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- Dichotomous Key
- Poaceae
- Poaceae Group 3
- Danthonia
- Danthonia compressa
Danthonia compressa — flattened oatgrass
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Facts
Flattened oatgrass is native to eastern North America, and fairly common in New England, found in forest edges and openings, trail edges, logging roads, and less frequently in fields. It is reported to inhibit establishment of tree seedlings when it establishes in openings within disturbed forests.
Habitat
Anthropogenic (man-made or disturbed habitats), forest edges, meadows and fields
New England distribution
Adapted from BONAP data
Native: indigenous.
Non-native: introduced (intentionally or unintentionally); has become naturalized.
County documented: documented to exist in the county by evidence (herbarium specimen, photograph). Also covers those considered historical (not seen in 20 years).
State documented: documented to exist in the state, but not documented to a county within the state. Also covers those considered historical (not seen in 20 years).
Note: when native and non-native populations both exist in a county, only native status is shown on the map.
Found this plant? Take a photo and post a sighting.
Characteristics
- Habitat
- terrestrial
- New England state
-
- Connecticut
- Maine
- Massachusetts
- New Hampshire
- Rhode Island
- Vermont
- Leaf blade width
- 2–4 mm
- Inflorescence branches
- the flowers are attached to branches rather than to the main axis of the inflorescence
- Spikelet length
- 7–16 mm
- Glume relative length
- one or both glumes are as long or longer than all of the florets
- Awn on glume
- the glume has no awn
- One or more florets
- there is more than one floret per spikelet
- Lemma awn length
- 6–10 mm
- Anther length
- Up to 2.2 mm
-
Flowers
- Anther length
- Up to 2.2 mm
- Anther number
- 3
- Awn on glume
- the glume has no awn
- Glume relative length
- one or both glumes are as long or longer than all of the florets
- Glume veins
-
- 3
- 5
- 7 or more
- Inflorescence arrangement
- the spikelets are uniform
- Inflorescence axis orientation
-
- the inflorescence axis is arched or curved outward
- the inflorescence axis is straight
- Inflorescence branches
- the flowers are attached to branches rather than to the main axis of the inflorescence
- Inflorescence length
- 50–100 mm
- Inflorescence type (general)
- the spikelets are borne on stalks or on branches
- Inflorescence type (specific)
- the inflorescence is branched, and the branches do NOT both grow from the same side of the plant AND look like spikes
- Lemma awn base
- the awn is attached right at the tip of the lemma
- Lemma awn coiled
- the lemma awn is coiled at least one half turn
- Lemma awn length
- 6–10 mm
- Lemma awn number
- the lemma has one awn on it
- Lemma awn orientation
- the awn of the lemma on dried or older plants is curved or bent outwards
- Lemma cross-section
- the lemma is flat or rounded if you cut across the midpoint
- Lemma surface
- the surface of the lemma is relatively smooth (not counting any longitudinal veins or hairs)
- Lemma tip
- the lemma tip is split into two or more points
- Lemma vein number
- 7 or more
- One or more florets
- there is more than one floret per spikelet
- Palea relative length
- palea is one half to fully as long as lemma
- Spikelet axis tip
- there is an extension of the spikelet axis beyond the tip of the spikelet
- Spikelet length
- 7–16 mm
- Spikelets spiny
- the spikelets do not appear spiny
- Upper glume shape
- the upper glume is widest at or below the middle
-
Leaves
- Leaf auricles
- the leaves do not have auricles
- Leaf blade cross-section
- the leaf blade is more or less flat in cross-section, or slightly folded or rolled inwards
- Leaf blade width
- 2–4 mm
- Leaf ligule type
- the leaf ligule is in the form of fine hairs
- Leaf sheath closed around stem
- the margins of the leaf sheath are overlapping and not fused together except in the basal half (or less)
- Leaf sheath hairs
-
- there are hairs on the surface of the leaf sheath
- there are no hairs on the surface of the leaf sheath
-
Place
- Habitat
- terrestrial
- New England state
-
- Connecticut
- Maine
- Massachusetts
- New Hampshire
- Rhode Island
- Vermont
- Specific habitat
-
- edges of forests
- man-made or disturbed habitats
- meadows or fields
-
Stem, shoot, branch
- Stem spacing
- the stems grow close together in compact clusters or tufts
Wetland status
Occurs most often in non-wetlands, but rarely in wetlands. (Wetland indicator code: FACU-)
In New England
Distribution
- Connecticut
- present
- Maine
- present
- Massachusetts
- present
- New Hampshire
- present
- Rhode Island
- present
- Vermont
- present
Conservation status
Exact status definitions can vary from state to state. For details, please check with your state.
- Maine
- unranked (S-rank: SNR)
- Massachusetts
- widespread (S-rank: S5)
From Flora Novae Angliae dichotomous key
2. Danthonia compressa Austin ex Peck N
Flattened oatgrass. Danthonia alleni Austin • CT, MA, ME, NH, RI, VT; throughout. Forest edges and openings, edges of shaded trails, old logging road beds, uncommonly in old pastures and fields.
Native to North America?
Yes
Sometimes confused with
- Danthonia spicata:
- leaf blades involute, usually curling later in season and inflorescence 2-5 cm tall with upright branches (vs. D. compressa, with leaf blades flat, usually not curling later in season and inflorescence 5-10 cm tall with spreading branches).
Synonyms
- Danthonia alleni Austin