The Fast-Growing Flowering Tree That Boasts Beautiful Blooms And Colorful Fruit

Some landscaping trees put on a show year-round. The Korean mountain ash (Sorbus alnifolia) is a perfect example. It bursts with miniature white flowers in late spring, crimson berries in late summer, and red and yellow leaves in the autumn. This rose relative's smooth gray bark stands out next to the jagged icicles and white snow drifts of winter, and its berries stick around after its leaves fall to the ground, offering sustenance to hungry birds. Eager to provide shade for you and shelter for wildlife, this ornamental tree races to reach a height of 40 to 50 feet, maintaining a pyramid-like shape until it matures and develops a rounded canopy. 

Though the Korean mountain ash has lots to offer, it demands little in return. It doesn't need much pruning, and it's not terribly vulnerable to the borer insects that bother other types of mountain ash trees. Ideal for USDA hardiness zones 3 through 7, this cool-climate tree relative prefers full sun, damp soil that drains water effectively, and a pH level that's slightly acidic. If a DIY soil health test or pH strip shows that your planting site is neutral or alkaline, don't fret: There are several ways to make the soil more acidic. One of your best bets is amending your Korean mountain ash's soil with elemental sulfur — for example, Earth Science fast-acting sulfur. If you only need to adjust the pH a little bit, try a nitrogen-containing fertilizer such as Milogranite all-purpose slow-release nitrogen 6-4-0 fertilizer.

Providing your Korean mountain ash with its preferred sun and soil conditions is your first order of business. After that, make sure to water it regularly and monitor it for evidence of pathogens and pest damage. Bacterial fireblight can cause trouble for this species. Its warning signs include scorched-looking branch tips and foliage. If your Korean mountain ash is losing lots of leaves, or if its leaves have developed spots, scab might be to blame. This type of disease can also hamper the tree's flower and fruit production. Stressed-out Korean mountain ashes sometimes fall prey to canker, which may proliferate beneath the bark, obliterating branches and making the tree susceptible to breakage on windy days.

Aphids aren't a fatal problem if they feed on your Korean mountain ash's leaves, but they can be a nuisance. Getting rid of aphids generally involves a soap-and-water treatment or application of neem oil product such as Natria neem oil spray for plants. Also keep an eye out for sawfly larvae, which can turn healthy leaves into skeletons of their former selves. The green-black larvae look like slugs and develop and orange tint as they grow. An insecticidal soap such as Garden Safe ready-to-use insecticidal soap can evict them from your tree. Scale insects look like bumps on your tree's leaves and stems, and they can cause foliage to wilt and drop. Neem oil or insecticidal soap can make them history, or just prune off plant parts containing infestations.