swamp stonecrop
(Crassula helmsii A. Berger)

Overview

Appearance

Crassula helmsii is an aquatic or semi-terrestrial succulent perennial herb that grows from 4-50 in. (10-130 cm) long. It has round stems that float on the water or creep along the ground. The stems root at the nodes. C. helmsii is native to Australia and New Zealand.

Foliage

The opposite leaves of C. helmsii are sessile and succulent. Leaves are from 0.16-0.8 in. (4–20 mm) long by 0.03-0.06 in. (0.7–1.6 mm) wide. They are linear-lanceolate to ovate-lanceolate with an acute apex.

Flowers

The inflorescence is borne singly in the axils of leaves. The flower has four petals which are white to pinkish and slightly longer than the sepals.

Fruit

The fruit of C. helmsii is a single carpel containing up to 5 elliptical smooth seeds.

Ecological Threat

C. helmsii can establish monocultures that displace native plants, increase oxygen levels, cause flooding, obstruct water flow, and reduce recreational value of lakes or ponds. This plant can lead to an overall reduction in biodiversity.

Maps

Invasive Listing Sources

• Florida Noxious Weeds
• Minnesota DNR invasive species list
• New Hampshire Prohibited Aquatic Species
• North Carolina Noxious Weeds
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40

References