It's the start of a new season! We are excited to meet new friends and share our knowledge with you. For our first post we will discuss weed identification.
The most important component in addressing noxious weeds is education; you need to know the weeds you are dealing with in Montana. Often, we approach control from a position of ignorance. As children, perhaps, we're told by someone misinformed on the subject that a particular noxious plant is called such and such, but it turns out to be an erroneous weed identification.
Weeds are most easily identified by their flower color, but sometimes you have to note other features including their leaf structure. There are many ways to classify leaf structure. All but two of the weeds on the Montana Noxious Weed list can be classified into three edges: smooth, toothed and lobed.
Some of the most common noxious weeds in Montana include Canada Thistle, Whitetop and Spotted Knapweed. I will give a description of each below.
Canada Thistle
Genus: Cirsium
Description
Plant height: 30-150 cm tall.
Growth habit: erect perennial from deep-seated creeping
roots, often forming colonies.
Stems: leafy, branched, not winged.
Leaves: alternate, lance-shaped, 5-15 cm long, spiny-
toothed and deeply lobed to wavy along edges, usually
stalkless, usually almost hairless, or the leaves more or
less white-woolly beneath.
Flowerheads: pink-purple or occasionally white, 12-25
mm wide, with disk florets only, usually either male or
female on 1 plant, more or less numerous on spineless
stalks in open, spreading clusters. Pappus of the female
heads exceed the corollas, that of the male heads are
shorter than the corollas. Involucre 1-2 cm high, its bracts
sometimes with weak spine tips about 1 mm long.
Flowering time: June-August.
Fruits: flattened, ribbed achenes, about 4 mm long,
with pappus of brownish to white, feathery bristles.
Distribution
A noxious weed of fields and waste places in parts of w. c.
and s. parts of MT. Native of Eurasia, now widely
introduced in n. U. S. and s. Canada.
Whitetop
Family: Brassicaceae, Mustard
Genus: Cardaria
Description
General: short-hairy to hoary-short-hairy, strongly
rhizomatous perennial, often growing in colonies. Stems
erect to creeping, 20-50 cm tall.
Leaves: several alternate on stem, ovate-oblong to
oblong-oblanceolate, small-toothed, 4-10 cm long, the
lower ones stalked, the upper ones stalkless and clasping,
arrowlike, with backward-pointed lobes at base.
Flowers: numerous in dense top clusters, together
forming a large, flat-topped cluster, without bracts at bases.
Flower stalks slender, about 1 cm long. The 4 sepals about
2 mm long, elliptic, white-edged, blunt-tipped, falling off
early. The 4 petals white, almost round, 3-4 mm long.
Flowering time: April-August.
Fruits: pods, almost round in outline, not notched at
base, not indented along the seam, inflated, 3-5 mm long,
4-6 mm broad, hairless. Style about 1 mm long. Seeds 1,
rarely 2 per cell, about 2 mm long, not wing-margined,
slimy on the surface when wet.
Distribution
Widely distributed in old fields, along roadsides, etc, in w.,
s.c. and n.e. parts of MT. Also throughout much of the
lowland of w. U.S., often becoming a noxious weed.
Introduced from Europe.
Spotted Knapweed
Family: Brassicaceae, Mustard
Genus: Cardaria
Description
General: short-hairy to hoary-short-hairy, strongly
rhizomatous perennial, often growing in colonies. Stems
erect to creeping, 20-50 cm tall.
Leaves: several alternate on stem, ovate-oblong to
oblong-oblanceolate, small-toothed, 4-10 cm long, the
lower ones stalked, the upper ones stalkless and clasping,
arrowlike, with backward-pointed lobes at base.
Flowers: numerous in dense top clusters, together
forming a large, flat-topped cluster, without bracts at bases.
Flower stalks slender, about 1 cm long. The 4 sepals about
2 mm long, elliptic, white-edged, blunt-tipped, falling off
early. The 4 petals white, almost round, 3-4 mm long.
Flowering time: April-August.
Fruits: pods, almost round in outline, not notched at
base, not indented along the seam, inflated, 3-5 mm long,
4-6 mm broad, hairless. Style about 1 mm long. Seeds 1,
rarely 2 per cell, about 2 mm long, not wing-margined,
slimy on the surface when wet.
Distribution
Widely distributed in old fields, along roadsides, etc, in w.,
s.c. and n.e. parts of MT. Also throughout much of the
lowland of w. U.S., often becoming a noxious weed.
Introduced from Europe.
Unfortunately, there is no one silver bullet effective in getting rid of invaders. Managing and preventing weeds can require a variety of techniques. This is called Integrated Pest Management (IPM). If you wish to know more about IPM, You may contact us at the numbers below for an onsite consultation.
Enjoy your spring!
Chris Aos (Manager) 406-928-4102
Gil Jones (Consultant) 307-277-2120
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