Tag Archives | invasives

Are Invasive Blackberries Haunting Your Property?

Invasive blackberry photo by Sam Leininger

Invasive blackberry photo by Sam Leininger

The beautiful autumn leaves with their reds and golds are a stark contrast to the thorny invasive blackberries looming at the edge of your field or backyard. Do not let those sweet summer berries sway your resolve to rid your property of this menacing invasive plant! Fall is a good time to begin control.

Protect Creatures and People!

Control blackberries in the fall to avoid disturbing nesting birds. In the spring, some birds will use the thorny fortress to build nests and hatch their eggs. If you are using chemical control, you will also want to avoid taking action when the plants are in bloom. Pollinators such as bees and butterflies may be at risk during flowering. When berries are on the canes, it is not only birds, but also people and other animals that are at risk from chemical applications. Remember, ALWAYS FOLLOW THE LABEL and put safety first, for you and any unintended targets.

Pull On Gloves!

For manual control, it is important to arm yourself against the sharp thorns by wearing thick gloves, sturdy long pants, and long-sleeved shirts or jacket. Those who are unprepared will suffer the consequences with nasty scratches. Use board or plywood to mash down blackberry canes, and to access densely infested areas.
If your ground is level or has little slope you may also be able to mow down the canes (sometimes a brush cutter is necessary). This will remove the bulk of the plant. If you wish to use the mowing method for permanent control, you will need to continue this process at least 4 times per year, for several years, to exhaust the energy in the root system. Remember to check for any nesting birds in the spring, but if you keep on top of the mowing there will not be a good place for the birds to build a nest. If using goats to remove the blackberries, you may still want to get rid of the old canes first and then let the goats periodically graze the new growth for long-term control.

Can You Dig it?

If you choose to remove the entire plant, including the roots, you will have much easier access with the top growth removed. Digging or tilling can take out the root system, but be sure to remove as much root material as possible. Even small pieces can re-sprout, so try raking up all remaining bits. If you are working on a slope, make sure you have enough time in the fall to reseed any disturbed areas to avoid erosion caused by fall and winter rain. If not, root removal might need to wait until spring.

Weed Alert

Warning: expect a flush of weeds in the old blackberry patch. A build-up of weed seed has remained dormant under the brambles for years and once exposed to sunlight they will sprout. Weed control is just another step in the process.

Removal of invasive blackberry requires persistence and patience, but success comes to those who persevere! For more detailed information on blackberry control, check out our WeedWise website.

Wildflowers and Native Plants – Not Always the Same

Native blue delphinium photo by Sam Leininger

Native blue delphinium photo by Sam Leininger

Wildflowers come in all shapes and sizes, from small plants with delicate blossoms, to large plants with sturdy flowers. Some wildflowers have foliage with barely noticeable flowers! Each are beautiful in their own way, but beware, not all wildflowers are native to this area. In fact, wildflowers that are not native to our area can be an invasive species. These plants can take over and crowd out the wildflowers that are actually native to our area. Even wildflower seed mixes may contain seeds for plants that are not native to our area.

How can you tell?

Figuring out what plants are native to our area may not be as difficult as you may imagine. There are resources on the Internet that will guide you to wildflowers that are native to your area, no matter where you live! Check out the Lady Bird Johnson Wildflower Center website. Here you will find information about native plants and a link to the native plant database. Use this database to identify wildflowers or select wildflowers that are native to your area. Once you identify what plants you want to grow, use the Native Seed Network from Corvallis to locate sources for native wildflower seed.

Oregon Weed Awareness Week

In celebration of Invasive Weed Awareness Week in Oregon (May 17-23), take the time to control the invasive species on your property. Technical assistance in identifying invasive plants and learning about control measures is available from your local Soil and Water Conservation District. In Clackamas County, you may check out tools, such as weed wrenches and lake rakes, to tackle invasive weed problems on your property. Contact Clackamas County Soil and Water Conservation District at 503-210-6000 for more information.

Help yourself, and help your neighbor, control invasive weeds!

