Question
Spike-Dracena.  I live in New Brunswick Canada, Zone 3.  This will be my 5th year with them and they reach from my knees (height of pot) to my nose.  They are outdoors in summer and stored in garage attached to house,  for the rest of year without watering.  This year, they look dried and one looks lifeless.  DO THEY ONLY LIVE A FEW YEARS OR DID THEY GET TOO COLD?

Answer
Dracaena indivisa (aka Cordyline indivisa) -- commonly called the "Spike Plant" or "Spike Dracaena" -- is barely frost hardy.  I can only surmise that in your heated garage, temperatures did not plunge anywhere near the nighttime chill that you must have in Canada.

This website, gardening.eu, states that D./C. indivisa will tolerate temps "a few degrees below zero."  But bear in mind, though, that this is Celsius zero they are referring to.  Fahrenheit zero is 32 degrees and then some BELOW that "zero" on their website.

The misunderstanding of hardiness is furthered by the fact that these are native to high altitudes of mountainous regions and do not thrive in blistering summer heat.  That they grow so happily in the cooler climes is misinterpreted, by some gardeners, to mean they rank with witchhazel and tundra in their accommodation of winter weather.

These commonly live to be at least 10 years old, if cared for.  I do not think they should bite the dust at age 5.

However, keeping a dormant plant is a very tricky transaction.  It could be the temperature, or it could be complete dessication (these need just the slightest moisture even when "dormant" similar to Dahlias; spray bottles are good tools for this), or they might even just still be dormant.  Give them some time to make sure before you give up on them.

Keep me posted.

L.I.G.