Argentine senna - Senna corymbosaSenna corymbosa is an evergreen or semi-evergreen shrub from the legume family (Fabaceae), native to the... Read more
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Senna corymbosa
Argentine senna tolerates only brief frosts. Well-rooted plants in dry soil can withstand temperatures dropping to around -6 to -8°C, and American nurseries recommend it for USDA zones 8–11. In zone 8, it may die back to the ground and regrow from the roots.
In the Polish climate, it is best overwintered in a pot in a bright, cool, frost-free room, such as a conservatory, an unheated porch or a cool stairwell. Water sparingly in winter, keeping the soil only slightly moist. Some leaf drop during this period is natural.
When cultivated, it usually reaches 1.5–2.5 m in height and a similar width; in the wild, it grows to around 0.8 to 4 m. It is very well suited to growing in a large pot, and its size is easy to control by pruning. Repot it into a larger container about every two years, in spring.
It grows at a moderate to fast rate and, in good conditions, forms a large shrub within a few seasons. It reaches its full size after many years, but flowers much earlier. Even after being damaged by frost, it can regrow from the roots and flower on new shoots.
The plant grows in sandy, clay and calcareous soils with an acidic, neutral or alkaline pH - good drainage is most important. In a pot, fertile soil-based potting mix with a clay base works well. Water regularly in summer, without letting the root ball dry out completely, and avoid waterlogging.
During the growing season, from spring to the end of summer, feed the plant about once a month with a balanced liquid fertilizer. Stop fertilizing in autumn and winter. Regular feeding of potted plants supports abundant flowering.
Argentine senna is an ornamental plant, and its leaves, pods and seeds should not be eaten. Plants in the genus Senna are known to contain compounds with laxative effects. Grow it somewhere inaccessible to children and pets that might eat it.
In Europe, it usually flowers from July to October, and even until November in a mild autumn. The golden-yellow flowers are about 3 cm in diameter and grow in clusters at the tips of the shoots. It flowers most profusely in full sun and with regular fertilization.
A sheltered spot in full sun is best, for example, against a south-facing wall or on a sunny patio. The plant tolerates light partial shade, but flowers less abundantly there. In the garden, move it outside only after the spring frosts have passed.
Senna corymbosa, known in Polish as Argentine senna and in English-speaking countries as Argentine senna, flowering senna, or buttercup bush, is a shrub in the legume family (Fabaceae), subfamily Caesalpinioideae. It belongs to the genus Senna, which, depending on the classification, comprises around 260 to over 300 species of trees, shrubs, and perennials, found mainly in tropical and subtropical regions. Argentine senna holds a special place among them as one of the species relatively tolerant of cold, which is why it has long been grown in gardens in warm temperate climates.
This is an upright, slender shrub or small tree that can develop a spreading, or even partly trailing, habit with age. According to the genus monograph compiled by the New York Botanical Garden, flowering plants range from about 0.8 to 4 m in height; in gardens, specimens 1.5–2.5 m tall and of similar width are most common. Young branches are greenish and finely ridged, while older ones turn brown and eventually become almost black. This dark color of the bark and shoots gave rise to the Spanish common name “rama negra,” meaning “black branch.”
The leaves are compound and paripinnate, about 5.5–9.5 cm long, and borne on a 13–28 mm petiole with a distinctly thickened base. They usually consist of 2–3 pairs of leaflets, with the terminal pair being the largest: the leaflets are 25–47 mm long and 5–12 mm wide, making them narrow and lanceolate, 3–6 times longer than they are wide. A distinctive diagnostic feature is a small gland on a short stalk, located between the lowest pair of leaflets. The stipules are narrow and linear-lanceolate, and fall early. As in many other legumes, the leaflets show nyctinastic movements – they fold at night and in deep shade, and spread out in full light.
Argentine senna grows at a moderate to fast rate. A well-fed plant in a warm, sunny spot quickly becomes bushy and forms a substantial shrub within a few seasons. The Royal Horticultural Society (RHS) states that it reaches its full mature size after around 10–20 years, but its ornamental effect and flowering appear much sooner. The species tolerates pruning well – in regions where it dies back to ground level in winter, it regrows from the roots in spring and flowers on new shoots in the same year. When grown in containers, its growth can be effectively controlled through pruning and pot size, making it easier to move the plant to winter quarters each year.
Flowers grow in clusters emerging from the leaf axils, usually with 4–15 flowers and, exceptionally, up to 18; later clusters may form a short panicle with a corymb-like shape at the tips of the shoots. Each flower has five sepals and five almost equal petals that are golden yellow, gradually turning brownish yellow; the longest petal measures 8–16 mm, and the whole flower reaches about 3 cm in diameter. The stamens vary markedly in length, and three of them are non-functional staminodes. This structure is typical of flowers pollinated by bumblebees, which release pollen from the anthers through vibration.
In its native range, Argentine senna flowers roughly from November to May, during the warm season in the Southern Hemisphere. In Europe and North America, flowering usually occurs from July to October, and in mild autumns continues into November or even December. In the southeastern United States, the plant is a valued late-season source of nectar, and its leaves provide food for caterpillars of the family Pieridae.
