Cassia javanica and its closely related species from my perspective

The species of Cassia in this group have been documented to be naturally distributed over large geographic ranges from north-eastern India, southern China, mainland southeast Asia to the Philippines, and from Sumatra and Java (Indonesia) to New Guinea and possibly upper Queensland (Australia). They were generally recognized as varieties of Cassia javanica species complex before being reclassified into several different species and subspecies. A few species are somewhat restricted to specific natural habitats while the others have larger ranges with partially or fully overlapping geographic distributions. Most species have been extensively grown in tropical areas worldwide as a garden or street trees. Variants and/or intermediate forms likely exist in both nature and cultivation. In the latest classification, four accepted species and three subspecies have been recognized as listed below.

Cassia javanica L.
Cassia agnes (de Wit) K. Larsen

Cassia renigera (Benth.) K. Larsen

Cassia nodosa (Roxb.) K. Larsen & S.S. Larsen

Cassia javanica subsp. pubifolia (Merr.) K. Larsen

Cassia javanica subsp. bartonii (Bailey) K. Larsen

Cassia javanica subsp. microcalyx (H.S.I rwin & Barneby) K. Larsen

Under a tree canopy of Cassia renigera at author's place in Patumthani, Thailand

As they are closely related species, it is difficult to tell them apart. They sometimes may be only forms or variants of the same species, or even hybrids of these species. Identifying and distinguishing between these species is quite challenging. In this article, four accepted cassia species (i.e. C. javanica, C. agnes, C. renigera and C. nodosa) and a C. javanica subsp. publfolia have been identified and described. It was done based upon author's interpretations of the information written in published literatures, and particularly by making close observations and examinations of the trees growing in author's garden in Patumthani, Thailand. Some previously unrecorded or hidden details on the specimens were also highlighted here. Note that the asterisk signs under the Key description sections indicated that the particular characteristics described in this article are not consistent with those written in some major published articles.

KEY TO Cassia javanica and its closely related species:

1. Stipules foliaceous

1.1. Ovary puberulous (hairy)

    1.1.a Leaflets upto 15(16) pairs. Inflorescence large, stiff, compound racemes (panicle). Flower size 5-7 cm across. Calyx dark red. Petals first solid pink later dark red, finally pale, obovate. Leaflet size 1.5-2.5 cm x 2.5-5.0 cm. Stipules reniform. Trunk thorny.

C. javanica

    1.1.b. Leaflets upto 12(14) pairs. Rachis of inflorescence slender, Inflorescence small, racemes. Calyx green or mixed green-red to red. Petals pink (fading white) or deep yellow, ovate or elliptic to oblong. Stipules reniform to crescentic.

            1.1.b1. Petal pink fading white. Calyx green to light reddish green. Leaflet apex acute, Stipules reniform.

C. nodosa 

            1.1.b2. Petal deep yellow/orange. Calyx green. Filaments beefy. Leaflet apex acute. Stipules reniform to crescentic.

C. nodosa var. orange

            1.1.b3. Petal pink fading white, mixed green/red to red. Leaflet apex obtuse. Stipules reniform.

C. javanica var. indochinensis

    1.1.c. Leaflets upto 10 pairs. Inflorescence small, corymbs. Flower size 3-4 cm across. Calyx reddish green. Petals pink fading white, ovate to spathulate, unequal size (bottom two slightly larger). Leaflet size 2.2-3.0 cm x 3.5-7.0 cm. Stipules small reniform to crescentic.

C. agnes

1.2. Ovary glabrous

    1.2.a. Leaflets upto 21(22) pairs. Inflorescence small, racemes. Flower size 4.5-6.5 cm across. Calyx red. Petals pink fading white, ovate. Leaflet size 1.2-1.7 cm x 4.0-6.0 cm. Stipules large leafy kidney shape (reniform).

C. renigera

    1.2.b. Similar to C. renigera but Stipules only half as broad (1 cm across). Petals pink or pinkish white, petal gradually narrowed towards the base, 15-18 mm long.

