Sporobolus compositus — rough dropseed
![Inflorescences: Sporobolus compositus. ~ By Elizabeth Farnsworth. ~ Copyright © 2024 New England Wild Flower Society. ~ Image Request, images[at]newenglandwild.org](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Poaceae/sporobolus-compositus-compositus-in-efarnsworth.jpg)
![Stems and sheaths: Sporobolus compositus. ~ By John Hilty. ~ Copyright © 2024 John Hilty. ~ john[at]illinoiswildflowers.info ~ Illinois Wildflowers - www.illinoiswildflowers.info/index.htm](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Poaceae/sporobolus-compositus-compositus-ss-jhilty.jpg)
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Facts
Widespread in the Great Plains and Midwest, rough dropseed is rare in New England. It occurs on a variety of open habitats, mostly with sandy substrates. As with other grassland species, the apparent decline of rough dropseed in New Enlgland may be due to widespread reforestation since the late nineteenth century. There are two varieties present in New England, both of conservation concern. One of them (Sporobolus compositus var. compositus) is found in Connecticut, Massachusetts, Rhode Island and Vermont, while the other (S. compositus var. drummondii) is found only in Maine.
Habitat
Anthropogenic (man-made or disturbed habitats), cliffs, balds, or ledges, coastal beaches (sea beaches), forest edges, grassland, meadows and fields, ridges or ledges, shores of rivers or lakes, talus and rocky slopes
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.
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enlargeCharacteristics
- Habitat
-
- terrestrial
- wetlands
- New England state
-
- Connecticut
- Maine
- Massachusetts
- Rhode Island
- Vermont
- Leaf blade width
- 1.5–10 mm
- Inflorescence branches
-
- the flowers are attached to branches rather than to the main axis of the inflorescence
- there are no branch points between the base of the inflorescence axis and the flowers, or they are not obvious
- Spikelet length
- 4–10 mm
- Glume relative length
- neither glume is quite as long as all of the florets
- Awn on glume
- the glume has no awn
- One or more florets
- there is one floret per spikelet
- Lemma awn length
- 0 mm
- Leaf ligule length
- 0.1–0.5 mm
- Anther length
- 1–2 mm
-
Flowers
- Anther length
- 1–2 mm
- Anther number
- 2–3
- Awn on glume
- the glume has no awn
- Floret lower bract texture
- the lemma is thin and flexible
- Floret types within spikelet
- all the florets within a spikelet are similar
- Glume relative length
- neither glume is quite as long as all of the florets
- Glume veins
-
- 0
- 1
- Inflorescence arrangement
- the spikelets are uniform
- Inflorescence axis orientation
- the inflorescence axis is straight
- Inflorescence branches
-
- the flowers are attached to branches rather than to the main axis of the inflorescence
- there are no branch points between the base of the inflorescence axis and the flowers, or they are not obvious
- Inflorescence length
- 50–300 mm
- Inflorescence type (general)
-
- the inflorescence is a spike, or is spike-like, lacking obvious branches
- 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
- NA
- Lemma awn length
- 0 mm
- Lemma awn number
- the lemma has no awn
- 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 a simple point, with or without an awn (long narrow extension ending in a point)
- Lemma vein number
- 1
- One or more florets
- there is one floret per spikelet
- Palea relative length
- palea is one half to fully as long as lemma
- Spikelet axis tip
- there is no extension of the spikelet axis beyond the tip of the spikelet
- Spikelet length
- 4–10 mm
- Spikelets spiny
- the spikelets do not appear spiny
- Upper glume shape
- the upper glume is widest at or below the middle
-
Growth form
- Lifespan
- the plant lives more than two years
-
Leaves
- Leaf auricles
- the leaves do not have auricles
- Leaf blade width
- 1.5–10 mm
- Leaf ligule length
- 0.1–0.5 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
-
Place
- Habitat
-
- terrestrial
- wetlands
- New England state
-
- Connecticut
- Maine
- Massachusetts
- Rhode Island
- Vermont
- Specific habitat
-
- cliffs, balds, or ledges
- edges of forests
- grasslands
- man-made or disturbed habitats
- meadows or fields
- ridges or ledges
- sea beaches
- shores of rivers or lakes
- talus or rocky slopes
-
Stem, shoot, branch
- Stem spacing
-
- the stems grow close together in compact clusters or tufts
- the stems grow singly or a few together (they may form diffuse colonies)
- Stem thickness at base
- 1–5 mm
Wetland status
Not classified
In New England
Distribution
- Connecticut
- present
- Maine
- present
- Massachusetts
- present
- New Hampshire
- absent
- Rhode Island
- present
- Vermont
- present
Conservation status
Exact status definitions can vary from state to state. For details, please check with your state.
- Vermont
- rare (S-rank: S2), endangered (code: E)
var. compositus
- Massachusetts
- unranked (S-rank: SNR)
- Rhode Island
- extremely rare (S-rank: S1), concern (uncertain) (code: C*)
var. drummondii
- Maine
- extremely rare (S-rank: S1), endangered (code: E)
Subspecies and varieties
Variety compositus is known from CT, MA, RI, VT. Variety drummondii is known from ME and is disjunct from other populations of this taxon. Both varieties are of regional conservation concern.
From Flora Novae Angliae dichotomous key
2. Sporobolus compositus (Poir.) Mer. NC
rough dropseed. 2a. Sporobolus asper (Beauv.) Kunth; 2b. Sporobolus asper (Beauv.) Kunth var. pilosus (Vasey) A.S. Hitchc.; S. drummondii (Trin.) Vasey • CT, MA, ME, RI, VT. River shores, banks, and outcrops, lakeshore headlands, sandy fields and coastal beaches, dry openings and barrens.
1a. Reproductive stems 2–5 mm thick; upper sheaths 2.6–6 mm wide; inflorescences with 30–90 spikelets per cm2 when pressed … 2a. S. compositus var. compositus
1b. Reproductive stems 1–2 (–2.5) mm thick; upper sheaths 0.8–2.5 mm wide; inflorescences with 16–36 spikelets per cm2 when pressed … 2b. S. compositus var. drummondii (Trin.) Kartesz & Gandhi
Variety compositus is known from CT, MA, RI, VT. Variety drummondii is known from ME and is disjunct from other populations of this taxon. Both varieties are of regional conservation concern.
Native to North America?
Yes
Sometimes confused with
- Sporobolus clandestinus:
- lemmas pubescent or scabrous, chartaceous, opaque, caryopsis mostly 2.4–3.5 mm long, and lower sheaths often sparsely pubescent (vs. S. compositus, with lemmas glabrous and smooth, membranceous to chartaceous, hyaline, caryopsis 1–2 mm long, and sheaths glabrous except near apex).
Synonyms
- Sporobolus asper (Beauv.) Kunth