by Trevor Key
Chamaerops No. 43-44, published online
on this article:
Click here to read them or to add your own.
Left: Yucca gloriosa grows only short trunks. Old
plants can form large clumps.
Right: Yucca recurvifolia flowers profusely.
Since I became interested in Yuccas I have been
surprised by the number of people who say " I have never noticed
them before" even from some keen and established gardeners.
Yet they have been in Britain since the middle of the sixteenth
century and some are extremely well established in Europe, particularly
around the Mediterranean, so much so that many people believe them
to be endemic to that area.
My own interest started in 1990 when I acquired
a specimen of Yucca filamentosa in flower and was impressed by a
flower spike some five feet tall with hundreds of flowers which
although lasting individually for only 48 hours or so the panicle
lasted for three to four weeks. I tried to obtain other specimens
of the genus, information and seeds, which proved difficult and
so as I gathered more data on these plants I became hooked as a
'Yuccaphile'. My own collection of plants and information has grown
but it is still difficult for any major detail about these plants
to be obtained by the average gardener.
There are in excess of 50 species of Yucca ranging
from ground hugging rosettes to tall 40 foot trees. Most are endemic
to the western half of southern USA down to California and Mexico
and are extremely well adapted to life in the deserts and foothills
of the Rockies. Examples of the western Yuccas are not normally
found in gardens but appear as specimens in botanical collections
since generally they are slow growing and take a number of years
to mature and flower. Yucca glauca is one that is occasionally offered
for sale and will produce a rosette similar to Y. filamentosa but
having tougher and thinner leaves which can have spiked ends (Names
and data to follow).
The examples most commonly seen and offered for
sale belong to a group which I term the eastern Yuccas. They are
the ones which were discovered first and have become the popular
plants which we frequently see in our gardens and scattered around
the Mediterranean: Yucca aloifolia, Y. filamentosa, Y. flaccida,
Y. gloriosa and Y. recurvifolia. Their native habitat extends across
the Florida peninsula, the Carolinas, Georgia, Alabama, Tennessee
and to the eastern edge of Mississippi. All the above including
a number of garden cultivars and hybrids were first put into a good
semblance of order by William Trelease in 1902 and the following
detail is mainly based on his criteria.
Yucca aloifolia (Spanish Bayonet)
A tree form which in its habitat can achieve a height
of 7 m. In my experience I find that specimens can grow to 1.5 m
within 5 years in a cold greenhouse. Not entirely frost hardy in
northern Europe and requires some protection. Ideal for a conservatory
and placing outside in summer. Occasionally available from nurseries
and is easily grown from seed. The leaves are finely toothed along
their edges and tipped with very sharp spines. Not recommended where
it can be a danger to children or animals. It is very common on
the east coast of Florida and Georgia and has become established
on most of the Caribbean islands due to human intervention. A number
of variegated garden forms exist but these are more difficult to
One of the most popular, very hardy, easy to grow
and readily available. It forms a rosette at ground level and flowers
well after 3-4 years and if planted in numbers or allowed to form
a reasonably sized clump will produce one or more flowers each year.
In habitat it is widely dispersed throughout Florida, Georgia, North
and South Carolina. Leaves 3 - 5 cm wide, 60 - 75 cm in length.
Flower stalk up to 1.5 m tall can be simple or branched.
This species is as popular and as easily obtained
as Y. filamentosa and although classed as a separate species is
thought by some to be a more northern form of Y. filamentosa, widely
dispersed throughout northern Alabama and Eastern Tennessee. Trelease
noted a number of variations between the two above species. It is
now very difficult to find any Y. flaccida or Y. filamentosa with
proven provenance. Trelease (1902) admitted that these two, due
to their long use as garden plants even in 1902 had led to the possibility
of numerous hybrids but that the two were separable. In Y. flaccida
the leaves are broader and recurve more strongly. The flower spike
is downy when in its early stages. The most common form seen is
"Ivory" having cream flowers much paler than any other
and standing out at right angles instead of hanging down.
