INVASIVE TREE WEEK - MIMOSA TREE

Any tree that shares it name with a delicious brunch beverage should be great. Alas, the Mimosa Tree (Albizia julibrissin) is the exact opposite of great.

Brought to the United States as an ornamental tree from Asia and Africa, the Mimosa Tree's ability to reproduce vigorously has allowed it to spread unchecked across eastern and southwestern states. The seeds, which are produced in abundance and long-lived are dispersed by animals and water. Mimosa trees go rapidly under good conditions but have week, brittle wood and are short-lived. They resprout quickly if cut or top-killed.

Since the Mimosa Tree prefers full sun you will frequently see them along roadsides, in open vacant lots, up against but not in forests and on riparian areas.

Yes, the Mimosa Tree is an attractive tree but just as you should do when dating, go for the good personality. Visit our website for a list of trees that do well in DC.

The Mimosa Tree does NOT qualify for the $50 Tree Rebate.
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Mimosa Tree 101

• Grows 20-40 feet tall
• Bark is thin and almost smooth
• Multi-part leaves like a fern; green; no fall color change
  
• Produces fragrant pink flowers between May and July

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INVASIVE TREE WEEK - PRINCESS TREE

My niece is a princess, this tree is not.

The Princess Tree (Paulownia tomentosa) was brought to North America from China in the 1840's for use as a landscape and ornamental tree. Since then it has become naturalized in the eastern U.S. and is also on the west coast. The Princess Tree can be found in 25 states from Maine to Texas. This is not good news.

What makes the Princess tree an invasive tree species?

Like the Tree-of-Heaven, it is a fast colonizer, reproducing from seed or root sprouts. A single tree can produce up to 20 million seeds that can be easily transported by wind, water or even on my flip flop. The Princesstree is not picky on where it grows. Rocky cliff? No problem. Acidic soil? Bring it on. Burned out area? Sure.

Do not for one second applaud the Princess Tree's pioneer spirit. It is a true invader. It crowds out native species.

Want two other reasons to not Facebook Fan the Princess Tree? Mature trees are generally structurally unsound and rarely live more than 70 years. No I am not an ageist.

The Princess Tree does NOT qualify for the $50 Tree Rebate. Check our website for a list of recommended trees that do well in the District and are eligible for the rebate.

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Princess Tree 101

• Can grow to be 60 feet tall and 2 feet in diameter
• Leaves are large, heart-shaped, opposite and fuzzy
• Bark is light to dark gray and rough
• Fragrant, pale-violet flowers appear from April to May
• Pecan-shaped capsules appear beginning in June; release tiny winged seeds in winter
• Other common names include the Empress Tree and Foxglove Tree

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INVASIVE TREE WEEK - TREE-OF-HEAVEN

This tree is no angel.

The Tree-of-Heaven (Ailanthus altissma), native to China, is a fast growing, deciduous tree that can reach up to 80 feet in height and 6 feet in diameter. Unlike me, it can flourish in unfavorable conditions and requires little care.

So what makes the Tree-of-Heaven an invasive tree species? It is a prolific seed producer - each tree can produce as many as 325,000 seeds - and it grows fast, nudging out native species. The tissue of the tree also contains a compound called ailanthone that is toxic to many other plant species.

Since the Tree-of-Heaven poses such an environmental threat its removal does not require replacement under the District Urban Forest Preservation Act. Removal is easiest as a seedling and after its rained when the soil is loose. Be sure to remove the entire root since broken fragments may re-sprout.

The Tree-of-Heaven is NOT eligible for the $50 Tree Rebate. Visit our website for a list of trees that Casey Trees has had great success in planting in the District.

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Tree of Heaven 101:

• Deciduous
• Grows up to 80 feet
  
• Odd or even pinnately compound leaves with 10-41 leaflets on 1 - 3 foot stalks
• Leaves smell like peanut butter when crushed
• Bark is light gray; rough
• Yellow-greenish flowers in April - June
• Wing-shaped fruit appears from July - February
  

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INVASIVE TREE WEEK - BRADFORD PEAR

Oh Bradfor Pear (Pyrus calleryana) - your name makes you sound delightful and even delicious but you are neither.

