- Name also: European Dodder
- Family: Bindweed Family – Convolvulaceae
(formerly Dodder Family – Cuscutaceae)
- Growing form: Annual, non-chlorophyllous parasitic herb.
- Height: The limp twining stem may be up to 1 metre (3.3 ft.) long.
- Flower: Regular. Corolla pink to white, four- or five-lobed, 3–4 mm (ca. 0.1–0.15 in.) long. Corolla-lobes pointing obliquely upwards, and with rounded tip. Small scales often present within the corolla-tube. Calyx five-lobed, pale. Pistil of two fused carpels, styles and stigmas two. Stamens five, attached between the corolla-lobes.
- Leaves: Alternate, minute. Scale-like, triangular with rounded tip, pale brown. (The leaves in the pictures belong to host plants.)
- Fruit: Rounded, thin-walled capsule.
- Habitat: Yards, surroundings of outhouses, waysides, streamside thickets.
- Flowering time: July–August.
Greater dodder is a non-chlorophyllous parasitic annual. Being incapable of photosynthesising and lacking ground roots it completely relies on the host plant. As soon as the seedling finds a host, its radicle withers, and the direct connection to the soil is lost. If no host is found in time, the seedling may move by allocating nutrients from the tissues of the basal parts to the tip of the shoot. In this way the tip grows, while the base withers. When a host is found dodder starts to twine around its shoot. The primordia of the haustoria develop on the inner surface of the twining stem. In propitious conditions the chemical stimulus of the host’s stem triggers the development of actual haustoria. The branching haustoria invade the tissues of the host and satisfy the needs of the parasite by ‘stealing’ anything from water to sugars.
In Finland, there are two subspecies of greater dodder, that differ in their habitat preferences. Ssp. halophyta has a less branching and more slender stem than the type (ssp. europaea), and it grows in seashore meadows. Both subspecies are parasitic on stinging nettle, hop and dozens of other, usually perennial herbs.
There are two other species of Cuscuta in Finland: field dodder (C. campestris) and common dodder (C. epithymum). Field dodder, which is parasitic mainly on carrot, has yellowish flowers, a yellow stem, and pin-like stigmas. Common dodder is parasitic primarily on clovers, and its stigmas are markedly elongated.