The fruit is a hanging, cylindrical pod 7.5–12 cm long and 0.6–1 cm in diameter, green at first and papery and brown when ripe. The pods do not split open spontaneously and remain on the now-leafless shoots for a long time, providing additional winter interest. They contain numerous seeds about 4.5–5.3 mm long, matte brown to chestnut brown. The species has a chromosome number of n = 14. In addition to propagation by seed, Argentine senna can be propagated vegetatively from semi-hardwood cuttings taken in summer.
In nature, the species inhabits scrub, riverbanks, wetlands, and forest edges in lowland areas, usually below 150–200 m above sea level. According to Plants of the World Online (Kew), it is associated mainly with seasonally dry tropical biome. This origin explains its great adaptability: the plant tolerates both occasional drought and higher soil moisture, provided water does not collect around the roots.
Argentine senna is not fussy about soil type. The RHS lists chalky, clay, sandy, and humus-rich soils, with acidic, neutral, or alkaline pH. Good drainage is essential, especially in winter, as frost damages the plant more severely when its roots are in waterlogged soil. It flowers best in full sun; it tolerates light shade, but produces fewer flowers in those conditions. Sources differ in their hardiness assessments: well-established plants in dry soil withstand short-term temperature drops to around -6.5 to -8°C, and occasionally even -10°C. American nurseries indicate USDA zones 8–11, with the caveat that in zones 7–8 the above-ground parts may be killed by frost, while the plant regrows from the roots. The more cautious RHS classification (H1c) recommends growing it under cover outside the summer season.
In Poland and most of Central Europe, Argentine senna does not reliably overwinter outdoors, so growing it in a large pot is the most practical option. From late spring, once the risk of frost has passed, move the plant to a sunny, sheltered patio, balcony, or garden. For winter, bring it into a bright, cool, frost-free place, such as a conservatory, unheated porch, cool stairwell, or greenhouse. In winter, keep the soil only slightly moist. The plant may shed some of its leaves, which is no cause for concern.
For pots, use fertile soil-based compost with added material to improve drainage. During the growing season, water generously without letting the root ball dry out completely, and feed about once a month with a balanced liquid fertilizer. Repotting into a larger pot about every two years in spring supports continued growth. In spring, remove shoots damaged by the cold, and after flowering you can prune the plant to keep it compact. In the warmest parts of Europe, along the Mediterranean and Atlantic coasts, the shrub is grown in the ground; elsewhere, a thick mulch around the base and horticultural fleece during the hardest frosts are recommended.
Argentine senna’s greatest asset is its late and prolonged flowering. As summer perennials finish flowering in the garden, the shrub becomes covered in clusters of bright yellow flowers that contrast beautifully with its dark green, finely divided foliage. In pots, it makes an attractive specimen on a patio, by the entrance to a home, or in a conservatory. In warm climates, it is used in informal hedges, shrub borders, Mediterranean gardens, and pollinator-friendly plantings.
Its tolerance of pruning means it can be trained as a small standard with a short trunk, which is especially practical for container growing. Plants with purple or blue flowers, such as salvias and lavenders, make good companions and highlight the senna’s vivid color. The pods that persist through winter also give the plant ornamental appeal beyond the flowering season. Cultivars and hybrids involving this species are also known in cultivation.
The species was scientifically described in 1785 by the French naturalist Jean-Baptiste Lamarck as Cassia corymbosa in the work “Encyclopédie méthodique. Botanique”. For nearly two centuries, it was classified in the broadly defined genus Cassia. Only in 1982 did American botanists Howard S. Irwin and Rupert C. Barneby transfer it to the genus Senna in their revision of the Cassiinae group, giving it the currently accepted name Senna corymbosa (Lam.) H.S.Irwin & Barneby. Synonyms include Adipera corymbosa, Chamaefistula corymbosa, Cassia bonariensis, and Cassia crassifolia; in the gardening trade, the plant is still sometimes offered under the name Cassia corymbosa.
The genus name Senna derives from the Arabic word “sanā”, used to refer to plants with leaves and pods that have a laxative effect. The specific epithet corymbosa refers to the Latin term corymbus, meaning corymb - an inflorescence whose flowers are arranged at roughly the same height, which aptly describes this plant’s terminal clusters of flowers. Thanks to its attractive appearance and cold tolerance, Argentine senna has become popular in gardens beyond South America and is now recorded as naturalized in, among other places, the southeastern United States, Spain, Italy, the Canary Islands, South Africa, India, and Pakistan.
Argentine senna is a good choice for people who want to start growing exotic flowering shrubs but do not have a heated greenhouse. The plant tolerates different soil types, responds well to pruning, and can cope with occasional watering mistakes; a cool, bright room is sufficient for overwintering. It is also ideal for owners of patios and balconies looking for a plant that flowers in late summer and autumn, gardeners in warmer parts of Europe, and anyone who enjoys gardens that welcome bumblebees.
Senna corymbosa is an undemanding, fast-growing shrub in the legume family, native to northeastern Argentina, Uruguay, Paraguay, and southern Brazil. It usually reaches 1.5–2.5 m in height, has delicate, feathery leaves, and is covered in golden-yellow flowers from summer through late autumn. It tolerates brief frosts of around -6 to -8°C, but in Poland it is best grown in a container and overwintered in a cool, bright place. Plants of the World Online does not list an IUCN threat category for this species; it occurs naturally in several South American countries and is widely cultivated as an ornamental plant.
Very Large plant choice
just I found it quite annoying that the majority was palm seeds,
not what i like the most
Snelle levering (vanuit Polen) en zaden zien er goed uit.