FREE Workshop for Early Detection of Invasive Weeds

The Mt Hood National Forest and the Clackamas SWCD’s WeedWise Program are pleased to host an Identification, Early Detection and Reporting of Invasive Plants Workshop for the Mt. Hood National Forest. Anyone working or recreating in the Mt. Hood National Forest will want to attend. This free training will teach you to identify priority weeds for the Mt Hood National Forest and teach you how to report your findings.

This training will be presented by Julie Combs of the Pacific Northwest Invasive Plants Council in cooperation with the Columbia Gorge Cooperative Weed Management Area. This training is the first of its kind in Oregon and builds upon a growing network of citizen science based trainings occurring throughout the Pacific Northwest.

Now for the details!

When: Thursday, April 30th; 10:00 am-12:30pm
Where: Mt. Hood National Forest Headquarters, 16400 Champion Way, Sandy, OR 97055
(Park in the visitor parking lot on the west side of the building (the building’s main entrance). Enter through the front door. Sign in at the front desk and get a visitor pass from the receptionists.)

These training workshops are free but space is limited!

If you would like to attend, PLEASE REGISTER WITH JULIE COMBS or call 615-812-5295 to reserve your place.

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Invasive Weeds Arrive Early This Year

Has the warm winter weather caught you off guard? It is easy to be distracted by the beautiful spring flowers that are gracing the landscape, but this warm weather is also causing invasive plants to show themselves earlier than normal. According to the National Weather Service, the average temperature in the Willamette Valley has been two degrees above normal in January, 5.5 degrees above normal in February, and 4 degrees above normal in March. The increase in average temperature has caused a leap in plant growth, including invasive species.

This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. Source: http://en.wikipedia.org/wiki/File:Garlic_Mustard_close_800.jpg

Garlic mustard flowers photo credit sannse

Jeff Lesh, WeedWise Specialist for Clackamas County Soil and Water Conservation District, tells us that now is the time to control biennial weed species before they bolt* and become more difficult to manage. Weeds such as tansy, bull thistle, garlic mustard, poison hemlock, and teasel have a short window in which various control methods are more successful. Cultural methods, such as pulling or digging, are easier when the ground is moist. Find out more about weeds and control methods from these references listed on the Four-County Cooperative Weed Management Agency website.


For folks with pastures that are struggling with weeds, now is the time to take action. Find out what your pasture needs by testing the soil. If you need assistance interpreting the results of your soil test, contact Clackamas County Soil and Water Conservation District at 503-210-6000. Applying the recommended soil amendments such as lime or fertilizers will help give plants what they need to thrive. Taking these steps will help make your pasture grasses healthy enough to out-compete invasive weeds. Time spent early in the season will give you more forage for your animals and reduce the amount of time and money you spend on weed control later in the season.

Home Landscapes

Lesser Celandine photo by Natalie S

Lesser Celandine photo by Natalie S

Homeowners who are battling lesser celandine, your window for control is closing quickly! Lesser celandine, an herbaceous perennial plant, was originally cultivated as an ornamental due to its attractive yellow flowers and ability to create a uniform groundcover in a short amount of time. It spreads by seed, plant sharing among friends, and when tubers and bulbils** tag along on mowers or digging equipment. Effective control measurements often involve spraying, but the time to spray is February – March, so if you plan to spray, you may want to get it on your calendar! Find control measures at the Washington State Noxious Weed Control Board website.

Invasive weed control is never easy and usually requires multiple treatments over several years. However, one thing is true: if you do not control your weeds, they will not control themselves!

*bolt – term used to describe when a plant prematurely produces seed

**bulbil – a small bulblike structure produced in the place of a flower or where a leaf joins the plant stem

What’s Up With Weeds: February 2015

Your cure for cabin fever

February is the time of the year when Oregonians start to experience the late stages of cabin fever. After the months of shortened days, cold temperatures, rains, and cloud cover our usually pale complexions rapidly trend toward translucence. But February also offers the first glimmers of hope of the spring ahead.

