SCIENTIFIC NAME: Citrus japonica
FAMILY: Rutaceae

I first fell in love with cumquat trees years ago when I saw a beautiful little bonsai tree covered in bright orange fruit, their size in perfect proportion to the tiny tree. I subsequently bought a small variegated cumquat but did not have the heart (or the skill for that matter) to bonsai the thing. Instead, I planted it in a tub where it thrived and fruited abundantly for several years before desperate drought-affected cattle broke the fences to get to it and every other green thing in the garden. However, I replaced it and have continued to happily grow the beautiful little trees ever since.

Cumquats belong to the citrus family. There are two common varieties: Nagami, which bears oval fruit and Calamondin (or Marumi), which produces loose-skinned round fruit. Both are sour, although Nagami is the sweeter of the two. Both are small trees, with Calamondin being the smaller variety and most suited for growing in a tub. Calamondin also comes in a striking variegated form. The immature fruit of the variegated Calamondin are striped green and yellow, only turning orange a week or so before becoming fully ripe.

Cumquats prefer much the same conditions as other citrus. Full sun is essential and every partial shape will reduce the cropping potential. Protection from strong winds should be provided, but light frosts can be tolerated. The trees are small enough to be given frost protection and severe climates. Pot-grown specimens are even easier to protect as they do not grow to their full height of about 3m (10ft) when grown in a container.

Like other citrus, cumquats prefer a well-drained soil and should not be planted in hollows where water is likely to accumulate. If planted in a container, several drain holes at the perimeter of the base are preferable to a single central drain. In any case, drainage must be adequate, as the trees will soon weaken if left in wet, sour soil.

Cumquats grow best if the soil is kept free of grass for about 45cm (18in) around the trunk. The bare soil may be mulched, but the mulching material should not come in contact with the trunk of the tree. This also applies to pot specimens. In fact, mulching is particularly desirable for potted cumquats to prevent over-heating of the soil in the summer months.

In general, cumquats should not need pruning, but as the trees mature, old dead wood can be cut out to encourage strong new growth. All shoots appearing on the trunk within a foot of the ground should be removed.

Cumquats like plenty of moisture, especially in the flowering and fruit setting periods. With pot specimens, particularly in warmer areas, the flowering and fruit can proceed nearly all year round, so adequate watering must be provided to ensure a continuous set of fruit. The pot should never be allowed to dry out completely.

When you purchase a cumquat from your local nursery, it will be either budded or grafted, usually on Troyer Citrange hybrid orange rootstock, or a fast-growing Swindell grapefruit. It should have bright, healthy leaves and be a compact little tree.

If the tree is to go into the ground, dig the area over deeply and prepare a hole wide and deep enough to accommodate the roots. Settle the tree in the hole carefully, firm the soil around the roots and water in well.

If the tree is to be potted, use a tub at least 50cm wide by 50cm deep (20in X 20in). Cover the drain holes with gauze and a few bits of charcoal before placing soil on top. A good general potting mix is suitable. Set the tree carefully on the soil and firm more soil around the roots. Fill the container with soil, leaving about 5cm (2in) of the tub above the soil surface. This allows room for mulching and prevents soil from washing out and exposing shallow roots when the tree is watered. Water the newly settled tree well. Planted out in Spring, your tree will very likely reward you with a respectable crop of cumquats in its first season.

Pests and diseases should not be a problem with healthy, well-managed trees. The occasional aphids can be controlled with a wash of soapy water, although bad infestation will require a complete pesticide. The trees are small enough to allow you to pick off bugs and caterpillars. Other pests may include wax scales which, if bad, can be controlled with white oil sprays, using 4 teaspoon to 4½ litres (1 gal of water). Spray for scales in December and again in January if necessary, but don't undervalue the effectiveness of soapy water, a stiff brush and elbow grease for getting rid of scale pests. Pyrethrum sprays at triple strength are effective against bad citrus bug infestation. All this sounds fairly horrific, but in my experience, cumquats maintain a fairly trouble-free existence. Finally, on the subject of pests and diseases, a guava planted close by is said to protect citrus from infection. This I fully believe, judging from the smell of guavas!

Cumquats in the ground can be fertilised with complete fertiliser at about a half a cup per square meter below the branches in spring, early summer and early autumn. Potted cumquats require only half that amount. For potted plants, wet the soil thoroughly before each application to wash out residue salts from the previous feeding. Animal manures can of course be used to feed the plants, but they should be well-rotted to avoid burning the shallow roots.

Marion Boetje, Brooweena, Qld

DATE: July 1993

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