C. javanica subsp. bartonii

2. Stipules subulate

    2.1.a. Leaflets upto 12(14) pairs. Inflorescence small, racemes. Flower size 4.0-6.0 cm across. Calyx large and green. Petals pink fate to white. Leaflet size 2.0-3.0 cm x 3.5-6.5 cm. cm. Stipules minute subulate (two each on opposite side).

C. javanica subsp. pubifolia

    2.2.b. Similar to subsp. pubiflora but having smaller sepals, petals and anthers.

C. javanica subsp. microcalyx

Cassia javanica L.

Syn.
Cassia javanica subsp. javanica L.
Cassia javanica var. javanica L.

Note: Most specimens of C. javanica listed in Kew's Herbarium and others before being reclassified into several different species and subspecies were a part of C. javanica species complex (which can be either C. javanica or agnes or renigera or nodosa or etc). But Cassia javanica listed right here is a distinct species after reclassification.

Native range: Monsoon forests at lower altitudes in Java (Indonesia) but rarely in Sumatra and Borneo. Widely cultivated as an ornamental throughout SE Asia. Commonly seen in Thailand. Cultivated in the US (Hawaii and Florida) and neotropic (but with much less widely distributed as compared to C. nodosa).

Key description: A medium sized and fast-growing semi-deciduous tree to about 15 m in height with a large symmetrical umbrella-shaped crown (broad canopy). Trunk armed with stumps of branches. Leaves up to 15 (16) pairs* of leaflets (rare 16 pairs found on water sprout branches but mostly 12 to 14 pairs on most mature branches). Leaflets (1.5-2.5 cm wide x 2.5-5.0 cm long), oblong to oblong-elliptic, apex acute** (more acute apex on young vigorous tree but less on mature tree). Stipules foliaceous (reniform). Rhachis of inflorescence stout. Inflorescences panicle (compound raceme),***  large, stiff, arising laterally along branches. Flower 5-7cm across. Sepals dark red in color. Petals first pink later deep pink to red, finally pale with maturity, large and long, obovate to narrowly obovate, and not overlap (at full opening of petals).

*up to 15 pairs (Flora of Thailand, Flora of China and Flora Malesiana),  up to16 pairs (author's specimens)
**apex rounded to blunt (Flora of Thailand)
***raceme (Flora of Thailand), compound raceme (Fig. 22 in Flora Malesiana ser.1, Vol. 12(2) 1996)

Author's comment:

Most characteristics of the specimens (C. javanica) described in this article are in agreement with those in most major publications with an exception of the type of inflorescences. Only the tree specimens with deep pink to red colored flowers (pink petals turning red before fading to white) and leaves up to 15-16 pairs of leaflets have been found to have compound raceme (panicle) inflorescences.

Figure 1. Cassia javanica cultivated in Patumthani, Thailand. A twenty year old tree at approx. 15 m tall (left) with large panicle inflorescences arising laterally along branches (right). Flowering period: Late April to May.

Figure 2. Cassia javanica. Left: Stiff compound racemes or panicles. Right: Deep pink to red flowers with petals of obovate to narrowly obovate shape and not overlap (when fully open), red calyxes, red pedicels, red bracts and pseudo-bracteoles.

Figure 3. Cassia javanica. Left: Leaves on a branch of a young vigorous tree having 15-16 pairs of leaflets with acute apex. Right: Leaves on a branch of a large mature tree having 12-14 pairs of leaflets with less acute apex.

Figure 4. Cassia javinica. Non-persistent reniform stipules on a young branch (left), and on a more mature branch (right).

Figure 5. Cassia javanica. A young water sprout shoot armed with stump-remnants of branchlets (left), and armed trunk of a large tree (right).

Cassia agnes  (de Wit) K.Larsen

Syn.

Cassia javanica subsp. agnes (de Wit) K. Larsen

Cassia javanica var. agnes de Wit

Note: Some specimens listed as C. javanica var. indochinensis in Kew's Herbarium and a few others were later identified as either C. agnes or C. nodosa.

