The Rue Family
What are they?
There are no native members of the rue family (Rutaceae) in the UK and it's a rather difficult family to define easily as its members are very varied. The family consists mostly of woody trees or shrubs but also includes some herbaceous species. Most species occur in the tropics or warm-temperate regions of the world. Most notably, many members of this family have glands on the leaves (and sometimes on the flowers) that produce aromatic oils which give off a strong scent if the leaf is crushed. Most of the species also have highly fragrant flowers, making them popular as garden ornamentals.
Where are they found?
These are all non-native plants that are widely grown as garden plants. They may occasionally be found as garden cast-outs, or where planted in amenity landscaping schemes.
Identification
Members of the rue family that have been recorded in the wider countryside in East Anglia are relatively easy to identify from a combination of their flower and leaf detail (and occasionally the fruits). However, it should be borne in mind that other species (particularly of Skimmia) are widely grown and may occur in the future. These can be difficult to tell apart but will be added here if they become established in our region.
Common Rue Ruta graveolens
Introduced from South-east Europe as a medicinal plant initially but also as a garden ornamental. Recorded as a garden throw-out just a handful of times but occasionally seen in parks and cemeteries. Flowers June to July. Grows to around 50cm in height, becoming wood at the base. Leaves richly blue-green and highly aromatic, but can cause a severe skin reaction from the sap if bruised during hot weather. Seed capsules covered in sunken glands.
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Mexican Orange-blossom Choisya ternata
Introduced from Mexico as a garden ornamental. Recorded as a garden throw-out just a handful of times but widely used in amenity plantings. Flowers mainly in May to June but occasionally at other times also. Grows to around 2m in height, forming a broad mound. Leaves with three, ovate leaflets and with a very rich, spicy aroma. Often found growing as one of the yellow-leaved cultivars.
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Narrow-leaved Choisya Choisya x dewitteana
This plant is an artificially produced hybrid between Choisya ternata and C. dumosa var. arizonica, originating in cultivation. The resulting cultivars have been widley planted in amenity areas in recent years. Flowers mainly in May to June but occasionally at other times also. Grows to around 2m in height, forming a broad mound. Leaves with three to five, narrow leaflets. Some plants in cultivation may be selected forms of Choisya dumosa but it is unclear how they may consistently be separated from C. x dewitteana except perhaps by having some leaves with more than five leaflets, as is the case with cultivar 'White Dazzler'.
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Japanese Skimmia Skimmia japonica
Introduced from East Asia as a garden ornamental. Recorded as a garden throw-out just a handful of times but widely used in amenity plantings. Flowers March to April. Grows to around 2m in height, forming a broad mound. Leaves simple, thick and leathery, often becoming chlorotic (turning yellow) on chalky soils. Male and female flowers appear on separate bushes in the true species, but some horticultural varieties are hermaphrodite. Male plants are most often the cultivar 'Rubella' which has deep pink flower buds, opening white.
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