Spring is finally here and we are watching our garden plants and trees flushing with beautiful flowers and bright green spring leaves.

You may be noticing the roadside vegetation coming into leaf as the days get longer, and you will also be eagerly watching your favourite bushes and plants coming into bloom.

At the same time, many plants not natural to British Columbia will also be sprouting. Many of these plants are invading our natural environment, our gardens, parks and open spaces.

We have accepted some of these non-native species, such as English ivy and Himalayan blackberry, since these plants have become so well established as to be part of the scenery we view every day.

But there are other invasive plants which are insidiously moving into our urban environment, such as Japanese knotweed, giant hogweed, Scotch broom, butterfly bush and creeping dead nettle.

You may well have seen these plants but you may not have recognized them for the danger they represent to our communities.

Our provincial government, local governments and various agencies are fighting many of these invasive plants and are trying to make the public more aware of the gravity of the situation.

There are three weeds in particular that have spread indiscriminately on the North Shore during the last few years, despite the efforts of local government and volunteer groups to try to contain and control them. Japanese knotweed, giant hogweed and Scotch broom are far from being the exclusive problem plants, but they are plants which seem to have been given the most attention by local governments and interested North Shore groups.

One of the most invasive and undesirable of these plants on the North Shore is giant hogweed. A native of the Caucasus mountains and southwestern Asia, this plant was introduced into Western Europe, the United Kingdom and North America as an ornamental garden plant due to its beautiful umbrella of lovely white flowers.

It turned out to be not such a nice plant. It became vigorous and invasive in its new environments, but it had other characteristics for which it became despised and are now a concern to our local governments.

It is most important to be able to recognize this plant, not only from its towering height of up to five metres and its lovely umbrella of white flowers, but also in its younger years when it is recognized by its large rhubarb-sized leaves.

Giant hogweed is so named because of its huge growth in height -- which it reaches on maturity in the third or fourth year of its growth. It has a sturdy but hollow stem, often four to five inches in diameter at its maximum growth, and it has large leaves which are heavily indented.

Young plants may not have flowering heads, but the rhubarb-sized leaves are recognizable by the heavily incised form.

The mature plant supports beautiful white flowers from late June through July and August. Don't pick them! The umbrella of flowers changes to a head of seeds in late August and through September. The heads support many thousands of seeds that can remain viable in the soil for up to six years.

The reason to be cautious in approaching or cutting this plant is that all parts of the plant contains a clear watery sap that can cause a reaction on the skin, creating redness, swelling and lesions. This is especially so if the skin is exposed to sunlight. It is not wise therefore to break or bend the leaves or cut the stems of the plant. If you do contact this plant with your hands or exposed parts of your body, be sure to wash any exposed parts with soap and water as soon as possible. Should the sap enter your eye, irrigate and seek professional medical help as soon as possible

The District of West Vancouver has been monitoring and mapping the locations of giant hogweed for several years, and it has maintained a control program by cutting back the growing weed during the summer months. This program has helped hold back the spread of this noxious weed and has reduced the possibility of unintentional human contact with the plant.

The District of West Vancouver is also working towards developing a policy on invasive plant species by 2012. If you notice hogweed on municipal land, you can call the parks department at 604-925-7192 to report your sighting, and most importantly give the location of the hogweed plant.

The District of North Vancouver has undertaken a mapping and GPS study of all district natural parkland, and that includes a layer of information specific to invasive plant species infestations. This mapping project identified approximately 20 hectares of municipal parkland dominated by invasive species.

In 2010, the district conducted a pilot-scale project to evaluate the effectiveness of manual versus specialized treatment methods for the eradication of a number of invasive species.

In 2011, the district is planning a comprehensive approach to combining all available district and community assets to launch a co-ordinated response to the threat of invasive species.

For more information on the North Vancouver Species Control Program contact the environmental service office at 604-990-2365 or the parks department at 604-990- 3810.

We need everyone's help to control this noxious plant from travelling any further into our communities.

Hugh Hamilton lives in West Vancouver. He is a retired professional forester with an active interest in natural history and streamkeeping. Through these interests he is working with a number of groups to fight the incursion of invasive species on the North Shore, and especially giant hogweed.