Native range: Evergreen forests and mountains in NE India (Assam), upper Burma, southern China (Guangxi, Yunnan), northern Thailand, Laos and northern Vietnam. Rarely in cultivation in Thailand. Introduced to neotropic and the US (Hawaii and Florida).

Key description: A small and slow-growing deciduous tree to 10 m or more in height. Leaves up to 10 pairs* of leaflets (rarely 10 but mostly 7 to 9). Leaflets large (2.2-3.0 cm wide x 3.5-7.0 cm long), elliptic, apex acute. Stipules crescent shaped. Rhachis of inflorescence slender. Inflorescences corymb,** small, arising laterally along branches.*** Flowers 3-4 cm across. Sepals reddish green. Petals pink fading white, ovate to spathulate, not overlap (large space between petals when fully open), slightly unequal size (the bottom two are slightly larger).

*up to 6-7 pairs (Flora of Thailand) but up to 10 pairs (Flora of China and author's specimens)
**corymb composed of 6-10 racemes (Flora of Thailand), panicle composed of 6-10 racemes (Flora of China and Flora Malesiana)
***terminal on young leafy shoots (in Flora of Thailand, Flora of China and Flora Malesiana)

Author's comment:

C. agnes is a small tree that can be easily distinguished from other cassias within this group by its large but fewest leaflets per a leaf.

Author's comment on types of inflorescences and number of leaflets:

All cassias in this group i.e. C. agnes (up to 10 pairs of leaflets), C. renigera (up to 21-22 pairs) and C. nodosa (up to 12-13 pairs) have simple raceme inflorescences. The only cassia with leaves up to 15-16 pairs of leaflets has panicle inflorescence with stout rhachis, and it is identified as C. javanica (not C. agnes).

Author's comment on inflorescences terminal on leafy shoots:

C. javanica, C. agnes, C. nodosa and C. renigera have inflorescences terminal on young and tiny leafy shoots (consist of zero to 3 leaves) but it is more pronounced in C. javanica.

Author's comment on stump-remnants of branchlets and armed trunk:

In C. javanica, stump-remnants of young branchlets become large thorn-like (the remains of fallen branchlets) in mature branches and main trunk.  Other Cassia species within this group (e.g. C. agnes, C. renigera and C. nodosa) also develop stump-remnants of branchlets (twig-like) but they are much smaller in size and may disappear when the trees get larger.

Figure 6. Cassia agnes cultivated in Patumthani, Thailand from the seed collected from a mountainous area in Nan province, northern Thailand where Bretschneidera sinensis (a subtropical species) grows naturally. Left and right: A ten to twelve year old tree at about 6 m tall.

Figure 7. Cassia agnes cultivated in Patumthani, Thailand. Leaves with 6-7 pairs of leaflets (left) and 7-9 pairs of leaflets (right) on the same tree.

Figure 8. Cassia agnes with non-persistent tiny crescentic stipules on new/young shoots (left and right)

Figure 9. Cassia agnes cultivated in Patumthani, Thailand. Flowering period: late February to March. Corymbose inflorescences (left) and flowers with rose pink petals of unequal size (the bottom two are slightly larger) and not overlap (when fully open), reddish green calyxes, green pedicels, red bracts and pseudo-bracteoles (right).

Cassia renigera (Benth.) K. Larsen

Syn.

Cassia javanica subsp. renigera (Benth.) K. Larsen

Cassia javanica var. renigera (Benth.) K. Larsen

Native range: Upper Myanmar. Introduced into Pakistan, India, Bangladesh, Malaysia and the US. Rarely seen in cultivation in Thailand

Key description: A small deciduous umbrella shaped tree up to 8 m tall. Branches and branchlets slender and drooping to form low spreading canopy. Leaves up to 21(22) pairs* of leaflets (rarely 22 pairs but mostly 18-20). Leaflets (1.2-1.7 cm wide x 4.0-6.0 cm long), oblong. Stipules large leafy kidney shaped (reniform). Rhachis of inflorescence relatively stiff. Inflorescences raceme, small, arising laterally along branches. Flowers 4.5-6.5 cm across. Sepals red. Petals rose pink fading white, ovate, concave and partially overlap (when fully open), two lower petals are slightly larger in size. Ovary glabrous.

