Agavaceae
In the American continent, the succulent monocotyledons have diverged into a number of important families of succulent plants, including the Agavaceae which form distinctive rosettes and flower spikes. The family Agavaceae includes Agave, Beschorneria, Furcraea, Hesperaloe, Manfreda, Polianthes, Prochnyanthes, and the genus Yucca which is the focus of this page. |
Yucca Linnaeus 1757
Name: from an Indian word: Yuca = cassava
There are at least 50 species of Yucca within the Agavaceae, and numerous subspecies, varieties, forms, cultivars and hybrids of horticultural merit have been described. Several variegated cultivars are available, but may be less vigor.ous than non-variegates. Some common names such as "Palma", "Spanish Bayonet", "Spanish Dagger" etc. are used for several species, so are unhelpful identifers. See also: About Yuca & Yucca
Yuccas occur exclusively in the Americas, distributed over a wide area from Canada into Central America and the Caribbean with species adapted to dry deserts, grasslands and tropical rainforests. Yucca lacandonica is unusual in growing as an epiphyte on trees of the tropical rainforest of Southern Mexico and Guatemala. Wet-cold-hardy species suitable for UK-type climates are available with growth habits ranging from stemless rosettes to substantial trees. Species photographed in the RHS gardens, Wisley, UK and at Royal Botanic Gardens Kew have been growing outside for many years and are worth trying as hardy plants in sheltered positions.
All but one species (Y. whipplei) can flower many times (polycarpic) and produce side-shoots to compensate for loss of the apical growing point by its conversion into a flower bud.
Self pollination of Yucca flowers of many species is impossible, although a few are self-fertile. Most Yuccas are pollinated exclusively by small Yucca moths with the plant and moth totally dependent on each other. The female moth visits flowers collecting pollen into a ball which is deposited on the surface of the stigma after she has laid eggs deep in the flower ovary. The flower is sufficiently pollinated to ensure a multitude of seeds and provides food for the larvae, which eat only a few seeds. In practice, the larvae may destroy more than they eat. Inspection of seed pods often reveals that a single grub has drilled a hole through all the seeds rendering them useless.
You can download higher quality images by clicking on the pictures below.
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Yucca aloifolia Linnaeus 1753
This is the type species for the genus Yucca. Yucca aloifolia is a slow-growing hardy succulent plant from the SE USA coast into Mexico, the Caribbean islands and into Mexico. It has been cultivated since 1605. Plants may have a single stem up to 20ft tall, sometimes branching near the top of the stem, often offsetting at the base to form a clump. The stiff erect leaves have fine sharp marginal teeth and a brown, sharp terminal spine which distinguishes it from Yucca gloriosa. Persistence of live leaves along the stem produces an elongated rosette. The inflorescence is a compact panicle of creamy-white bells with a hint of pink or purple, usually held close to the rosette.
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Fibres from the leaves of Yucca aloifolia have been used to make string and twine. Its tolerance of humid and dry climates has made it a popular architectural succulent plant in many temperate countries. However, plants should be sited well away from paths because of the sharp terminal spines on the leaves. Several selected cultivars are available.
Left: A plant labelled as Yucca aloifolia variegata, although the lax foliage suggests this is really a form of Yucca recurvifolia or a hybrid. A range of leaf variegation may be seen in the offsets at the base of the main stem, suggesting some genetic instability. Photographed in the RHS gardens, Wisley, UK.
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Yucca aloifolia 'Vittorio Emanuele II'
Named for: Victor Emanuel II (1820 - 1878), last King of Sardinia (1849 - 1861), first King of a unified Italy (1861 - 1878)
This succulent plant is a hybrid of Y. aloifolia x Y. recurvifolia created by Carl Ludwig Sprenger, German botanist and supervisor of Kaiser Wilhelm II's garden "Achilleion" on Corfu.
Photographed at Royal Botanic Gardens, Kew.
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Yucca angustissima Engelmann ex Trelease 1902
Four varieties are recognised.
Yucca angustissima subsp. kanabensis Reveal 1977 (Narrow Leaved Yucca)
flowering at an altitude of around 1500 metres above sea level in a grassy clearing within the Coronado National Forest to the North of Phoenix, Az. This Yucca is distributed through Northern Arizona into Utah and in view of its range is likely to exhibit a degree of hardiness, although as is often the case wet winters may be a problem. This species is sometimes subsumed under Yucca glauca.
