Strobilus

strobilus [ stroh-BAHY-luhs ] noun, plural strobili: cone-shaped mass of ovule- or spore-bearing scales or bracts; reproductive structure of conifers

Tsuga canadensis (eastern hemlock) strobili: yellow male strobili along leaf axils; green female strobilus at branch terminal; and brown seed cone. — *Tsuga canadensis* (eastern hemlock) strobili: yellow male strobili along leaf axils; green female strobilus at branch terminal; and brown seed cone.
Photo © Elaine Mills

Some seed-producing plants, like conifers, cycads and gingkos, do not have flowers and fruit. Instead their reproductive structures are strobili: microstrobilus (in place of male flowers) and megastrobilus (in place of female flowers and fruit).

The male strobilus (commonly called a pollen cone) produces pollen grains, which are dispersed by the wind so that they can reach female strobili on other trees of the same species. After it releases its pollen, the microstrobilus dies away. Although male strobili look similar in structure from conifer to conifer, female cones are larger and distinctive among the species.

The female strobilus (also known as an ovulate cone or seed cone) contains ovules, which in the Pinaceae (pine family) are located in pairs side-by-side on the surface of each scale. After fertilization, each ovule develops into one seed. A pine seed cone may take two to three years to mature and may remain on the tree of some species for more than ten years before it drops to the ground. To keep its seeds viable during this time or even after it falls to the ground, it can close its scales in cold, windy, or wet weather–submerged in water this takes less than 30 minutes. Scales open when the weather is warm and dry enough for seed dispersal by wind or animals or for germination.

We may easily recognize the female strobili of pine, but people often mistake the fruit of some species like juniper and yew for berries. The fleshy seed cone of cypresses (and sometimes junipers) is also called a galbulus.

Strobili of Various Conifers

Immature male strobili of Cedrus libani — Immature male strobili of *Cedrus libani* ‘Nana’ (dwarf cedar of Lebanon) in Sept. Photo © Christa Watters

Dehisced male strobili of Cedrus libani — Dehisced male strobili of *Cedrus libani* ‘Nana’ (dwarf cedar of Lebanon) in early January.
Photo © Mary Free

Male strobili of Juniperus virginiana — Male strobili of *Juniperus virginiana* (eastern redcedar) appear in large groups at the tips of branches in August. Photo © Elaine Mills

Birds eat the bluish, berry-like seed cones of Juniperus virginiana — Birds eat the bluish, berry-like, female (seed) cones of *Juniperus virginiana* (eastern redcedar) dispersing the 1–3 seeds found within each.
Photo © Mary Free

Pollen-laden male strobili of Pinus densiflora 'Umbraculifera' — Pollen-laden male strobili of *Pinus densiflora* ‘Umbraculifera’ (Tanyosho pine) in May.
Photo © Mary Free

Developing female strobili at the base of branch buds of Pinus densiflora 'Umbraculifera' — Female strobili at branch bud base of Tanyosho pine in December.
Photo © Mary Free

Developing male strobili encircling a branch bud of native Pinus palustris — Developing purple-blue male strobili, which will produce pollen in spring, encircling a branch bud of native *Pinus palustris* (longleaf pine) in February. Photo © Elaine Mills

Male and female strobili of Pinus taeda — Male (yellow-brown) and female (maturing in 2 years and shedding seeds soon thereafter) strobili of *Pinus taeda* (loblolly pine) in April.
Photo © Christa Watters

Female strobilus of native Pinus strobus — Female strobilus with resin drops at scale tips of *Pinus strobus* (eastern white pine).
Photo © Mary Free

Male strobili of Taxus x media — Male strobili of *Taxus x media* (yew) arising from leaf axis on undersides of branches in March.
Photo © Elaine Mills

Female strobilus of Taxus brevifolia (pacific yew) produces a fruit, which is a red, cup-shaped aril that holds one poisonous seed. Photo courtesy of VA Tech Dendrology

Female strobili of Taxodium distichum — *Taxodium distichum* (baldcypress) in July. The scales are fused into a rounded, fleshy cone called a galbulus.
Photo © Elaine Mills

Hardened galbuli of Taxodium distichum — Hardened galbuli of *Taxodium distichum* in November. At maturity each cone disintegrates to release 20–40 seeds. Photo © Elaine Mills

Other Strobili

Left (or above): The spore-producing structures of Equisetum hyemale (horsetail), a non-flowering evergreen perennial, are called strobili.

Right (or below): Hops, used in beverages like beer, are the flowers of the climbing, herbaceous perennial Humulus lupulus and are called strobili.

The seeds from female pine strobili, known as pine nuts, piñón, or pignoli, are edible although those most widely consumed in the United States are from southwestern U.S. native Pinus edulis (pinyon pine) and in Europe are from northern Mediterranean native Pinus pinea (stone pine). However, the strobili, as well as other plant parts, of many conifers are poisonous.

NOTE: Plants in the wild should not be eaten without consulting an expert or authoritative field guides for information on identification and food preparation. It is easy to confuse plants in the wild, so you should be 100% sure they are edible before consuming them. Remember:

Just because a plant is not identified as toxic does not mean that it is safe to eat.
Sometimes only certain parts of a plant are edible and other parts of the same plant are toxic.
Sometimes parts are only edible at a certain time in their life cycle or when prepared in a certain way.

Reference

Arnett M. December 15, 2016. Unlocking the Secrets of the Pinecone. Scientific American.

Burns RM, Honkala BH, tech. coords. 1990. Silvics of North America: 1. Conifers, 2. Hardwoods. Agriculture Handbook 654. U.S. Department of Agriculture, Forest Service, Washington, DC.