Bur-reeds (Sparganioideae)

Bur-reeds (Sparganioideae)

The second subfamily — the bur-reeds — is also represented by a single genus, Sparganium (bur-reed). About 15–20 species of Sparganium are known, widely distributed in subarctic, temperate and subtropical regions of the Northern Hemisphere. Only two species reach the Southern Hemisphere (Australia and New Zealand). Sparganium has a thin cordlike rhizome with two types of roots, as in cattails (Typha). Stems may be branched or simple, erect or floating.

Sometimes they are robust, 1.5–2 m long in Sparganium erectum, or thinner and weaker, only 8–30 cm long in Sparganium minimum.

Leaves are cauline. In erect forms they slightly exceed the stem and, gradually decreasing, pass into the bracts that subtend the inflorescence. Many Sparganium species have submerged forms that live in deep or fast-flowing waters. In these plants the leaves are ribbon-like, up to 2 m long and only 0.1–0.3 to 1.5–3 cm wide (hence the genus name, from Greek sparganon — ribbon). The leaves of these forms are either entirely submerged, or their upper parts are at the water surface where they form mats. Erect leaves are often keeled on the abaxial side (sometimes triangular in cross-section). Floating leaves are usually flat. All parts of the plant are provided with a system of air canals divided into chambers, ensuring aeration.

Flowers of Sparganium are sessile or pedicellate, gathered in small, about 1.5 cm in diameter (up to 2.5 cm in fruits), globose axillary or extra-axillary heads. In fruit these heads resemble a hedgehog (hence the Russian name), because the fruits projecting in different directions and closely packed are usually narrowed at the top and retain style remnants. The heads, in turn, are arranged in a simple spike-like or compound paniculate inflorescence, mostly branched, sometimes up to 70 cm long. They may be clustered or dispersed, the lower ones pedicellate, the upper ones mostly sessile, usually numerous; less often there are 2–4, rarely 1, female as well as male heads. The perianth consists of 3–6, more rarely 1–2, free linear or spatulate scales. In some species (Sparganium erectum) they are thick, at the apex light- or dark-brown to black, in others (Sparganium emersum) thin, pale-colored or colorless. Male flowers have 3, more rarely 1–8 stamens; their filaments, unlike those of Typha, are free or united only at the bases; anthers are linear. Pollen grains are single. The perianth of the female flowers persists after flowering. Fruits are one-seeded, but sometimes 2- or 3-seeded.

Fruits ripen in autumn. Mature female inflorescences of cattails (they are sometimes called "cones") seemingly burst or split, and the fruits equipped with tufts of hairs energetically protrude from them. They are picked up by the wind and carried long distances (anemochory). During flight the hairs of the fruit bend downward toward the base of the stalk, and the fruitlet turns 180° and ends up (together with the stigma) below the "opened parachute" of hairs. In this form the fruits are easily held in air currents. Upon landing on the water surface, the fruits of Typha remain afloat for the first 1–4 days due to their hairs and are carried by the current for some distance (partial hydrochory). According to G. Ridley (1930), the fruits of Typha angustifolia can remain on the water for up to four weeks and are carried far from the parent plant during that time. Then they sink to the bottom, where they open and release the seeds. Fallen ripe fruits of Sparganium remain afloat for a long time thanks to the well-developed spongy tissue of the exocarp. According to the same Ridley, fruits of Sparganium erectum can float for 12 months, and those of Sparganium minimum and Sparganium emersum for 6 to 15 months, being carried by currents (hydrochory). They are also easily transported over the water surface by wind for long distances (partial anemochory). Sometimes Sparganium fruits are dispersed after being eaten by wild ducks (ornithochory). Sparganium seeds also germinate on the bottoms of water bodies. The seedling emerges through a narrow opening (pore) at the upper end of the seed. From the moment of germination to the appearance of the first leaf takes 1–1.5 months. By the third year the plant becomes mature and produces reproductive shoots. Species of Sparganium, as well as species of Typha, often hybridize with each other.

Humans use typhaceous plants, more often Typha. The starch-rich rhizomes of Typha were previously used as food in Russia, and in some regions of East Asia still are, boiled or baked; flour is also made from them. Typha flour is similar to potato flour, as it lacks gluten and consists almost entirely of starch. In pure form it is used for kissels, to prepare kvass, and to make starch. Mixed with rye or wheat flour, Typha flour is used to bake bread, gingerbread, and sponge cakes. Rhizomes cut into pieces and dried are stored for later use. In boiled form young shoots of Typha substitute for asparagus, resembling it in taste. A decoction of Typha roots is used in folk medicine against scurvy, and Sparganium rhizomes are used for snakebite. Young stems and rhizomes of Sparganium and Typha serve as food for valuable fur-bearing and game animals — muskrat, nutria, beaver, desman, brown bear, and wild boar. Sparganium is also eaten by spotted deer and wild ducks. Young shoots are readily eaten by carp. Typha stems are used as building material, for roofing, and for wattle. Leaves and stems, after preliminary soaking, are used by locals for weaving baskets, mats, rugs, and the like. Ropes made from Typha are used to tie vine shoots. Numerous hairs of the perianth (the "fluff") of the female part of the Typha inflorescence are used as packing and stuffing material (for pillows, life belts), and mixed with animal wool — for making felt. The female parts of the inflorescence (the "cones") are often used to decorate interiors.