Nyssaceae

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This small Family has been constituted, as a result of modern DNA determinations, to contain, inter alia, the two genera - Nyssa and Camptotheca – these genera had been previously included in the Cornaceae; the Family Davidaceae was also created, and separated from the Cornaceae, to house Davidia – which however is sometimes attributed here.

 

Nyssa

 

This small genus contains about three species of deciduous trees and large shrubs, which have potential ornamental value for use in temperate climate areas and are reasonably commonly seen in cultivation. Five species - N. aquatica, N. biflora, N. ogeche, N.sylvatica and N. ursina are native within Eastern North America and four species - N. leptophylla, N. sessiliflora, N. sinensis and N. yunnanensis are all native to milder parts of China. Virtually all the species are found in damp or aquatic habitats.

 

Their ornamental value lies in the ‘guaranteed’ autumnal hues which usually finally (after passing through other colours) become a brilliant scarlet. In general all the species produce a tap root and are difficult to transplant and establish - as a result of disturbing this feature – hence they should be planted at a small size and initially grown in suitably configured containers.

 

The flowers are small, inconspicuous and greenish white - in clusters on a long stalk in late spring (usually about bud break) – they provide excellent honey forage. The flowers are unisexual and generally the plants are monoecious but are usually functionally dioecious, same sex flowers making up the cluster - usually the female flowers are individually larger.

 

The fruit is a smallish one-seeded drupe with an astringent flesh. It is nominally oblong in shape and thin fleshed. It contains a linear, ridged ‘stone’ or ‘pit’. The skin is, typically, basically black but in the case of N. ogeche is red. The fruits are taken by birds.

 

The seed (‘stone’ or ‘pit’) is long and narrowish with a reasonably substantial, brown, ridged (in some degree) surface. The embryo is large and linear and sits in an oily endosperm. Hence storage is only suitable in the short term – under water conserving conditions.

 

The seeds are separated, fairly readily, from the fruit by maceration and floating the skin and flesh away in running water.

 

N. sylvatica (the Black Tupelo) – can develop into a tree to 30m – with a single dominant upright trunk with the branches produced stiffly at right angles to the trunk. The leaves are generally oval – but can be variable about this shape. The species has an extensive geographic distribution, in Eastern North America, from New England south to Florida and from the eastern seaboard across to southern Ontario and Eastern Texas.

 

The fruits develop on the end of the long stalk – up to three but more commonly one from each flower cluster. They are about 15mm long and round to oval in shape; the skin is blue-black when ripe with an astringent flesh. The seed is a ridged stone about 10-12 mm long, brown in colour.

 

The Swamp Tupelo (N. biflora) grows in swamps and flood plains and is often under water at times of inundation – it is sometimes regarded as a sub-species of N. sylvatica. It has a trunk which is swollen at the base and which tapers ultimately to 20m+. The fruits have a purplish-blue coloured skin and the seeds are slightly larger than those of N. sylvatica and have more prominent longitudinal ridges.

 

The seeds of both these entities will germinate without treatment but N. sylvatica, with its extensive north-south distribution, will germinate with better synchronisation and greater numbers at emergence if seeds from northern populations are chilled for 60 days at 3˚C; seeds collected from the mid-range populations will benefit from a 30 day chill.

 

Nyssa aquatica, the Water Tupelo, occurs in wetland areas in the Southeastern United States. The trees are tall and single trunked - they develop a swollen bole. It flowers (the trees are functionally dioecious) at bud-break and the fruit, which is produced in early autumn, is tear drop shaped about 25mm long, initially purple but ripening off to blue-black. The stone is deeply grooved. The seeds will germinate without pre-treatment but emergence is enhanced if they are chilled for 30 days at 5˚C.

 

Nyssa sinensis, the Chinese Tupelo, also occurs in damp conditions and is native to Southern China and Vietnam. It is a small, single boled tree to 10m or so. The young leaves are red throughout the growing season. Autumnal colours are brilliant. There are no constraints to germination - which will be rapid at 20˚C+.

 

Camptotheca

 

This small genus of only two species - of which only one (C. acuminata) appears to be in cultivation - is a native of Southern China through to Tibet. It thus has an extensive geographical and hence climatic range. In cultivation in the UK it is only suitable for planting in the mildest niches but this is probably associated with the provenance of the original seedlings and thus selections from cooler provenances may prove hardier.

 

It is a deciduous tree to 20m tall with the young leaves appearing red – which continues while new material is produced. Interest, currently, in this species is high because it produces a phytochemical – camptothecin - which appears to have useful properties in the treatment of some cancers.

 

The globular aggregations of insignificant white flowers are produced in early summer and give way to eye-catching globular clusters of elongated pale skinned, one seeded drupes.

 

Extraction is the same as for Nyssa and although the seeds will germinate without pre-treatment they appear to benefit from a short (30 day) chill at 5˚C; before germination at 20˚C+.