The main "evil" of hogweed is the presence of coumarins and furocoumarins in the plant sap, which increase the body's sensitivity to the perception of sunlight. The sap of a plant that gets on the skin, under the influence of ultraviolet radiation, can increase the pigmentation of the skin of humans and animals, cause dermatitis, which is often called "burns". The photosensitizing properties of furocoumarins are manifested not only with local contact with the skin, but also with the intake of drugs inside. Many tanning creams and sprays have been created on this effect of coumarins.
The Russian name for the plant was given for its use, Siberian hogweed, for food, specifically in borscht. In a number of regions of our country, in early spring, young growing leaves were used to add to soups. Young shoots were pickled, candied fruits were made from the stems, the leaves were salted, dried, pre-soaking or boiling to remove essential oil and coumarin compounds. And from the roots, rich in sugars, they got sugar and drove vodka. The flowers produce a lot of pollen and nectar and are good honey plants. The use of hogweed in folk medicine is very wide. Most often it is Siberian hogweed.
State interest in the species of this genus was caused at one time by the need to solve the problem of feed production in the country, especially in the northern regions, where there was not enough traditional legume-oat mixture. The attention of scientists was attracted by the use of Sosnovsky hogweed (Heracleum sosnowskyi) for ensiling in the Kabardino-Balkarian Autonomous Soviet Socialist Republic. And already in 1947, in the Polar-Alpine Botanical Garden, this species was introduced into the primary culture. It turned out that the Non-Chernozem and Chernozem zones of our country are the best for growing this crop, the yield of the green mass of which was higher than that of corn. Further you know ... The imaginary benefit turned into evil.
Whoever hinders us will help us
Knowing the features of the biology of growth and development of hogweed, it is possible to plan and develop measures to combat them.
Hogweed - biennial monocarpic (i.e., flowering only once in a lifetime) or perennial plants. The two-year-old Sosnovsky hogweed produces on average from 10 to 20 or even up to 35 thousand fruits per plant! The fruit of the hogweed is a columnar droplet, splitting into two mericarps. Mericarp consists of two halves, in fact, we call them seeds. This means that one monocarpic plant can produce from 15-20 (in rare years, powerful individuals even up to 70) thousand viable seeds! And so - every year. Another "dangerous" feature of hogweed fruits is the presence of outgrowths, or "wings" on them, which significantly increase their volatility and also contribute to active spread.
The wind is the main assistant for the capture of new territories by hogweed. That is why the hogweed so easily occupied many thousands of hectares in different regions of the country.
The second feature of hogweed is the variability of their seeds. In the first year, 20 to 70% of the seeds usually germinate. In the second year - from 30 to 60% of seeds that did not germinate in the first year. Some fruits can germinate only after 5-6 or even 12-15 years! And since the seeds remain in the soil for so long, it means that the fight against these plants must continue until the “last seed” is completely destroyed, so that there is no opportunity for a new individual to grow and give new flowering plants, and, accordingly, new viable seeds.
The seeds of hogweed have essential oil channels, as a rule, 2 on the inner and 4 on the outside of the fruit. Falling to the ground, the shells rot during the winter, and essential oils, resins and other biologically active substances flow to the soil surface. They have a pronounced allelopathic (more often - inhibitory) effect on the germination of seeds of other plant species, thereby ensuring uncompetitive germination with the subsequent capture of the territory.
Hogweed seeds are their weakness. It is worth destroying the seeds (fruits or ovaries), and the plant will no longer be able to reproduce. Hogweed do not give root shoots, do not grow back from the root! Their weakness also lies in the fact that the seeds on the plant are formed with an underdeveloped embryo. For their germination, special conditions are needed, variable temperatures, humidity.In dry conditions, from 50 to 90% of seeds lose their germination. But in nature, the seeds fall into the soil, where it is not dry at all, and, therefore, they retain their germination capacity longer, and the embryos go through all the stages of their additional development over a number of years. At the first suitable conditions, they will rise.
End justifies the means
A good effect in the fight against hogweed gives spring destruction of seedlings. You can use weeding, plowing, but it is important to carry out all these work on time, while the seedlings are in the state of the first two or three true leaves.
The most effective method of destruction in small areas is pruning flowers during budding and early flowering plants. But this is also one of the most dangerous ways - it is easy to splash with juice and get severe dermatoses on different parts of the body. The juice from the plants should not only not get on unprotected areas of the body, but also wet clothes.
If the deadlines for trimming the buds and flowers by hand were nevertheless missed, and all the plants were simply mowed, you need to carefully monitor so that new side umbrellas do not appear from the roots in the root socket. As soon as the plant gives new umbrellas and the flowers form ovaries in them, there will be a new generation of seeds, sufficient to restore the thickets.
Burning Is a very effective way of destroying plant seeds. It is important not to miss the moment of the event. It is better to carry it out before the full ripening of the fruits in the central, largest umbrella. This method requires the utmost care and accuracy.
Herbicide treatment (roundup, tornado, grauntup, etc.). Processing time - from the beginning of regrowth and always before flowering. Doses (concentration) of herbicides used to treat hogweed should be double or even triple from the capital for each given type of herbicide. The effect can be achieved with two repeated treatments with a break between them 15-20 days. It is necessary to ensure that the drug falls not only on the leaf surface, but also flows down the petioles into the leaf outlet.
Manual method. Starting in early spring, as soon as the plants begin to grow, it's time to go out with a bayonet shovel to destroy the villain. It is important to cut the growth point, which the plants tighten by 3-5 or 7-10 cm (hogweed is characterized by geotropism - deepening the growth point below the soil level). The depth of the kidney depends on the type of soil, climatic conditions of the region. If you cut it down higher, a few dormant buds will remain at the root in the leaf axils, they will grow and have time to give seeds - the main breeding unit of hogweed. Annual shoots are easy to destroy with choppers, shovels, weeding. Seedlings can appear not only in spring, but also during the summer (especially the variability of seeds). It is important not to allow new plants to bloom!
An effective way to kill plants - mowing, but only on condition that it will be carried out before the plants emerge "into the tube", that is, necessarily before the flowering of hogweed, with a repetition not later than 3-4 weeks after the first mowing. This technique is needed to destroy ALL shoots bearing inflorescences and flowers.
Mowing once and in the middle of flowering only contributes to the further reproduction of plants. The cut material must not be thrown in place. The hogweed shoot has a large supply of nutrients in the stem, sufficient for the seeds that have already set to ripen on the fallen plant in the main umbrella, that is, they have reached the wax phase of their ripeness, already quite sufficient for new plants to grow from these seeds in the spring. It is unacceptable to mow or cut the plants when the fruits have already ripened on them, and it is unacceptable to do this in windy weather. All this will contribute to the spread of the species to new territories. The mowed plants must be immediately heaped and burned.
And one more way - breeding of natural pests. To date, only one "pest" is known - the hogweed moth, the larvae of which penetrate into the trunk and move inside to the inflorescence, having time to largely eat the flowers before blooming. Eating flowers in buds, the moth greatly reduces the seed productivity of plants. But won't you also have to fight with it ...