*up to 21 (Flora of Thailand and Flora of Pakistan), 22 pairs (author's specimens).

Author's comment:

C. renigera can be easily identified by its unique low spreading crown with the largest number of leaflets (up to 22 pairs) and large kidney shaped stipules.

Figure 10. Cassia renigera cultivated in Patumthani, Thailand from the seeds from Burma. A fifteen year old tree at about 6-7 m tall with over 7 m spreading canopy (left), and leaves with 18-20 pairs of leaflets (right).

Figure 11. Cassia renigera. Large leafy kidney shaped stipules (left and right).

Figure 12. Cassia renigera. Small racemes along the tree branches (left), and flowers with rose pink petals fading white, ovate, concave and partially overlap (when fully open) (right). Flowering period: Late April to early June.

Figure 13. Cassia renigera. Rosy pink flowers with concave petals. Two lower petals are slightly larger in size (left). Deep red calyxes and pedicles, deep red bracts and pseudo-bracteoles, and large green leafy bracts near the base of raceme (right).

Cassia nodosa  (Roxb.) K. Larsen & S.S. Larsen

Syn.

Cassia javanica subsp. nodosa (Roxb.) K. Larsen & S. S. Larsen

Cassia javanica var. indochinensis Gagnep.

Link: C. javanica var. indochinensis

Note: Some specimens listed as C. javanica var. indochinensis in Kew's Herbarium were referable to C. agnes.

Native range: S. Thailand, S. Laos, Cambodia and S. Vietnam, Malay peninsula to Java and the lesser Sunda Is. Widely cultivated in the US (Hawaii and Florida) and neotropic. Also cultivated in China and S. Asia. Rarely seen in cultivation in Thailand.

Key description: A medium sized and deciduous tree up to 20 m in height. Leaves up to 12 (14) pairs* of leaflets (rarely 14 pairs but mostly 10 to 12 on mature branches). Leaflets (1.7-2.2 cm wide x 3.0-4.5 cm long), elliptic to oblong, apex acute or obtuse.** Stipules foliaceous (reniform). Rhachis of inflorescence slender. Inflorescences raceme, small arising laterally along branches. Flowers 4-6 cm across. Sepals green to off-red or deep red.*** Petals pale pink to deep pink fading white, small, ovate, concave and partially overlap (when fully open), almost equal in size.  

*up to 12 pairs (Flora of Thailand, Flora of China and Flora Melasiana), 13 pairs (Flora of Pakistan), up to14 pairs but mostly 12 (author's specimens).
**acute or obtuse (Flora of China), acute (Flora of Thailand), obtuse on C. javanica var. indochinensis
***green (Flora of Thailand, Flora of China, Flora of Pakistan and Flora Melasiana), red on C. javanica var. indochinensis

Author's comment:

C. javanica var. indochinensis was classified as a variety of the C. javanica (a species complex). After reclassifying and splitting of C. javanica complex species into several species and subspecies, the status of C. javanica var. indochinensis remains uncertain. However, it is listed as a synonym of C. nodosa in The Plant List. In this article, C. javanica var. indochinensis is listed a variant of C. nodosa as they share morphological similarities especially their flowers with the exception of calyx's color (the former is red while the latter is green). In general, some characteristics including colors may vary within a single species.

Is C. javanica var. indochinensis a distinct species or a hybrid rather than a C. nodosa?

Author's comment:

Although appearance is helpful in identifying species, it does not define species. Classification based on morphological characters alone is sometimes inaccurate. More works on morphological analysis (especially on the reproductive parts of the flowers) and at molecular level may reveal if it is a distinct species or a variant or simply a hybrid. This cassia has long been cultivated in Hawaii and Florida where the trees have been generally propagated through their seeds. Its progeny may have some characteristic variations within its population. C. javanica var. indochinensis is listed in this article as a C. nodosa unless new information becomes available and proven otherwise.

