Coaxing flowers from a yucca

Credit: iStock / Rosen Dukov

Q: About seven years ago, I dug up a dozen baby yucca (Adam’s needle) plants from a friend’s overgrown plant and planted them in my garden. They are planted in full sun, in a very hot part of my yard near my paved driveway, in poor soil.

Each year, they re-emerge and are only slightly bigger than the year before. After seven years, the largest is still only about 18″ wide x 18″ tall. My question is: I have never seen any sign of a flower. What can I do?

I did read that they should not be fertilized, but I am tempted to give them a blooming fertilizer, like a 10-60-10 in the spring.

Is it possible that they are all male plants or female plants and they need the other to self-pollinate?

I am in zone 4b. —Lynn

I think the issue with your yucca may be the zone in which you live. I’m also not clear whether your friend, from whom you got the “babies,” lives in your same zone (4b).

Nevertheless, I suspect you may have either one of two species. Yucca filamentosa (Adam’s needle) has erect leaves with peeling filaments on their margins. It matures at about 30 inches high but makes “babies” to form a clump about 5 feet wide. The other likely candidate is Y. flaccida (soft yucca), which gets to about the same size and has arching leaves. Both of these are hardy to zone 5.

One of the most common yuccas in lower mainland gardens is Y. recurvifolia, which is hardy to zone 7. All of three yucca species are native to the eastern United States, but the zone-5 species grow in more northern states, which accounts for their extra hardiness.

Normally, yuccas are completely evergreen and do not die back in winter. Your plant is dying back due to the cold and then has to start all over again each spring. The only solution I can suggest is to grow it in a large pot and bring it into a sun-porch or cool greenhouse (down to about – 7 degrees C at the coldest) for the winter. This is the approach taken with yuccas that are hardy to zone 9 when they are grown in the lower mainland. Since it is evergreen, it will need light, so a dark garage won’t work.

Fertilizer wouldn’t do any harm to the plant’s overall vigour, but I suspect that it’s the cold that’s the real culprit.