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Frequently Asked Questions

Poison Ivy
Giant Hogweed
Dispose Plants

How do I deal with Puncturevine?

Landowners are encouraged to learn to identify puncturevine, and then understand how to control it. Puncturevine forms dense mats along road shoulders, vacant lots, beaches and unpaved parking sites, its stems reaching up to 10 feet (3 metres) in length. The stems are covered by hairy leaves that are divided into six to eight leaflets. Tiny, yellow flowers first appear in late spring or early summer, and spiny seedpods emerge a few weeks later. Each seedpod consists of 5 sections that, at maturity, break into tack-like structures with sharp spines.  These sharply pointed seedpods stick painfully in bare feet and flatten bicycle tires. Flowering and seed production typically occurs from mid-June to October.

The best method of controlling puncturevine is to prevent establishment by destroying the first plants found in an area before seeds begin to form.  Young puncturevine plants are easily controlled by hoeing, shallow tillage or by carefully hand-pulling plants. If seedpods have not yet developed or are immature (small and green), the plants can be composted. If plants have already matured and the seedpods have ripened (turned brown and easily fall off the plants), plants should be carefully pulled and bagged, then taken to the local landfill. Tipping fees are waived for invasive plant disposal at all landfills operated by the Regional District of Okanagan-Similkameen.

One of the greatest challenges this weed poses is its ability to germinate throughout the summer months; therefore, one treatment at the beginning of summer is not enough. Landowners must be vigilant, checking puncturevine prone sites approximately every three weeks, starting in June and continuing until September.  New plants need to be continually destroyed to ensure seeds do not form.  It is also important for landowners to be able to recognize puncturevine at an early stage of growth, as this is when it can most easily be controlled, as opposed to when it is large and seedpods have matured.

Like most other weeds, puncturevine prefers areas of disturbed, bare ground. Landowners can help by not providing an opportunity for weeds to grow, as well as by patrolling their properties in the summer and controlling any puncturevine they discover. Areas of soil disturbance should be reduced and re-seeded immediately with a suitable dryland seed mix.

For Best Management Practices, click here.

For more information on Puncturevine, click here. 

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How do I deal with Poison Ivy?

While poison ivy (Toxicodendron rydbergii) is a native plant, it can have invasive tendencies. Poison ivy is also known as western poison ivy to distinguish it from eastern poison ivy (T. radicans), and often incorrectly referred to as poison oak. Western poison ivy, hereafter referred to simply as ‘poison ivy’, is the most northerly occurring taxa within the Toxicodendron complex, ranging across southern Canada from British Columbia to Nova Scotia. In BC, poison ivy occurs east of the Cascade Mountains and is scattered and locally abundant mostly in the dry Okanagan Basin, but also in widely scattered locations north to Williams Lake. Poison ivy commonly grows in open Douglas-fir and ponderosa pine forests, frequently in moist gullies, along lakeshores or at the base of talus slopes. Poison ivy is considered a ubiquitous weed throughout much of its distribution and easily invades disturbed areas such as roadsides, floodplains, fence lines, cutblocks and railroad rights-of-way.  Throughout the western portion of its distribution, poison ivy is usually associated with riparian (river, creek or lakeside) communities, with plants frequently found on floodplains and river terraces. Popular walking and biking trails, such as along the Okanagan River channel near Oliver, is where people typically come into contact with this plant.

Poison ivy is a spreading, deciduous shrub, typically reaching heights of less than 1.0 metre tall, although plants can reach heights of up to 3 metres which I have personally observed along the old railway bed near Oliver. Stems are somewhat woody, arising from a heavily branched rootstock.  Long-stalked leaves are borne alternately near the summit of the stem and are divided into three coarse-toothed leaflets, hence the saying “leaves in three, let them be”. The shiny green leaves turn to bright scarlet in the fall. Ivory-coloured fruits are usually well developed by fall and often persist on the plant through the winter. 


