BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Baccharis halimifolia | Groundsel-Tree 



GENERAL BOTANICAL CHARACTERISTICS : 
Groundsel-tree is a much-branched, common shrub that seldom exceeds 16
feet (5 m) in height or 6 inches (16 cm) d.b.h. [5,6].  Its leaves are
toothed, alternate, deciduous, and borne on green twigs [6].
Groundsel-tree leaves secrete a sticky resin, thought to deter herbivory
by all but the most specialized insects [15].

The unisexual, yellow flowers are borne on heads surrounded by bracts.
The fruit is a small achene tipped with straight bristles.
Groundsel-trees are dioecious and display some sexual dimorphism,
although positive sexual classification of the plant requires flower
examination.  Male plants generally have longer shoots, more tender
leaves, grow faster, and flower and senesce earlier than female plants
[15].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Seedling establishment is the primary method of groundsel-tree
regeneration.  Its flowers are wind pollinate, and its seeds are wind
dispersed [15,22].  DeLoach and others [4] reported that groundsel-trees
will resprout if clipped above the ground, although descriptions of
vegetative reproduction are lacking.  Seedlings require 2 years of
growth after germination before reproduction can occur [21].


SITE CHARACTERISTICS : 
Detailed descriptions of groundsel-tree site requirements are lacking.
General descriptions indicate that groundsel-tree grows in moist sites
on soils with a high organic content including pond and bay margins,
swamps, wet prairies, marshes, raised portions of salt marshes, and
everglades hammocks [2,6,8,27].  It also grows on anthropogenic sites,
such as fencerows and abandoned fields [5,15].  Descriptions of
groundsel-tree as an early invader of interdune swales [2,6] suggest
that organic content is less important than high moisture content for
groundsel-tree establishment.  Growth in salt marshes and brackish
southeastern Louisiana swamps indicate a high salt tolerance [6,17,24].


SUCCESSIONAL STATUS : 
Groundsel-tree is an early successional, woody invader of disturbed
lowlands throughout its range [27].  It replaces sawgrass (Cladium
spp.), freshwater marsh, and marl, wet prairie communities following
drainage in southern Florida [27,29].  It is characteristic of cut-over
and partially drained, deep-water swamps in southeastern Louisiana [23].
Overgrazing and drainage favor groundsel-tree invasion and convert salt
marshes into shrublands [9].

Despite its early-seral nature, groundsel-tree is shade tolerant.  It
persists under a pine canopy and may reach carrying capacity in as
little as 4 years.  Self-thinning, graminoid competition, and heavy
litter reduce seedling establishment and maintain a stable stem density.
Disturbance and the creation of overstory gaps stimulate seed
production.  Shade tolerance allows groundsel-tree to maintain a pool of
seedlings in the understory until disturbance provides an opportunity
for release and continued regeneration [19].


SEASONAL DEVELOPMENT : 
Groundsel-trees flower from August to October, and their fruit ripen
from October to November [3,6,24].  A population near Gainesville,
Florida, had the following phenological sequence [22]:

Phenological event              Time
flower bud appearance           late Sept. - Oct.
flowers bloom                   late Oct. - early Nov.
fruit ripens                    mid Nov.
leaves drop                     mid Dec. - late Feb.
dormancy                        late Nov. - Jan.

Related categories for Species: Baccharis halimifolia | Groundsel-Tree