Crassula arborescens ssp. arborescens, C. arborescens ssp. undulatifolia and C. ‘Blue Bird’ PDF Imprimer E-mail
Crassula - Species
Écrit par Margrit Bischofberger   
Jeudi, 12 Mai 2011 07:18

Crassula arborescens ssp. arborescens:
Crassula arborescens has been in cultivation since around 1730 but has only been described by Miller in 1768 as Cotyledon arborescens and in 1798 published by Willdenow as Crassula arborescens. The most recent description is by H. Toelken in Flora of Southern Africa, vol. 14, 1985, p.136 ff. What follows is a summary of this description :
Perennial shrubs or treelets, up to 2 m high and more , stems up to 20 cm thick at base, much branched, old leaves deciduous. Leaves obovate to orbicular, 20-30(-40) mm broad, carnose, somewhat convex on both surfaces, red margins and red spots above, glaucous, spreading. Inflorescence a round-topped thyrse with 1 – several rather few-flowered dichasia, peduncle 30-70 mm long. Corolla star-shaped, white or cream tinged red, petals 7-10 mm long, sharply pointed, spreading at right angle, anthers purple.

C. arborescens resembles the other tree Crassula, C. ovata, but its leaves are wider and thicker. It is widespread in western and eastern Cape and Natal.

Crassula arborescens ssp. arborescens (photo Margrit Bischofberger)

Crassula arborescens ssp. arborescens (photo Margrit Bischofberger)


Crassula arborescens ssp. undulatifolia:
This subspecies is a comparatively recent discovery, first described by Toelken in 1974, known only from the southern parts of the Klein Winterhoek Mountains in the eastern Cape Province. It is growing near plants of C. ovata but has a different flowering time. It differs from ssp. arborescens in its leaves which are elliptic to elliptic-oblanceolate, 8-15(-20) mm broad, only slightly fleshy, with wavy margins, erect not spreading.
In cultivation two somewhat different forms are grown – one with fairly big leaves and one with smaller and more undulated leaves, the latter has been distributed as ISI 2005-16. Both forms are C. arborescens ssp. undulatifolia, they have no cultivar names.
The ISI text reads :

ISI 2005-16 : Crassula arborescens ssp. undulatifolia TOELKEN.
C. arborescens is well represented in cultivation by the typical form of ssp. arborescens, with thick orbicular leaves that have earned it the common name of silver dollar jade. Subspecies undulatifolia has more elongate leaves that are less fleshy and tend not to rest in one lane, giving rise to the subspecies epithet. It eventually grows to be a large shrub to 2 m similar to the jade plant, C. ovata. The form offered here has particularly glaucous leaves, very stout succulent branches and a natural bonsai-like aspect. Rooted cuts of H G 84988, a plant collected by Ernst van Jaarsveld at the type locality, Sapkamma Station, E Cape, S. Africa."

Crassula arborescens ssp. undulatifolia (photo Margrit Bischofberger)

Crassula arborescens ssp. undulatifolia (photo Margrit Bischofberger)

Crassula arborescens ssp. undulatifolia (photo Margrit Bischofberger)

Crassula arborescens ssp. undulatifolia (photo Margrit Bischofberger)

Crassula ‘Blue Bird’
In his article “Crassulas in Californian Gardens” (CSJ US vol. XLIV, 1972) J.R. Brown shows two photos of a plant called Crassula ‘Blue Bird’. This plant had been published by Boom in the Dutch journal Succulenta 42 (6), 1963, as C. portulacea ‘Blauwe Vogel’ and again in Succulenta 59 (6), 1980, as C. ovata ‘Blauwe Vogel’ (‘Blauwe Vogel’ meaning the same as ‘Blue Bird’).
This plant had been introduced to Europe as a cutting found among cuttings of C. ovata and was considered as a hybrid of C. ovata and C. arborescens, strongly resembling the latter. After Toelken had received leaves and inflorescences of this supposed hybrid he explained that it is identical with the plant he had described as C. arborescens ssp. undulatifolia.
This means : Crassula ‘Blue Bird’ is not a hybrid of C. ovata and C. arborescens. It is the same as C. arborescens ssp. undulatifolia, a name validly published by Toelken in 1974. C.’Blue Bird’ is a synonym.
Summary:
C. arborescens has 2 subspecies :
- ssp. arborescens and
- ssp. undulatifolia (synonym C. ‘Blue Bird’) with two somewhat different forms in cultivation, both without a cultivar name.

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