A fast grower and a hearty survivor, the tree-of-heaven has been considered a Class C noxious weed in Washington since 2012. Native to China and Taiwan, it’s an attractive tree with grayish bark and small clusters of light green or yellow flowers. But its fast growing and its reproductive prowess has caused it to outcompete native plants, allowing it to come up along forest edges, woodlands, fence rows, roadsides, old fields, urban parks, and even through cracks in cement. The tree-of-heaven also leaches a variety of allelochemicals into the soil that have demonstrated toxic effects on neighboring plants. It’s a prime example of an invasive plant that can end up causing serious problems. All states have a list of problematic plants. With summer being the prime time for family vacations it’s good to be aware of that, and that those “beautiful plants” along the roadside might not be the best thing to bring back as a souvenir. What you thought would make an attractive landscape addition might end up being your yard’s, your neighbor’s yard and your state’s worst nightmare.