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Photo: Robin Howard
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Yucca baccata Torrey 1859 (Banana Yucca, Datil Yucca)
Name: Latin baccata = with berries
The thick succulent blue-green leaves have filamentous edges and wicked greyish terminal spines.The common name refers to the large edible fruit pods that are banana-like in shape. The pods, eaten raw, roasted or ground up and made into cakes, were an important source of food for Native Americans. The leaves were used to make mats and baskets.
Upper left: Yucca baccata flowering at an altitude of around 1500 metres above sea level in the Coronado National Forest, North of Phoenix, Arizona. In this area Yucca baccata grew and flowered as delightful minatures, suitable for the smallest garden.
Native to a huge range of the South-Western USA including Arizona, California, Nevada, New Mexico, Texas and the North-Western Mexican states of Chihuahua and Sonora. Three sub-species are recognised.
This succulent plant is hardy and may even survive outside in a damp climate provided that its roots are very well drained.
Middle: Yucca baccata has been seen growing outside for several years in the Royal Botanic Gardens Kew, UK. Plants in pots have survived on the author's patio through several winters but have not really grown well.
Lower right: Yucca baccata at Colorado Springs. Here the plant is dwarfed by the harsh climate.
However, the same species seen in New Mexico was much larger. Photo: Robin Howard.
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Yucca brevifolia Engelmann 1871 (Joshua Tree)
Name: the twisted branches reminded Mormon settlers of the story of Joshua holding out his hands in prayer.
This distinctive Yucca is an indicator succulent plant for the Mojave desert and probably the most famous of all Yuccas, with a National Park named after it. Large specimens grow up to 30ft tall and branches bend down or stick out at odd angles. The inflorescence is a short panicle of greenish-white bells held close to the foliage.
Yucca brevifolia is tolerant of cold but not of damp.
This plant was near the Extraterrestrial Highway US375, just South of Rachel, Nevada. The exotic foliage of this succulent plant can be seen in the landscape of 'distant planets' in a few episodes of 'Star Trek' and other science fiction movies.
More about Yucca brevifolia
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Yucca constricta Buckley 1863 (Buckley Yucca)
from southern to central Texas. These succulent plants are stemless or with a very short stem carrying a clump of disorganised rosettes of thin flat leaves with white filamentous margins. The inflorescence is up to 10 ft tall with small greenish-white flowers.
Photographed in the RHS gardens, Wisley, UK.
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Yucca decipiens Trelease 1907 (Palma China)
is a huge 30ft tree from central Mexico, growing at altitudes of 5000 - 8000 ft. Although hardy to both drought and freezing cold, it is unlikely to tolerate wet-cold.
The thick trunk, branching with age, carries a crown of many dense rosettes of stiff, blue-green leaves with brown edges which detach to form curled marginal filaments. Leaf tips are very sharp.
A similar plant to Y. filifera but the inflorescence of cream-coloured flowers is more erect.
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Yucca elata Engelmann 1882 (Soaptree Yucca)
flowering South of Phoenix, Az. Yucca elata is distributed from South Arizona into West Texas and Northern Mexico. Subspecies are found as far North as Utah.
The roots and trunk, up to 5m tall, contains toxic saponins that were extracted and used as soap to wash clothing and hair by Native Americans. The long narrow leaves are highly suitable for weaving into baskets. Wild Yuccas are sometimes seen where the lower leaves have been removed for this purpose.
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Photo: Peter Hodgkiss
Temperate House, RBG Kew
Yucca elephantipes Regel 1859
Syn. Yucca guatemalensis Baker 1872, Yucca gigantea Baker 1880
becomes a very large 30ft tree with a thick trunk. The large, soft, glossy green succulent leaves have smooth edges and no terminal spines. A panicle of many creamy white flowers is produced within the rosette of leaves.
Yucca elephantipes is native to the East coast of Mexico and Guatemala and will only survive the lightest of frosts. It is commonly seen as an ornamental succulent plant in shopping malls because it tolerates poor light, and is planted outside in areas with frost-free Mediterranean or tropical climates.
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Yucca faxoniana Sargent 1905 Syn. Yucca carnerosana (Spanish Dagger)
growing on limestone at Dagger Flats, Big Bend National Park. The stiff succulent leaves have curly filamentous edges and a wicked brown terminal spine. The dead leaves are retained on the trunk.
This impressive succulent plant grows up to 20ft tall, with a 4ft inflorescence held above the leaves. The large greenish-white flowers are tubular at their base.
It is found in Texas west of the Pecos river and in the Mexican states of Zacatecas and San Luis Potosi.
