horsetails

genus Equisetum

Member of horsetail family (family Equisetaceae)
horsetails (order Equisetales)
horsetails (subclass Equisetidae)
ferns (class Polypodiopsida)

Except for historical records that I'm ignoring, there are no other wild species of this genus in the bay area.

Leaves are extremely small, in a whorl from stem nodes, and fused into an appressed sheath. The number of sheath teeth equals the number of leaves.

Branches are much longer, also in a whorl from stem nodes. Photosynthesis generally takes place in the stem and branches.

Some species make separate sterile and fertile stems. Sterile stems are green, but fertile stems may not be.

Key features:

basal internode of branch < or > subtending nodal sheath
number of teeth per sheath
branch hollow or solid

Separate sterile and fertile stems

great horsetail
Equisetum telmateia

sterile stem 30–100 cm tall, light green, regularly branched

basal internode of branch < subtending nodal sheath [significantly?]
branch is solid, has 4–5 grooved ridges lengthwise

[do these look like 4–5 pairs of ridges?]

sheath teeth 14–28

fertile stem 17–45 cm tall, brown, unbranched, fleshy

sheath teeth 20–30

very common

field horsetail
Equisetum arvense

sterile stem 10–60 cm tall, green, regularly branched

basal internode of branch > subtending sheath [but maybe not by a lot]
branch is solid, has 3–4 rounded ridges lengthwise
sheath teeth 6–14

fertile stem 11–32 cm tall, brown, unbranched, fleshy

sheath teeth 6–10

common

Single type of stem

marsh horsetail
Equisetum palustre

stem 20–80 cm tall, green
basal internode of branch < subtending nodal sheath [significantly?]
branch is hollow, has 4–6 rounded ridges lengthwise
sheath teeth 5–10
very rare

western scouringrush
Equisetum hyemale ssp. affine

stem 60–210 cm, green, no branches
sheath generally with 2 dark bands: 1 at base and 1 at tip
sheath teeth 22–50
common

smooth horsetail
Equisetum laevigatum

stem 30–180 cm, green, no branches
sheath generally with 1 dark band at tip
sheath teeth 10–26
uncommon

Toxicity of foxtail, horse willow, horsetail, mexican horsetail, rush (Equisetum spp.):
4 – Ingestion of these plants, especially in large amounts, is expected to cause serious effects to the heart, liver, kidneys or brain. If ingested in any amount, call the poison center immediately.

2 observed taxons / 4 unobserved taxons / 2 keys

Chris’s observations: 23 (13 are research grade)

Locations:

Big Basin SP: 3
Pescadero Creek CP: 3
Ansel Adams Wilderness: 2
El Corte de Madera OSP: 2
Murray Ranch SP: 2
Alum Rock Park, San Jose
Castle Rock SP
Garrapata SP
Golden Gate National Recreation Area
Mt. Tamalpais Watershed
Nisene Marks SP
Portola Redwoods SP
Purisima Creek Redwoods OSP
Russian Ridge OSP
San Bruno Mountain State & County Park
Skyline Ridge OSP

Months:

Apr.: 2
May: 5
Jun.: 0
Jul.: 6
Aug.: 7
Sep.: 3

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Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora