Invasive Plants - Illustrated

Cape ivy ( Senecio mikanoides ) is an extremely invasive recent arrival from South Africa. It smothers all other vegetation, and may be toxic to aquatic life. Look for bright green, hairless leaves shaped like ivy but more delicate, with a pungent smell; pinkish to woody stems, and yellow flowers in winter. The roots, often bright magenta, are shallow and easily dug out, but all parts must be bagged and hot-composted or otherwise destroyed. Any node can start a new plant, and stems can root after prolonged drying or if left in an ordinary compost heap.

Giant Bindweed, white morning glory (Calystegia sylvatica)  is an extremely invasive vine from Southern Europe, with heart-shaped leaves and large white morning-glory flowers. It forms dense, deep networks of fleshy white to pink roots. The vines themselves die back in winter, but in spring come roaring back, covering ground and twining their way up to cover bushes and even trees. Pulling out the aboveground parts is ineffective. One must follow the stems to where they enter the ground (often many feet); roots, which also may extend many feet and go down a couple of feet in several layers, must be dug out or tarped. (Herbicide is not likely to be effective.) 

Algerian, Canary, or English ivy (Hedera canariensis, Hedera helix) are invasive woody vines that covers large areas, excluding other vegetation and providing habitat for little except rats. Clinging by rootlets, it climbs and eventually covers and kills trees. In old age, it takes on bushy form, with small flowers and abundant black berries that are carried by birds. Algerian or Canary ivy has larger leaves and grows faster. On trees, removing a short section of vine will kill the growth above, and may be less harmful to the tree than pulling off the rootlets. But to get rid of the plant, roots must be removed. Roots are generally shallow and often can be dug or pulled out -- sometimes the mats can be rolled up like a carpet. 

 

Perennial pepperweed ( Lepidium latifolium ) is a major threat to local wetlands, especially salt marshes. The first picture shows this invasive plant in bloom, note the many tiny white flowers on top of erect dark green stems. The second picture shows the young plants invading through creeping rhizomes.

Giant cane or Giant reed ( Arundo donax ) is an extremely invasive, tall, bamboo-like grass with the ability to take over streamsides by spreading through rhizomes under the soil surface.

Three non-native grasses that displace natives:

Ripgut brome, left, can be distinguished from native bromes by the long awn - the thread-like fiber projecting from the seed. In ripgut, the awn is much longer than the seed, 1/2" long or more. As the grass matures, the seeds will be more visible individually, many on each stalk.

Italian ryegrass, center, is a shiny-leaved grass whose seeds form a slight zig-zag outline on the sides of the thin, upright flower stalk.

Wild oats, right, is a tall grass with awns framing heavy, stout individual seeds.