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Yucca gloriosa

Asparagus Family [Asparagaceae]

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10th Oct 2018, a garden area, Freshfield, Sefton Coast. Photo: © RWD
These may be cultivated varieties. Spanish Dagger grows up to 2m tall, occasionally up to 5m!

10th Oct 2018, a garden area, Freshfield, Sefton Coast. Photo: © RWD
These may be cultivated varieties. The leaves are less than 1m long and up to 5cm wide and either with no teeth os inconspicuous teeth.

22nd June 2010, Grange-over-Sands, Cumbria. Photo: © RWD
A single substantial flowering spike arises from a crown of sharp dagger-shaped leaves. Red-Hot-Poker behind.

22nd June 2010, Grange-over-Sands, Cumbria. Photo: © RWD
The lower bracts are green and reddish-beetroot in colour, from behind of which reddish-beetroot flowering stalks grow. Leaves have dangerously stiff and sharp points!

22nd June 2010, Grange-over-Sands, Cumbria. Photo: © RWD
As-yet un-opened flower buds are reddish, and upright and look as though they mean business.

23rd July 2010, Read, Lancs. Photo: © RWD
An architectural or monumental plant. Leaves stiff, dagger-shaped with sharp point at tip and angled upwards. A tall spike of creamy-white bell-shaped flowers, hanging down, reminiscent of a 'golden rain' firework.

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
Un-opened flowers.

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
The bell-shaped flowers hang downwards.

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
The six petals are in two inter-leaved sets of three; inner and outer sets. The petals are narrow at the top, broad in the middle and taper to a purple-hinted point at the ends.

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
Looking up, braving the extremely sharp points on the leaves, the flower is seen to consist of six 'L'-shaped anthers surrounding a triple stigma, all white.

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
Your author risked life and limb to take these photos! The pain was only slightly lessened by the reward of a pint or two of real ale :-)

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
The six anthers are tipped with small patches of creamy yellow pollen. The stigmas are creamy-green nearer the base.

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
Un-opened flower.

3rd July 2010, The Woodlands PH, Silverdale, Lancs. Photo: © RWD
If you dare go near this plant be extremely careful; the points on the ends of the very stiff leaves are exceedingly sharp, and can easily puncture arteries or permanently damage your eyes. Wear full body armour and goggles! Some gardeners wisely truncate (or butcher) the leaves.

Many similarities to : variation Yucca recurvifolia, which does not have straight leaves, but ones which arch backwards.

It is a neophyte which survives on sand dunes, gravel pits and grows mostly near the sea.It persists in South West England and South Wales, but is less persistent in South East England north to Flintshire and West Lancashire. Also in The Channel Islands, and in parts of Ireland: Southern Kerry and County Waterford.

Some similarities to : New-Zealand Flax in the long sharp sword-shaped leaves.

Uniquely identifiable characteristics

Distinguishing Feature : Looks like a 'golden rain' firework in full steam.

Recently moved from the now defunct Agave Family [Agavaceae] into the Asparagus Family.

Contains saponins. The juice obtained from the leaves has been used as a fish poison in stagnant water. The leaves contain Tigogenin, a steroid.

The long linear shaped leaves are stiff, pointing 45° upwards, and are very dangerous: the sharp tips of the leaves can easily pierce skin, also allergic reactions can result.

You are very much more likely to find this in a garden setting rather than in the wild on sand-dunes and gravel pits where it can occasionally be found.


Stilbene has a double-bond which can assume two differing geometrical configurations, a trans-form and a cis-form, but which are nowadays often re-designated (E)- and (Z)- respectively although the two terminologies are not directly interchangeable, but are in this specific case.

Of those, (E)-Stilbene, the straighter of the two, is the most energetically favourable configuration (lowest energy), it is fully planar and thus retains aromaticity between the electrons on the two benzene rings and the connecting link (resonance hybridization). (E)-Stilbene and its derivatives are also used in the manufacture of synthetic oestrogens as well as possessing intrinsic oestrogenic activity themselves. It is thought that (E)-Stilbene forms liquid crystals, which is not possible with the non-planar (Z)-Stilbene form.

(Z)-Stilbene, on the other hand, is twisted out of plane by the forces between the hydrogen atoms on opposite benzene rings (steric hindrance - and is therefore in a higher energy state). The slight twist causes it to lose much of its aromatic character (the pi-orbitals do not overlap as well and then it cannot share electrons between the benzene rings). It is not very common and almost unknown in the natural world. The huge electronic differences between the two geometric isomers affect the stacking of the molecules and hence the melting point, with the weaker (Z)-Stilbene having a much lower melting point of, 6C as opposed to 125C for the (E)-isomer, a remarkably large difference (most cis/trans isomers have much lower melting point differentials than this).

