By Caroledawe
United Kingdom 
I bought a yucca elephantipes 5 years ago and planted it outside in a sunny , wind proof place in the ground - not a pot. It has gone from 6 feet to now being 18 feet and is gorgeous. However lots of brown fronds are coming off ( usual but only about 50 at a time normally) and the place where they were on the trunks is squishy and black. Has it died? The top leaves are still green. Can I cut some the branches off where they are mushy?
27 Mar, 2011
Answers
Um, are you sure its Yucca elephantipes and not Cordyline australis? It's just that this particular variety of Yucca is not hardy outside in Britain, and is grown as a houseplant. Google to check if you're not sure.
28 Mar, 2011
Bamboo, I, too, was surprised at the possibility of that tropical species surviving any winter outside in the UK!
Here's a quick check:
Leaves~ Yucca has leaves 4+ cm wide, with a thin, crescent-shaped cross-section, while Cordyline leaves are rarely more than 3 cm wide, with a prominent midrib.
Stems~ Just below the crown of leaves, the Yucca's stems are usually 4-7 cm thick, while the Cordyline's stem runs 10-13 cm, except when very young, or grown in much shade.
30 Mar, 2011
It has probably been frost damaged at the mushy spots. I would cut the stems off just below the mushy parts, even if the leaves are still green above. If the stem cortex is damaged enough, the top will probably die off later anyway. On the other hand, a Yucca is usually much more enthusiastic about stump sprouting than a Cordyline!
28 Mar, 2011