Yellow Loosestrife

Yellow Loosestrife (Lysimachia vulgaris), also known as Circle Flower.

There are different species of Loosestrife, most common is Purple Loosestrife from the Lythraceae Family.

Yellow, however, comes from a different family, Primulaceae. This family has many primrose flowers.

Yellow is different from Dotted Loosestrife, which is also yellow in color.

Loosestrife is the genus Lysimachia from the Primulaceae family.

This family has about 69 genera and are herbaceous perennials and annual plants.
Flowers are often cup-like and have five petals.

Most noted species within the Lysimachia genus are Yellow (Lysimachia vulgaris) and Dotted Loosestrife (Lysimachia punctata) which are often mistaken for each other because of their yellow cup-like flowers.

Others that are popular include Gooseneck Loosestrife (Lysimachia clethroides), Tufted Loosestrife (Lysimachia thyrsiflora) and Whorled Loosestrife (Lysimachia quadrifolia).

The genus Lysimachia spreads by rhizomes. Because of this they are
collectively referred to as Creeping Loosestrife.

Many Primulaceae Loosestrifes are native to sub-tropical regions and also grow widely across Europe, Central Russia and China. Non-native Lysimachia are aggressive and invasive (Whorled Loosestrife is a native, non-invasive wild flower).

All Primulaceae thrive in moist environments, especially swampy areas but are able to adapt well to a wide range of soils. Many gardeners are attracted to these flowers for medicinal purposes along with visual and may not be aware that they can become invasive.

Because the genus Lysimachia spreads by creeping rhizomes it is important to keep the area highly controlled. A pre-emergent herbicide will not work for removal.

Although different post-emergent weed control methods work with rhizomes up to a point. Removal will be more manual and over time. Burning weeds is effective but apply caution. Pulling and tilling will kill roots and the use solarizing black plastic or other inorganic mulch types help speed the process. Once area is under control use organic mulch types for better appearances in your garden.

FYI:

Outside of Loosestrife, other examples from the Primrose flower family include:

Scarlet Pimpernel (Anagallis arvenis), which is invasive.

Many ‘Star’ flowers, such as Shooting Star flower, Star of Bethlehem flower, Lavender Star flower, Pacific Star flower and many more. Most non-invasive native wildflowers.

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