An Invasive Violet for Western Oregon

Phil Thornburg • May 17, 2018

It is not uncommon for people to ask me about violets which seem to be taking over their yard.

Violets come up in planting beds and lawns in the early spring, with purplish-blue flowers and purple leaves in the sun but darker-green leaves in the shade. They can grow here in Western OR, even in gravely, dry soil where not much else will grow. They are not fragrant.

Purple violet flower blooming in green grass.

European Dog Violet

This is the European Dog Violet or technically, Viola riviniana ‘Purpurea Group’.   Sometimes V. riviniana plants are sold as Viola labradorica purpurea and sometimes even Viola hederacea, but I am told that those plants are not generally sold or even found growing in the NW.  Buyer beware!

V. riviniana can spread from its running fleshy roots which can plunge rather deeply, making this plant quite drought tolerant.

These plants can out compete smaller plants such as Mentha requenni  and can mar the look of a stand of slightly taller plants such as Ophiopogon p. ‘nigrescens’.  However bigger plants can comingle with no problems.  For instance, the currently invasive common exotic ivy, Hedera helix, can easily quash this violet but then who wants a groundcover of ivy?

V. riviniana can spread easily by seed as they shoot their seeds explosively, up to 8’ away when they are brown and ripe. Therefore, once established, they can become very numerous. On top of that fact, the seeds may stay viable for up to 5 years in the ground.

Some Suggested Methods of Removal Are:

  • Covering a densely growing area, where they are to be removed, with cardboard and 2” of bark mulch. Anything that dares to come up from far flung seeds, immediately remove with your handy Hori-Hori! This may take more than one year.
  • I personally have removed all of my V. riviniana with only a hoe over the past 15 years. If I see one riding piggy back in the potting soil around a plant from a nursery, I immediately dispose of that violet in the garbage, not the compost pile! I wait to plant it in the ground, watching the potted plant and digging out any other unwanted Violets over the course of a year. I have seen several come up around a piggy-backed plant from a nursery!
  • There was a location in my garden, after the 10 th year, where violets repeatedly came up from seed or old roots around the base of my largest old Azalea. Ultimately, I crawled on my hands and knees and surgically removed them with my Hori-Hori. They have not returned since.

Plants from the Genus Viola th at you may want to cultivate in Western Oregon.   

A close-up of a yellow wildflower with dark brown veins blooming amidst green leaves.

Viola Sempervirens

We have some lovely native  violets here in the Pacific NW, but many are robust growing as well. Try them where they will not cover smaller plants and you will be fine. You may find different species on-line. I have grown (and particularly like) a yellow one that is local and evergreen, Viola sempervirens . It is cheery in the spring. It spreads by stolons as well as  seeds.

There are plenty of other lovely exotic violets that are not invasive. These Violas include the plants which we commonly call Violas and Pansies  in the nurseries. They have been bred to have large blooms and are available in many colors.

From what I have read, the most fragrant form of this plant is Viola odorata ‘Rosea’,  which is a bright pink form.

Final thoughts:

Clearing a property of Viola riviniana is not a task for the faint of heart.  It requires persistence and boldness and a ready willingness to dig in the rainy season, because that is when it is easiest to pull/dig out of the ground.  In the dry season of summer, it can be almost impossible to extract this Viola from the concrete-like dry ground. Your Hori-Hori is your best friend if you would like to rid yourself of these invasive plants.