Author's comment:

Cassia x nealiae (a hybrid from Hawaii) has been reported to be a cross between C. fistula and C. javanica (= C. javanica complex species and it possibly is C. javanica var. indochinensis). According to a recent DNA study, C. fistula is a parent of Cassia x nealiae  but C. javanica subsp. javanica (now C. javanica) is not one of them. In my opinion, C. javanica var. indochinensis (which is listed as a C. nodosa in this article) is likely the other parent. DNA study is needed to confirm this hypothesis.

Figure 14. Cassia nodosa cultivated in Patumthani, Thailand from the seeds of an unknown source in Thailand. Left and Right: Small simple racemes arising laterally along branches. Flowering period: Late April to June.

Figure 15. Cassia nodosa cultivated in Patumthani, Thailand. Left: Flowers with pale pink petals pink fade to white, ovate, concave and partially overlap (when fully open) and almost equal in size. Right: Off-green calyxes, green pedicels, off-green bracts and pseudo-bracteoles.  The flowers of C. nodosa are smaller than those of C. javanica.

Figure 16.Cassia nodosa cultivated in Patumthani, Thailand. Leaves with 10-14 pairs of leaflets (left), and foliaceous stipules (right).

Figure 17. A variant of Cassia nodosa (syn. C. javanica var. indochinensis) cultivated in Maui, Hawaii, US. Left: A tree with leaves up to 12 pairs of leaflets, obtuse apex, and raceme inflorescences arising laterally along branches. Right: Flowers with pale pink petals, fate to white, petals almost equal in size, concave and partially overlap (when fully open). Deep red calyxes and red pedicels, red bracts and pseudo-bracteoles. (Photos courtesy of Forest & Kim Starr)

Figure 18. A variant of Cassia nodosa (syn. C. javanica var. indochinensis) cultivated in Naples, Florida, US. Left: A tree with raceme inflorescences arising laterally along branches (left). Right: Flowers with pale pink petals, petals almost equal in size, concave and partially overlap (when fully open). Red calyxes and red pedicels. (Photos courtesy of Hetty Ford)

Cassia nodosa (Roxb.) K. Larsen & S.S. Larsen

Orange flowered Cassia nodosa

Syn.

Cassia javanica subsp. nodosa (Roxb.) K. Larsen & S.S. Larsen

Cassia javanica var. nodosa (Roxb.) K. Larsen & S.S. Larsen

This cassia has been classified as C. nodosa in Flora of Thailand and Flora of China publications and a few reference books in Thailand.

Native range: Mixed evergreen forests and mountain slopes at lower altitudes in western and southern Thailand (Kanchanaburi and Ranong provinces).  Rarely seen in cultivation.

Key description:  A medium sized semi-deciduous tree to 20 m in height. Leaves up to 12 pairs of leaflets. Leaflets large (2.5-3.5 cm wide x 4.5-8.0 cm long), elliptic to ovate, leathery and slightly glossy, apex acute. Stipule small foliaceous (crescent). Rhachis of inflorescence slender. Inflorescences raceme, small, arising laterally along branches (which is unique among the cassias within this group). Flowers 4.0-4.5 cm across. Sepals off-green. Petals deep yellow to red-orange*, elliptic to oblong, lean backwards when fully open. Stamens 3 long curved stamens with large nodules in the middle of filament and beefy** at the filament base, 5 reduced stamens with beefy** filaments, and 2 beefy reduced stamens or staminodes.

*either pink or deep yellow to red orange (Flora of Thailand and Flora of China) for C. nodosa

**beefy filament is an unique characteristic of this orange C. nodosa

Author's comment:

Like all cassias in this group, the racemes of this orange C. nodosa borne laterally along branches. It is a unique and very interesting but less known cassia which should be subjected to further studies.

