Hablitzia tamnoides, or Caucasian spinach, the sole species in the genus Hablitzia, is an edible, herbaceous perennial plant, native to the Caucasus region. It is in the family Amaranthaceae, subfamily Betoideae, related to Beta, but unlike that genus, is a vine, climbing to 3 m or more tall in summer. Caucasian spinach is a long-lived herbaceous perennial climber. In fact it is one of the very few vines in its family (Kadereit et al. 2006) - as one source put it, Hablitzia 'is remarkable and altogether anomalous in the order to which it belongs by its tall climbing habit’. It is also likely one of the longest lived plants in its family - one plant growing in Norrtälje, Sweden is reported to be over 50 years old. It is a diploid (2n=2x=18) with a basic chromosome number of 9 (Darlington & Wylie, 1955, p. 76).
Description
Leaves and stems
Caucasian spinach has green, heart-shaped (cordate) leaves, often slightly crimped, but without serration or lobing, which taper to a narrow point (acumiate), and sometimes have very soft, almost silky hairs on them. Hablitzia's leaf-surface is more or less matt, and the veins are arranged around a single, central axis. The stems are generally green, with noticeable ridges running their length and can be flushed red. The leaves are edible, similar to those of the related spinach.
Flowers
Hablitzia flowers are individually quite small, a lighter green than the foliage, perhaps greenish-yellow, and like little five-pointed stars, a fact that is reflected in the Norwegian name, Stjernemelde, which means Star-chenopod (Barstow 2014). They are borne profusely in an racemose, paniculate and/or thyrsoid arrangement. The flowers appear from late May through July. The flowers have a noteworthy quality, and that is their scent. Individually it isn't particularly pronounced. Even when flowers abound, you probably wouldn't notice it from any great distance. But if you draw close to a particularly floriferous Hablitzia, you might notice the air filled with scent almost exactly like crushed Coriander (Cilantro) leaf - rather unpleasant. What makes that interesting is that there is a story behind why some people have a strong aversion to Coriander - of a cluster of olfactory-receptor genes, one, called OR6A2, encodes a particular receptor that is highly sensitive to aldehyde chemicals such as those which contribute to the flavour of Coriander. Perhaps Hablitzia contains similar compounds to the unrelated umbellifer - if so OR6A2 may well play a role in our perception of Hablitzia flowers too. Flowers are hermaphrodite.
Seeds
Hablitzia produces tiny, glossy black seeds, sometimes in abundance.
Roots
In autumn, the aerial parts of both plants die back, but where the Tamus (or Dioscorea) retreats to a large, irregularly shaped subterranean tuber, Hablitzia almost always has its head either above the ground or very close to the surface. Even over winter, you can usually find, at the base of the old stems, a crown of more or less elongated buds or incipient shoots, which usually remain dormant until around February. Around the primary shoots, there are often many smaller, secondary buds ready to take over if the first flush is damaged (or eaten), which can be seen if you carefully remove the soil around the base of the plant. Occasionally the crowns seem to raise up out of the ground – or the surrounding soil washing away – exposing the thick, fleshy roots, which are somewhat like those of Sea Kale, and giving the dormant plant the appearance of an insane caudiciform.
Height
Hablitzia plants can easily grow to a height of around three meters with adequate support. However, they don't have tendrils or suckers and their stems seem to be only very weakly twining, so they climb mostly by twisting their leaf stalks around the structures upon and through which they grow, as many Clematis species do. Where support is lacking, they seem fairly happy sprawling almost horizontally across the ground or cascading down over the edges of the container, raised bed, or similar. Across their native range, they have even been observed hanging over the openings of caves.