By Dale Hickey October 6, 2025
On Saturday, September 27th, we held our fall plant sale at Thornhurst Garden—and what a day it was! The garden itself provided the perfect backdrop, with the changing leaves and late blooms showing off the season’s beauty. It was such a joy to see so many friendly faces—neighbors, friends, and new visitors alike—coming together to share their love of plants. Events like these remind us how much community is at the heart of gardening. The sale helped us find new homes for much of our overstock, and many folks walked away with treasures for their own gardens. Moist fall soil means these plants will settle in happily, making this truly the best season to get them in the ground. We also held a raffle, and we’re excited to announce that Sarah Reid was our winner! Congratulations, Sarah! Thank you to everyone who came out to support us, explore the gardens, and bring home plants. We’re already looking forward to the next time we can gather and celebrate together. (Here’s a look at some of the wonderful people who joined us that day!)
By Dale Hickey October 6, 2025
October might just be the best month of the year. Leaves turn gold and crimson, the first steady rains return to refresh thirsty plants, and the garden hums with renewed activity—birds darting through the branches and insects busy among the late blooms and fallen leaves. Soon, the season’s magic spills beyond the garden as little goblins and witches knock on our doors, candy bags in hand. For gardeners, fall is more than just a feast for the senses. Cooler days and moist soil create the perfect conditions for transplanting trees, shrubs, and perennials—plants settle in more easily now than in the heat of summer. (Unless we're talking Agaves, transplant those after the Spring rains) The softened ground also makes digging and dividing far less of a chore. Even challenging tasks like ivy removal become easier when the soil gives way beneath the roots. Autumn truly is a season of opportunity: a time to plant, to tidy (or not!), and to prepare the garden for the year ahead while savoring every bit of its fleeting beauty. The last week of October, but sometimes the first week in November, is the last time that we mow weekly. Be watching your lawn so that you can decide the best time for yourself. Occasionally, we will have a warm Winter, and a touch-up may be needed. Eco-lawns- Depending on the seed mix, you can leave these as is, allowing them to form more of a meadow look. This can help create more habitat for wildlife and insects. October is the first month when we have a higher probability of transplanting from moist, soft soil into a damp, soft new hole. All plants of course prefer to be dormant (asleep) when being transplanted. So, the coolness of October and the (hopefully) moist soil are perfect for the beginning of the transplanting and planting season. The best planting time typically extends from the rainy season until approximately the middle of March. Now is the best time to plant in Western Oregon! If you want Spring blooms, make a trip now to your local nursery and purchase Spring bulbs to plant in the ground! October/November are the traditional months for planting Spring bulbs. You can also plant fall bulbs now, such as Saffron Crocuses and Colchicums. The rain will bring out the dormant, sleepy slugs, so getting slug bait out in your beds now will hopefully thwart off a winter and spring invasion of new baby slugs! The Fall leaves will start to drop all over your yard. Remember to keep them off the lawn/grass areas and instead rake or blow them into your beds. The wet leaves will damage your lawn if left on, sometimes only in a day or two, but they can become great free compost/mulch for your planting beds. Lots of insects use this leaf litter as their habitat. This is a great way to invite more birds and wildlife into your garden as they forage through the leaves! I love watching them! This month, place mulch around potentially tender plants such as Cannas, Fuchsias, Dahlias and Calla Lilies. This will insulate them from frost or freezes. Get some bark mulch or chips and spread them 2” thick over any bare areas in your beds for the rainy season. This will prevent erosion and help choke out weed seeds from sprouting. If you are seriously into gardening, here are some more tips. Plant garlic bulbs now for harvesting next summer Pick any green tomatoes and bring them into the garage to ripen. Harvest Sunflower heads and bring them into the garage to dry. These are great for birds and human snacking. Sow native hardy annuals- you can sow these on any bare soil, or you can use gravel mulch and direct sow on that! Some great hardy annuals are California poppy (Eschscholzia californica), Red Maids (Calandrinia ciliata), Farewell-to-spring (Clarkia amoena) Gilia capitata, to name a few. Feel free to reach out to us if you have any questions about hardy annuals! A hardy annual is an annual plant you can sow in the Fall, and it will germinate, survive the Winter Months, and grow enough roots to sustain itself. Most of our natives will not require additional water the following year, and if they are happy, they will seed around and come up where they are thriving.
September 3, 2025
We look forward to seeing and catching up with so many of you! This is a great time to add new plants to your garden for discount prices as low as $5.00! Bring your friends! Please RSVP for the event at the link below: https://www.winterbloominc.com/contact
By Dale Hickey September 3, 2025
