Woody plants of the modern collection of the Peter the Great Botanic Garden introduced into cultivation by the Garden

There are 150 species of 70 genera of 31 families of woody plants in the collection of the Peter the Great Botanic Garden of the Komarov Botanical Institute RAS (former Imperial St. Petersburg Botanical Garden) which were introduced into general cultivation by this Garden. In fact, all of them represent the flora of Russia and of the bordering countries. The majority of species were introduced in the 19th century. The main contribution into the primary introduction of plants was made by C.I. Maximowich (1827-1891) after his two travels to the Far East of Russia in 1853-1857 and 1859-1864

New forms of maples (<i>ACER</i> L., <i>Aceraceae</i>) cultivated at Peter the Great Botanic Garden (ST. Petersburg, Russia)

The article contains description of two new maple forms - Acer miyabei Maxim. f. suberosum Byalt et Firsov forma nova (Aceraceae) and Acer saccharinum L. f. variifolium Byalt et Firsov forma nova – cultivated at Peter the Great Botanic Garden of the Komarov Botanical Institute RAS in St. Petersburg, Russia. The article contains a brief history of the introduction of A. miyabei Maxim. and A. saccharinum L., information about the origin of the planting material in the park of the botanical garden of RAS, basic differences between the new forms and similar taxa (incl. Latin diagnoses), as well as data about standard samples and their storage. The article has color photos of the alive plants located in the botanical garden of RAS. Both maple forms are very decorative and appear to be very useful for a large-scale implementation in the urban landscape planting

The modern state of elms (Ulmus L., Ulmaceae) in arboretum of Peter the Great Botanic Garden under conditions of epiphytoty of the Dutch elm disease

The dying of elms (Ulmus L.) at Peter the Great Botanic Garden of the Komarov Botanical Institute RAS in Saint-Petersburg has been observed since the beginning of the 1990’s, soon after the considerable St.-Petersburg climate warming in 1989. During the period from 1981 (the year of the last total inventory of the Botanic Garden) to 2015 three hundred and eighty five trees died, were cut down and removed. They belonged to 12 Ulmus biological and cultivars species: U. laevis – 317 (11 trees are still alive, but all of them are infected, stem dried out from 25 to 70%), U. glabra – 40 (died completely in 2013); U. glabra ‘Camperdownii’ – 6 (died completely in 2014); U. minor – 6 (died completely in 2011); U. аmericana – 4 (died in 2007); U. × hollandica ‘Wredei’ – 3 (died in 2013); U. macrocarpa – 2 (died in 2006); U. pumila ‘Argenteo-variegata’ – 2 (died in 2007); U. japonica – 2 (1 tree is still alive); U. laciniata – 1 (died in 2015); U. parvifolia – 1 (3 trees are still alive); U. pumila – 1 (5 trees are still alive). The most severe dying began after abnormally warm winter 2006/07, the largest amount died in 2013. The most resistant to Dutch elm disease taxa were U. parvifolia and U. pumila. Further research is needed for other two taxa (U. × arbuscula and U. japonica). Selection of elms for resistance to Dutch elm disease seems to be possible. Frost damaging of many exotic tree species in St.-Petersburg has been considerably diminished because of climate warming during the previuos decades. However, introduction of some species is became limited by new negative factors, especially biotic ones (new plant diseases and pests). The future arboreal species assortment for parks and gardens of St.-Petersburg and surrounding settlements should be considerably revised in respect to this climate change

Species of <i>Juglandaceae</i> at Peter the Great Botanic Garden at Apothecaries Island

The first exotic species of Juglandaceae family at Peter the Great Botanic Garden of the Komarov Botanical Institute RAS in Saint-Petersburg was Juglans regia - mentioned at M. M. Terechovskij ‘s Catalogue in 1796. Twenty five taxa from 4 genera have been tested since then: Carya - 6, Juglans - 14, Platycarya - 1, Pterocarya - 4. There are 14 taxa from 3 genera in modern collection: Carya - 2, Juglans - 9, Pterocarya - 3. All species besides Carya cordiformis and Juglans nigra produce fruits. Four species of Juglans (J. ailanthifolia, J. cinerea, J. cordiformis, J. mandshurica) and its hybrids produce self-sowing. There are 2 species, Juglans ailanthifolia and Pterocarya pterocarpa, which are included into the Red Data Book of Russian Federation (2008). They need In situ and Ex situ conservation and may be recommended for Saint-Petersburg’s city planting. There are considerable prospects for both repeated introduction (Carya illinoensis) and primary introduction (Juglans sigillata)

Evaluation of larch trees (<i>Larix</i> Mill., <i>Pinaceae</i>)

Peter the Great Botanical Garden of the Komarov Boranical Institute has 148 larch samples (Larix Mill., Pinaceae) which represent 22 taxa. They are long-lived large trees, up to 200 years of age, representing the base for a forest stand of an arboretum and forming alleys in the oldest regular part of the Garden. The tallest trees reach 31,6 m (L. dahurica) and 113 cm in diameter (L. decidua and L. dahurica). Due to the warming in the St. Petersburg area, there is a noticeable drying found on the trees' crowns. Based on the results of an inventory in 2015, 43 trees can be assigned to the first category; the other 105 trees suffer from drying of shoots, twigs and branches. The degree of drying corresponds with the age of trees. One of the possible reasons of the deterioration in the conditions of larch trees at the arboretum of the Komarov Botanical Institute may be the influence of the Phytophthora species. Soil research samples show presence of Phytophthora syringae (Berk.) Kleb. in the risosphere of L. decidua. It is the first time, this species of Phytophthora has been discovered at the Peter the Great Botanical Garden