Ask Mr. Smarty Plants

Water Hyacinth and Pickerel Weed Pontederia cordata (Pickerelweed) are both aquatic plants in the Water Hyacinth Family (Pontederiaceae).  Although both have purple flowers, they are easy to distinguish by the arrangement of the flowers and the shape of the leaves. Click on each of the links below to compare these features.

Pickerel Weed 

  http://www.vplants.org/plants/species/species.jsp?gid=32287

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Water Hyacinth

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Pickerel Weed is a native plant and by definition is not considered to be an invasive species , although it is an aggressive grower. The Water Hyacinth, being introduced from Brazil in the 1880’s, is listed as an invasive species and is the more aggressive grower of the two. This can be attributed to the difference in their growth habit. The Pickerel Weed is an immersed plant, growing in shallow water (< 2 ft). It has roots and rhizomes that attach it to the  substrate, and is thus restricted to growth along the edges of ponds, lakes, and streams. The Water Hyacinth, on the other hand, is a floating plant that has spongy parenchyma tissue in the petioles of the leaves that serve as flotation devices, and fine roots that obtain nutrients from the water. With no attachments, it can quickly cover the entire surface of the body of water where it is growing. It also has a high growth rate (studies have shown that populations can double in as little as six days).