Garden Tips and Tricks for September September and October are my favorite months of the year. The air cools, the light shifts, and the season takes on that autumn magic that always makes me think of Halloween. Summer is winding down, but the garden is still alive with tasks that prepare it for the darker months ahead. Unlike spring’s dramatic storms and sudden frosts, fall eases in gently, carrying us toward the rainy season by late October. September Gardening Tasks: Ease off watering – Let plants harden off for winter, but check the soil and water if it’s dry. Keep weeding – Persistence now makes for an easier spring. Renovate or seed lawns – September and October are prime months while the air is cool and the soil is workable. Beware of fallen leaves on newly seeded areas. Slug baiting – Use traps or the beer-in-a-jar trick to keep them in check. Monitor areas and determine your threshold for damage. Slugs are also part of our habitat gardens. Trim back perennials – Clear away browned foliage to tidy beds before winter, or for habitat and sustainable gardening, leave perennials for mulch/habitat and forage for birds and insects. Planting and transplanting – September through March is ideal, with November the peak month. If you haven’t yet, begin planning which hardy annuals to seed in late October-November. Harvest – Gather winter squash, tomatoes, and potatoes while they’re ready. Winter vegetables – Early September is the last chance west of the Cascades for kale, Brussels sprouts, turnips, cabbage, and other winter favorites. Lawn fertilizer – This is the last month for summer fertilizer; switch to a fall/winter mix in November. Rhododendron cuttings – This is a good time to start new plants if desired. Prep compost piles – Stock them with fall leaves and garden trimmings for rich soil next year.  Houseplants – Bring them indoors when nights turn too chilly.
A close-up of small white and yellow flowers with a bee pollinating one.
By Phil Thornburg and Dale Hickey May 6, 2025
May Tips for a Habitat-Friendly Garden Plant annuals (but wait on heat-lovers): May is a good time to plant annuals in containers and beds. Hold off on heat-loving crops like tomatoes and basil until nights are reliably warm and the soil has warmed—planting too early can stress or stunt them. Start mindful watering: If rainfall has been low, begin deep, infrequent watering (about once a week). This encourages strong root systems and conserves water. Avoid overhead watering in the evening to reduce fungal issues. Rethink the lawn: If you maintain a lawn, mow higher to reduce water needs and encourage deeper roots. Consider letting some areas go wild or replacing turf with native groundcovers to increase habitat value. Weed wisely: Focus on removing weeds that are going to seed first. Even five minutes of weeding helps! Leave less aggressive weeds in place if time is short—many provide cover or nectar for insects. Support natural pest control: Promote beneficial insects like ladybugs and lacewings by planting a variety of nectar-rich flowers. For aphids, try a spray of soapy water or simply hose them off. Avoid broad-spectrum pesticides, which harm pollinators and beneficial bugs. Slug and root weevil control: Use methods that target pests without harming other wildlife. Nematodes work well for root weevil larvae. For slugs, try beer traps, copper tape, or manual removal. Diatomaceous earth can be effective but may also harm beneficial insects—use sparingly. Leave the mulch: Let leaf litter and composted mulch remain under shrubs. It feeds the soil, retains moisture, and supports beneficial microbes. Fertilize only if plants show signs of stress, and choose fish emulsion or compost tea when needed. Plant for fall and for pollinators: Now’s a great time to plant perennials like chrysanthemums (for fall color) and native flowering plants that bloom through summer and into fall—providing nectar for pollinators and habitat for insects. Plan your veggie garden: By late May or early June, plant warm-season crops like tomatoes, peppers, cucumbers, squash, beans, pumpkins, and kale. Consider letting a few vegetables bolt (like dill and kale) to attract bees and butterflies. Watch for cabbage pests: Small holes in leaves may be flea beetles or cabbage worms. Use floating row covers, handpick pests, or apply BT sparingly. Companion planting with herbs like dill or nasturtiums can help deter pests naturally. Prune thoughtfully: After spring-blooming plants finish flowering, prune only if necessary. Leaving seed heads can provide food for birds and shelter for overwintering insects. Consider leaving trimmings in beds to decompose, except those trimmings of perennials with seed heads you don't want to spread. Avoid major trimming of trees, many birds are still nesting. Skip spraying trees unless necessary: If tent caterpillars are present and damaging fruit or shade trees, remove egg masses or nests manually. Spraying should be a last resort—consider how many caterpillars you can tolerate as part of a healthy ecosystem.
A group of people sit in a room with presents, talking.
By Dale Hickey December 18, 2024
A Heartfelt Thank You and Holiday Cheers from  Winterbloom Landscaping Cooperative  As the year winds down, we find ourselves reflecting on the incredible journey we’ve taken together over the past months. Transitioning to a cooperative has been a transformative experience, and it’s one we couldn’t have navigated without the trust and support of our amazing customers. You’ve been with us through the changes—whether you’ve been a client for years or just joined us this season, your belief in our vision has kept us going. Your loyalty has allowed us to reimagine how we work, creating not just beautiful landscapes but a thriving, sustainable community. Thank you for being part of this new chapter with us.  On December 7th , we celebrated all that we’ve accomplished together at our annual Winterbloom Holiday Party ! We gathered as a team to share laughs, stories, and some well-earned joy. Phil and Barb even joined us, making the celebration even more special! One of the most meaningful parts of this transition has been seeing the way our team has embraced this new model. Their hard work, creativity, and passion bring life to every project, and we’re so grateful to have such a dedicated and talented group of people by our side. This team isn’t just the heart of Winterbloom—they’re the reason we’ve been able to dream bigger and build something truly unique. Here are a few photos from the party: