Chalk hyssop Hyssopus cretaceus Dubjan.

Chalk hyssop Hyssopus cretaceus Dubjan. (treated in Flora Europaea and other western sources as Hyssopus officinalis subsp. montanus (Jord. & Fourr.) Briq.)

You can barely imagine chalk hills without a bunch of spectacular endemic plants but one of them is especially significant. It is a species whose name was used by renowned botanist B.M. Koso-Polyanskiy to mark a group of endemics of chalk hills in Don & Volga rivers’ basins. It is a so-called ‘hyssop flora’, a cohort of species of southern origin, derived from Mediterranean antecedents, and namely a chalk hyssop.

Chalk hyssop is without doubt a flagship species. His nearest relative, common hyssop (Hyssopus officinalis) is a plant which is well-known to herbalists and physicians: flower stems have been used to cure chill and cough since ancient times. Common hyssop is native to Mediterranean, Caucasus, Iran and further east to Western Himalayas. It grows on dry slopes of hills and mountains. Hyssop has been cultivated since the Middle Ages and now is grown around the globe. The range of chalk hyssop is rather smaller but nevertheless it occupies vast areas in southern and central parts of Eastern-European plain. It can be found at a few sites in Dnieper basin but more usually on chalk outcrops in valleys of the tributaries of Don river and in adjacent areas of Volga river basin.

It is a dwarf semi-shrub (up to half a meter tall) with narrow greyish-green leaves and semi-woody bases of the stems. Beyond the blossoming period it is rather average. Chalk hyssop becomes noticeable in mid summer when slightly asymmetrical spike-shaped inflorescences of brightly blue flowers appear. They are unusual because white and yellow colours predominate in flowers of the majority of chalk plants. Since late summer dwarf shrubs of hyssop are best told by the combination of greenish and yellow colours since lower leaves start to shrivel and yellow earlier than upper ones.

Everyone who visits chalk slopes in mid summer steps into the world of strong fragrance. Its backbone is a fragrance of chalk thyme but chalk hyssop adds own note as well. One may crumble the hyssop leaves in fingers only once to memorize its fragrance forever… By the way, common hyssop is widely used to flavour fish and meat dishes or to add to the composition of alcoholic beverages e.g. Absinthe and Chartreuse & Benedictine liqueurs.

Chalk hyssop is a common but not numerous species. Even at sites overgrown by this species the distance between any neighbour hyssop shrubs usually isn’t less than half a meter. And indeed the sites which clearly meet the requirements of chalk hyssop rarely occupy considerable area. These are ‘living’ steep screes where small and big chalk fragments roll down the slope owing to the constant flow of water originated from spring snow melting or summer rains. It’s a hard task to survive in such a ‘vehement’ world but chalk hyssop copes with it. Upper parts of its root resemble an anchor and hold the plant in place despite constant pushes of chalk chips. The long tap root penetrates into chalk rock mass for several meters and grows up not down thus as if the plant hang on it. The root can reach 7-8 m length or generally 5-6 times longer than in plants of similar size which grow on the plain. Semi-woody stem bases bravely resist the pressure of chalk chips. Well-developed hyssop shrub is semi-spherical because all sprouts grow more or less uniformly right and left. But such fully-grown individuals can be seen only rarely.

Interestingly, chalk hyssop regenerates very well in abandoned chalk quarries. Just here on vast chalk screes you can easily find seedlings of this species.

Text by M. Banik
Photos by Eu. Skorobogatov, M. Banik, A. Korshunov