2. 2
Abstract
Dalmatian toadflax is an escaped herbaceous perennial, with an extensive
creeping root system and bright yellow and orange flowers.
Dalmatian toadflax’s flowers make it distinguishable from other invasive
weeds as its showy flowers are grouped towards the end of their stems and
possess a spur resembling a snapdragon flower.
Two forms of Dalmatian toadflax are found in the United States:
Narrowleaf and Broadleaf Dalmatian toadflax, with both forms able to
hybridize.
3. 3
Abstract
Dalmatian toadflax was originally native to the Mediterranean region of
the world; and was first reported being grown as an ornamental in North
America in the late 1800s.
Since its initial escape, Dalmatian toadflax has spread throughout the
North America, with the worst infestations occurring in the western United
States and Canada.
Dalmatian toadflax reproduces by seed and by underground rootstalks.
Dalmatian toadflax is considered a pest as it can significantly reduce crop
yields, desirable livestock forage, and out-compete native and sensitive
plant communities.
4. 4
Taxonomic Classification
Family
Dalmatian toadflax is a member of Scrophulariaceae, the Snapdragon or
Figwort family. The Snapdragon or Figwort family is a group of 220
genera containing about 3,000 species of herbs, shrubs, and small trees.
Species in the figwort family include Penstemen, Monkeyflower,
Mimulus, Snapdragon, and foxglove.
Some figworts, such as Monkeyflower, are edible. The drug digitalis,
used for heart ailments, comes from a kind of foxglove. Yellow toadflax
was used as a source for fabric dye. Scrophularia, from which the family
name comes from, is a medicinal figwort. People at one time believed that
Scrophularia could cure Tuberculosis.
5. 5
Taxonomic Classification
Genus
Linaria, a generic name derived from the Latin linon or linum meaning
flax. There are about 130 species in the genus Linaria, most being native to
Eurasia.
Species
Linaria genistifolia (L.) P. Miller ssp. dalmatica (L.) Maire &
Petitmengin. Although two varieties are found in North America, Broadleaf
toadflax has a wider distribution.
Common Names
Common other names for Dalmatian toadflax are Broadleaf toadflax and
Wild Snapdragon.
6. 6
Description
Dalmatian toadflax is an aggressive, highly competitive noxious
weed that was introduced into North America as an ornamental, but
was also used for fabric dyes, and folk remedies.
It soon escaped from host gardens invading farmland, pastures, and
rangeland across North America, disrupting native plant communities,
livestock forage, and wildlife habitat.
Dalmatian toadflax continues to be sold commercially as an
ornamental plant, and is recommended for xeric landscape planting.
However, Dalmatian toadflax can thrive in a wide range of habitats
and climates and is difficult to eradicate.
7. 7
Description
A mature Dalmatian toadflax plant
can contain many vertical floral
stems reaching up to four feet in
height. These stems, which are
robust and woody at the base, are
composed of thick- walled, fibrous
xylem.
8. 8
Description
The flowers of Dalmatian toadflax,
which reside towards the apical end
of each stem, near the base of the
leaves, are bright yellow with
orange throats each possessing a
spur, resembling a snapdragon.
9. 9
Description
Leaves of Dalmatian toadflax are
light green in color, heart-shaped,
pointed, waxy to the touch, and
clasp closely to the stem.
10. 10
Description
Its taproot may penetrate
up to 10 feet into the soil,
with its lateral roots
extending several meters.
Dalmatian toadflax lateral
roots develop adventitious
buds that can develop
independent plants.
11. 11
Life Cycle
General
Dalmatian toadflax can
reproduce either by seed or
vegetative propagation and can
live up to 5 years.
Once a colony is established
Dalmatian toadflax's high seed
production and ability to
reproduce vegetatively allows it
to spread rapidly, making it
highly resistant to eradication.
12. 12
Life Cycle
Seed Reproduction
Dalmatian toadflax usually begins flowering in June,
continuing until September or October.
As plants are self-incompatible and cannot pollinate
themselves, bumblebees and halictid (mining) bees are
the primary pollinators.
Seeds are produced for about three months, starting
late June or early July, lasting until early September.
During this time, a Dalmatian toadflax plant can produce
up to 500,000 seed, which can remain dormant for up to
ten years.
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Life Cycle
Seed Reproduction
Seed dispersal begins in July
and can continue into the
winter and following year.
Dalmatian toadflax seeds are
small and angular with a small,
irregular wing.
