Exotic Grasses Identification in the Pacific Northwest

1. 2015 Hoyt Arboretum and Herbarium, HAH
Intro to Grass Identification/Morphology
Exotic Grasses in
Spiranthes Research Site
Erin Riggs HAH Curator, Systematic Botanist

2. Goals for this class:
• Increase botanic visual literacy focusing
on grass morphology
• Expand knowledge of native grasses and
their potential for restoration use
• Expand knowledge of exotic grasses, they
are here to stay

3. List of resources:
Oregon Flora Project online www.oregonflora.org , Poaceae treatment is posted (artificial
key)
Flora of North America, Poaceae, Vol. 24, 25 (FNA are natural keys)
Flora of North America, Juncaceae, Vol 22
Flora of North America, Cyperaceae, Vol 23
Field Guide to the Sedges of the Pacific Northwest (artificial key)
Flora of North America Manual of Grasses online www.herbariua.usu.edu/webmanual
Manual of Grasses for North America, field manual of grasses, complimentary to FNA online
CAVEAT! Out of date publications, handy for field use, images still nice, names and
taxonomy out of date.
Manual of Grasse of the United States, 1971, Hitchcock (44 years old)
Flora of the Pacific Northwest, 1969, Hitchcock and Cronquist (46 years old)

4. Definitions:
Artificial key: sequential groupings of the key by intention do not reflect
natural groups; aims to most easily identify a given taxon, usually
regionally focused. Does not include entire global groups- usually easier
key to use.
Natural key: diagnostic features are used to delimit “natural”
groups/formal taxa, include all characters for entire global groups –
usually more difficult key to use
Ployclave key: consists of a list of numerous character states, the user
selects all of the states that match the specimen. This is becoming more
common with online keys.

5. GRASS MORPHOLOGY AND ID

6. Grass flower morphology

7. Inflorescence- the flowering part of a plant; a flower
cluster; the arrangement of the flowers on the flowering
axis. Composed of many spikelets.
Panicle
Spike
Drooping panicle

8. Rachis- the main axis of a structure, as in a compound leaf
Spikelet - a flower cluster in grasses and sedges consisting of
1- many flowers subtended by two glumes. Glumes delimit the
spikelet.
Pedicel- the stalk of a single flower or of a grass spikelet
Rachilla- the axis of a grass or sedge spikelet, with nodes and
internodes
Glume- one of a pair of empty bracts at the base of a spikelet.
Empty because they do not have buds or flowers in them.
Bract- a reduced leaf or leaf like structure at the base of a flower,
inflorescence or spikelet.
Awn- narrow
bristlelike appendage
Many flowered spikelet
One flowered spikelet; this one unable to distinguish
upper or lower glume
Upper glume
Lower glume

9. Lemma- the lower bract which subtends a grass flowerPalea-the upper bract
of two that subtend a
grass flower
Pistil = female parts, made up of:
Stigma- part of pistil that is receptive to pollen
Style – connects stigma to ovary
Ovary- contains ovules/seeds
Stamen = male parts, made up of:
Anther-pollen bearing portion of stamen
Filament- the stalk of the stamen
The Grass floret/flower

10. Lower glume
Upper glume
Lower glume
Upper glume
lemma
palea
Floret/flower parts

11. Upper glume
Lower glume
Disarticulation - separating at maturity at a joint.
An important ID character among all grasses
Disarticulation above the glumes below the floret
Disarticulation below the glumes
floret

12. Petals and sepals absent Petals and sepals look the same = tepals
Grasses have
Highly modified petals and sepals-
We wont look at them, not used in ID

13. Grass Culm/stem morphology

14. Sedges have edges Rushes are round Grass has joints
Culm = stem
Node =joint

15. Grass Culm/stem- morphology
Node – position on stem where leaves or branches
originate
Sheath – the base of the leaf that surrounds
the stem*
Blade – broad part of leaf
Ligule- the membranous appendage arising form the
Inner surface of the leaf at the junction of leaf sheath
Auricle – a small “ear shaped” appendage, usually very small
Collar – the junction of
blade and sheath
Internode – portion of stem
between nodes
Budshoot-flowers grow out this
portion
*Most of our grasses will all have hollow culms, occasionally we have
Culms that are solid.

