Theaceae

 

Those genera, in the Tea Family, which contain relevant species with a temperate climatic distribution include Camellia, Franklinia, Gordonia (excluding Polyspora), and Stewartia. However also included here, as a result of recent DNA assessments by taxonomists, are those genera which were previously designated as belonging to the Ternstroemiaceae and have now been subsumed into this Family. Thus Cleyera, Eurya, Schima and Ternstroemia which all have species with a warm temperate climate provenance are treated here.

 

Camellia

 

This large genus contains more than two hundred species of evergreen trees and shrubs. They are native to Central, Eastern and South East Asia - where they occur from temperate climates to the tropical.

 

The genus is notable for containing the Tea plant (C. sinensis) and several species (including C. oleifera, C. japonica and C. reticulata) which are grown as plantation crops and from which edible oil is extracted by pressing the seeds; this is widely used in China for cooking. C.japonica, C. reticulata and C. sasanqua are among several important ‘horticultural’ species which have given rise to the vast array of ornamental selections and hybrids – historically in the Orient but in the last two hundred years - around the world.

 

Virtually all of the species cited above can be propagated vegetatively by stem cuttings but seedling production is necessary for breeding programmes; for the production of the species and for rootstocks for grafting (esp C. reticulata cultivars) and for the production of plantation crops for oil production (although elite selections will be propagated from stem cuttings).

 

Seed production in most of the UK is dependent on high levels of light and temperature during the summer although in milder areas seed production, at least of the hardier species, occurs in most years although, usually, on a limited scale. Seed is not normally produced prolifically until a plant has reached a substantial size and age.

 

The fruit of C. japonica is a dry, woody, three lobed, locular capsule (c25mm across) which contains up to five compartments each with a potential for up to eight seeds. The individual seeds are dispersed when the dry capsule splits in October- November. The seeds are more or less roundish but uneven, about 5mm across and have a brittle skin which is purple brown in colour. The seeds contain high levels of oil and hence quality and viability can deteriorate rapidly without suitable storage conditions – ie water conserving conditions at cool temperature. The fruits of some species (eg C. oleifera) are large and can be up to the size of a tennis ball with proportionally large seeds.

 

When the seed is collected as the fruits split, behaviour in response to the provision of conditions for germination can be erratic. The most consistent results can be achieved by collecting the fruits when they are still soft and shiny and just becoming brown – usually August in the UK – at this stage the seeds are fully isolated and mature. This means that extraction, necessarily, has to be done by hand.

 

Propagation should then be carried out with this fresh seed. A twelve hour, warm water soak will ensure full imbibition and the seeds can be station sown and maintained at 20+˚C for germination.

 

However those species with the more northerly distributions (this includes C. oleifera) will germinate with the above regime but emergence will be slow and erratic. A synchronised, uniform and speedy response can be achieved if the imbibed seed is previously chilled for 63 days at 3˚C.

 

If the seedlings are ultimately to be container grown it is recommended that they are transplanted at germination and that, in the process, the radicle is tipped to encourage a fibrous, branching root system; however if the seedlings are intended for growing in the open ground then the radicle is allowed to develop naturally - as a deeper penetrating root system will be developed.

 

Franklinia

 

This narrowly endemic (to Georgia, USA), monotypic genus (Franklinia alatamaha) and its story are the stuff of legends - it has not been seen in the wild since the late eighteenth century. Fortunately it was found and collected by Samuel Bartram and so has survived in cultivation. It is a small tree with thick, shiny, bright green leaves and spectacular white flowers - in the autumn – but, usually, only after a hot summer. These are five-petalled, 7 to 9cm in diameter and are produced solitarily in the leaf axils.

 

The fruit is a five-valved, globular, leathery, fleshy capsule maturing to a woody dehiscent condition. Each cell contains 6 to 8 wingless, angular seeds - 12 to 14mm long, which are dispersed in the following autumn.

 

The fruits should be collected just before they open and are then gently dried – when the seeds will shake out. Viability is generally low.