14. 14
Life Cycle
Seed Reproduction
Although wind is consider as the means of seed dispersal,
other studies have indicated that 90% of the seeds fell within
2.5 feet of the plant.
Seedlings generally germinate in the spring; with a primary
stem and one to three adventitious stems.
Emergent seedlings are quite vulnerable, with survival
depending on little competition from other plants for soil
moisture.
Adventitious shoots generated from rootstock are very
competitive for soil moisture. It is this feature that allows
Dalmatian toadflax to out-compete native plant
communities.
15. 15
Life Cycle
Adventitious Reproduction
Dalmatian toadflax reproduces vegetatively. The above
ground portion of the plant dies back in the fall. In spring,
erect shoots begin growing from the root and may produce
one to 25 floral stems.
These stems develop from adventitious buds on primary
and lateral roots. Adventitious growth is possible from root
fragments as short as 1 cm in length.
These buds then grow their own root and shoot systems,
and become independent plants. Vegetative propagation can
allow a stand of toadflax to spread rapidly.
16. 16
Distribution
Origins
Dalmatian toadflax was originally native to the Mediterranean region of
the world. Its original range spanned from the coast of Croatia
northeastward to the Romanian regions of Transylvania and Moldavia;
and to the south and east around the Black Sea into the countries of
Bulgaria, Albania, Greece, Crete, Turkey, Syria, Iran, and Iraq
In its region of origin, Dalmatian toadflax evolved in plant
communities that were grazed by herbivores. Because much of the arable
lands were aridic in its region of origin, Dalmatian Toadflax has adapted
to dryness and periodic disturbances caused by agriculture.
17. 17
Distribution
Dispersal
The first known
occurrence of Dalmatian
toadflax in the United
States was in 1874.
Dalmatian toadflax has
since spread throughout
the United States. The
worst infested states
being in the west.
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Distribution
Dispersal
In California, Dalmatian
toadflax is found almost in
all of its counties with the
exception of Amador,
Fresno, Imperial, Kings,
Marin, Mariposa, Orange,
Riverside, San Benito, Santa
Clara, Santa Cruz,
Stanislaus, Sonoma, Sutter,
Tuolumne, and Yuba.
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Distribution
Dispersal
In Butte County, a Dalmatian toadflax infestation took place in and
around the Town of Paradise. The infestation was thought to have
initially come from an escaped ornamental. Most Paradise sites were
located along roadsides and in residents’ front yards.
As Dalmatian toadflax is classified as a Class-A noxious weed in the
state of California, the outbreak needed to be completely eradicated.
The infestation was eradicated through handpulling and application or
Tordon (Picloram) over a period of 5 years. As of 5/8/92 there has not
been any reoccurrence of Dalmatian toadflax in Paradise.
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Habitat
Dalmatian toadflax generally grows in open, sunny places,
up to elevations of 9,000 feet and has a north/south
latitudinal range between 330 and 560 degrees. Aspect is
also implicated as it also to be found on sometimes-steep
south and southeast facing slopes and hillsides.
Dalmatian toadflax is highly competitive in places where
summer moisture is limited (xeric). It is often found in well
drained, relatively coarse textured soils varying from coarse
gravels to sandy loams.
22. 22
Habitat
Sites subject to invasion include areas of low interspecific
competition, sparsely vegetated drier soils, and open
rangelands. sites include roadsides, near dwellings, vacant
lots, cemeteries, gravel pits, fields, waste areas, overgrazed
pastures, and other disturbed sites.
Once established, the root system of Dalmatian toadflax
makes it very competitive with other species, with
infestations forming large colonies, displacing desirable
vegetation. Because of this fact, it can significantly reduce
crop yields, desirable livestock forage, and will stress native
plant communities.
23. 23
Management
Economic Impact
Dalmatian toadflax is a California Class-A noxious weed.
Noxious weeds are those plants that are considered by the
state to be “troublesome, aggressive, intrusive, detrimental,
or destructive to agriculture, silviculture, or sensitive native
species, and are difficult to control or eradicate".
Class-A rated noxious weeds are considered the most
detrimental and are subject to mandatory enforcing actions
including eradication, quarantine, containment, rejection, or
other holding actions.
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Management
Economic Impact
In one 1992-study costs associated with managing
Dalmatian Toadflax on one Montana Ranch averaged $40 per
acre. Thirty percent of the 1,064 acres located on this ranch
was severely infested with Dalmatian toadflax. As Dalmatian
toadflax has been known to cause poisoning in cattle, the
lost cattle-carrying capacity and lost land values associated
with infestations increases the economic impact.
