What used to be called Yucca whipplei is a popular landscape plant in Melbourne's Royal Botanic Gardens. The pin-cushion clumps are ultra-neat and pastel-grey in colour. They fit nicely into our Californian Garden because that's where they hail from (south-western North America), and in our Guilfoyle's Volcano collection (pictured here) due to their succulence and tolerance of dry conditions.
Also called Our Lord's Candle, this yucca is now in a separate, less memorably named, genus, Hesperoyucca. There are two species, one named after Mr Amiel Whipple, the other after Mr John Newberry. Ours is therefore now Hesperoyucca whipplei.
The 'hespero' part of the genus name presumably refers to their western distribution in North America, and they differ from the rest of the yucca cohort in subtle details of their flowers and fruits. The leaves clasping the flower (bracts) are usually bent backwards and the receptive part of the female structure (the stigma) is 'head-shaped' rather than with three lobes (each sometimes split in two) as in Yucca. (The stalk supporting the flowers and fruits is also wider in Hesperoyucca than in Yucca.)
None of ours are in flower at the moment so here is what they don't look like! These are images I took of a Yucca (not Hesperoyucca) flowering in a street near my home. Note too the very cool anthers, looking like pipe cleaners tipped with a blob of gold paint (the pollen).
I got excited a few weeks ago when a succulent which seemed to be labelled as Hesperoyucca started to flower in the California Bed. It produced a massive flowering stalk, much bigger than I was expecting. And that because it was an agave (same family but quite different). The Hersperoyucca whipplei had died recently, so the sign seemed to the untrained eye (sigh) to refer to the next door agave. Clearly a lapse in my botanical logic given the agave had whopping great thick leaves and the flower-buds were, not surprisingly, starting to look more like an agave than a yucca...
So you don't get any pictures of the Hesperoyucca flowers I'm afraid. Or any discussion about what, if any, variant of Hersperoyucca whipplei we might be growing. Sometimes Hesperoyucca whipplei is split up further into subspecies or varieties based on the way they produce 'offsets' (the plants that bud off at the base, surviving the death of the main clump after flowering) and the size of clump and flower spike.
I'm not sure where to go with the common name Our Lord's Candle. I'm tempted to say I won't touch it. Instead let me tell you it refers to the candle-like flowering structure, with hundreds of white typical-yucca-like flowers.
The flower-less plant is pretty enough, but do take care. Each leaf is terminated by a sharp pungent point. The finely toothed margins (which you can almost make out in this next photograph if you squint a little) you needn't worry about. At most they gently massage your finger-tips.
Each cushion takes about five or more years to flower, then like the agave (in the same family and subfamily) it dies, with off-shoots from the base taking over to run through the same cycle again. In its native California a moth pollinates the flowers at night, contributing a small moth egg as well as pollen to the receptive flower. This egg grows into a larva that will eat some, but not all, of the seed.
Here in Melbourne, without the moth, we may not have any problem with caterpillars eating our seed, but then we may also not get any seed. Which, according to this sign, means ropes, nets, baskets and soap, but no flour.
Postscript: I can't resist adding this picture taken today, 12 November 2015, of the plant in full flowering splendor...