Have you ever been caught behind a slow-moving car that’s obviously sightseeing? It might be me.

A favorite summer pastime is driving around town looking at trees, flowers and landscapes, and if the lineup of cars behind us gets too long, my wife, Mary, always suggests I pull over, which helps keep the horn-honking to a minimum.

Apparently, we aren’t the only ones noticing what’s growing, because an eye-catching tree currently in full bloom is prompting many questions as it’s viewed in yards and along city streets. It’s the Japanese tree lilac, whose botanical name is Syringa reticulata, with its large, billowy white flower clusters. If you didn’t know better, you might not even recognize them as lilacs, although they’re cousins of common shrub-type lilacs.

Japanese tree lilacs can be grown as single-trunked trees, or in a multi-trunked clump. They’re becoming more popular because they’re so versatile. The eventual height of a Japanese tree lilac is about 20 or 25 feet high, which classifies it as a small-scale tree, when compared to our large shade trees that can reach 60 feet.

Their neat shape makes them an ideal feature in small spaces such as courtyards, narrow side yards and close to decks and patios. The leafy canopy stays fairly low-headed, making them a great screening tree between neighboring yards, or to add privacy to backyard patios and decks. There’s a lot to like about Japanese tree lilacs.

Its prime feature, of course, is showy flowers. When the spring blooms of ornamental crabapples have faded, the Japanese tree lilac takes center stage with its display of creamy white flowers, usually blooming from about mid-June through early July, later than shrub-type lilacs.

The Japanese tree lilac even adds winter beauty. The bark is somewhat glossy and copper-colored, providing interest if planted where it can be viewed in winter. The seedheads usually persist, adding further interest. It’s one of the toughest and most trouble-free trees for landscapes.

Japanese tree lilac is winter-hardy throughout the region and is well-adapted to alkaline soil types. They grow well even in dry sites, once they become established. They can’t, however, tolerate wet, poorly drained soil, which is a common trait among all lilacs.

Like other lilacs, they require full sunshine to bloom their best. The Japanese tree lilac is a great choice for boulevards as well as yards and public landscapes. Its rounded canopy and 25-foot height fits nicely where overhead power lines are a challenge.

Japanese tree lilacs require little extra care, and they don’t have major disease and insect problems. Extra shoots or branches will occasionally sprout from the lower trunk region, and they should be pruned flush while small.

Japanese tree lilacs are readily available at garden centers, especially those locally owned. You’ll find named cultivars, including Ivory Silk, Summer Snow, Signature, and First Editions Snowdance, whose sterile flowers don’t produce seedheads.

Here’s an exciting locally developed cultivar to watch for in the near future: North Dakota State University’s Woody Plants Improvement Program has recently introduced Summer Flare Japanese tree lilac, which will hopefully be on the market soon. For locations where a somewhat higher, dramatic flowering tree is wanted, Summer Flare becomes an upright oval, taller than wide, maturing at 30 to 35 feet high instead of the usual 25, yet with a width of only 14 to 16 feet.

Fielding questions

Q: I’m enclosing a picture of a problem with my large evergreen. A lot of dry ends dropped off the tips of branches this spring. You can see the dry ends in the photo. Can you tell me what’s wrong? — Fargo.

A: I have great news: nothing is wrong. Did you know that spruce trees, and other evergreens, produce flowers? The dry objects at branch tips are the withered blossoms from this year’s bloom.

When we think of flowers, we think of something colorful and pretty. Most trees do produce flowers, but many aren’t showy, instead appearing green or brownish, and go unnoticed until they result in seed, which is more noticeable.

Spruce trees have separate male and female flowers on the same tree. The dried structures at the branch tips in your photo are the male flowers, which shed pollen earlier and will eventually dry up and fall off. On your tree, the pollen reached female flowers, which has resulted in the start of at least one “pine cone” being formed, which is the green cone shape at the tip of another branch. This cone will eventually produce seeds inside.

So this is all part of the tree’s circle of life. Spruces don’t produce flowers and cones every year, which is why you might not have noticed it before. Some years are heavy flowering or seeding years for trees.

Q: Every year my white Annabelle hydrangea plants start out beautiful and then the leaves develop crisp edges, and the leaves look ragged. What am I doing wrong? — Casselton, N.D.

A: Annabelle hydrangea, with its huge, white clusters of flowers, has fairly tender leaves. The foliage is large and somewhat soft, which makes it vulnerable to the elements.

These soft leaves are often affected by wind, low humidity and other weather-related factors that cause crisp edges and ragged-looking leaves. Insect feeding can contribute also.

The word “hydrangea” means “water-loving.” To keep foliage healthier, it helps to provide hydrangea shrubs with plenty of water. Begin by working peat moss into the soil around the hydrangea, which will make the soil less compact and more hydrangea-friendly, while adding a moisture-holding component.

Mulch around your hydrangea with 3 to 5 inches of shredded bark, which will keep the soil cool and moist. As leaves are unfolding in spring, you might monitor for insects, which might be causing foliage problems, also. A good organic insecticide to keep on hand is spinosad.

Q: This spring, I removed a mature, diseased quaking aspen, and now I’m inundated with little shoots sprouting all over the yard. Internet sources seem to agree to just mow and pull them repeatedly and they’ll go away, or spray them with chemicals. The sprouts come up only a week after mowing. I have no problem with pulling, mowing or spraying, but I’m wondering if you have any advice? — Fargo.

A: As long as the “mother” tree is gone, judicious use of lawn weed herbicides will eventually lessen the sprouting, as will pulling and mowing. Keeping the sprouts from establishing is important so the underground roots will eventually decompose. If little trees are allowed to establish, they’ll nourish the underground roots, keeping the system alive.

Several sucker-stopping chemicals are on the market, but most reports have proven them unsuccessful in keeping little sprouts like these from popping up in the lawn. As with many things in gardening, persistence is the key.

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Email him at kinzlerd@casscountynd.gov or call 701-241-5707. Questions may be published, so please include your name, city and state for appropriate advice.

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