geophytic and non-geophytic bulbs; was: RE: [pbs] Beschorneria/Serapias

Jim McKenney
Mon, 20 Jun 2005 10:09:10 PDT
Alberto's response seems to imply that bulbs and geophytes are the same
thing. Even allowing for the use of the word "bulb" in a very inclusive
sense to include corms and other similar structures, I still think it is a
mistake to equate bulbs and geophytes. 

In an earlier post I teased Alberto for his use of bulboid as a noun. Now
I'm going to present the case against the use of the word geophyte as a
noun. We would save ourselves a lot of potential confusion by using it as an
adjective - geophytic. 

I agree with Alberto that Beschorneria, Beaucarnea, Doryanthes or Yucca are
not geophytes. Nor are tree peonies or any other plant which keeps living
parts above ground all year around. The "geo" in geophyte, after all, refers
to the ground, and most would agree that geophytes are those plants which
persist from season to season by retreating under ground for at least a part
of their life cycle. 

I don't know the origin of the word "geophyte" - I don't know who coined
this word or what precisely that person had in mind. But given the ambiguity
associated with the words bulb, corm, tuber et al., it's not surprising that
someone would try to introduce such a seemingly all-inclusive concept. 

But there is a hidden problem here: most gardeners are not all-inclusive. We
gardeners tend to specialize: most of us on this list, for instance, are
probably comfortable being described as "bulb growers". And the bulbs we
have in mind are the traditional bulbs, plants which are members primarily
of the Liliaceae, Amaryllidaceae and Iridaceae (I'm using those words in
their old, broadly inclusive senses). Because the plants in those three
families are all related and built on somewhat similar lines, the bulbs
(again in the broad sense) which occur in those groups have many
similarities. And from those similarities has emerged the typical gardener's
sense of the word "bulb". 

I can still remember when, as a young gardener, I read that many of the
Oxalis I grew had bulbs: I fought that concept because Oxalis are not
related to traditional bulbous plants. It wasn't until I began to understand
what a bulb is morphologically that I was finally at ease with this.  

Sometimes two plants which are in a general way very similar in structure
fall on different sides of the geophyte/non-geophyte divide. For instance,
in a recent post I referred to the similarities between lily bulbs and
plants of Sempervivum or Echeveria. To my way of thinking, the salient
characteristic of bulbs is that the primary storage tissue is leaf tissue.
The scales of a lily bulb are modified leaves. Morphologically, a lily bulb
and a Sempervivum are very similar. We call the lily bulb a bulb because it
is underground and functions to keep the plant going when the transient
above-ground parts of the plant are not functioning. Most people don't call
the Sempervivum a bulb because it remains above ground under normal
circumstances and the storage leaves function as true leaves all year

If you view "bulb" as a morphological concept, then lily bulbs and
Sempervivum plants are "bulbs".  If you define "bulb" in terms of function,
then you come to a different conclusion. And of course there is nothing to
prevent you from combining the morphological and functional approaches. 

All of this raises some interesting problems. For instance, Florence fennel
is often described as a bulb because the primary storage tissue in that
plant is leaf (petiole) tissue. For purposes of discussion, let's accept
that it is a bulb. But is it a geophyte? I would say no because the bulb in
this case is not underground. It's a bulb which grows on the surface of the
ground, not a geophyte. For the same reason, although I consider such things
as Ledebouria socialis and epiphytic Hippeastrum to be bulbs, I don't think
of them as geophytes. Why? Because their bulbs are not typically under

This will drive some people crazy, because their common sense says if one of
two closely related genera is a bulbous geophyte and the other genus looks
like it, then it too must be a geophyte. But I say NO. 

In other words, the term geophyte does not describe morphology, it describes

Is a geophyte any plant which retreats below ground during some part of its
life cycle? I think it would be hard to define it otherwise without running
into lots of complications. For instance, the genus Iris provides plants
which grow from true bulbs, from true corms, from stolons, from rhizomes -
given the size of this genus, there may well be other arrangements of which
I am not aware. Many of these are pictured on the wiki and I have not heard
any vigorous complaints about this on this list. 

But suppose someone wanted to add pictures of a typical herbaceous
perennial. I'll bet there would be howls of protest. Are typical herbaceous
perennials geophytes? Why not? Many would say they are not because they do
not die back to a discrete storage structure without functioning roots
during their dormant period (i.e. they do not die back to a "bulb").

There are members of the genera Delphiniuim and Gentiana which qualify as
geophytes even in the stricter senses, yet most of us would balk at
including the general run of delphiniums and gentians - certainly as bulbous
plants and probably as geophytes, too.

But wait a minute: lilies undoubtedly have bulbs, and they do die back to
what is without doubt a bulb during their dormant period, but that bulb
keeps living, functioning roots during the dormant period. How is that any
different from the situation which prevails with most herbaceous perennials?
There may not be a bulb in those plants, but there is a crown or something
which protects the buds for next season's growth. 

This word "geophyte" seems to be acquiring a sort of taxonomic meaning, as
if it referred to a group of related plants. I think that is the source of
the discomfort some people feel when someone wants to discuss a "bulb" which
is not a member of the plant families traditionally associated with the
concept "bulb". Used as a noun, "geophyte" or the even more deceptive
"geophytes", seems to assert the existence of a taxon. I say get rid of
"geophyte" and use instead the unambiguous adjectival form geophytic. That
way, if your bulbs of Ledebouria are buried deep in the pot, you can
accurately and unambiguously describe your Ledebouria as geophytic. And if
your neighbor's Ledebouria is a cluster of bulbs on the surface of the soil,
the neighbor can say that that plant is something else (epichthonic?)  

But let's not make such all-inclusive statements as "Ledebouria is a

Jim McKenney
Montgomery County, Maryland, USA, USDA zone 7, where the very few bulbs
which are part of the indigenous flora all seem to be geophytic. 

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