off the trunk.

In the month before you want flowering, hold back water for a few weeks so the tree feels a mild dry stress — the leaves dull and curl slightly, but do not let it wilt hard or drop its leaves.

Then give a good, deep watering (and a feed) to break the stress — this rush of water triggers the tree to burst into bloom together, in one even flush.

In cool subtropical areas you can skip the dry trick — the winter cold already sets the bloom; just keep the tree well watered as it comes into flower.

If your variety needs cross-pollination, make sure a pollinizer tree (a different, compatible citrus that flowers at the same time) is nearby so bees can carry pollen between them.

From two weeks before flowering and right through the first month of new flush, check the soft young shoots every 7–10 days.

Look for psyllids — insects no bigger than a rice grain — sitting tail-up at an angle on the new shoots, their white, waxy curly threads, and the twisted, curled young leaves their feeding leaves behind.

Look too for greening (HLB) signs on nearby trees: blotchy, uneven yellowing across the leaf midrib, and stunted, lopsided, part-green fruit.

Act on the very first psyllids — open the psyllid / greening guide and treat the flush across the whole block; do not wait for numbers to build.

If a tree shows clear greening, mark it for removal — an infected tree left standing feeds psyllids that carry it to the rest.

Spray in the two weeks before flowering, as the flower buds swell — this is the window when zinc and boron do the most for fruit set.

Foliar means leaf-fed: mix the zinc and boron your recommendation gives and spray it onto the leaves until they are just wetted, not dripping.

Spray in the cool of early morning or evening, with the wind behind you, so the leaves take it in and the spray does not scorch the tree or blow back onto you.

Cover your skin, eyes, nose and mouth while spraying, keep it off any food, and wash well afterwards.

Do not overdo the boron — a little helps, too much harms. Use only the amount your recommendation gives.

If flowers still drop badly after spraying, have the tree's zinc and magnesium checked and step up the leaf feeds next season — repeated poor set usually means a trace-element shortage to fix over the year.

Judge the crop 1–3 months after flowering, once the tree has finished its own natural fruit drop (a wave of tiny fruitlets it sheds by itself a few weeks after flowering).

Only thin in a clearly heavy 'on' year — a tree carrying far more small fruit than it can ever size up. In a light 'off' year, thin nothing.

While the fruitlets are still small (marble-sized), pick or snip off the smallest, blemished and tightly-clustered fruit, leaving the rest evenly spaced along the branches.

Thin hardest where fruit is jammed together in bunches and on over-loaded branches bending under the weight.

The tree then keeps fewer but bigger, better fruit this year, and flowers properly next year — the aim is a steady crop every year, not a feast then a famine.

From about two weeks after flowering right through fruit growth, check the fruit every 3–4 days, and hang fruit-fly traps in the trees to catch the first flies.

Fruit fly: look for tiny sting marks (small punctures) on the fruit, soft rotting patches around them, and fruit dropping early; cut a suspect fruit open and look for small white maggots inside.

False codling moth: look for a small entry hole with crumbly droppings, a single fruit that colours and drops early, and a caterpillar inside when you cut it.

Black spot: look for dark, sunken spots with pale centres on the rind, worst on the sun-facing side as the fruit colours.

Collect and bury (or deep-bin) every fallen and stung fruit twice a week — this breaks the fruit-fly and moth life cycle better than any spray on its own.

If trap catches rise, or you find the first stings, start the fruit-fly management task now — do not wait.

Water every 7–10 days (more often in heat and on sandy soil), keeping the soil evenly moist through the whole fruit-growing period.

Even is everything: never let the tree go bone-dry and then flood it — that sudden swing splits the fruit and knocks it off.

Water out at the drip line where the feeder roots are, and keep the trunk base dry to avoid foot rot.

Hold a mulch ring under the tree (off the trunk) to even out the soil moisture between waterings.

If water is short, flowering and this stage are the last two you should ever let go dry — protect them ahead of everything else.

Start on the first stung or dropping fruit, or the first rise in trap catches — usually from about two months after flowering, as the fruit sizes and sweetens.

Protein bait works because the flies must eat protein before they can lay eggs: spray small bait spots (a dab on part of each tree, not the whole tree) so flies come to it and die before they sting the fruit.

Collect and bury (or deep-bin) all fallen and stung fruit twice a week — sanitation starves the next generation and is the backbone of control.

Keep the traps hung and topped up, to keep knocking down and tracking the adult flies.

When you spray any bait or pesticide: cover your skin, eyes and nose, spray in the cool with the wind behind you, keep it off fruit you will eat soon, respect the pre-harvest interval (the least number of days the label says to wait between spraying and picking), and wash after.

Pick from about 7–10 months after flowering, when the fruit is fully coloured, sweet and juicy on a taste-test and peels easily — taste a few from different trees first, because colour alone can mislead.

Never pull or twist the fruit off — the loose rind tears and leaves a hole ('plugging') that rots. Clip each fruit with scissors or secateurs.

Clip the stalk flush with the top of the fruit (leave no sharp stub) so the fruit do not pierce and bruise each other in the picking bag.

Pick every 10–21 days across the harvest window, taking the ripe fruit each round — mandarins ripen in flushes and do not all come at once.

Pick in the cool of the day and keep the fruit out of the sun; handle it like eggs, because the thin rind bruises easily.

If a taste-test says the fruit is not yet sweet, leave it — but check often, as ripe mandarins soon go coarse or drop if left too long.

Handle the fruit gently at every step — tip, don't drop, and don't overfill bags and crates; the thin rind bruises, and each bruise turns to rot.

Cure freshly-picked fruit for a few days in a cool, shaded, airy place — this heals tiny skin nicks and toughens the rind against rot before storage.

Degreening (colouring up): where the fruit is ripe and sweet inside but the rind is still green (common in warm areas, where the nights are too warm for the green to fade), hold it with ethylene gas in a closed, ventilated space to bring out the orange. If you have no way to do this, sell the green-but-ripe fruit locally — it is just as sweet.

Store the fruit as cool as you can (a cool room, a shaded store, or a cold room if you have one) and out of the sun — cool fruit keeps far longer than warm fruit.

Sort out any bruised, stung or split fruit before storing or selling — one rotting fruit spreads to its neighbours in the crate.