By late February we start to see the cold and dreary days of winter giving way to a few sun breaks. The catkins start forming on Red Alder (Alnus rubra), and the first green leaves and white blossoms of Indian Plum (Oemleria cerasiformis) make their first appearance. Home landscapes become dappled by the ever popular crocuses and daffodils that start tempting us back outdoors.

Western Bleeding Heart (Dicentra formosa)

Western Bleeding Heart (Dicentra formosa)

The best part of February is that even though we still have several months of wintry weather remaining, it gives us hints of spring and assures us that the worst of the season is over. This makes February the perfect time to plant new plants outside. The cool wet weather still to come helps to promote root growth of new plantings, helping keep new plantings from drying out. So if you are looking to plant, February could be the best time to get outside and cure your cabin fever.

Report Weeds!
Early detection is the key

The enemy of my enemy is my friend

The approach often used to control invasive weeds amounts to “subtractive restoration.” We focus on the invasive species and often feel a sense of accomplishment when eradication results in bare ground without those nasty weeds. But Nature abhors bare ground and will not tolerate it for long. We hope that the surrounding vegetation will respond to fill in the gaps we have created, but if we are not careful we end up replacing our weeds with a new set of weeds. Planting or seeding disturbed areas is one of the best ways that you can help to combat this problem.

Planting desirable plants is one way to control invasive weeds. One of the most common and desirable ways to combat a species like Reed Canary grass (Phalaris arundinacea) is by planting into patches with woody shrubs and trees that will eventually shade out this weed. In this way, plantings are a great tool that should be in everyone’s management toolbox. For some great tips on planting check out the Riparian Tree and Shrub Planting Guide.

This February — while you are trying to figure out who first calculated the importance of a groundhog’s shadow in relation to climate — take the long President’s Day weekend to plant some plants with your valentine. I recommend the native bleeding heart (Dicentra Formosa) to help set the mood. The little bit of time spent outside will provide the shot of vitamin D you just might need to help shake off the winter blues and cure your cabin fever.

So what is up with Weeds in February?

Grass-like plants

  • Jubata grass (Cortaderia jubata) is an annual shrub that follows the same timeline as Pampas grass. Plants have seeded. Dig up the entire plant.
  • Common reed grass (Phragmites australis) is a grassy perennial. Plants that were emerging in April, May, and June have seeded, dig up any plants and dispose in trash.
  • False brome (Brachypodium sylvaticum) is a perennial grass. Plants have seeded and going dormant. Please contact us if you see false brome!

Herbaceous flowering plants

  • Russian knapweed (Acroptilon repens) bolts in May with flowers appearing in June, July, and August. Control can be through handpulling, tilling, mowing, or digging. Root fragments resprout so it’s important to get all of the plant out of the ground.
  • Garlic mustard (Alliaria petiolata)was forming rosettes through the winter and flowers in April and May. Seeds may be present and viable from June through September! You can hand pull plants, although root fragments can resprout. Please contact us if you see garlic mustard!
  • Spotted knapweed (Centaurea biebersteinii) follows the same timeline as Diffuse knapweed. Dig up the entire plant (easier when soil is moist in the spring).
  • Purple starthistle (Centaurea calcitrapa) sprout from seed in winter and develop into rosettes in spring. Starthistle plants flower from July to Spetember. Please contact us if you see purple starthistle in your area.
  • Meadow knapweed (Centaurea debeauzii) follows the same timeline as Diffuse knapweed. Dig up the entire plant (easier when soil is moist in the spring).
  • Diffuse knapweed (Centaurea diffusa) is a herbaceous perennial. In May, plants bolt. Flowers appear in May, June, and July. Dig up the entire plant (easier when soil is moist in the spring).
  • Yellow starthistle (Centaurea solstittialis) sprout from seed in winter and develop into rosettes in spring. Starthistle plants flower from May to July. Please contact us if you see yellow starthistle in your area.
  • Rush skeletonweed (Chondrilla juncea) bolts in April, May, and June. When it flowers in July, it sets seed quickly!
  • Paterson’s curse (Echium plantagineum) emerges in March and April, flowering all summer.
  • Orange hawkweed (Hieracium aurantiacum) can be dug up in March and April. Be sure to get the roots and runners. Flowering occurs in May and June, and can extend later, with flowers and seeds occurring from July through September. More information is available on the Oregon Department of Agriculture’s page about Orange hawkweed. Please contact us if you see Orange hawkweed!
  • Yellow-flag iris (Iris pseudacorus) is a herbaceous perennial that emerges in April and flowers in May and June. Seeds are set from July through September
  • Yellow archangel (Lamiastrum galeobdolon) is a herbaceous perennial the grows throughout the winter and flowers from April to June. Seeds are set in July and August.
  • Kudzu (Pueraria lobata) is a vining perennial. Leaves emerge in April, May, and June. Flowers emerge in July. Please contact us immediately if you think you have spotted Kudzu in Clackamas County!
  • Lesser celandine (Ranunculus ficaria) is a herbaceous perennial. Rosettes form in January and February, and the plants flower in March. In April, seeds are set. Remove all of the bulblets and tubers.
  • Tansy ragwort (Senecio jacobaea) is a herbaceous biennial. Rosettes form in March and April, and flowers in May, June, and July. If soil is moist, dig up the rosettes. If you remove the plant during flowering, bag the plant so seeds can’t spread.