16. Three ligule types, out of many forms
Auricle
Not all grasses have auricles

17. All Bromus have a closed
collar/closed leaf sheath, at times it can
split open so look carefully.
Our Bromus vulgaris will be
more hairy.
Brachypodium sylvaticum
Leaf sheath open but overlapping
all the way to the node/joint.
B. sylvaticum is much more hairy
Arundo donax
Node/joint
Leaf sheath is a good diagnostic character

18. Root and specialized stems

19. Perennial or annual form is Important in grass ID
Perennial - a plant living 3 or more years
Annual – a plant that germinates from seed,
flowers, sets seed, and dies in same year
How can you tell? Sometimes you cant
Rhizome - perennial, a specialized horizontal underground
stem, with nodes and internodes, sending out root and
shoots at nodes (bamboo, ginger)

20. Caespitose both annual and perennial –
• look for multiple old leaves
• Size of clump can be a clue
Sometime you just cant tell
Perennial annual

21. Stolon- a specialized horizontal stem creeping along the surface of the ground, sending out
roots and shoots at nodes (strawberries)

22. Annual roots
How do you know its annual?
Some times it is difficult to tell
If you cant tell if its annual or perennial
you have to key two directions.
Common annual fibrous root

23. Exotic grasses found on Hoyt Arboretum Citizen Science
Spiranthes research site.
HAH=herbarium specimen on hand to study
Some fresh specimens as well

24. Agrostis capillaris - bent grass
Agrostis genus characters
you must have 40x + dissecting scope to ID to species.
Difficult to ID
• All spikelets alike
• Inflorescence a narrow panicle, aging to spread out
• Lemmas 1.2-2.5mm
• Root stolons absent
• Palea 0.5mm
• Ligule 1.7- 8mm very wide range
• Open sheath
• Inflorescence feels slippery and smooth

25. • Ligule 1.7- 8mm very wide range
Agrostis capillaris - bent grass
• Inflorescence a narrow panicle, aging to spread out
• Inflorescence feels slippery and smooth

26. Aira caryophyllea – hair grass
Characters:
• Small annual tufts
• 1-55 cm tall, very elastic height
• Lemmas awned
• Sheaths open
• Inflorescence contracted or open

27. Anthoxanthum odoratum – sweet vernal grass
Characters:
• 25-60 cm tall
• Auricles pilose-ciliate (long soft hairs)
• Ligule 2-7 mm membranous, lopsided

28. Anthoxanthum odoratum – sweet vernal grass
• Auricles pilose-ciliate (long soft hairs)

29. Arrhenatherum elatius - tall oat grass
Characters:
• 150cm tall (4+feet)
• sheaths open and smooth
• Sturdy joints, smooth
• Ligule 1-3 mm

30. Bromus carinatus - HAH,
look-a-like! Native Bromus sitchensis
Characters:
• All Bromus have a closed
collar/closed leaf sheath.

31. Bromus sitchensis - HAH
Characters:
• All Bromus have a closed
collar/closed leaf sheath.

32. Bromus sitchensis – Alaskan brome
Ligule – 1-3 mm
Glumes – glabrous
Lemma- glabrous
Leaves – 2-9 mm wide
compared toBromus carinatus var marginates –
Mountain brome
Ligule – 3-4 mm
Glumes – pubescent
Lemma- pubescent
Leaves – 1-12 mm wide
I have to compare with flora key for positive ID 98% of the time

33. Bromus tectorum (cheat grass) -HAH
ALL true bromes have closed collars,
All Bromes are VERY difficult to ID, make
collections for Erin to ID.
Characters:
• Closed collar
• Drooping inflorescence
• Sheath softly pubescent
• Awns 10-18 mm, big!

34. Cynosurus echinatus (dog tail grass)
Characters:
• early in the spring look close at the collar and ligule.
• Ligule NO pilose hairs (long soft hairs)
• The inflorescence one sided.

35. Dactylis glomerata – orchard grass
Characters:
• early inflorescence congested and narrow,
opens as it ages.
• Ligule membranous 3-11 mm
• Culm keeled, flattened

36. Blade cross section
Festuca rubra– fescue
Characters:
• Ligules higher on the sides than in the back
• Perennial caespitose
• Leaves conduplicate, involute –folded
they look thin and wiry

37. Holcus lanatus - velvet grass
Characters:
• Culm 2-100 cm tall
• whole plant is velvety
• Inflorescence contracted to open with age

38. Juncus species –Likely native, I will ID this summer.
Characters:
• Round culm NO nodes
• Base of stem dark brown clasping stem leaves

39. Lolium perenne -perennial rye grass
Characters:
• 2-10 florets per spike
• One glume
Lolium multiflorum-annual rye grass
Characters:
• 10-22 florets per spike
• One glume

40. Poa – Kentucky blue grass, lawn grass,
Poa are notoriously difficult to key bring to Erin to ID
Characters:
• Leaf tips prow shaped
• Inflorescence panicle, contacted to open
• Sheaths mostly open
• Long cobwebby hairs at base of floret

41. Schedonorus arundinaceus -tall fescue
Characters:
• 1.5-2 m (6ft) tall
• Look VERY close at collar auricles, they are ciliate
• Wide coarse leaves.