Gundelia
Gundelia or tumble thistle is a low to high thistle-like perennial herbaceous plant with latex, spiny compound inflorescences, reminiscent of teasles and eryngos, that contain cream, yellow, greenish, pink, purple or redish-purple disk florets. It is assigned to the family Asteraceae. The flowers can be found from February to May. The stems of this plant dry-out when the seeds are ripe and break free from the underground root, and are then blown away like a tumbleweed, thus spreading the seeds effectively over large areas with little standing vegetation.
The main species in this genus is native to the eastern Mediterranean and the Middle-East. Opinions differ about the number of species in Gundelia. Sometimes the genus is regarded monotypic, G. tournefortii being a species with a large variability, but other authors distinguish up to [|nine species], differing in floret color and pubescence. Young stems are cooked and eaten in the Middle-East and are said to taste like a combination of artichoke and asparagus.
Description
Gundelia tournefortii is a spiny hemicryptophyte with stems that branch from the base. The first growth of the plant consists of a rosette of leaves. All parts contain a milky latex. The parts above the surface break from the root and may be blown away by the wind as a tumbleweed, assisting in the dispersion of the seed. All counts executed so far arrive at eighteen chromosomes.Root, stems and leaves
The plant develops a woody, vertical rootstock of up to 4 cm in diameter, at the surface usually covered by the remains of old leaves. The leaves are sessile or decurrent at their base with spiny wings, and alternate set along the stems. The lowest leaves are usually 7–30 cm long and 4–16 cm wide, pinnately dissected and the sections of the larger leaves may be pinnately parted themselves, and have a dentate or serrate margin, all tipped with spines. The midvein and sideveins are prominent, whitish, sometimes tinged purple. The leaf surface may be covered in spiderweb-like hairs, that tend to wither away quickly.Inflorescence
The stem divides into ten or more branches, each of which is topped by a compound spiny ovoid inflorescence of 4–8 cm in diameter, which may be covered in dense arachnoid hairs. This inflorescence is unusual for members of the family Asteraceae, as each true flower head is so far reduced as to only contain one floret, which is surrounded by its own involucre. Five to seven of these monofloral flower heads combine into secondary flower heads, each subtended by a spiny bract hardly or substantially longer than the secondary flower heads, with only the centre floret developing a cypsela, and the surrounding ones only producing pollen. These secondary flower heads later break free from the globose assembly of flower heads that sit on the end of each branch of the stem during the tumbleweed-stage. Remarkable for a member of the tribe Cichorieae are also the disk florets, a trait that is further only present in Warionia saharae.The pentameric corollas are usually 7–10 mm long, gloomy purple or yellowish outside, white to bright yellow, greenish, flesh colored or silvery to red purple inside, with spreading narrow lobes of 3–4 mm mm long and about 1 mm wide, the tube hairless inside. The five merged anthers form a cylinder of 4–6 mm long, yellow or brownish in color. The style arms are also brownish.
Pollen is covered in acute spines.
Fruit and seed
The involucral bracts of the secondary flower heads are merged into a brown, durable, hard cup with a fibery fringe. Each contains only one cypsela of about 8 mm long, 5 mm at its widest, somewhat dorsally compressed, narrow at its base and widest beyond halflength, with the pappus at its tip consisting of a 2 mm high cup, narrowest at its base.Characters common to all Asteraceae
Like in all Asteraceae, the pentameric flowers have anthers that are fused together forming a tube through which the style grows. The style picks up the pollen on hairs along its length and splits into two style branches at its tip. These parts sit on an inferior ovary that grows into an indehiscent fruit in which only one seed develops. All florets are set on a common base, and are surrounded by several rows of bracts, that form an involucre. A particular character of Gudelia that is rare among the Asteraceae is that florets are gender specialised, with the central floret being functionally hermaphrodite and the marginal florets being functionally male.Characters common to Cichorieae
Tumble thistles are assigned to the Cichorieae-tribe that shares anastomosing latex canals in both root, stem and leaves, and has flower heads only consisting of one type of floret. In Warionia and Gundelia these are exclusively disk florets, while all other Cichorieae only have ligulate florets. Gundelia is unique in the complex morphology of the inflorescences.Differences with other genera
Warionia and Gundelia share a thistle-like appearance, anastomosing latex-ducts, floral heads that only contain disk florets, spurred anthers, and styles with branches and highest part of the scape covered with long hairs. Gundelia however is herbaceous, has monofloral primary flower heads combined into groups of five to seven, the centre floret hermaphrodite, the marginal florets functionally male, and those groups combined in ovoid spiny florescences at the end of the stem, and spiny leaves, florets dull yellow to dull purple on the inside, purple to rusty on the outside. Warionia is a shrub, has many dandelion-yellow florets in each flower head, single or with two or three together at the end of the branches, the leaves dentate but not spiny.Scolymus is also a thistle-like herbaceaceous perennial with anastomosing latex-ducts, related to Gundelia, but it has many yellow, orange or white ligulate florets in each flower head, which are arranged with many in a spike-like inflorescence, or with a few at the end of the stems.