Weeds
Plant Body
•
•
•
Shoot system =
leaves + stem
Root system
Meristem = cells
that divide for life
of plant, can give
rise to all plant
structures
Plant Body
Leaf = blade + petiole
Functions
Exposes surface to sunlight
Major site of photosynthesis
Conserves water
Provides for gas exchange
Blade
Petiole
Plant Body
Stem
Functions
Holds leaves up to light
Transport of substances
through vascular tissue
Xylem conducts water
and minerals
Phloem transports
sugar
Plant Body
Root
Functions
Anchors plant in soil
Takes up water and
minerals from soil
1 Tree Tobacco
Nicotiana glauca
glauca = bluish-gray,
referring to leaf color
Leaves contain high
levels of nicotene
Introduced from
South America by
missionaries, from
imported grain or on
purpose…?
2 Cheeseweed
Malva neglecta
Seeds and leaves
are edible.
Seeds are shaped
like rounds of
cheese.
3
Castor Bean
Ricinus communis
Ricin in seeds
--used to kill a spy on London Bridge
--recently discovered in the US mail
--possible cancer treatment
Oil from seeds has laxative and
wound-healing properties.
4 Sweet fennel
Foeniculum vulgare
• Petioles are eaten,
like celery.
• Folkways medicine:
Dried Leaves may
repel fleas
• Priests spread on
mission floors for
fragrance
5 Scarlet Pimpernel Anagallis arvensis
Folkways Medicine:
May repel witches
Poisonous to humans
and livestock
6 Poison hemlock
Comium maculatum
Conin causes muscle
paralysis, found in all
parts of plant.
• Fruit shape is long and
pointed
– Filaree comes from the
Spanish name for
needle
– Erodium refers to heron
• Young foliage is edible
7 Filaree
(Storksbill)
Erodium
Large numbers of
nutritious seeds,
Used by native
Americans for flour
8 Saltbush
Atriplex canescens
9 Sweet clover
Melilotus albus
Enhances production of
cumarin by molds
Original source of heparin
Important source of honey
Morphine and codeine from
developing seed pods
10 Opium poppy
Papaver somniferum
11 California Poppy
Eschscholtzia californica
Young foliage is edible
Roots used for toothache
12 White Goosefoot
Chenopodium
Young foliage and
seeds are edible
13 Mexican Tea
Chenopodium ambrosioides
Folkways Medicine:
Seeds act against
intestinal worms.
Dried plant is used
as seasoning.
14 Horehound
Marubium vulgare
Flavoring in candy,
cough drops, and beer
Folkways Medicine:
good for sore throats
Member of
the Mint family
15 California Mugwort
Artemisia douglasiana
Folkways medicine: Uses for intestinal,
respiratory and skin ailments.
16 Jimson weed
Datura meteloides
All parts of plant have
alkaloids like atropine.
--medical use
--religious observances
by Native Americans
--hallucinogen in the 60’s
DANGEROUS!
Recent hospitalizations
and deaths reported in
LA County.
17 Sea Fig
Charpobrotus chilensis
• Edible fleshy fruit
forms below the
flower
• Helps to stabilize soil
on hillsides or sand
near ocean
18 Tumbleweed
(Russian Thistle)
Salsola tragus
• Noxious weed =
targeted for
eradication
• Shoot breaks off
close to base and is
pushed by wind to
distribute seeds.
• Contains high levels
of nitrates or soluble
oxalates
19 New Zealand Spinach • Leaves can be eaten
Tetragonia tetragonioides
raw or cooked
• Contains harmless
levels soluble
oxalates
20 Water Cress
Rorippa nasturtium-aquaticum
• Leaves and shoots
can be eaten.
• Rich in Vitamin C
• Be sure it comes
from unpolluted
waters!
21 Wild celery
Apium graveolens
• Escaped from
cultivation
• Petioles are eaten
• Wild plant has strong
taste made milder by
cooking
22 Chicory
Cichorium intybus
• Root scrapings used
as coffee flavoring or
substitute
• Leaves of C. endiva
used in salads
23 Western Ragweed
Ambrosia
The pollen is a
common respiratory or
hay-fever allergen.
24 Sow Thistle
Sonchus
• Young leaves are
edible
• One species is a
noxious weed
25 Plantain
Platago potagonica
• Young leaves are
edible
• Folkways medicine:
wound healing,
laxative
26 Curly Dock
Rumex crispus
• Young leaves are
edible
• Folkways medicine: to
treat cough, blood
pressure, itching,
sprains
• Toxic to livestock
27 Dandelion
Taraxacum officinale
• Young leaves and roots
are eaten
• Dried roots used as
coffee substitute
• Seeds dispersed by
wind
28 Black Mustard
Brassica nigra
• Young leaves are eaten
• Seed oil used to make
mustard
• Possibly introduced by
missionaries who
scattered it along the
Camino Real to mark
the way between
missions
29 Wild Radish
Raphanus sativus
Scrapings from
young roots or young
seed pods taste like
radishes
30 Wild oats
Avena fatua
• Escaped from
cultivation
• Seeds are edible
31 English Ivy
Hedera helix
• Juice causes skin
irritation
• Berries and leaves
are toxic
A related species provides treatments for
Hodgkin’s disease, leukemia and other
cancers
32 Periwinkle
Vinca major
33 Garden Nastursium
Tropaeolum majus
• Leaves are eaten in
salads
• Hallucinogenic
properties unproven
34 Blue Gum Eucalyptus
Eucalyptus globosus
Added as a
flavoring to
candies and
cough medicines
35 Spurge
Euphorbia
• Milky sap (latex)
causes skin irritation
• Relative of the
mildly-toxic
Poinsettia plant
36 Narrow-Leaf
Milkweed
Asclepias
• Cardiac glycoside acts as
– Medicinal heart stimulant
– Arrow poison
– Insect defense mechanism
37 White and
Purple Nightshade
Solanum
• Berries are poisonous
• Relatives of the potato
Worksheet
• Complete page 169 from lab manual
• Be sure your instructor checks your
completed worksheet before you leave
the lab