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Yucca filamentosa Linnaeus 1753
a stemless clumping Yucca that spreads by underground stolons. The thin leaves are generally straight although some of the older leaves around the edge of the clump may recurve. The leaf margins carry numerous white curled filaments which catch the light, giving the species its epiphet. The inflorescence up to 15 ft high carries large white flowers well above the leaves. Photographed in the RHS gardens, Wisley, UK.
This cold-tolerant Yucca is naturally distributed on the SE coastal plains from New Jersey to Florida and widely cultivated in the USA as far north as Vermont and in Great Britain and Europe.
Yucca filamentosa cv. bright edge is a stemless clumping variegated form whose yellow leaf margins light up in the sun, especially when back-lit.
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Yucca filifera Chabaud 1876 (Palma China)
is a very large tree reaching up to 30 ft tall, with many branches from a thick trunk adorned with old leaves. The rigid olive-green leaves have filamentous edges and a sharp terminal spine. Spherical clusters of leaves are carried on the ends of branches. Old leaves remain attached to the branches and trunk. The panicle of creamy-white flowers is distinctively pendulous, which distinguishes the plant from Y. decipiens.
Yucca filifera is native to the Chihuahuan desert in North-Eastern Mexico. This young specimen was photographed at the Boyce Thompson Arboretum, Arizona.
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Yucca flaccida Haworth 1819
a small stemless clumping Yucca that spreads by underground stolons. It is distributed through the Appalachian Mountains of North America from North Carolina to Alabama. Being tolerant of cold, damp climates it is hardy in the UK. The margins of the lanceolate leaves produce long straight filaments. The lax outer leaves recurve and rest on the ground justifying the "flaccida" epiphet. The 6ft inflorescence carries clusters of creamy-white fragrant flowers.
Yucca flaccida cv. Garland's Gold is one of several selected forms that are available with variegated or stiffer foliage, and in some cases without marginal filaments. Seen here in the RHS gardens, Wisley, UK.
Yucca flaccida is sometimes subsumed under Yucca filamentosa.
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Yucca glauca Nuttall 1813 (Great Plains Yucca)
flowering in the monocotyledon border of the RHS gardens, Wisley, UK in September 2003. It is widely distributed in North America and is hardy in the UK.
This narrow-leaved succulent plant grows as a stemless clumping rosette, or may form a short 1ft stem with age, and is suitable for the smaller dry garden. Leaf margins carry white filaments.
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Yucca gloriosa Linnaeus 1753 (Adam's needle, Spanish Dagger)
was the very first (AD 1596) Yucca to be introduced into the UK from coastal sand dunes of the SE. USA (S. Carolina, NE. Florida). Its tolerance of a wide range of growing conditions has contributed to its worldwide cultivation as an ornamental.
Left: Yucca gloriosa "nobilis" Syn. Y. ellacombei hort ex Baker
a horticultural selection, flowering in the RHS gardens, Wisley in September 2003. This typically late flowering makes the inflorescence prone to damage from early frosts.
With time, this hardy succulent plant forms a branching trunk up to 5m tall. Branches can be cut off and root easily to propagate the plant. Leaf ends are less sharp than those of the similar Yucca aloifolia, but still advisable to plant this Yucca well back from paths.
A range of selected cultivars are available in the horticultural trade, including forms with variegated leaves (left).
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Yucca aff harrimaniae Trelease 1902 (Harriman's Yucca)
The short-stemmed or stemless rosettes form clumps. The leaves have a marginal brown stripe splitting into white filaments. The inflorescence is a dense 3ft raceme of ivory-white bell-like flowers.
A variable succulent plant with three varieties recognised. Native to mountains of Utah, Colorado, and Northern Arizona and New Mexico where it experiences cold winters at elevations up to 8500 ft.
Photographed in the Royal Botanic Gardens, Kew.
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Yucca queretaroensis Piña 1989
has a 15ft trunk bearing a symmetrical head of hundreds of very narrow (2mm), bright-green leaves with a square cross-section. Old leaves are retained as felting on the trunk. The inflorescence is a dense upright panicle of cream-coloured flowers.
This succulent plant was described quite recently and is restricted to river gorges in the Mexican states of Queretaro and Hidalgo at elevations of 3000 - 4000ft.
Yucca linearifolia Clary 1985
is a similar succulent plant to Y. queretaroensis, from the North-Eastern Mexican state of Nuevo León, but has blue-green leaves with a flat cross-section.
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Yucca rigida Trelease 1902 (Blue Yucca)
grows up to 15 ft tall, usually branching near the top. The 3ft long, 1 inch wide light blue-gray leaves have yellow margins and a brown terminal spine. Old leaves remain attached to the stem.
