BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Geranium maculatum | Wild Geranium 



GENERAL BOTANICAL CHARACTERISTICS : 
Wild geranium is perennial herb 8 to 24 inches (20-60 cm) tall [29].  It
grows from a stout, branched, underground rhizome that spreads
horizontally up to 6 inches (15 cm).  The rhizome bears 10 to 30
sparsely branched roots from the sides and undersurface.
Vesicular-arbuscular mycorrhizal structures are present, increasing with
decreasing fertility of the soil [7,27,29,32].  A small proportion (4
percent) of populations are male-sterile; these female plants produce an
average of 60 percent more seed than hermaphroditic plants [1].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte
   Geophyte


REGENERATION PROCESSES : 
Wild geranium perennates from a stout rhizome with blunt white tips that
hold the following year's bud [27,32].  Fragmentation of the rhizome
results in new individuals [28].  Natural stands are mosaics of clones
that appear to have enlarged from old, individual plants and persist by
vegetative means only [27].  Wild geranium is long-lived and has a low
mortality rate [1].  When crowded, the roots may rise above the soil
surface, exposing the buds to freezing [32].  Martin [27] noted that the
rhizomes are found at the soil surface (A1 horizon) under closed
canopies but in open communities are as deep as 3 to 4 inches (7-9 cm)
below the surface.

Young plants usually bloom for the first time in their second or third
year but will flower the first year following germination in the
greenhouse [27,32].  Production of flower buds, which will expand the
following year, takes place when sufficient nutrients are stored
[12,27].  Under closed canopies, only 18.8 percent of the plants flower,
as opposed to 97 percent in full sunlight [27].  Wild geranium is
self-compatible but depends on pollinators for seed set.  The most
common pollinators are bees (honeybees, bumblebees) and syrphid flies.
Other visitors to the flowers include beetles and ants [1,27,28,37].
Seeds are produced in a dehiscent fruit and are scattered by explosive
dispersal an average of 10 feet (3 m) and a maximum of 30 feet (9 m).
There is no obvious secondary dispersal vector (i.e. not carried by
rainwash or animals) [27,32,33].

Schiffman [31] reported wild geranium seeds in the seed bank of a
chestnut oak (Quercus prinus)/scarlet oak (Q. coccinea) forest.  The
seed coat is only slightly permeable, and the seed requires
stratification before germination will take place.  The longer the cold
treatment, the higher the germination rate [27].  The seeds can have a
dormancy period in excess of 400 days.  In a study of savanna
restoration, Bronny [8] reported that wild geranium reappeared when
cattle grazing was prevented on an oak savanna site, indicating either
its presence in the seed bank or the persistence of rhizomes in the
soil.


SITE CHARACTERISTICS : 
Wild geranium is found in woods, coves, thickets, and meadows [15,29].
It appears to prefer more mesic sites such as those found on mid to
lower slopes with northern and eastern aspects; preferred soils are clay
loam to sandy clay loams and sandy loams [9,20,21,23,27], of average to
above-average fertility, and from slightly alkaline or neutral to
slightly acidic [7,27,32].  In a study of plant distribution and soil
acidity, Wherry [36] found wild geranium in abundance on a rich
bottomland site on Long Island with soil pH of 6.5.  Fifty years later,
on the same site, Greller and others [18] found that the soil pH had
declined to 4.08, and wild geranium had become a very minor component of
the community.

Wild geranium is abundant in dense patches in natural openings
throughout mesic woodlands [27,37].  It is found on sites protected from
strong winds, in open shade on hillsides, and on shaded roadsides [32].
Cull [11], working on a project to establish native plants on old
highway verges in Illinois, found it already present on the site.

In a study relating understory herb distribution to overstory trees,
Crozier and others [10] reported that the highest positive association
of wild geranium is with white oak when compared with its other common
associates:  beech (Fagus grandifolia), yellow-poplar, red maple (Acer
rubrum), sweet birch (Betula lenta), black cherry (Prunus serotina), and
northern red oak.  This association may be a result of higher calcium in
the soils under white oaks, due to runoff down the trunk of the tree.

Tree associates in addition to the above named include shagbark hickory
(Carya ovata), white ash (Fraxinus americana), eastern hophornbeam
(Ostrya virginiana), sugar maple (Acer saccharum), and American elm
(Ulmus americana) [4,9,19,20,24].

Common understory associates include Solomon's seal (Polygonatum
pubescens), false Solomon's seal (Smilacina racemosa), snow trillium
(Trillium grandiflorum), Anemonella thalictroides, common mayapple
(Podophyllum peltatus), sedge (Carex spp.), and bellwort (Uvularia
grandiflora) [9,10,12,34].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Wild geranium is moderately shade tolerant.  It is found on disturbed
sites, but populations of wild geranium are best established in open,
undisturbed forest [27].  In a study of secondary succession on the New
Jersey Piedmont, Bard [4] found populations of wild geranium on
undisturbed sites and did not find it in abandoned fields at any stage
of succession.  This may indicate that its presence in seed banks is
short-lived and/or that wild geranium is not an effective colonizer.


SEASONAL DEVELOPMENT : 
The basal leaves of wild geranium emerge in early spring (around the
period of vernal canopy closure) over a period of 4 to 6 weeks,
attaining 50 percent of total growth between late April and the first
week of May [7].  The stems elongate in April, and blooms appear from
April to June, setting fruit 3 to 5 weeks later [27,29,32].  Flower buds
are formed in the year previous to flowering and are enclosed in the
winter bud.  Cauline leaves senesce around October, turning red and
yellow, and are lost shortly therafter.  The basal leaves die down in
October and November in the midwestern states, later in the southern
states [27].

Related categories for Species: Geranium maculatum | Wild Geranium