However, the cis form of Anthracene called Phenanthrene has a larger temperature differential between the two isomers, m.p. 101C for the cis-form Phenanthrene against 218C for the trans-form Anthracene. However, in the case of Phenanthrene, it retains planarity and thus its full aromaticity. Note the similarity between Phenanthrene and (Z)-Stilbene caused by the addition of just another bond between the two rings (and the loss of two hydrogen atoms). (Neither Anthracene nor Phenanthrene occur in Yucca, they are just shown for comparison).

Stilbene and many derivatives of it are found in many plants, Yucca being just one. Stilbene is used as one of the saturable gain mediums in dye-lasers. The two forms can inter-transform into one another under the influence of light, a process called photoisomerization.

Stilbene, and some other linear-chain dimers of Stilbene, are used as the active saturable gain mediums in tunable dye-lasers. This makes use of Stilbene and its dimers to fluoresce under UV illumination rather than for its ability to transform into the more energetic (Z)-isomer since the relaxation time for a conformational change back into the (E)-isomer would be far too long for any lasing effect to occur. It is also used in the manufacturing of dyes and optical brighteners, perhaps in washing powders.

Resveratrol too can exist in two geometrical isomers, the cis- (Z)-Resveratrol and the more stable trans- (E)-Resveratrol which is much more abundant. The two absorb at differing wavelengths in aqueous solution (λmax) 286nm versus 304nm respectively). The trans geometric isomer can also be transformed into the cis-form under the influence of UV light of 350nm wavelength (photoisomerisation).

Resveratrol is a stilbene derivative found in both grapes in red wine and which is believed to by a phytoalexin, which are produced by plants in response to and to repel fungal attack. Resveratrol is a phytoalexin, a compound produced naturally as a defence mechanism in plants under attack by a fungal or bacterial pathogen. However the Grapevine fungal pathogen Botrytis cinearea is able to oxidize Resveratrol into derivatives such as  Pallidol (a dimer of Resveratrol) or δ-Viniferin (a Resveratrol de-hydro dimer) which have reduced anti-fungal activity.  δ-Viniferin is particularly interesting because it is a dimer between the trans- and the cis-forms of Resveratrol.

It is found in several other fruits but has particularly high concentrations in the skins of red Grapes and in minuscule amounts survives the fermentation process in the production of red wine. Its numerous 'reported' health benefits (or detriments) are so far un-proven. It was first found in the very poisonous White Hellebore (Veratrum album).


Yuccaols are novel spiro-structures which have various hydroxy or methoxy stilbenoids (similar to the Tetrahydroxymethoxystilbene shown above) linked by a lactone at a point to a residue probably derived from a flavone. Yuccaols contain two Phloroglucinol residues (leftmost and bottom right rings).

Larixinol, superficially similar to the Yuccaols but when inspected turns out to have many differences, is a compound previously identified in the Asian tree Dahurian Larch Larix gmelinii. Larixinol is a spiro-biflavonoid which contains two Phloroglucinol residues (central ring and bottom right ring). The flavonol component is possibly derived from DiHydroKaempferol. It too is also a lactone and is found in the bark only of Yucca gloriosa.


Yucca gloriosa contains several Yuccaloeside steroidal glycosides (aka saponins) based upon the aglycone steroid Tigogenin, a spirostanone, only two of which are shown here, Yuccaloeside B and C. Presumably Yuccaloesides A, B and E are also present (certainly in the bark of Yucca schidigera species if not in Yucca gloriana itself). They contain a mixture of glycosides shown in red, mainly glucosyl (gly), with the odd rhamnosyl (rha) and galactosyl (gal).
Yucca also contains many other steroidal glycosides based upon the aglycone steroids Smilagenin, Samogenin, Sarsapogenin, Neogitogenin, Mexogenin, Gloriogenin and Manogenin, some of which are spirostanol steroids whilst others are furostanol steroids. The glycoside containing Smilagenin contains ten glucosyl units whilst the Smilagenin glycoside just two. Saponins are poisonous by affecting the permeability of intestinal cells. They also form complexes with Cholesterol in protozoal cell membranes causing lysis, thus they are anti-protozoal too.

  Yucca gloriosa  ⇐ Global Aspect ⇒ Asparagaceae  

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Yucca gloriosa

Asparagus Family [Asparagaceae]

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