Occurs as a mainly coastal plant in habitat from
the southern edge of South Carolina through Georgia to the north
west tip of Florida. The plant has been in cultivation since 1896
and several garden forms have been described in which the leaves
vary in length, thickness, colour and also the flowers vary in the
shape of the raceme, being simple or complex. Y. gloriosa will form
a small 'tree' having a stem up to 2 m high with numerous rosettes.
(A recently published book, not available at
the time this article was written, "Agaves, Yuccas, and Related
Plants" by Mary and Gary Irish, claims that Y. gloriosa is
a plant with multiple trunks up to 4.6m tall, thin and pliable leaves
30 to 50cm long with very minute serrations on the edges and an
acute but spineless tip. It is said to be hardy to about -6°C.
This description corresponds with plants commonly grown as indoor
plants all over Europe and invariably labelled Y. elephantipes.
The true Y. elephantipes, according to the Irish' book should be
a similar but much larger plant with leaves around 1m in length
and is very sensitive to frost. Such plants can be commonly found
in cultivation for instance in southern Spain, southern Italy and
California among others. If this is true, the hardy plants commonly
cultivated as and treated in this article under the name Y. gloriosa
would then have to be regarded as forms of Y. recurvifolia or possibly
as hybrids between this and another species. Hopefully, a book currently
under preparation by renowned Yucca expert Fritz Hochstätter
will clarify this problem once it is ready for publication. In the
meantime, please refer to "Agaves, Yuccas and Related Plants"
by Mary and Gary Irish, which can be obtained through the EPS bookstore
at www.palmsociety.org. ed.)
This species is similar to Y. gloriosa except that
the leaves are longer, softer and smoother. They recurve naturally
forming a nicely rounded plant with the outer leaves drooping. Again
there are a number of garden forms which have been developed and
named over the years. The habitat area is more limited than that
of Y. gloriosa, to the coast of central Georgia. I have found from
my own experience that a number of cultivars of gloriosa and recurvifolia
are often misnamed.
Cultivation and garden value
The Yuccas as earlier stated have been available
as garden plants for a considerable time. They were extremely popular
towards the end of the 19th century and on into the early 20th century.
At this time they were put into some botanical order by Trelease
at the Missouri Botanical Garden. Later work has been carried out
by other botanists and though considerable it is not easy to locate.
Much work was done at the turn of the century on hybridisation.
However after a hundred years or so, most hybrids have been lost
Most of the large gardens have examples of Yuccas
as specimen plants, the rarer ones being found in botanical gardens
and I have found it ironic that where a considerable number of plants
are named these are just known as a "Yucca".
Y. gloriosa and Y. recurvifolia are particularly
impressive as specimen plants especially in flower. Y. filamentosa
and Y. flaccida need to be seen flowering in numbers especially
on a good moonlit night!
Soil and position are not demanding provided the
area is well-drained and plenty of sunlight is available. Specimens
can be grown for foliage value by deliberately keeping them in the
Seed is not always readily available and has to
be obtained from specialised sources. Propagation from non-rooted
cuttings is very easy. Remove a suitable cutting, treat with rooting
compound and place in a mixture of compost and mainly sand until
roots are established, then re-pot or place in the garden. If grown
in pots for the patio it must be stressed that they need a large
amount of root space otherwise plants will be "bonsaied."
Plants are available from most plant centres. A relatively large
plant can be expensive but then it may be 15 to 20 years old.