Keep your distance from this plant. Approximately 90 percent of North Americans are allergic to poison ivy. It has a milky oil called urushiol (pronounced oo-roo-shee-ohl) which can cause redness, swelling and blistering of human skin within a few hours of contact.  For the first time sufferer, it generally takes longer for the rash to show up – generally in 7 to 10 days. Plants must somehow be damaged in order for the oil to be emitted.  Skin rashes can result from contact with either the liquid oil or its dried, blackened residue. Secondary objects such as boots, pants, hand tools or the fur of pets can also transmit the poison. Since the skin reaction is an allergic one, people may develop progressively stronger reactions after repeated exposures, or show no immune response on their first exposure, but show sensitivity on following exposures. As urushiol oil stays active on any surface, including dead plants, for up to 5 years, anyone that comes into physical contact with poison ivy must take extreme caution.

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Most importantly, learn to identify poison ivy plants in all stages and be fully aware of the precautions that should be taken to prevent exposure. Teach your kids and grand children about the “leaves in three” and explain the importance of not touching the plant. If exposed to poison ivy, cleanse exposed skin with generous amounts of isopropyl (rubbing) alcohol.  Wash exposed skin with water, then take a shower with soap and warm water. Do not use soap before this point because soap tends to pick up some of the urushiol from the surface of the skin and move it around. Clothes, shoes, tools, and anything else that may have been in contact with the urushiol should be wiped off with alcohol and water.

If you have poison ivy on your property and desire removal, click here for further information or contact your local Invasive Plant Coordinator for advice. Its removal requires considerable caution and because of the creeping roots, it can prove challenging.

Despite the negative associations most people have with poison ivy, it does possess some redeeming qualities. Poison ivy helps protect the soil and adds beauty in the summer with its dark green leaves and in autumn with bright colors to forests and shrub lands. Although it causes browsing animals no ill effects, western poison ivy is low in protein and energy and consequently is only occasionally grazed by domestic animals and wild ungulates. However, quail, wild turkeys, and some songbirds eat the fruits. It does provide cover for small mammals and birds. In herbal medicine, extracts of the leaves of this and other Toxicodendron species have been and still are used to treat the herpes virus, palsy and rheumatism.

How do I recognize Giant Hogweed?

Giant hogweed (Heracleum mantegazzianum) is a perennial in the parsley family. It occurs in the Lower Mainland, Fraser Valley, Gulf islands, and central to southern Vancouver Island. A small infestation has also been found in the central Kootenays. There are no confirmed infestations of this plant in the Okanagan or Similkameen Valleys. However, it could be covertly growing somewhere and we just have not discovered it yet. So please inform your neighbours of this invasive plant and keep your eyes peeled. Each and every possible sighting is appreciated, so please report any suspect plants.


  • Extremely tall, reaching heights of up to 5 m at maturity

  • Numerous small white flowers clustered in a large umbrella-shaped head

  • Flower heads reach up to 1.5 m in diameter, bloom in mid August

  • Dark green leaves are coarsely toothed in 3 large segments with stiff underside hairs

  • Lower leaves can exceed 2.5 metres in length

  • Stalks have purple blotches, streaks or spots, and stiff bristly hairs.

  • Usually found growing on agricultural lands, riverbanks, vacant lots, and along roadways.

Giant hogweed will colonize a wide variety of habitats, but is most common along roadsides, in ditches, along river or creek banks, wetlands, agricultural areas and other disturbed sites. It is a highly competitive plant due to vigorous early-season growth, tolerance of full shade and seasonal flooding, as well as its ability to co-exist with other aggressive invasive plant species. Each plant can produce 50,000 to 100,000 winged seeds that remain viable in the soil for up to 15 years. Interestingly it requires 2-4 years from germination to develop a flowering stem.


The most disturbing feature of giant hogweed is the clear, highly toxic sap that is found in the stem and leaves. When in contact with the skin, this sap can cause a hypersensitivity to sunlight resulting in burns, blisters and scarring. It is so toxic that WorkSafe BC has issued a “toxic plant warning” that requires workers to wear heavy, water-resistant gloves and water-resistant coveralls that completely covers skin while handling giant hogweed.

Similar looking plants in our region include cow parsnip and blue elderberry. Both of these are native plants that closely resemble giant hogweed. Cow parsnip is much smaller in height (1.5 – 2.5 m), has coarse hairs at the base of leaf stalks and hairy leaves. Reddish-purple spots are not present on stems and leaves are not as incised or sharply toothed. Blue elderberry is also shorter (2 – 4 m), with leaves that are opposite and divided into 5-9 leaflets in a feather-like arrangement. It is also lacking the reddish-purple spots on the stems.

Before you call with a sighting, refer to the Invasive Species Council of Metro Vancouver  website where you will find a page dedicated to giant hogweed and a video. 

For more information on Giant Hogweed, click here.

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How do I dispose of invasive plants?

Knowing how a particular plant reproduces indicates its method of spread and helps determine the appropriate disposal method. Most are spread by seed and are dispersed by wind, water, animals, or people. Some reproduce by vegetative means from pieces of stems or roots forming new plants. Others spread through both seed and vegetative means. Some plants continue to grow, flower and set seed even after pulling or cutting. Seeds can remain viable in the ground for many years. If the plant has flowers or seeds, place the flowers and seeds in a heavy plastic bag “head first” at the weeding site and transport to the disposal site.

Is burning an effective disposal option?

Burning does not tend to be the magical answer that many landowners are hoping for. In fact, invasive plants with airborne seeds may disperse by the hot air created by the fire. Also, there are many burning restrictions that must be adhered to and its probably best to avoid putting more smoke into the atmosphere.

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Bagging, tarping and drying

Bagging (also known as solarization) is a suitable technique for plants with softer tissue. Use heavy black or clear plastic bags (contractor grade), making sure that no parts of the plants poke through. Allow the bags to sit in the sun for several weeks and on dark pavement for the best effect. Tarping and drying is another method that can be effective if done correctly. Plant material should be piled on a sheet of plastic and covered with a tarp, fastening the tarp to the ground and monitoring it for escapes. Let the material dry for several weeks, or until it is clearly nonviable.


On some properties, burying plant material may be an option. This is risky, but can be done with watchful diligence. Check with me before trying this technique, as some species require fairly deep burial. Japanese knotweed, for example, must be buried at depths of 2 metres. Other species, such as puncturevine, only require burial of 15-20 cm.


Probably the most commonly used disposal technique is composting. However, composting of invasive plants must be done with extreme care. These aggressive plants can take root in compost. Species such as knotweed, morning glory (bindweed), sheep sorrel, ivy, several kinds of grasses, and many other plants can re-sprout from their roots or stems in the compost pile. Do not compost any invasives unless you know there is no viable (living) plant material left. Use one of the above techniques to render the plants nonviable before composting.Keep this in mind when you dispose of the annual plants in your planters and hanging baskets. Improper disposal of garden waste can result in undesirable ornamental plants moving into natural areas or parks adjacent to your property.

Closely examine plants before composting and avoid composting seeds. The majority of composting practices and processes often do not reach and maintain the temperatures needed to assure the destruction of all viable seeds; this is particularly the case with backyard composts. A study by Agriculture Canada indicated that some species of weeds, including wild mustard and stork’s-bill, were killed early in the composting process, with the temperature held at just 39 degrees Celsius for a week – a fairly low temperature for compost piles, which should be generating temperatures of 55-60 degrees Celsius. However, a graduate student in Washington recently showed that temperatures in excess of 100 degrees Celsius were required to effectively destroy the seeds of Dalmatian toadflax.

Disposal at the Landfill

Any mature invasive plants with seeds should be carefully bagged or loaded into the back of a truck (covered with a tarp or canopy), and disposed of at the landfill. Be sure to inform the landfill operator that you have invasive plants and not simply yard waste, to ensure that your weeds are disposed of in the proper location. And if you have curbside pick up, do not include any invasive plants with your yard waste. In the RDOS, the tipping fees are waived for disposal of invasive plants.

How do I learn what invasive plants are toxic?

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Invasive Plants Toxic to Livestock

This factsheet is intended to assist landowners in protecting their livestock from toxic invasive plants in the Okanagan-Similkameen region. Although some native plants are poisonous, only introduced species are discussed.

How do I find out about biological control options?

Insects That Attack Invasive Plants in the Okanagan-Similkameen

This brochure describes what biocontrol is, what type of agents are available in the Okanagan-Similkameen, and how to tell if biocontrol is the right option for you property.

For additional information, visit the BC government website. 

How do I report an invasive species?

Toxic Plants

Please visit our Report a Species page. 

Learn invasives

How do I learn about invasive species in the Okanagan?

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