Antirrhinum coulterianum: A New World Snapdragon with a Unique Rosette
Antirrhinum coulterianum, also known as Coulter’s snapdragon or white snapdragon, is a species of flowering plant in the family Plantaginaceae. It belongs to the genus Antirrhinum, which includes about 40 species of snapdragons native to Europe, North Africa and North America.
This species is endemic to southern California and Baja California, where it grows in desert shrublands and in the coastal hills and mountains, especially in areas that have recently burned. It is an annual herb that produces an erect stem up to 1.5 meters tall, which often clings to objects or other plants for support. It is mostly hairless, except for the inflorescence at the top, which can be quite woolly.
One of the distinctive features of this plant is that it forms a basal rosette of leaves at the base of the stem; this is the only Antirrhinum that does so. The leaves are sparse and generally linear, up to 10 centimeters long. The flowers are arranged in a raceme at the top of the stem, and are white with lavender or pink tints, especially when newly opened. Each flower is about a centimeter wide, with a typical snapdragon shape: a tubular corolla with two lips, the upper one arched and the lower one spreading. The flowers are pollinated by bees and butterflies.
Antirrhinum coulterianum blooms from March to June, and produces small brown capsules containing many tiny seeds. The seeds are dispersed by wind or animals. The plant can also reproduce vegetatively by rooting at the nodes of the stem.
This plant is not widely cultivated, but it can be grown as an ornamental in sunny and dry locations. It prefers sandy or rocky soils with good drainage. It can tolerate some frost, but not prolonged cold or wet conditions. It can be propagated by seeds or cuttings.
Antirrhinum coulterianum belongs to the tribe Antirrhineae, which includes about 300 species of snapdragons and related plants in the family Plantaginaceae. This tribe is divided into two subtribes: Antirrhininae and Maurandyinae. The former includes Antirrhinum and its close relatives, such as Misopates, Pseudomisopates and Sairocarpus. The latter includes genera such as Maurandya, Asarina and Lophospermum.
The genus Antirrhinum is further divided into three sections: Antirrhinum, Orontium and Saerorhinum. The first section includes the Old World species, mostly perennials with a chromosome number of 2n=16. The second section includes two annual species with a chromosome number of 2n=18, A. orontium and A. molle. The third section includes the New World species, mostly annuals with a chromosome number of 2n=14 or 12.
Antirrhinum coulterianum is placed in the section Saerorhinum, along with about 10 other species from North America. This section is characterized by having a basal rosette of leaves, a woolly inflorescence, a corolla tube with a spur-like projection at the base, and a capsule that opens by pores at the top. Some of the other species in this section are A. multiflorum, A. nuttallianum and A. vexillo-calyculatum.