The Fieldman’s Files – White cockle (Silene alba, S. latifolia, S. pratensis)

White cockle flower and calyx, photo courtesy Nicole Kimmel, Alberta Agriculture and Forestry.
White cockle flower and calyx, photo courtesy Nicole Kimmel, Alberta Agriculture and Forestry.

Normand Boulet
Ag fieldman, CCA
M.D. of Smoky River No. 130

About this time of year you might be seeing White cockle showing up, White cockle has to be one of my favourite “love to hate it” weeds. The flowers are strikingly lovely and the fuzzy almost furry leaves and stem make it quite distinctive in appearance. Sure, it’s a decent looking plant as far as plants go, but it is also invasive, tenacious and an aggressive weed. White cockle is a member of the Pink family. A person would automatically assume the flowers must be pink, right? They aren’t. White cockle, like most other plants in the pink family has bright white flowers (I suppose the “white” in White cockle might have tipped a person off). People who are into sewing may find this little factoid interesting; the Pink family is named after the notching in the flower petals, which look to be made by pinking shears. On White cockle the ‘pinking’ makes notches so deep the flower looks as though it has 10 petals instead of 5. Other invasive plants you might recognize from the pink family include Chickweed, Night flowering catchfly (NFC) and Corn spurry. NFC is the one most often mistaken for White cockle, they are very similar except White cockle will bloom for most of the day, whereas NFC (as the name implies) blooms at dawn or dusk and on overcast days. As well NFC is much stickier than White cockle, you’ll often see small insects stuck to the stem and base of the flower. NFC also only grows as an annual or winter annual, not also as a perennial like White cockle.

White cockle plants are about one metre in height, the leaves are oblong with pointed tips and are opposite, emerging from swollen nodes. The lower leaves are stalked while the upper ones are stalkless. The plants are dioecious, meaning there are separate male and female plants. The calyx (the group of sepals behind the flower petals) forms a bulb that hides the ovary on the female plants. You’ll see the bulb swell as the ovary fills with seed on the female plants, on the male plants it stays deflated. The female calyx is usually greenish in colour where the male is often reddish. So at a glance you can tell in a patch which plants are the troublemakers (the females, because they produce seed allowing the weed to spread). For more precise identification check out a weed book like Weeds of Alberta or the Alberta Invasive Species Council website as the number of veins on the calyx can also differentiate male and female plants.

White cockle can act as an annual, biennial, winter annual or even a short-lived perennial. This means it can adapt to any type of crop or habitat. It is often a problem in hay and pasture, but also causes losses in annual crops. It produces seed extremely quickly so baled hay with White cockle often has viable seed in it. One situation I recall was a White cockle infestation in alfalfa, the producer thought by cutting the alfalfa three times in the season he could get rid of the cockle. The White cockle was setting viable seed before the alfalfa came into bloom after the first cut, it’s that quick. It spreads only by seed, yet the massive root system keeps the plant alive through difficult conditions, robbing the soil of moisture and nutrients that could go to your crop. Hand picking White cockle is almost fruitless (it could be compared to hand pulling small willows). Tillage can control White cockle but the root system needs to be destroyed or the plant can reestablish, and you can potentially break up the root and “transplant” it if conditions are right.

Although White cockle is an introduced species, it can be found throughout Alberta. If you are curious, check out the Weed Survey maps under the “Maps and Multimedia” section of the Alberta Agriculture and Forestry (AAF) website.
White cockle seed is difficult to separate from most forage seeds, so that is one way it has been able to spread throughout the province. When buying forage seed be sure to ask for the Certificate of Seed Analysis before you agree to purchase, and if the analysis says the seed lot has White cockle (or any other invasive species you don’t have yet) refuse it and ask for a different lot.

There are very few herbicides effective on White cockle. One issue is the hairiness of the plant which makes getting the herbicide into the leaf difficult. Coverage is extremely important as is using surfactants to get the droplets to penetrate the leaf hairs. In field scale infestations I have seen excellent results using a pre-seed burnoff followed up in Barley or Wheat with PP23235 in-crop. Unless something I’m not aware of has been newly registered on White cockle, PP23235 is the only herbicide registered to control it in crop. The herbicide should be tank-mixed with MCPA or 2,4-D for best control and to reduce the likelihood of creating a resistance issue. Small patches should be controlled early in the season to prevent seed set. Hand pulling is possible in moist coarse soil conditions, but you are likely going to need a spade if attacking it in that way.

If you find White cockle, or need help confirming a plant’s identity contact the Agricultural Fieldman in the municipality (County, M.D., Specialized Municipality or Special Area).


White cockle seed pod, the seeds are still immature, they will be reddish or grey when ripe - Photo credit Norm Boulet.
White cockle seed pod, the seeds are still immature, they will be reddish or grey when ripe – Photo credit Norm Boulet.

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