Yucca rigida is distributed across Northern Mexico, and widely grown as a drought-tolerant ornamental succulent in the South-Western USA. Photographed at the Boyce Thompson Arboretum, Arizona.
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Yucca rostrata Engelmann ex Trelease 1902 (Beaked Yucca, Thomson's Yucca)
at Dagger Flats, Big Bend National Park. The single trunk may be up to 15 ft tall and can carry more than one rosette of bluish-green leaves. A smaller variety that grows up to 8ft tall and may branch is sometimes referred to as Yucca thompsoniana.
The white flowers are held well above the leaves. The fruits have a characteristic beaked appendage; hence the common name.
Yucca rostrata is found in W. Texas and in the Mexican states of Chihuahua and Coahuila. As it is drought and cold-tolerant, Yucca rostrata is a popular ornamental succulent plant throughout the South-Western USA.
Left: Yucca rostrata may be distinguised from similar Yuccas by the characteristic yellow edges of the long narrow leaves. The leaves are narrower than those of Yucca rigida.
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Yucca schidigera Roezl ex Ortgies 1871 (Mohave Yucca)
flowering in the Mohave Desert Reserve, Nevada in April 1995. This succulent plant has a large range from S. Nevada into NW. Arizona and S. California into N. Baja California. Although old plants may produce a trunk up to 2.5m tall, stemless rosettes are also common. Old trunks may branch near their top. The thick rigid concave succulent leaves have markedly curled filamentous edges and sharp terminal spines. The spike of globular flowers is compact and close to the rosette.
The small fleshy fruits can be eaten and the leaves are a source of fibre for making rope.
Yucca schidigera is extremely drought tolerant and moderately frost hardy under dry conditions.
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Yucca torreyi Shafer 1908
flowering North of Marathon, Texas in April 1990. The rigid succulent leaves are arranged in a disorganised manner along the stem and have filamentous margins. The trunk is typically unbranched and felted with persistent dead leaves. These burn off spectacularly in the event of a brush fire but the plant usually recovers. The large cream globular flowers have a reddish purple tinge.
The fleshy fruits can be eaten. The dried flowers have been used to make a tea and as a cough remedy.
This Yucca is moderately frost hardy and is sometimes seen used as an ornamental plant in Texas. |
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Yucca treculeana Carrière 1858
from flat chaparral of S. Texas and N. Mexico. The single trunk up to 20ft tall has attractively fissured bark and may branch near its top with one or more rosettes of stiff, thick succulent leaves terminating in a sharp brown spine. These dark green leaves have brown margins, sometimes with a white edge. The 2-3 ft inflorescence of small globular cream flowers is partly obscured by the foliage.
The fleshy fruits were traditionally fermented to make a beverage. The leaves were used for thatching and as a source of fibre for rope. This moderately frost hardy Yucca is widely used as a striking architectural plant in Mediterranean climates. Photographed in the RHS gardens, Wisley, UK. |
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Yucca valida Brandegee 1889 (Datilillo)
has short, stiff, dark green leaves with curled filaments and a sharp terminal spine. The succulent leaves form an elongated head along the trunk. The trunk, up to 15 ft tall, is often unbranched or branches at the top and is felted with old leaves. The panicle of creamy-white flowers smells like fennel.
Yucca valida originates in Baja California. Photographed at the Boyce Thompson Arboretum, Arizona.
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Yucca whipplei Torrey 1859 (Our Lord's Candle)
appropriately flowering at Easter in the Anza-Borrego Desert State Park, April 1995. This is the only monocarpic species of Yucca and the flowers are self-fertile. Engelmann placed this succulent plant in the monotypic genus Hesperoyucca but this synonym does not seem to have been widely adopted. Several subspecies are recognised, of which subsp. whipplei remains as a solitary rosette and so dies after flowering. Other subspecies spread by offsets or via stolons.
This plant was part of a splendid group covering a hillside, each with an outstanding inflorescence. Large numbers of plants were seen flowering in this area May 2006. |
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Yucca near Persimmon Pass, just outside the Big Bend National Park.
This succulent plant with its very long straight-edged leaves without filaments and disorderly appearance, was markedly different from other Yuccas growing in this area.
Thanks to Dave Ferguson, Rio Grande Botanic Garden, Albuquerque, NM for identifying this plant as a hybrid. Such plants are not rare, and most Yucca species will hybridize where they grow and flower together.
This one is likely to be Y. torreyi X Y. rostrata as both parents were present nearby and this hybrid is known in the Big Bend.
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