Figure 19. Cassia nodosa (orange form) in its habitat in southern Thailand. Leaves up to 12 pairs of leaflets with acute apex (left). Non-persistent crescentic stipules (right). (Photos courtesy of G Rawit Sichaikhan)

Figure 20. Cassia nodosa (orange form) from southern Thailand. Small racemes arising laterally along branches (left). Petals lean backwards when fully open, green calyxes, green pedicels, off-green bracts and pseudo-bracteoles (right). (Photos courtesy of G Rawit Sichaikhan)

Figure 21. Cassia nodosa (orange form) from southern Thailand. Side view and top view of flowers with its beefy filaments (left and right). (Photos courtesy of G Rawit Sichaikhan)

Cassia javanica subsp. pubifolia (Merr.) K. Larsen

Syn.

Cassia javanica var. pubifolia Merr.

Native range: Open and thin forests at low altitudes in Philippines archipelago. Widely cultivated in the Philippines. Rarely seen outside of The Philippines.  Introduced into Malaysia, Solomon Is. and Thailand.

Key description: A medium sized and deciduous tree up to 20 m. in height. Leaves up to 14 pairs of leaflets (rarely 14 but mostly 10 to 12). Leaflets (2.0-3.0 cm wide x 3.5-6.5 cm long),  ovate to elliptic or oblong, unequal sided, base broad, apex acute. Stipules minute subulate* (two each on opposite side). Rhachis of inflorescence slender. Inflorescences raceme, small, arising laterally along branches. Flowers 4.0-6.0 cm across. Sepals green to reddish green, small. Petals pale pink fading white, small, ovate, concave and partially overlap (when fully open), almost equal size.

*linear and acute (Flora Malesiana)

Author's comment:

C. javanica subsp. pubifolia has not been recognized as a distinct species yet. Its morphological characters (especially the flowers) are similar to those of pink flowered C. nodosa with a few differences. Its unique characteristics include subulate leaf stipules and large green (to reddish green) calyxes.  Note that the stipules of other cassia in this group (i.e. C. javanica, C.agnes, C. renigera and C. nodosa) are foliaceous while those of C. javanica subsp. pubifolia (and subsp. microcalyx) are subulate.

Author's comment:

When the tree of C. javanica subsp. pubifolia is in full bloom, its overall appearance from a distance is somewhat similar to C. bakeriana. Upon a close observation; however, its flower buds and newly opened flowers with deeply pink in color contrast with pale to off-white older blossoms.  In addition, the color of calyxes and pedicels of C. javanica subsp. pubifolia are green to reddish green in color while those of C. bakeriana are totally red.  Seedpods of C. javanica subsp. pubifolia are smooth (and green in color when they are young) while those of C. bakeriana are highly pubescent (and brownish in color when they are young).

Figure 22. Cassia javanica subsp. pubifolia. Left: A large tree (cultivated in Nonoc Island, The Philippines) was in full bloom. (Photo courtesy of Tina, the author of "I Went Anyways"). Right: A small tree (cultivated in Cebu, The Philippines) with small racemes arising laterally along branches. (Photo courtesy of milai, the author of Thoughts Tales and Whatnot)

Figure 23. Cassia javanica subsp. pubifolia cultivated in Cebu, The Philippines. (Photos courtesy of milai, the author of Thoughts Tales and Whatnot)

Figure 24.Cassia javanica subsp. pubifolia cultivated in Patumthani, Thailand from seeds collected on Guimaras Island, The Philippines. Flowers with pale pink petals fade to white, ovate, concave and partially overlap (when fully open) and almost equal in size (left). Flowers with green to reddish green calyx, green or pale red pedicels, bracts and pseudo-bracteoles (right).

Figure 25.Cassia javanica subsp. pubifolia cultivated in Patumthani, Thailand from seeds collected on Guimaras Island, The Philippines. Leaves with 10 to 14 pairs of leaflets, unequal sided, broad base, pointed apex (acute) (left), and ovate leaflets and non-persistent subulate leaf stipules (right).