Summer Weeds to Watch for

The first step in successful weed control is making sure that you have the right plant.

Winter plant identification (ID) is a challenge as many plants die back and lose their leaves, spring ID is easier as new leaves unfurl, but the best time to ID most weeds is summer when plants are boasting their full leaves and brightest blooms.

Learn 7 weeds you should be watching for this summer here in western Washington; prevent spread by controlling these weeds before they can flower! Your yard, neighborhood, and local pollinators and wildlife will thank you. Interested in learning more about plant ID? Check out our summer weed ID blog post here.

Hot tips for cool summer weed management

  • Mind the bees! Avoid pollinators by working on cooler days or times (early morning and evening).
  • Prioritize seed prevention! If your plant is flowering or seeding, start by cutting & bagging flower clusters, dispose of them in garbage (does not apply for all species). After, other parts can be removed and composted.
  • Moist soils help manual control! Not necessary, but digging and pulling is easier in moist soils. Optionally, wet the soil with a hose or watering can the day before or the day of control.
  • Sheet mulch and plants! To discourage new weeds, lay down a papery layer (like cardboard!) followed by a thick sheet of coarse mulch. You can start making a plan for what plants you want to put in come fall (wet season=planting season).
  • Read the label! Some weeds/infestations are best controlled with herbicide. Summer is the ideal time for most controls-the weather’s right, and plants are actively growing. but again…ALWAYS READ THE LABEL!
  • Better with friends! Take turns helping each other out while enjoying the summer sun.

7 Weeds to watch for

Listed from most to least widespread (roughly). Want to learn more? Click on any plant’s name to be directed to its respective fact sheet.

Himalayan Blackberry (Link)

Rubus armeniacus

Where: anywhere it can take root! Does particularly well in disturbed areas & roadsides.

Identification: arching stems (canes) with large thorns are boxy and reddish, toothed leaflets grow in groups of 5.

Summer growth: spring’s white to pink flowers turn into large, juicy, blackberries from late June to early August.

Bindweed aka Morning Glory (Link)

Calystegia silvatica

Where: can survive most anywhere, but most often found in crops and in landscaping.

Identification: arrow to heart shaped leaves grow alternately along a trailing stem that lacks roots, appears to “climb” vegetation and other objects when not trailing along the ground. Extensive root system makes it hard to control.

Summer growth: reddish green buds sprout white trumpet shaped flowers from July to September.

Tansy ragwort (Link)

Jacobaea vulgaris

Where: prefers open spaces with full sun and drier soils, most often found along roadsides and in pastures.

Identification: wavy, dark green, kale-like leaves grow low to the ground on purplish stems in 1st year plants, then stalks grow out and up in its 2nd spring.

Summer growth: clusters of bright yellow daisy-like flowers form towards the top of tall 2nd year stalks from June – October. Flowers begin to brown and form fluffy white seeds starting in August and die shortly after. 1st year leafy plants typically grow close by simultaneously.

Purple Loosestrife (Link)

Lythrum salicaria

Where: freshwater and brackish (semi-salty) wetlands. Most often found on lake shores, waterways, and other marshy areas.

Identification: stiff boxy (4-6 sided) stems grow 6-10 ft. tall, dark green leaves are very narrow and have smooth edges, each cluster has several stems that may branch towards the top.

Summer growth: tall spikes of bright magenta flowers form at the top of main stems from July to September. As the flowers brown and die back, each plant can form up to 2.5 million pepper-size seeds.

Policeman’s helmet (Link)

Impatiens glandulifera

Where: wet areas – wetlands, streams, and moist woodlands.

Identification: hollow stem is succulent (watery) and gets reddish towards the bottom where shallow roots & nodes are exposed, leaves are egg shaped with serrated edges and come to a point at the tip.

Summer growth: White to pink to purple flowers are pea-like (5 parts, shaped like an English policeman’s helmet) bloom July through October. Simultaneously produce green teardrop shaped capsules that launch seeds when touched.

Spotted knapweed (Link)

Centaurea stoebe

Where: roadsides and in pastural and agricultural lands.

Identification: resembles a thistle without spines, silvery-green leaves are deeply lobed and sparse with smaller and less leaves closer to the top of their upright branched stems (plants grow low until their 2nd year).

Summer growth: small oval flower bases have triangular black spots, pom-pom like pink to purple petals burst from the top from June to October. Post-bloom, petals die back and are replaced with fuzzy white seeds, then the plant dies and the cycle starts from the seeds they left behind.

Sulfur cinquefoil (Link)

Potentilla recta

Where: anywhere except full shade, often in rangelands and pastures in Western Washington.

Identification: 5-7 toothed leaflets fan out from leaf base (resembles cannabis leaves), leaves grow more sparse towards the top of their upright hairy stems.

Summer growth: 5 light yellow heart-shaped petals form around a darker yellow cetner, blooms from early June – July then die back to brown nut-liked capsules of seeds.

Do you have any of these weeds? Did we miss one you’ve been dying to identify? Good news-we have a blog post that’s just for you. Check out our latest summer weed ID blog post here.

Happy weeding!