A collection of examples of phytoremediation plants representing different methods of action and growth conditions and the morphological diversity of such plants.

One of the biggest problems of our time is environmental pollution. Environmental pollution can be successfully addressed through the use of herbaceous and woody plants, i.e., phytoremediation (Greek φuτo (phyto) - plant; Latin remedium - restoration). Phytoremediation is the process by which plants remove pollutants in the soil by breaking down or accumulating them in their roots, stems or leaves and by stimulating the activity of micro-organisms that break down hazardous substances. With the right selection of plants, taking into account their physiological characteristics, species and symbiosis with micro-organisms, it is possible to remove low concentrations of pollutants from soil and surface water. The phytoremediation process of plants depends on the rate and concentration of degradation of harmful substances. The biological significance of this phenomenon is still not fully understood: it could be argued, for example, that a high accumulation of toxic substances protects the plant against pests and makes it more resistant to disease. Phytoremediation can be characterized by the following different processes: phytoextraction, rhizofiltration, phytotransformation, rhizodegradation and phytovolatisation. These processes may occur together or separately. A collection was launched at the VU Botanical Garden in Kairėnai in autumn 2011 to introduce visitors to plants capable of stimulating spontaneous soil remediation processes, representing different modes of action, growth conditions and morphological diversity of plants. The project and the idea were initiated by the Public Enterprise "Soil Cleaning Technologies". The project was implemented with the support of Soil Cleaning Technologies and Vilnius City Municipality.

The first research on phytoremediation was carried out in Israel in the 1950s, but it was not until the early 1980s that more intensive research began. In Lithuania, a number of physical, chemical and biological methods for cleaning and restoring contaminated soil/ground were developed and discovered about two decades ago. Recently, more and more attention has been paid to phytoremediation or phytoremediation technology.

Plants selected for the phytoremediation collection shall reflect the morphological diversity of plants suitable for phytoremediation: life form (liana, tree, shrub, bush, shrubby, herbaceous) and roots (tufted, trunked, filamentous, cylindrical, ropy); the different modes of action of the phytoremediation process (phytoextraction, rhizofiltration, phytotransformation, rhizodegradation, phytovolatilisation); and the growth conditions of the plants: soil type (loam, sandy loam, sand and clay), soil contamination with petroleum products and heavy metals, salts, toxins and non-toxic substances.

		Wild thyme (Thymus serpyllum L.) A deciduous semi-shrub 10-30cm tall, forming a luxuriant shrub. The stem is woody at the base, rounded and hairy throughout. Leaves are short-stemmed, inverted-ovate. Inflorescences are head-shaped. Crown reddish-purple, pink, whitish, less often white. Blooms in the months of June to July. Fruits are dark brown nuts. Overwinters in zones 5-9. Thyme accumulates Benz(α)pyrene.
		Common dandelion (Taraxacum officinale F. H. Wigg.) Perennial herbaceous plant 5-40cm tall. Leaves are scrotal, pinnately divided, sometimes continuous. Inflorescences are erect, rounded, hollow, ending in a large yellow raceme. Blooms in the months of April to May, some flowers bloom until September. The fruit is a brown, husk-like fruit with an umbrella-shaped stalk. The common dandelion is a rather pesky weed. Overwinters in zones 5-9. Accumulates zinc (Zn), iron (Fe), cadmium (Cd), manganese (Mn), nickel (Ni), lead (Pb), copper (Cu).
		Field bindweed (Convolvulus arvensis L.) A perennial climber 20-80cm, sometimes up to 170cm, long. Leaves oblong-ovate or broadly lanceolate, the base lanceolate or arrow-shaped. Crown funnel-shaped, white, or pink, with 5 red stripes on the outer side. The flowers cluster in a bell-shaped inflorescence. Blooms in the months of June to September. The fruit is a brown, round nut. The ground creeper is a ruderal plant. Overwinters in zones 4-8. Accumulates oil.
		Hare’s-foot clover (Trifolium arvense L.) Herbaceous annual plant 8-30cm tall. Stem is steep, branched, hairy. Leaves trifoliate, oblong-linear. Flowers clustered in dense heads. The corolla is whitish, later pink. Blooms in the months of June to September. The fruit is generally ovoid, slightly flattened, yellowish-green or yellow and slightly shiny. Overwinters up to zone 10. Accumulates oil and molybdenum (Mo).