Dangerous weed Galinsoga small-flowered - Galinsoga parviflora
In connection with the noticeable warming of the climate, especially over the past 5-6 years, relatively "new" weeds, previously not characterized by high harmfulness to our region, have begun to conquer "living space".
The summer heat of 2003 was particularly favorable for them, and the weather conditions of cool May and part of June 2004, when they were able to develop their root system and "clog" other weeds and crops with their growth, were probably optimal.
This applies primarily to Galinsoge small-flowered (Gali nsoga parviflora Cav.) - a weed, which, in principle, was previously available in the North-West (including the Leningrad Region), but its influence and harmfulness in cultivated plantings were not so noticeable.
Small-flowered Galinsoga (family Asteraceae) is an early annual spring weed. The emergence of the first wave of its seedlings is extended from early spring to early June. The plant develops throughout the growing season. Its seeds are capable of germination even at 6 ... 8 ° C, the maximum germination depth is 2-3 cm; the optimum temperature for weed growth is 16 ... 20 ° C. Under favorable conditions during the growing season, each plant is capable of producing from 50 to 300 thousand seeds. An interesting feature of small-flowered Galinsoga, according to scientists, is the relatively high level of germination of its seeds.
This weed, reaching a height of 60-70 cm, has an erect, oppositely branched stem with numerous branches and ovate or lanceolate leaves with short, almost fused petioles. It blooms and bears fruit all summer and autumn, but reaches its full development in the second half of summer. In the plant, the marginal flowers are female (almost always there are 5, sometimes 7), white or slightly creamy; internal - bisexual, numerous, funnel-shaped, yellow. Achenes are conical-tetrahedral, dark gray, covered with light hairs.
The flyworms are composed of white, very short ciliate (almost linear) films. Thanks to these ciliated filaments, the seeds can be carried over very long distances by the wind. In the scientific literature it is noted that achenes can also ripen on plants already torn out of the ground. If, when pulled out, many types of weeds wither naturally (even while on the surface of the earth), then Galinsoga has an amazing vitality - an ineradicable desire to put aerial roots from many internodes, which soon find themselves in the ground, starting to supply the plant with a solution of nutrients from the soil. She stubbornly does not want to wither, and sometimes it seems that she is able to absorb moisture from the air (especially during the rainy season) in order to continue her development.
In the Pskov region, small-flowered Galinsoga is popularly called "American", in Belarus it is called "Cuban". It is likely that these weed nicknames are related to its "American origin". His real homeland is South America (Peru). The first European country where the small-flowered Galinsoga was introduced in 1800 was France: from here it began a victorious advance to the east and rather quickly spread across the continent. Therefore, it is sometimes called "French grass". In Germany, small-flowered Galinsoga was first noticed by specialists already in 1812. Then she "conquered" the territory of Poland, Lithuania, Belarus, Ukraine, the North Caucasus; also found it in the 30s-40s of the last century in the middle zone of the European part of the Russian Federation.
However, on the territory of this vast region, its density and harmfulness were low: the weed had a tendency to "conquer" territories with a warmer climate. But the appearance of small-flowered Galinsoga in flower beds in Tashkent at the end of the 50s was already noted as the advent of a potentially dangerous weed with very high harmfulness in the future.
And then there was a powerful surge of its activity in the summer of 2004 in the gardening sector throughout the Pskov region, a weed appeared on certain fields in the Leningrad region and even in the center of St. Petersburg and in the city of Pushkin. And in 2005 small-flowered Galinsoga showed itself very actively. Apparently, this was facilitated by the presence of a high stock of seeds in the soil. And this active promotion of the weed to the more northern regions inspires fear that the small-flowered Galinsoga in the next 2-3 years will become a serious weed in fertile, well-cultivated soils in the North-West of Russia. The growing seasons are especially favorable for it, characterized by a sufficient amount of precipitation, even with a relatively small sum of effective temperatures, as it was in 2003.
A. Lazarev, Candidate of Biological Sciences, Senior Researcher, All-Russian Research Institute of Plant Protection