Ornithogalium tenuifolium - Cactus Club

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Ornithogalium tenuifolium

Plant of the Month > Species O to P
 
 

by Bruce Brethauer


Ornithogalium tenuifolium
is a plant which I have been growing for about 4 years - I was initially drawn to it because it reminded me of a miniaturized version of the so called "Pregmant Onion" (Ornithogalum caudatum). Both plants have interesting above-ground bulbs, with similar looking "Star of Bethlehem" flowers. Unlike "The Pregnant Onion", the leaves of O. tennuifolium are more linear, typically held more or less upright. Also, while both plants will readily produce multiple offsets, this plant produces its offsets at, or barely below ground level, but the offsets are produced on the outsides of bulb surfaces, and do not rupture through the surface of the bulbs as they do in the "Pregnant Onion". The small size of this plant makes it better suited for smaller spaces - it has a lot of character, and has proven to be an easy plant, tolerating a wide variety of growing conditions, and producing a  reliable display of attractive starry white flowers with greenish midstripes on their petals.

       I acquired a single rooted bulb of this plant from The Glasshouse Works. In its first growing season, it quickly began producing multiple offsets. The largest bulb on my plant approaches about 1.5 inches in diameter, and its foliage grows to no more than about 12 to 14 inches in height (most of the foliage is considerably shorter). As I recall, my plant had a virtually all green appearance when I acquired it, but in time, all of the bulbs on my plant developed a grey/brown envelope of "onion skin".   By my plant's its second year, it completely filled a 6 in pot with its offsets - Had I continually repotted this plant into ever wider pots, I am convinced that this plant would have produced dozens of additional offsets, and would today be filling a 12 in pot. Maintaining a plant in a smaller pot will limit its growth. Flowering usually occurs anywhere from late spring to about mid summer - depending upon how quickly it would break from its winter dormancy - If I recall, there could also be a odd flowering spike produced in later summer or early fall - perhaps this was not so much a second bloom as it was a late flower from a bulb which took a little longer to get started.           

           Tamara Bonnemaison, writing in her University of British Columbia  Botany Photo of the Day article (Sep 9, 2015) said this about this plant:

       Researching this species was difficult, since I was not sure which name to use. Until fairly recently, the flowering herb shown today was known as Ornithogalum tenuifolium. This is the label given on an early 19th century botanical illustration by Pierre-Joseph Redouté, and the name seems to have been valid until the current century. In 2009, John Manning and his colleagues used DNA sequence data to reclassify this species as Albuca virens. This name was quickly contested in 2011 by Martinez-Azorin et al., who found two clades within subfamily Ornithogaloideae (Hyacinthaceae), rather than Manning's three. Martinez-Azorin recognize today's species as Stellarioides tenuifolia, based on morphological features including small flowers on dense and many-flowered inflorescences. These flowers later yield small capsular fruits.

       Stellarioides tenuifolia is a bulbous perennial found from the eastern cape of South Africa to tropical Africa. It has few to (more often) many linear leaves that begin to develop during the flowering stage. The flowers of Stellarioides tenuifolia are white to yellow with a green line along the centres of the tepals. This green line is visible on the flower buds of today's photo. As per the morphological features noted above, the flowers are held on a long-stemmed compact inflorescence, with the eventual capsular fruits bearing 5mm-long seeds.

       One unusual feature of Stellarioides tenuifolia cannot be seen from a photograph. This species has the lowest chromosome number known to-date in the plant world. Monica Ruffini Castiglione and Roberto Cremonini (PDF) explain that chromosome number is one of the most basic factors in reconstructing phylogenetic relationships. The lowest possible chromosome number is 1 (n=1, or 2n=2 if diploid), which occurs in only a couple species (e.g., male ants of Myrmecia pilosula). By contrast, the fern species Ophioglossum reticulatum has the highest number of chromosomes currently known at 2n=1440. Stellarioides tenuifolia is one of only six plant species known to have the second-lowest possible chromosome number, 2n=4. Castiglione and Cremonini explain that current theory posits that evolution favours ever-larger chromosome numbers, meaning that species with extremely low chromosome counts are "relicts conserving the karyotype of ancestral eukaryotes".
       View the entry with full-sized photographs: Stellarioides tenuifolia.


    Propagation of additional plants is easy: probably the most reliable method is to divide plants or to transplant individual offsets. But I have found that it is even easier to allow the seeds which invariably follow flowering, to ripen and to fall amongst the pots of other plants in my collection. Invariably, some of the seeds will germinate, and the seedlings can be separated out and potted up to establish another plant. The seedlings look just like the seedlings of onions or chives, and will quickly establish themselves: while I imagine that it may be possible to grow these to flowering size within a year, 2 years may be more typical. Curiously, the seeds which I collected and planted showed very low germination rates - so I simply allow my plants to drop seed where they may, and transplant the seedlings the following year.

    While I have no specific information on toxicity in this plant - many of its cousins are regarded as toxic - so to be safe, I would assume that this plant is probably toxic - so it may not be suitable for all households. This is nevertheless an interesting and attractive species, easy to grow and flower, and is of a size that makes it more suited to smaller spaces than its cousin, the "Pregnant Onion". In spite of its ease of culture, and propagation, this plant remains uncommon in cultivation; I have never seen it at any of the "Big Box" nurseries. It can still be purchased through The Glasshouse Works, and I imagine that it can also be located at sales of local cactus and succulent societies. If you are looking for a trouble free plant which is virtually indestructible - this is a good candidate.

 
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