Shrubby plants

  • Blessed milk thistle (Silybum marianum) overwinter as rosettes that bolt in March, April, and May. The plants flower in June and July. Mow or hand pull before flowers fully develop.
  • Butterfly bush (Buddleia davidii), a tall deciduous shrub, displays new leaves in April, May, and June, but doesn’t generally flower until July and August. Control by digging up the entire plant. Our Weed Wrench might work!
  • Giant hogweed (Heracleum mantegazzianum) is a tall herbaceous perennial. Plants emerge in March and April from winter rosettes, and accelerate in growth in April and May. When the plants flower in June and July, remove the heads and cut off the plant at the base…but be very careful because the sap of this plant is caustic. ODA says this about Giant hogweed: “This plant is a public health hazard. Do not expose bare human skin to the plant or breathe the smoke from fires if it is being burned. The plant exudes a clear watery sap which sensitizes the skin to ultraviolet radiation. Humans often develop severe burns to the affected areas resulting in blistering and painful dermatitis. Blisters can later develop into purplish or blackened scars.” Please contact us immediately if you spot this plant!
  • Gorse (Ulex europaeus) is a single to multi-stemmed spiny shrub that buds in February and flowers in March, April, and May. It goes to seed in June and July. Dig up small plants. Please contact us if you see gorse!
  • Policeman’s helmet (Impatiens glandulifera) is a herbaceous annual the begins to emerge in April and grows through May. Flowers appear in June and July.
  • Purple loosestrife (Lythrum salicaria) is a herbaceous perennial that emerges in May and June. Flowers begin to appear in July.
  • Scotch thistle (Onopordum acanthium) is a herbaceous biennial that overwinters as rosettes. Flower stalks emerge in June and flowering is in July and August.
  • Spurge laurel (Daphne laureola) is an annual shrub that emerges in March and flowers in April, May, and June. Berries appear in June and July. Dig up as much of the plant and root system as possible. Please contact us if you see spurge laurel!
  • Knotweeds include Japanese knotweed (Polygonum cuspidatum), Giant knotweed (Polygonum sachalinense), Himalayan knotweed (Polygonum polystachyum), and hydrid knotweeds began emerging in April. With warmer temperatures, growth accelerates throughout May and June. Flowers emerge in July and August. Mechanical control requires frequent, persistent effort: cut twice each month from April through August. In the fall, additional steps are needed, including cutting and covering the plants. Knotweeds are so persistent that you need to do this repeatedly for five years to achieve control.

Aquatic plants

  • Parrot’s feather (Myriophyllum aquaticum) is a perennial with underground rhizomes that overwinter. Stems emerge in April and May. Flower stalks appear in June and July. Removing the entire plant, including root fragments, is necessary.

Report weeds!

Visit our page on reporting weeds to file a report.

Report Weeds!
Early detection is the key

Photo courtesy of: Walter Siegmund, Wikicommons

Photo is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.