Davey Tree Flipbooks

40 PURPLE LOOSESTRIFE (Lythrum salicaria) PLANT DESCRIPTION Purple loosestrife is a broadleaf perennial weed that is typically found growing in wet areas along with cattails. This weed grows 4–6 feet tall by summer. The mature plant has distinct purple to pink spike flower heads. In the spring, it can be seen as a seedling with typically opposite leaf arrangements. LEAF: The leaves attach directly to the stem, are narrow and lance shaped, and form a pointed or rounded tip. Leaves may or may not be covered in fine white hairs. STEM: Purple loosestrife can be single stemmed or multi stemmed. The stem is distinctly square shaped and branches occur in the upper portion of the plant. FLOWER: Flowering spikes can be over 1 foot long and are composed of small purple to pink flowers. Flowers are directly attached to the stalk and may be hairy at the base, with six delicate petals with yellow pollen heads in the center. SEED: After flowering, tiny tear-drop-shaped seeds are abundantly produced and are usually held until disturbed. REPRODUCTION: Seeds significantly contribute to reproduction, but purple loosestrife can also spread by its root system. The perennial roots will live for many years creating new shoots in the spring with multiple stems. Mature purple loosestrife plants may produce up to one million seeds that can stay viable for up to 20 years. WHY IT IS NOXIOUS: Purple loosestrife is a major threat to wetlands and wet areas due to its large seed production and perennial nature. Dense colonies can cause drainage issues. SEASONAL IDENTIFICATION WHEN TO FIND: Purple loosestrife is most noticeable when it is flowering in summer. Look for purple flowering spikes and lance-shaped leaves. SPRING IDENTIFICATION = MODERATE When purple loosestrife emerges as a seedling, its leaves typically grow opposite on the stem. The leaves are lance shaped with a pointed tip or rounded tip. Leaves can have hairs on all surfaces. SUMMER IDENTIFICATION = EASY As the plant elongates, the stem is identifiable by its distinct square shape. The upper branches extend towards flowering spikes, which have many purple–pink flowers with six petals. Purple loosestrife often dominates large wet areas and ditches. FALL IDENTIFICATION = EASY As the flowers fade, they drop hundreds of thousands of seeds. The leaves and stems change to a reddish purple color in the fall. WINTER IDENTIFICATION = MODERATE The plant may persist through the winter as a thin, dead, skeleton. The seeds will lie dormant in the soil until the spring when they germinate. SIMILAR-LOOKING SPECIES BLUE VERVAIN (Verbena hastata) grows in a similar form. It has many small flowering spikes with very small blue to purple flowers, but the leaves have a toothed margin. SWAMP MILKWEED (Asclepias incarnata) looks similar before flowering. Its leaves have a very short leaf stalk. Leaves are longer than purple loosestrife leaves. The flowers are pink with stamen twice as long as the petals. The flowers grow in round clusters at the top of the plant. SWAMP LOOSESTRIFE (Decodon verticillatus) leaves look similar but have a very short leaf stalk. The purple flowers grow individually in leaf pairs. LOW HIGH ohio distribution roadside distribution growth seeds ability to dominate difficulty of control WHERE TO FIND: Purple loosestrife is prevalent in Ohio's wetlands. It is typically found in wet areas, including areas with poor drainage, ditches, and near waterways that are infrequently mowed. CONTROL METHODS: MECHANICAL: Mow in summer to reduce height and maintain visibility, but expect regrowth. CHEMICAL: Make directed or broadcast applications to purple loosestrife with non-selective or selective herbicides in the spring to fall. Use aquatically-approved herbicides when appropriate. CULTURAL: Improve drainage in ditches. RECOMMENDATION SUMMARY: Purple loosestrife is an aggressive, perennial plant with a persistent seed bank that is capable of dominating wet areas. Since accomplishing complete control may take several seasons, persistence is important. For best control results make herbicide applications from spring to summer until the end of the flowering stage. Make applications to actively growing plants even after flowering to reduce seed production. Control may not be as effective at this time, but will help weaken the perennial root systems. Plan herbicide applications for consecutive years to ensure control is achieved. Increase drainage in wet ditches and similar places to reduce potential habitat for purple loosestrife. Mowing will have little effect on controlling a purple loosestrife population, but can reduce seed production if properly timed. Failure to control purple loosestrife will allow dense, perennial monoculture colonies to form. Individual plants can produce up to one million seeds that can remain viable for up to 20 years. perennial RIVM LEVEL OF CONCERN

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