Why won’t my yucca bloom? I get that question all the time from frustrated gardeners wondering what they did wrong, because their yuccas have beautiful leaves and seem to be thriving, but either don’t bloom or don’t bloom very often. Why?
Some Yuccas May Never Bloom
First of all, there are some 60 species of Yucca, some of them very reluctant bloomers.
This is especially the case of the shrub yuccas and tree yuccas (think of the Joshua tree as an example). Even in the wild, they need to reach maturity before they bloom and that can take 50 years or more! In gardens, these yuccas may be even less likely to bloom than in their native territory, as, unless you live in Mexico or the southwestern US, your garden conditions rarely match their natural ones. Especially, gardeners tend to try growing these treelike species in zones where they are barely hardy, thus decreasing even further their chance of blooming.
Things are even worse when you consider yuccas grown as houseplants, like spineless yucca (Yucca elephantipes). They simply aren’t getting enough light to ever bloom.
You should grow all tree and shrub yuccas, plus houseplant versions, for their foliage and form only. Flowering is unlikely.
Yuccas That Will Bloom
For most temperate climate gardeners, the two species most likely to bloom and also the two that are the most widely available are common yucca or Adam’s needle (Y. filamentosa) and weak-leaf yucca (Y. flaccida). The latter is considered by many authorities to be a subspecies of common yucca (think of it as a Y. filamentosa with floppier leaves) and from here on in this text, I’ll therefore use the name “common yucca” for both.
The common yucca is indeed the yucca you’re most likely to see in gardens, at least, in gardens outside of the arid Southwest US. It has fairly broad, spearlike leaves with characteristic curly white filaments along the edges (that is why it is called Y. filamentosa).
Although most gardeners consider common yucca to be a perennial, it is in fact a shrub with short, partly underground woody stems, but they are well hidden by foliage, so the plant looks like a perennial. And behaves much like one too, slowly spreading from offsets rather than growing in height.
Its branching flower spike is impressive: it can reach 4 to 8 feet (1.2 to 2.5 m) in height, even 12 feet (3.5 m) in warmer climates, and is covered in ivory white bell-shaped flowers. They droop during the day, but rise up again at night when they give off an enchanting scent. Seeds are not produced in many areas, because only one type of insect, the yucca moth, can ensure pollination and it isn’t present everywhere. After flowering, therefore, most people cut the flower stalk off. If left intact, it will sometimes remain it place for 2 or 3 years.
Common yucca is hardy to USDA zone 5 (AgCan zone 6), but is often grown in colder climates, to USDA zone 3 (AgCan zone 4) where it suffers various degrees of winter damage. Sometimes people tie the outer leaves together over the central bud of the plant over the winter to protect it from the cold. In the spring, there is often a lot of cleaning up to do, removing leaves that died over the winter, but as long as the center of the rosette is still green, the plant will recover.
Each Rosette Only Blooms Once
What must be understood about yuccas is that each rosette flowers only once, and then slowly dies. (Don’t worry, the plant will produce one or more other rosettes long before the first is gone.) Plus, it can take years to reach its flowering size.
Common yucca is a fairly fast grower for the genus and produces offsets quite rapidly. Under very favorable conditions (when the plant grows in full sun in well drained soil), its main rosette can bloom in as little as 2 or 3 years. When conditions are less favorable – when the plant grows in shade or partial shade, for example, or in moister soil – it can take 5 or 6 years to bloom, sometimes even more. If you add to this the fact that the rosette may be damaged by the cold, causing the flower bud to abort, you will understand that flowering can be considerably delayed.
Most common yuccas you buy are fairly mature and should bloom the second or third year after you plant them, maybe even the first year if you picked one with signs of a flower stalk starting to appear. But after that, no flowers will normally appear the following year or the year after that, as the secondary rosettes are still too immature. But as the plant grows, it will produce more and more rosettes (and will take up more and more space in the garden). So, over time, when there are many rosettes of different ages, flowering will start to be more frequent. Often large specimens 10 to 15 years old are able to bloom every year, even producing more than one spike at a time if several rosettes mature the same season.
Patience, Patience, Patience
If you want to see yucca in your garden the first year, buy a new plant that is already budding up. Then buy a new one every year, but leave the older plants in place. As they mature, they’ll flower again, plus they’ll produce more and more rosettes, eventually resulting in plants that do bloom annually. But your hair may well turn gray before that happens!
The Hardiest Yucca
Living as I do on the northernmost edge of where you can garden, I’m always looking for hardier-than-average plants. That would be the soapweed yucca (Yucca glauca), so called because soap can be made from its roots. It can take my USDA zone 3 (AgCan zone 4) climate with no damage.
You can guess it will be hardier than common yucca by looking at the natural distribution of the two species. Common yucca is native to the southeastern US, from Florida and Louisiana to Virginia, so growing it in most temperate gardens means pushing it beyond its normal limits, but soapweed yucca is from the Great Plains and lower Rockies, from Texas and New Mexico right up into Alberta and Saskatchewan, where winters are bitterly cold. As a result it will grow in USDA zone 2 (AgCan zone 3), even on windy, snowless sites… although it certainly doesn’t mind a covering of snow. Its leaves are tough and stiff, much narrower than those of the common yucca, with tips as sharp as a bayonet. Watch your eyes!
Unfortunately, its bloom is even scarcer than that of the common yucca: it can take 10 years to flower for the first time! I suggest growing it for its original appearance (it looks rather like a round green hedgehog) and its ease of cultivation (no winter protection is necessary), not its flowers. Then when it does bloom, and it will, you can just count the flowers as icing on the cake.