Catalogue of names
can easily be grown from seed or cutting
The following garden forms are listed for interest and although
sometimes found in botanical gardens, I have not yet obtained any
||edges tinged with yellow or white
||median yellow or white band bordered green
||clustered trunks, leaves broader
||leaves falcate and purplish
å Yucca filamentosa
Variegated forms. A number of variegated forms are available and
more seem to be coming on to the market. They vary from being merely
striated to having edges or median lines of yellow or white. Various
names are used e.g. Bright Edge, Golden Sword. I have a number of
these which have been planted out for a few years. Although attractive
none have reached the stature of normal plants. They all appear
to be somewhat less vigorous in size, number of leaves and size
of flower. Leaves up to 45 cm long and flowers not more than 1 metre.
||very large form
||larger plicate leaves
||odes simple flowered form
||more glaucous and large complex flower
||a more recent, pale flowered form
Other names do exist but I have not been able to
Yucca gloriosa and Yucca recurvifolia
I have grouped these two together since I have found that due to
misnamed specimens and earlier hybridising attempts there is considerable
overlapping of the two. I have collected a number of Y. gloriosa
and Y. recurvifolia specimens from various gardens which show the
variations possible. The leaves of Y. gloriosa are much shorter
than Y. recurvifolia and are very plicate. Y. recurvifolia leaves
are at least twice as long and have a smooth surface often serrulate
(finely toothed edges). I cannot give data as to differences in
flower as I have not seen enough in flower. Trelease has suggested
that Y. recurvifolia may be a long established hybrid of Y. gloriosa
and Y. flaccida.
Additionally several hybrids between the preceding
named species were apparently produced between 1874 and 1910 by
Willy Müller, Andre Deleuil and Karl Sprenger. It is possible
that some of these remain in cultivation somewhere. Although many
of their original names and provenance have been lost, a few have
retained their identity and include:
Yucca gloriosa nobilis Leaves very similar
to filamentosa but with spiny tips
Yucca X floribunda data indicates this to be a Y. gloriosa
X Y. filamentosa hybrid
Yucca Emmanuel II Vittorio this is apparently a popular and
well distributed hybrid from 1907 by Sprenger and would appear to
be a hybrid of Y. gloriosa and Y. aloifolia
Uses of Yucca
In Europe, Yuccas generally have been used for ornamental
qualities in the garden. None of the Yuccas have any poisonous or
toxic properties. In fact, most parts of the plants can be used
for making household items or are edible. The Yucca was most important
to the native Americans but their use has declined since colonisation
from Europe. More recently Yucca juice has been used a treatment
for arthritis in horses. Yucca leaves have also been tried on pig
farms to reduce the ammonia content of their urine. Attempts to
grow Yucca on a large scale as a source of fibre have not been very
Propagation and seed availability
Propagation is quite simple involving removal of
a suitable offshoot or semi-rooted cutting. Treatment with hormone
rooting compound helps and a compost comprising at least 50% sand
is suitable. Shoots can be obtained after flowering. The flowers
appear from the centre of each rosette and after flowering that
rosette will not produce further flowers until a shoot from beneath
has grown to a suitable size. Removal of rosettes which have flowered
is possible provided that this will not spoil the appearance of
the plant. This will improve the growth of subsequent rosettes and
the removed stem can have all its leaves reduced to approximately
2" and be potted up. Any shoots from these can then be removed
when they reach a suitable size to produce more plants.
All the Yuccas can be grown easily from seed when
available. Growth in the first few weeks is rapid and small plants
will first produce a mass of roots compared to their size above
soil level. Most of the Yuccas mentioned here will produce flowers
within five years. In the case of the western Yuccas (see list below),
growth is slower and some plants may not flower for a considerable
number of years. I have found that seed is available from the following
Mesa Garden, P.O.Box 72, Belen, New Mexico 87002,
I mention and describe pollination since it is a
specialised procedure carried out by moths which have a symbiotic
relationship with the plants. The female moths collect a quantity
of pollen and place it on the stigma of individual flowers and then
pierce the ovary and lay one or two eggs. The larvae develop with
the seed pod and utilise a small percentage of the eggs. They then
drop off and pupate in the ground until the following year when
fresh flowers and moths appear.
