Are these two plants the same species? List your reasons for why

you think they are or are not.

One is a noxious weed, the other is an increasingly rare native

• The native– Caltha palustris, Marsh Marigold. 5-9 deep yellow

petals. Leaves round to kidney shaped.

• The Alien– Ranunculus ficaria, 8 yellow petals, leaves heart

shaped.

How would you define a weed?

• A valueless or unwanted plant that is growing wild, usually crowding out or out competing desired plants or crops

• How big a problem do you think weeds are in the country?

• In 1984, the United States lost $7.4 billion in average annual crop yield because of noxious weeds.

• Noxious weeds are estimated to inhabit over 100 million acres in the United States, and could be increasing by as much as 8-20% every year (US Department of the Interior 1997).

Can you name any examples of weeds that could have a negative impact on

human health?

Hint Simon suffers from this.

Greater Ragweed, Artemisia trifida

Common ragweed, Artemisia artemisiifolia

Plants with lobed and dissected leaves, with spikes of green flowers often carrying yellow pollen

Ragweeds

Describe this plant

Poison Ivy, Rhus radicans Fruit

• It can be pretty to look at, but often spreads to places where humans work (gardens, garden walls, forest trails, road sides).

How would you decide whether or not a plant you come across in the garden

is a weed?

• Group workList some criteria you think fit our definition of a

weed

1. Its not a plant you put in the garden. The best way to recognize a weed is to know what is not a weed

2. Is it taking over the garden?

3. Is it outcompeting other plants for light and food?

Sometimes someone a little new to plants or gardening can get tricked.

Describe any differences you see

Jack in the pulpit

Poison Ivy

• Leaves of three (actually 3 leaflets)

• Each leaflet has a stalk

• The plant is a vine, growing up trees and walls

• Flowers are small with obvious petals

Jack in the PulpitArisaema triphyllum

• 3 parted leaf (3 leaflets)

• Leaflets have no stalk

• The plants is terrestrial, growing up to 1 foot high only

• Flowers are big, no obvious petals