Are Crimson King Maple Leaves Poisonous to Dogs?

Crimson King

• "Crimson King" is a cultivar of the Norway maple, which is desirable for its round crown, deeply lobed leaves and brilliant, long-lasting fall color. Not all Norway maples are prized for their fall colors, however. Some have colorful leaves from the start. As its name implies, the leaves on the "Crimson King" maple are a deep maroon-green color as soon as they unfold in the spring. The color persists through late summer. In autumn, the leaves sometimes darken to a brownish-maroon color that the University of Connecticut calls "bizarre."

Climate and Culture

• "Crimson King" maple thrives in U.S. Department of Agriculture plant hardiness zones 3 through 7. Although it has a shallow root system, the tree is drought-tolerant and adaptable to a wide range of soil conditions. It grows equally well up to 40 feet high and wide in full sunlight or partial shade and enjoys moist but well-draining soil.

Toxicity

• Although "Crimson King" maple leaves do not pose a threat to dogs, they may be dangerous for horses. Red maples (Acer rubrum) are extremely dangerous -- even deadly -- for horses if consumed. Scientists believe that gallic acid, which is present in the maple's red leaves, is the culprit. The more wilted the leaf, the more toxic it is. Horses that ingest wilted red maple leaves often die within a day. Red maples are hardy in USDA zones 3 through 9. It is not known if other maples with red leaves -- including Acer platanoides "Crimson King" -- will poison the animals, but caution should be taken to keep horses well away from any red-leaved maple trees, just in case. In fact, according North Dakota State University's Extension Service, all maple trees should be considered toxic to horses until scientists prove otherwise.

Other Considerations

• Norway maples in general, including the "Crimson King," are considered invasive in many areas of the United States. The hardy nature of the tree allows it to outcompete other, more valuable native species and understory plants. Although this makes it a good urban tree -- it can even withstand pollution -- home gardeners should think twice about planting it where it may cast too much shade over desirable perennials.