Tufted Loosestrife (Lysimachia thrysiflora)

Tufted Loosestrife (Lysimachia thrysiflora)

Tufted Loosestrife (Lysimachia thrysiflora), also called Swamp Loosestrife, is a perennial forb/herb in the Primrose family (Primulaceae) and Primulales order. It is in the same genus as the Earth Loosestrife but the flowers are quite different. The order and family names are from the Latin for "primrose." The genus name is likely from the Greek for" release from strife (lysis mache)." The species name means flowers in a thryse where "flora" is from the Latin for "flowers" and "thrys" is the Latin for "pinecone-like bunch." This plant can grow to a height of 30 inches (76 centimeters). The Purple Loosestrife (Lythrum salicaria) when lacking flowers can be mistaken for this plant but the Purple Loosestrife has a square rather than round stem. These two plants are not even in the same order.

The leaves are opposite, entire, linear to lance-like, up to six inches (15 centimeters) long and two inches (548 centimeters) wide. As with other plants in this genus, the leaves may have black dots particularly along the main vein on the underside of a leaf. The axial (main or support) stem may be green to reddish purple. Leaves at the bottom of the axial stem are diminutive and the same color as the stem. The white arrow in the photograph below points at one of these small leaves. The leaves become larger as they are higher on the axial stem.

Tufted Loosestrife (Lysimachia thrysiflora) Lower Stem

The flowers are in ball-shaped spikes (racemes) up to 1¼ inches (3 centimeters) in diameter on stalks from the middle axial stem. Sometimes, the Tufted Loosestrife will hybridize with the Whorled Loosestrife (Lysimachia quadrifolia) in which case one of the racemes will be terminal, that is, at the top of the plant. Each flower has five to seven yellow, linear petals about 1/3 inch (8.5 millimeters) wide. The stamens are longer than the petals. This plant blooms from May to July.

Tufted Loosestrife (Lysimachia thrysiflora) Flower

The fruit is a seed capsule about 1/8 inch (3 millimeters) in diameter containing a few triangular-shaped seeds. Much of the raceme shown in the photograph above is developing seeds as the flower petals turn brown.

The root system is a shallow rhizome.


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