Monday, July 7, 2008

Mimosa, Exotic Beauty or Garden Pest?

Mimosa trees (Albizzia julibrissin var. rosea) are currently in full bloom at Powell Gardens and throughout Greater Kansas City. When I first moved to the area 12 years ago, I was surprised to see so many of them growing here (I thought they would not be hardy here). I was also bombarded by gardeners commenting that they either love them or hate them! Now that I have been here and observed the trees through 12 seasons I feel like I can weigh in on them: The successful trees in the area are of the variety rosea which noted plant explorer E. H. Wilson brought back from Korea to the Arnold Arboretum. These trees are more refined and hardy (to -15F or more) than the typical species "monster" you see escaped along the roadsides in the South. Mimosas are a long blooming tree, at a season when their bright color adds to our tropical-like weather. The fragrant flowers are nectar-rich and attract a plethora of beneficial insects (including butterflies) and hummingbirds. The trees have a horizontal form that seems to fit in our prairie landscapes even though they originated in Asia. The ferny foliage is delightful and airy; folding up each night to give the tree a whole new look.
The negatives are that past severe winters clipped many of them to the ground. It is no fun removing such a large plant! Virtually all of them recovered with stump sprouts. Some local trees amazingly survived the big freezes of the 1980's and many are over 50 years old according to their owners. The seeds of mimosa are prolific and germinate with abandon in disturbed soils in the garden landscape. Fortunately they do not germinate into undisturbed soils or wildlands so I would not consider it invasive like it is in southmost Missouri and points south. It is a nuisance to pull up all the seedlings as weeds in the garden!
Mimosa in mid-day, over 90F heat north of the Visitor Center (the flower color does bleach out to pink in extreme heat).
Powell Gardens Mimosas are grown from local hardy trees or regional sources. I would advise anyone wanting this tree to do the same: local seedlings "Brian's Choice" are available at Greeson's or trees wholesale grown by Forrest Keeling Nursery sold at Colonial Nursery are good bets. The beautiful purple-leaved variety 'Summer Chocolate' is a beautiful plant but was killed to the ground out here by 2007's Easter Freeze. It came back and did not dieback last year. We look forward to how it will perform over the years at is always a plant that attracts attention. I will leave it up to you whether you want a mimosa in your landscape -- good or bad, the choice is yours! You can always come out and experience them at Powell Gardens: most north of Visitor Center surrounding the Dwarf Conifer, Butterfly and Fountain Gardens. Three seed grown trees from an old (now removed) tree in Brookside we call "KC Red" can be seen at the Rock & Waterfall's trolley stop. This strain grows with shocking sturdiness and vigor but is still of the hardy rosea variety. We usually grow some of these trees for our spring plant sale.

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