Salix X fragilis (Crack Willow)

Plant Info
Also known as: White Crack Willow
Genus:Salix
Family:Salicaceae (Willow)
Life cycle:perennial woody
Origin:Eurasia
Status:
  • Invasive - ERADICATE!
  • Weedy
Habitat:sun; average to wet, disturbed soil; stream banks, shores, ditches, fields, roadsides, landscape plantings
Bloom season:May - June
Plant height:10 to 100 feet
Wetland Indicator Status:GP: FAC MW: FAC NCNE: FAC
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: spike

[photo of male catkins] Male and female flowers are on separate plants (dioecious) in spike-like clusters (catkins) at the tips of short branchlets along 1 year old branches, emerging with the leaves in spring. Male catkins are 1¼ to 2½ inches long, the flowers loosely arranged in whorls around the stalk, each flower with 2 yellow-tipped stamens that have a few hairs on the lower half of the stamen stalk (filament).

[photo of female catkins] Female catkins are slender, up to 3½ inches long, the flowers narrowly pear to bottle-shaped with a long beak, hairless, and on slender stalks .5 to 1.5 mm long. At the base of each male and female flower stalk is a hairy, yellowish scale-like bract; bracts drop off soon after flowering.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of leaves] Leaves are alternate, 2½ to 7 inches long, to 1+ inch wide, 4 to 7.5 times as long as wide, narrowly lance-elliptic, widest below or near the middle, wedge-shaped to somewhat rounded at the base, with a long taper to a pointed tip, often with a slender, tail-like extension at the tip. The upper surface is dull or shiny, medium to dark green, the lower surface dull, pale blue-green. Edges are finely toothed. Leaf-like appendages at the base of the leaf stalk (stipules) are small and egg-shaped, taper to a pointed tip, and drop off early.

[photo of elongated glands on older leaves] Glands at the tip of the leaf stalk may be obscure on young leaves but a pair often grows into hair-like protrusions as leaves age.

[photo of leaf hairs] New leaves are green to reddish and covered in straight, white, silky hairs on both surfaces, more densely on the lower surface, becoming mostly hairless with age; the hairs can appear to be a dense fringe on young leaves.

[photo of 1-year-old twigs] New branchlets are hairless to variously hairy, yellow turning yellow-brown the second year.

[photo of mature trunk] Older bark is gray to gray-brown with deep furrows and irregular coarse or flat ridges. Trunks are single or a few in a clump, erect to leaning or even prostrate, and can reach 40+ inches diameter at breast height (dbh).

Fruit: Fruit type: capsule/pod

[photo of developing fruit] Fruit is a hairless capsule 4 to 6 mm long but viable seed is rarely formed. Reproduction is primarily vegetative through suckering or from broken branches that can take root and form clones of the parent tree.

Notes:

There are over 20 species of Willows in Minnesota; Crack Willow is one of the non-native tree willows in the state, found in a variety of moist to wet places, especially areas prone to seasonal flooding such as lake shores and river banks, where it can reproduce like mad from broken branches. It is recognized by the finely toothed, narrowly lance-elliptic toothed leaves up to 4 inches long, shiny or dull green on the upper surface and paler on the lower; new leaves covered in long, straight, silky hairs, soon becoming mostly hairless; leaf-stalks with glands at the tip near the blade, usually elongating with age; male and female catkins both long and slender. Catkins emerge with or just after the leaves and flowers are subtended by a pale yellowish to greenish bract that falls off soon after flowering. Stipules are mostly absent. Branches are brittle at the base and easily break off. Twigs are yellow to yellow-green or yellow-brown. In the spring, look for the yellow twigs, long, straight leaf hairs, and male flowers with 2 stamens; later in the season, look for the extended glands that should be on many leaf stalks just below the blade.

All of Minnesota's tree Willows have similarly shaped leaves but there are subtle distinctions. The two natives—Peach-leaved Willow and Black Willow (Salix nigra)—both have crinkly hairs on new leaves; the non-natives—Crack Willow (Salix X fragilis) and Bay Willow (Salix pentandra)—have new leaves that are hairless or with straight, silky hairs. All but Peach-leaved Willow typically have glands at the tip of the leaf stalk; they are only sometimes present on Peach-leaved Willow. Only Black Willow has leaves a similar shade of green on both the upper and lower surface; all the others are pale green to blue-green on the lower surface. Bay Willow has very shiny leaves that are stiffer and broader than the others.

Crack Willow has some variability and there was a time when it was considered distinct from Whitecrack Willow (Salix X rubens) but they are now considered the same species, a hybrid of S. alba (White Willow) and S. euxina (Brittle Willow), both of which are native to Europe or Eurasia.

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More photos

Photos by K. Chayka taken in Anoka and Ramsey counties. Photos by Peter M. Dziuk taken in Anoka, Otter Tail, Pennington and Ramsey counties.

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