That the plants can be pollinated by hand is evident
from the results of earlier enthusiasts. I myself have produced
seed of Y. filamentosa in two years to date 1993 and 1995 and these
have produced two batches of plants in the garden. One of these
batches has produced a number of flowers in 1998 and the second
should flower in 2000.
Brief description & names of the western
||stemless, alternative for Y. glauca
||stemless. Similar to Y. glauca
||eventually short stemmed. Leaves straight
|baccata var. vespertina
||short stemmed, leaves falcate
||large desert tree
|brevifolia var. jaegeriana
||tree, smaller than above
||stemless, recent discovery
||the supermarket yucca (enough said!)
||short stem, similar to Y. glauca
||small stemless variety
||short stem similar to Y. glauca
||small tree similar to Y. elata
||stemless similar to Y. filamentosa
||short stemmed similar to Y. baccata
||short stem, similar to Y. baccata
||short stem similar to torcellii
||stemless, has 5 subspecies varying in size
|whipplei ssp. parshii
||the smallest up to 30 cm high
|whipplei ssp percursa
||up to 18 inch
|whipplei ssp intermedia
||up to 2 inch
|whipplei ssp caespitosa
||forms a number of offsets
|whipplei ssp whipplei
||up to 3 inch
The following are references which have been published
in Great Britain.
Bean W. J. Trees and shrubs hardy in the
British Isles. pp 761 - 770 inc. Bloomfield, F. (1985) Miracle plants
Jojoba and Yucca (small booklet) Century Hutchinson Ltd.
Bishop, J. (1994) Yuccas in cultivation.
British Cactus & Succ. Journal, Dec 1994 pp. 136 - 143.
Borland, J. Yuccas. Growing from seed. Seed
raising journal of Thompson & Morgan. Vol 4 No. 1 Winter 1989/1990,
pp. 31 - 33.
Bowles, E.A. (1922) Yuccas for English Gardens.
Journal of the RHS Vol 47 pp 105 - 109.
Bussell, J. (1971) Yuccas in Britain. Journal
of the RHS pp 491- 495.
White, A. (1992) Yuccas not Yukkies. Chamaerops
- Journal of the European Palm Society, July 1992 pp 17 - 20.
Anyone wishing to pursue research further could
refer to the following references through the libraries system -
these are the major works available to my knowledge.
Matuda & Lujan, P. (1980) Las plantas
mexicanas del genero Yucca.
McKelvey, S. D. Yuccas of the southwestern
United States Part 1 (1938), Part 2 (1947).
Mitich, L. W. Uses of the genus Yucca. Excelsa
No 7 Dec 1977.
Molon, G. (1914) Le Yucche.
Trelease, W. (1902) The Yucceae. Report of
the Missouri Botanical Garden No 13, pp27 - 133.
Trelease, W. (1907) Additions to the genus
Yucca. Report of the Missouri Botanical Garden No. 18 pp 225 - 230.
In addition the pollination process by Yucca moths
is detailed in:
Riley, C. V. (1892) The Yucca moth and Yucca
pollination. Report of the Missouri Botanical Garden No. 3 pp 99
- 158 + plates.
In Britain, there are two National Collections of
Yuccas available for viewing.
My own which is held at Renishaw Hall, Eckington,
nr. Sheffield, by permission of Sir Reresby and Lady Sitwell is
open to the public with the garden on Friday, Saturday & Sunday
from Easter to September (10 am - 4:30 pm). Viewing by appointment
can be arranged by writing to:
Trevor Key, 15 Newbold Avenue, Newbold, Chesterfield,
S41 7AR, U.K.
The second collection is held by:
Colin Smith, "Spring View", 10, Spring Close, Burwell,
Cambridge, CBS 0HF, U.K., Telephone: (01638) 742993
Open by appointment.
Editor's note: For further details consult the
NCCPG National Plant Collections Directory 2000 or visit their website
(No comments yet. Be the first to add a comment to