Dalmatian toadflax (Linaria dalmatica) - Early Detection Species

Dalmatian toadflax flowers.

 
 

Dalmatian toadflax is a perennial plant that has a yellow snapdragon-like flowers and can grow up to four feet tall. Plants can form dense cover in sunny areas and can reduce native plant habitat and forage for livestock. In Minnesota, Dalmatian toadflax is a prohibited noxious weed on the eradicate list so any plants found must be killed. Dalmatian toadflax is an early detection target in Minnesota and it has limited distribution in the state. Butter and eggs (yellow toadflax) is a widespread plant in Minnesota that looks similar to Dalmatian toadflax.

Description

Appearance

Dalmatian toadflax can grow up to four feet tall, has waxy heart-shaped leaves that clasp the stem, and has yellow flowers that look similar to snapdragon flowers.

Leaves and Stem

Dalmatian toadflax leaves clasp the stem giving the leaves a heart-shaped appearance. Leaves are 1-3 inches long and have a waxy coating. Stems and leaves are smooth and have no hairs. Leaves attach to the stem one at a time in an alternate pattern.

Flowers

Flowers are yellow and have a tubular shape similar to snapdragons. They have a long, thin extension called a spur coming off the bottom of each flower. Flowers sometimes have an orange center. Flowers are on small stalks and come off the central stalk one at a time. Plants flower from May through September.

Seeds and Reproductive Structures

Plants produce ½ inch seedpods which can contain 140-250 seeds. Seeds are the main way that Dalmatian toadflax spreads to new areas. Within a site, Dalmatian toadflax can also spread vegetatively by sending up new plants from underground roots.

Roots and Rhizomes

Dalmatian toadflax plants have a taproot that can grow six feet deep or deeper. Additionally, underground stems called rhizomes extend sideways from the plant and can send up new stalks near the parent plant.

Biology

Dalmatian toadflax is a perennial plant. Each year it sends up a flowering stalk that dies back over the winter. The next year a new stalk is grown from the surviving roots. Plants reproduce sexually by producing seeds and plants spread asexually by underground stems called rhizomes, which can send up new plants near the parent plant. Individual plants generally live for three to five years. Dalmatian toadflax grows well in dry, sandy soils.

Origin and Spread

Dalmatian toadflax is native to Europe and Asia. It was planted in the United States for its ornamental, fabric dye, and medicinal properties. Plants spread from where they were planted. Dalmatian toadflax is widespread in the western United States. Dalmatian toadflax is an early detection target in Minnesota and it has limited distribution in the state. This means you are highly encouraged to report sightings of this species so that new infestations can be identified and managed.
Refer to EDDMapS Distribution Maps for current distribution.

Don't be fooled by these look-alikes

  • Butter and eggs (yellow toadflax), Linaria vulgaris (invasive) - Butter and eggs leaves are linear and narrow while Dalmatian toadflax leaves are wide and heart shaped.
  • Snapdragon, Antirrhinum majus (non-native) – Snapdragons are commonly sold as annuals for gardens. They can come in many colors. Snapdragon flowers do not have the long spur at the base of the flower that butter and eggs and Dalmatian toadflax have.
 
Regulatory Classification

Dalmatian toadflax is a Minnesota Department of Agriculture Prohibited Noxious Weed on the Eradicate List meaning that the above and belowground parts of the plant must be destroyed. Additionally no transportation, propagation, or sale is allowed.

Threat to Minnesota
  • Dalmatian toadflax forms dense monocultures that can overtake habitat and outcompete native plants.
  • Cattle avoid eating Dalmatian toadflax so it can become abundant in pastures and reduce forage for livestock, causing economic impacts.
What you should do

One way that invasive plant seeds and fragments can spread is in soil. Sometimes plants are planted purposefully. You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals & mud from boots, gear, pets & vehicle.
  • CLEAN your gear before entering & leaving the recreation site.
  • STAY on designated roads & trails.
  • PLANT non-invasive species.
Native Substitutes
 
Control Methods

Mechanical control can be done by pulling the plant by hand or with equipment such as a shovel. Take care to remove as much of the taproot and underground stems (rhizomes) that spreads sideways from the plant to limit resprouting. View the Minnesota Department of Agriculture's guidance on disposal of pulled noxious weeds. Mowing and burning are not recommended methods of control as they can stimulate additional plant growth and vegetative reproduction.

Herbicide control can be done using systemic herbicides which are taken up by plants and move within the plant, which can kill leaves, stems, and roots. Due the thick, waxy leaves of Dalmatian toadflax, it can be challenging for herbicides to penetrate the leaves and get taken up by the plant and surfactants are generally needed. Consult with your local county agricultural inspector for detailed recommendations. People have reported success with herbicides containing chlorsulfuron, dicamba, imazapic, or picloram. The most effective months for applying herbicides are April, May, September, and October.

Biological control insects are used in western states where Dalmatian toadflax is abundant and can sustain the insect populations. Biological control is not an appropriate tool in Minnesota at this time because Dalmatian toadflax in Minnesota has a limited distribution so the goal is to eradicate small populations to prevent Dalmatian toadflax from becoming widespread in the state.

Reporting

Report new occurrences by submitting a report through EDDMapS Midwest, emailing Arrest The Pest, calling Arrest the Pest (1-888-545-6684), or contacting your local county agricultural inspector.

Resources