Another "not really a bulb", but a geophyte

Joe Shaw
Sat, 02 Sep 2006 18:32:02 PDT

Hi Gang,

Many Eucalyptus species, and some related plants, make a lignotuber.  I'm 
not sure what a lignotuber is anatomically, but I think it is some sort of 
stem-perhaps like a potato storage organ.

Lignoubers allow Eucalyptus species (and Corymbia species, which used to be 
classified as Eucalyptus) to regrow after fire or other damage.  The 
lignotuber is a tough storage organ, and because it is underground can allow 
some species to survive 1 or 2 zones of colder temperatures than they might 
prefer.  I've had good luck with Eucalyptus citriodora (Corymbia 
citriodora), the lemon scented plant.  In the wild the tree can reach 60-100 
ft-tall.  In my garden growth is more modest.

However, the benefit of a lignotuber is that (at least some) eucalypts can 
behave as dieback perennials in areas that are much too cold to allow tall 
tree growth.

Many mallees, some trees, and some odds-and-ends species will perform well 
in climates that are too cold to allow a "real" tree or shrub to develop. 
The plants freeze back each winter and sprout stems that can reach 6-8 
feet-tall each growing season.  The benefit is especially nice with plants 
that make beautiful foliage or which have strong and acceptable scents.  I 
do enjoy E. citriodora, a sprig can perfume a room with a pleasant lemony 

One other Eucalyptus that I grow is E. viridis.  This plant does well here 
and, so far, has not suffered from root diseases that plague other eucalypts 
I have tried to grow.  E. viridis is a modest appearing plant, but has 
wonderfully fragrant leaves that provide oils that are used in soaps and 
cough drops, etc.

The main thing is that, for me, I treat these plants as bulbous-growing 
things.  If/when temperatures threaten to go very low, I mulch the plants 
heavily, and let to tops freeze.  In the spring, with warmth and some water 
(warmth is key), the plants return and make a garden into a better place, 
pleasing the nose as well as the eye.

NOTE:  I've tried various eucalypts here in the greater Houston, TX area. 
Many survive the climate and thrive for 2-3 years only to succumb to root 
diseases.  I've had some luck growing the plants from seeds in sterile soils 
(microwave baked) and letting them get large before planting out-then I give 
them the best drainage I possibly can.


1.  Eucalyptus citriodora

2.  E. viridis

I hope to try more mallee types in the future (shrubby or with many stems 
from the base, not trees but 10-30 ft-tall).

LINK:  Australia Plants, source of many seeds and some seedlings

NOTE:  Eucalypts can grow 4-8 feet in a year, even from seed.

LINK:  The Hardy Euclalyptus Page

LINK:  Eucalyptus camaldulensis, a lignotuber seems optional in this species

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