|Seed sinks to bottom, then following spring, sends one stem
to the surface, which forms a spreading rosette of leaves up
to a foot across. Seeds form underneath. Click to enlarge.
|Volunteers in canoes pull the water chestnut rosettes by hand,
then bring the baskets ashore to be disposed of. Hot, wet work.
Ailanthus altissima is the Latinate name for tree-of-heaven, a tree native to
Trees are either male or female. Both have flowers, but only the female trees create seed clusters. A mature tree can produce more than half a million seeds in a single season. These disperse by wind, and are rarely eaten by birds, mammals or insects. Deer will not eat the leaves nor nibble on the bark of saplings. Trees - both male and female - also are producers of new shoots from a far-reaching root system, so what starts as one tree can easily become a thicket.
This species does not play well with others. As with garlic mustard, this plant produces chemicals which inhibit the growth of other plants, a trait that is referred to as being allelopathic. Combine that with prolific seed production, a growth rate much faster than any native tree, plus resistance to pollution and drought, and this tree is a nuisance in urban and semi-urban environments unless vigorous combated.
|Young trees have smooth bark
Tree-of-heaven is difficult to kill. Cutting results in new growth from the stumps that can exceed ten feet in the first year. Cutting will also stimulate a massive production of shoots from the surviving roots as far away as ninety feet from the original trunk. Any site where a mature tree was cut down will require follow-up cutting of new shoots several times a year for at least five years.
Systemic herbicides that kill roots (for example, triclopyr and glyphosate) currently provide the best chemical control for tree-of-heaven. These can be sprayed on shoots, or holes can be drilled in the stumps of freshly cut trees and the high concentration herbicide products applied directly. Both application methods can cause collateral damage to nearby plants.
|Garlic mustard: second year plants 1 to 3 feet tall
|Cross-shaped flowers appear in May
Japanese knotweed (Polygonum cuspidatum), also known as Japanese bamboo, is a winter-hardy transplant from
|Japanese knotweed clusters spread from roots
|Volunteer cutting large bittersweet vines on Summer Hill
Bittersweet likes full sunlight. It tends to grow fastest on trees bordering roads and open spaces. Growth rates are 5-10 feet/year. Stems up to an inch or so in diameter are smooth, with increasing roughness as mature stems thicken to 3 to 4 inches in diameter. These vines are easy to differentiate from other vines. Poison ivy clings to the bark of the trees with thousands of fuzzy rootlets and rarely exceeds 15-20 feet in height. Wild grape vines have a brown, flaking bark.
|Wreath, showing bittersweet berries