Diferrence between evergreen perennials and deciduous perennials

Hello,

This has been unclear to me for some time now: Can someone please help me understand the difference between evergreen perennials and deciduous perennials?

Here are my 3 questions:

1) I thought all perennials would be considered "deciduous" since perennials die back (essentially disappear underground) during dormant seasons (fall and/or winter)....is that a correct statement?

2) Would sub-shrubs such as lavender be considered evergreen perennials? If so, why? What do sub-shrubs (such as russian sage, lavender, thyme etc.) look like in the dormant seasons in the Pacific Northwest?

3) What is the definition of an evergreen perennial and how does it compare to the definition of a deciduous perennial? And what about semi-evergreen perennials? And how do these definitions relate to the definition of a sub-shrub?

Thank you.

 

Part of the confusion perhaps stems from ambiguity about the word "perennial" -- do you mean it in the gardening sense (which often refers to herbaceous or woody at the base plants) or in the scientific sense (in which case, anything with a life cycle at a mature stage beyond a couple years is a perennial, including trees)?

 

Thanks for the reply. I guess I am approaching this from a gardening sense, since what prompted this post was a garden design problem where I want to add perennials (for colour and seasonal interest) but do not want perennial areas to be bare patches during fall and winter.

 

There are evergreen herbaceous perennials, which have leaves above ground all year round. A good example is Helleborus.

 

So does any plant that is considered an "evergreen perennial" mean that it has leaves above ground all year?

 

That is how I would define it, yes.

 

Because, as mentioned above in gardening perennial refers to non-woody perennial plants.

Trees
Shrubs
Vines
Perennials
Annuals
Bulbs

So if you look for evergreen perennials on web pages and in print references aimed at gardeners and gardening that term should get you what you want most of the time. Ambiguous types may be referred to as sub-shrubs.

Commercial sites may perhaps be more prone to listing and describing low shrubs like lavender in the same sections as those talking about herbaceous perennials.