A fast-growing, flowering tree native to China, the Callery Pear, more commonly known as the Bradford Pear after the first introduced cultivar, was heavily promoted and planted in the 1960's as suburban development took off. Developers and municipalities wanted to soften new development with landscaping, and the Bradford Pear was the answer. They showed up in front yards, office park landscaping and as street trees. And why not plant it? The Bradford Pear was not thorny like other pear trees, it did not self-pollinate and put on a flashy spring and fall show.

But here is the first problem - other Callery Pear varieties, those that do allow cross pollination were introduced and bam, Bradford Pears everywhere. You can blame the birds who go after the fruit and drop their seeds. Since the species grows so fast, it pushes out other native species. Rude.

The other problem with Bradford Pear trees is that they grow upright and have very tight branch crotch angles which make them very susceptible to breakage during wind and snow storms. Most do not stay in tact during their lifespan. Think about all the cars and houses located below these trees that have paid the price.

Lastly, the tree is relatively short lived. They last just about 20 - 30 years. In that short time span they can cause a significant amount of environmental harm and expensive damage to personal property.

Today's lesson - Do not plant the Bradford Pear. Consider alternatives such as the delightful and non-invasive Serviceberry or one of these other great trees. And, also ask your local nursery to stop carrying the Bradford Pear if it is currently.

Please also note that since the Bradford Pear is considered an invasive tree species, it does NOT qualify for the $50 Tree Rebate.

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Callery Pear 101:

• Deciduous
• Can grow up to 60' tall but most commonly found between 20-30' tall; 20-30' wide
  
• Alternate, simple, ovate leaves - approximately 3" long
• Light gray bark
• Clusters of white flowers appear before leaves in April and May

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UNNATURAL BORN KILLERS

Scary title? Deservingly so. Invasives are scary business.

By definition, an invasive plant or tree is a non-native species whose introduction causes or is likely to cause economic or environmental harm, or harm to human health.

And just like in a good murder mystery, you can't always tell which plant or tree will cause the messy mayhem. Some invasives have pretty flowers, sweet scents, cirque de soleil worthy climbing abilities and innocent sounding names. This is just deception. Do not be drawn in by these sirens.

So which plants should you shout Stranger Danger at? On June 3rd and 5th, Casey Trees will host Unnatural Born Killers where guest instructors Ken Ferbee (NPS) and Mary Farrah (UDC) will teach you about the area's most pernicious plant invaders and how to combat them. This course includes an evening lecture and weekend field component.

Advance registration is required and space is limited. As with all of our classes and programs, Unnatural Born Killers is FREE.

Since Unnatural Born Killers will focus on invasive plants, I am officially declaring it Invasive Tree Week here on Tree Speak. All this week we will highlight tree species you should just say "NO" to. These trees along with others are listed on our Do Not Plant list. It is important to note that these trees do not quality for our Tree Rebate. Nope, not on my watch.

CITIZEN FORESTER IN THE NEWS - MARGARET MISSIAEN

Kudos to Casey Trees Citizen Forester Margaret Missiaen, recipient of a Capitol Hill Community Achievement Award.

Margaret epitomizes what one person can do to protect and grow their neighborhood's tree canopy. A co-founder of Trees for Capitol Hill, Margaret has helped plant hundreds of trees and care for countless more throughout Capitol Hill. Just this past fall, Margaret led an inspiring tree tour of South Capitol Hill’s big parks and has served as a guest speaker at Casey Trees.

Many thanks to Margaret and her husband Ed for being educators and tireless advocates for trees in Capitol Hill and throughout the District. The honor is well-deserved.

Margaret will receive her award at the Capitol Hill Community Foundation’s benefit dinner on Thursday, May 6. Click here for information related to the event.