Citrus reticulata Seeds | Mandarin Orange
LATIN NAME: Citrus reticulata
COMMON NAME: Mandarin
Plant Profile
The mandarin is the easy member of the citrus clan, and the trait that names it is the rind. Where a sweet orange clings to its flesh, Citrus reticulata carries a puffy, leathery skin that slips off in the hand, and the segments separate cleanly because the internal membrane is fine and loose. The species name reticulata means ‘netted’, a reference to the prominent network of white pith threads on the inside of the peel that shows once the skin is pulled. That loose, netted construction is the single character that separates a mandarin from every other citrus fruit.
Beyond the fruit, the plant is a small evergreen tree with slender twigs and leaves whose blades narrow into distinctly winged petioles, the leafy ‘wings’ that mark the looser-skinned citrus group. The flowers are small, white and very fragrant, opening among the leaves in flushes through the warm season and drawing bees in numbers. The fruit is round, slightly flattened and bright orange when ripe, and because the crop ripens on the tree it can be picked as wanted rather than all at once.
Commercial mandarins are almost never grown on their own roots, because the scion and the root want different things; the top wants a certain fruit, the bottom wants a certain soil and a certain cold tolerance, and the two are joined by grafting.
The usual understock is trifoliate orange (Poncirus), a cold-hardy, thorny relative whose roots shrug off damp cold that would rot a mandarin’s own, and which also confers dwarfing and disease resistance to the graft. Other understocks are chosen for tolerance of lime, of flooding, or of specific soil pests, so the same scion can be grown from a Florida sand to a Mediterranean limestone by changing what it stands on. The union is the real secret of a productive orchard, more than the variety name on the label.
You can grow a mandarin from the seed in the fruit, and often it will be a decent tree, but if you want a known variety the graft is the honest route.
Science & Biotechnology
The grower buds a single eye of the chosen mandarin onto the seedling understock just above the soil line, wraps the join, and removes the understock top once the bud takes. The result is one tree with two genomes: mandarin above, trifoliate below, each doing the job it is good at. This is also how a single tree can carry two mandarin varieties on one root, a trick used to guarantee pollination or to stretch the harvest across the season without planting two trees.
Uses & Benefits
The fruit is eaten fresh more than anything else in the citrus world, and its mild, sweet flesh suits uses that a sharper orange would overwhelm.
The segments go straight into lunch boxes and salads, where the loose membrane means no pith to trim, and the zest is mild enough to use where a lemon would be too sharp. The outer peel, cured in syrup, becomes candied peel, and the oil pressed from the rind flavours everything from tea to confectionery. Because the fruit is small and the segments tidy, it is the citrus most often given whole to children, which is part of its worldwide popularity.
Grafted onto a dwarfing understock and grown in a tub, a mandarin makes a tidy patio tree that can be wheeled under cover when frost threatens, which is how gardeners outside the subtropics still pick their own fruit. Keep it in full sun, water it when the top of the compost dries, and feed it with a citrus fertiliser through the warm months; the fragrant flowers and the orange crop together make the pot worth the space. A winter rest in a bright, cool room keeps it from dropping leaf.
Growing from Seed
Mandarins are famous among citrus for polyembryony, the habit of producing several embryos inside a single seed, most of them clones of the mother tree grown from the nucellus rather than from fertilisation. Sow one such seed and several sprouts may appear, and the majority will be genetically identical to the parent, which is why a seed-grown mandarin often comes true while a seed-grown lemon or grapefruit does not. The trait is a quirk of the ovule and a gift to the home grower who wants a free copy of a favourite tree without grafting.
Clean the seeds from a ripe fruit, sow them fresh into a warm, bright seedbed, and keep the compost evenly moist so the embryos swell and push; the nucellar clones will appear alongside the occasional sexual seedling. Grow the strongest on until they are pencil-thick, then either keep them as own-root trees or use them as understock for budding. Remember that while many will be true to the parent, a few will be hybrids, so label the uncertain ones and judge the fruit only after a few seasons.
Take a bud from a named mandarin you trust and chip it onto a seedling trifoliate or onto a young own-root plant, binding the cut and shading it until the union closes. A successful graft fixes the variety beyond doubt and brings a crop years sooner than a seedling would, because the scion is already mature wood. This is the method nurseries use and the one to copy if you have a favourite fruit and want its clone rather than a lottery.
Our Take
I keep a dwarf mandarin in a tub for the scent of the flowers as much as the fruit, and I bud it onto trifoliate orange for the cold buffer. If you want to widen the citrus bench, bitter orange, yuzu and citron each bring a different rind, acid and cold habit to the same warm corner.
Related Reading
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