In the central Europe, particularly Hungary the forest means the forest cultivation of native and non-native trees species in various patches. The native plant is generally the poplar and non-native is pines, both have economic importance. With this, there are few more plant species easily find which are not cultivated in those patches; few among those are invasive and occupying the empty areas, edges of the forests. The silkweed is one of those plant species.
The silkweed or known as common milkweed due to its characteristic of white sticky milk like sap in the stem. This herb is native to northern America and play important role in the ecology of that area particularly provide the habitat to few insects including the monarch butter fly. Although this plant is hated by many farmers, the wildflower gardeners like that in their stocks. For the conservation of butter fly particularly the red colored monarch butterfly, this plant is introduced to many places in the world.
In Hungary it is introduced by honey bee keepers in the 18th century and now it became one of the most abundant invasive plant species in Hungarian forest plantations. The plan to make milkweed honey is almost failed as it is not so much popular throughout Europe. This light, colorless milkweed honey with its crystallizing nature within few months due to different composition of sugars make it poor quality. But honeybees play important role in the pollination of this plant, which give it chances to make more and more seeds and make it one of the most successful invasive plants.
Already major parts of Europe are invaded by non-native plants which are now show self sustaining ecosystem but dominating to the native plant species. Invasion of any exotic plant has threats to native species assemblages which lead to degradation of natural habitats. Silkweed is most dominating invasive plant is capturing speedily the great Hungarian great plain by dispersion of its silky threads attached seeds and by underground rhizomes.
In this spring, you can see the large numbers of new buds of this plant rising from the soil, ready to overlap the forest ground and at the same time still there are few silky seeds in the dried cones on the dead plants are waiting for the wind. The germination of these seeds require the sandy soil in sunny areas which can drainage the water easily but keep soil moist. The major part of Hungary is geologically made up of river mud and sand in the prehistoric period. The soil of major part is sandy with very small size granules which is perfect for the silkweed to germinate seeds.
Its glossy, thick leaves are not important to feed the animals due to alkaloids and other toxic substances. They may provide the feeding for few pollinators but grooming period is short and it is in the late spring- early summer when other sources are available for pollinators. With this, the big size insects including the bundle bees, and sometimes honey bees can be captured in the flowers due to their special structure. These flowers show the V shaped hooks in the pollen sacs in which the legs of visiting insects can be snagged. Few bees can escape, few may lose legs and for few this can become the deadly trap.
As all invasive plants, silkweed also has potential to adversely impact on vegetation diversity which can alter the habitat structure, composition of vegetation, interactions of flora-fauna and overall ecosystem functioning. Small-scale or limited area invasion also influences the native ground-dwelling herbivores insects which are primary consumers in that local ecosystem. The changes in the distribution and community structure of these insects make changes on other fauna which is dependent on them. Once the local ecosystem get affected entirely, it becomes difficult to recover it even after total eradication of invasive species. If tomorrow these silkweed plants spread overall places including agricultural areas, it will not only impact on biodiversity, but will create some serious issues in front of food security too.
Total removal of these plants from current occupied areas, is almost impossible now because they are capable to face the herbicides and it is not possible to use any chemical in all area as that can show more adverse impact. Mechanical removal also expensive and the plant has rhizome deep under the ground spread horizontally too.
To tackle the problem of silkweed invasion, first it should be mapped to know how much area this is occupied. This map should show all Protected Areas, national parks, biodiversity hotspots, agricultural areas, barrel land, water catchments and all other landscape structures. Then the detailed plan should be require with integrated management approach which includes chemical, mechanical and biological methods to tackle this problem.