Studies on related toadflax have shown that infestation free
plots produced 2.5 times more grass than plots where
toadflax infestations were present.
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Management
Cultural Controls
Prevention. Disturbance appears to be closely related to
the invasion potential of Dalmatian toadflax. Further, since
seedlings of Dalmatian toadflax do not compete well for soil
moisture against perennial and annual winter crops, it would
be worthwhile to plant these types of crops to reduce the site
availability.
Pulling. Dalmatian toadflax by hand may be effective for
controlling small infestations, but pulling must be repeated
several times a year for many years. Hand pulling, however,
may not be practical with larger colonies as Dalmatian
toadflax has an extensive underground network of lateral
roots with numerous dormant root buds.
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Management
Cultural Controls
Mowing. Mowing has been shown to prevent seed production, but it
will not remove it extensive lateral root system, which can extend down
into the soil up to 10 feet. Mowing can also reduce the competitive effects
of surrounding vegetation. Mowing can have the effect of dispersing
toadflax seeds.
Cultivation. It was found that zero tillage practices could lead to
infestations of Dalmatian toadflax. Therefore, intensive clean cultivation
has been used to eradicate Dalmatian toadflax infestations. Cultivation
needs to be done every 7-10 days during the growing season for at least
two years. Cultivation is expensive and has ecological effects (soil
structure destruction & increased erosion potentials). Cultivation can also
bury Dalmatian toadflax seeds, which can remain viable for over ten
years.
27. 27
Management
Biological Controls
Literature search indicates that there are three insect species have the
potential for being biological control agents for Dalmatian toadflax.
However, studies that have been conducted so far have not yet proven
that these insects may be effective in controlling Dalmatian toadflax:
a. Brachypterolus pulicarius is a shoot and flower-feeding beetle that
feeds on young toadflax stems and shoot tips.
b. Calophasia lunula is a defoliating moth that is native of Eurasia and
was introduced into the United States in 1968 to help control
Dalmatian toadflax.
c. Gymnaetron antirrhini is a seed-eating weevil native to
Eurasia that has been adapted to Dalmatian toadflax. Adults feed
on young toadflax stems and larvae feed on immature seeds.
28. 28
Management
Chemical Controls
Herbicides Glyphosate, Dicamba and Picloram have been found to be
effective in controlling Dalmatian toadflax. Their persistence and
toxicity potentials make their application problematic.
a. Glyphosate. Alias: Roundup, Rodeo, and Accord. Glyphosate is
recommended for spot treatments. Subsequent regrowth from deep
and extensive root systems will occur the following year.
b. Dicamba. Alias: Banvel, Clarity, Vanquish, and Veteran. Dicamba is
considered effective at controlling Dalmatian toadflax. Dicamba does
not bind to soil and because of that may leach into groundwater.
c. Picloram. Alias: Tordon. Causes bending and twisting of the leaves
and stems almost immediately.
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Management
Grazing and Burning
Grazing. Overgrazing by livestock can increase Dalmatian toadflax’s
competitive advantage, by creating a disturbed site. Timing of grazing
can help reduce seedlings, but will not eradicate existing colonies.
Dalmatian toadflax can be toxic to cattle. Sheep have been found to
be effective at managing Dalmatian toadflax, as they are able to graze
Dalmatian toadflax without toxic effect.
Burning. Burning is not effective as soil temperatures are not high
enough to kill the extensive root system of the plant or any buried
seeds. Burning can also destroy indigenous plants, increasing the
competitiveness of toadflax. However, spot use of propane burners to
destroy vegetative shoots has been shown to help prevent seed
production.
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Management
Integrated Management
Prevention is the most practical and important means for the effective
control of Dalmatian toadflax. Using desirable ground covers of
perennials and annual crops will exclude Dalmatian toadflax. Further,
Dalmatian toadflax will readily invade disturbed areas where open
biological niche occurs. Filling these niches is essential in efforts to
control Dalmatian toadflax.
Early detection is also an important effective control for Dalmatian
toadflax. Community education is an important tool of an early
detection program. When the infestations is small, there are far more
options for the successful eradication. However, if an infestation is
not detected until it occupies several acres, successful control is
unlikely without great expense and the heavy and repeated use of
herbicides and other control methods.
