While fire is usually considered to be a bane to the forest, some plants actually require fire to proliferate. One of these species is the bigberry manzanita.
Arctostaphylos glauca is a species of large shrub varying in size from one to well over six meters in height, known by the common name bigberry manzanita. It is one of several types of manzanita, which include Arctostaphylos glandulosa (Eastwood manzanita) and Arctostaphylos patula (greenleaf manzanita), Arctostaphylos parryana (Parry manzanita), Arctostaphylos pringlei (pinkbracted manzanita), and Arctostaphylos pungens (pointleaf manzanita).
The bigberry Manzanita is native to California and Baja California, where it grows in the chaparral and woodland of coastal and inland hills.
Arctostaphylos glauca growing in desert regions tend to be shorter than those on the coast. Leaves are light gray-green, somewhat waxy, oval in shape to nearly round, and smooth or toothed along the edges. They are up to five centimeters long and four wide and grow on short petioles about a centimeter long. The bark is red-brown and its branches crooked.
The inflorescence holds hanging clusters of narrow urn-shaped white flowers. The edible fruit is a round or egg-shaped drupe 12 to 15 millimeters wide. It is light red in color and has a thick pulp covered in a tough, sticky coat. The fruit contains three to six nutlets fused into a single mass or single large stone.
The Arctostaphylos glauca branchlets of the typical variety are glabrous.
The shrub reproduces by seed and by layering. Seeds require exposure to fire before they can germinate.
It is a long-lived species, reaching 100 years of age or more, though it does not begin to fruit until it is around 20 years old. The shrub is allelopathic, inhibiting the growth of other plants in its understory when rain leaches toxic arbutin and phenolic acids from its foliage. These compounds prevent the germination and growth of annuals for a distance of 3.3 to 6.6 feet from the edge of the canopy drip line.
Arctostaphylos glauca tolerates sand and clay. Arctostaphylos glauca does well in heavier soils but also excels in decomposed granite. It needs water for the first year but is quite drought tolerant afterwards. Bigberry manzanita is distinguished from other manzanitas by its large, viscid fruits. Unlike some manzanitas, this species does not have a lignotuber. It is shallow-rooted. The root habit is radially spreading, with coarse lateral roots exceeding the length of vertical roots.
Arctostaphylos glauca’s fruit is edible. The fruit is sour but does contain some sugar. Partially ripe berries make good manzanita jelly. Among the Cahuilla Native Americans of southern California, manzanita was regarded as a primary food source since it could be collected in volume and stored. It was once considered an important food additive. Typically, manzanita was used as an aspic, a thickener, or a sweetener to other foods. It also makes a pleasant beverage.
The leaves of various manzanita species are also used medicinally. Because the leaves contain arbutin, a glycoside that is broken down to hydroquinone in the urine, manzanita leaf tea has disinfectant qualities. This tea can be used in cases of mild urinary tract infections, chronic kidney inflammations, and water retention. The tea from the leaves also acts as a mild vasoconstrictor for the uterus and therefore can be helpful during painful and heavy menstruation. However, this is not advisable for use during pregnancy.
It is usually not a dominant chaparral species except in mixed chaparral of the San Gabriel and San Bernardino mountains. It occasionally forms dense, pure stands or codominates with Eastwood manzanita in manzanita chaparral.
Bigberry manzanita may hybridize with pointleaf manzanita (A. pungens) and Eastwood manzanita (A. glandulosa)
Bigberry manzanita flowers from mid-February to mid-March in chaparral and from mid-February to early April in pinyon-juniper woodlands.
Plants flower sporadically after these times, but later flowers do not set fruit. Fruit ripens from late February to mid-May in chaparral and from late February through May in pinyon-juniper woodlands. Seeds are dispersed in late summer. Germination occurs from mid-March to mid-April following fire scarification of seed. Fire kills bigberry manzanita. High-intensity fire may kill some seed, but merely cracks the seedcoat of most seeds without harming propagules.
One propagule usually outcompetes the others, resulting in establishment of one seedling per seed. Seedlings do not compete well with annuals or sprouting species but generally establish in greater numbers than other obligate seeders. Its large seed apparently gives this species a competitive advantage over other obligate seeders. Seedling mortality is high. Most seedlings are outcompeted or die from summer drought. Surviving seedlings grow rapidly, and mortality of adult plants is extremely low until the next fire.