Arceuthobium pusillum (Eastern Dwarf Mistletoe)

Plant Info
Also known as:
Genus:Arceuthobium
Family:Viscaceae (Mistletoe)
Life cycle:perennial
Origin:native
Habitat:sun; principally black spruce trees
Bloom season:April - May
Plant height:less than 1 inch
Wetland Indicator Status:none
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: 3-petals Flower shape: 4-petals Flower shape: indistinct

[photo of male flowers] This parasitic plant has separate male and female flowers on separate plants (dioecious), typically on separate host plants as well but occasionally on different branches of the same tree. A single tiny flower is at the top of the plant, sometimes with opposite branches along the stem just below it, with smaller flowers than the terminal flower. Male flowers mostly have 3 or 4 petal-like sepals and an equal number of conspicuous yellow stamens; the terminal flower is less than 1/8 inch across. The female flowers are diminished within the short stem leaf structure and appear more like a small abnormal growth than a flowering plant. Unlike most dioecious plants, the males bloom before the female flowers.

Leaves and stem: Leaf attachment: opposite Leaf type: simple

Tiny scale-like leaves on the short fleshy stem that emerges from the bark of the host plant. Color is brown to greenish. All plant parts are smooth.

Fruit: Fruit type: berry/drupe

Fruit is a tiny oval berry that matures in late summer. When ripe it forcefully ejects seed coated with a sticky substance that adheres to whatever it touches.

Notes:

This unusual wildflower infests native stands of principally black spruce (Picea mariana) less frequently on white spruce (P. glauca) and rarely tamarack (Larix laricina). Dwarf mistletoe is studied by foresters as it affects stand quality. As an infective agent it behaves epidemiologically as a disease organism - having an infection center diminshing out toward the edges. Witches brooms (unusual clustering growth of branches) are commonly produced on infected trees making it visually observed in the crowns from some distance but not all witches brooms seen periodically on spruce are caused by dwarf mistletoe. It has persisted along with its host naturallly and is not perceived as a serious forest management pest. 

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More photos

Photos courtesy Peter M. Dziuk, taken on state forest land just east of Iverson, north of Hwy 210 in Carleton county.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Gary - Carlton County
on: 2017-08-11 17:30:58

Arceuthobium pusillum grows on the black spruce in a tamarack/spruce swamp on my land. I think the black dot on the map (Carlton County) is one of my collections. It gas not caused, as far as I can tell, any serious decline in the black spruce. Fungal organisms seem to be a bigger problem for them.

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