 

Germination of the imbibed seeds at 20˚C will occur but a synchronised and speedier emergence will occur after a chill of 30 days at below 5˚C.

 

Gordonia

 

This genus of evergreen trees and shrubs has, nowadays, been drastically reduced in size as the majority of species, which were included have been transferred to the genus Polyspora – and these have warmer provenances in South East Asia than the climates represented in these notes. Gordonia lasianthus - the Loblolly Bay occurs in various disjunct populations in the South East and South of the United States; it is an evergreen large shrub or small tree.

 

The white flowers are produced, singly in axillary clusters, at midsummer and are sweetly scented.

 

The fruit, which is produced in October, is a five-valved, dehiscent, locular, ovoid, woody capsule which sheds its seeds by December; about 12mm in diameter and 20mm long. To avoid losing the seeds to an early dehiscence the capsules can be collected when they are still ‘leathery’ and brown and then gently dried in a paper bag until they open and the seeds can be shaken out; do not overdo the drying as this could lead to a loss of viability. Each fruit produces between 10 and 40 smallish, winged seeds.

 

There are no constraints to germination and at 20˚+C the imbibed seeds will emerge in 7 to 10 days.

 

Stewartia

 

This small genus of decorative small trees and shrubs consists of between eight and twenty species native to South Eastern Asia, China, Japan and Korea with two species (S. malacodendron and S. ovata) found eccentrically in the South Eastern United States. They are deciduous (the evergreen species are assigned to Hartia). All the species are ornamental – for their autumn colour; their late flowering habit (July and August) with showy white flowers which are produced prolifically for several weeks and their brilliant ‘orange’ and flaking bark during the winter.

 

The relatively large fruits are five-valved capsules - more or less globular but with a ‘beaked’ shape at the top; they are initially leathery but mature to be woody; each locule contains, normally between two and four seeds. They dehisce and disperse the seeds quite quickly when ripe. Thus they should be collected, at the latest, as the first fruits dehisce and gently dried in a paper bag - the seeds separate readily from the capsules to produce a clean sample – however in S. malacodendron the seeds are tightly packed in the capsule and have to be persuaded manually to release! At maturity the seeds have a high water content (c80%) and viability, naturally, declines quickly – especially if dried - thus it is important not to dry any more than is required to extract the seeds and even in short term storage it is essential to maintain the water status – so store under water conserving conditions.

 

As the seeds require a long pre-treatment prior to germination (naturally the seeds do not germinate until the second spring following dispersal) it is the practice to collect the fruits at an immature stage – as the embryo matures early in the development of the fruit. Hence the fruits can be collected as they change colour from green to brown. This early collection will allow the treatments to be carried out in time for germination during the following spring.

 

Seeds of Stewartia, effectively, do not germinate after a simple exposure to warm temperature after imbibition. In order to germinate the seeds require a relatively long period (84 days) of warm stratification (but it is not clear what action is promoted within the seed) followed by a substantial chill to overcome an endogenous dormancy – the recommendations of up to seven months of chill for maximum germination response, however, seem to be excessive as none of the species experience such exposure in their natural habitats. The sanest protocol offered is:-

a) twenty four hour warm water soak to achieve imbibition;

b) four months period of warm stratification; 

c) three months chill and

d) germination at relatively cool temperature – c15˚C.

 

 

There are four genera of the ‘old’ Ternstroemiaceae - with species which have a temperate provenance – Cleyera, Eurya, Schima and Ternstroemia which are included here. They are dealt with, collectively, in one package as they do not have any particular issues in relation to the germination of their seeds. All of these genera are principally tropical and sub-tropical in their distribution chiefly in Southern and South Eastern Asia; however a very few species have a warm temperate provenance - eg Cleyera japonica, Eurya japonica, Schima argentea, S. khasiana and Ternstroemia gymnanthera - and can be cultivated in milder niches in the British Isles.

 

They are all evergreen trees or shrubs and have scented white or yellow flowers - which mature to capsules (a berry in Ternstroemia) from which the seeds are readily extracted.

 

Germination of the imbibed, viable seed at 20˚C is normally prolific.