In a Tree Profile over 10 years ago, I raved about the American hornbeam, Carpinas caroliniana and still feel the same today. With the more recent arrival of several new cultivars which display some of the best characteristics of this species, an update on this tree is in order.
Let’s start with its generic attributes. The pioneer nicknames of “Blue Beech”, “Muscle Tree” or “Ironwood” of the species are suggestive of what a tough Midwest native tree this is. Considered a small tree, the ultimate mature size is approximately 30-feet tall by 20-feet wide. They may grow larger under optimum conditions. It has few, if any, disease or insect pest concerns in this region and as the name implies, has branches “of steel”. In my experience, branches can bend like rubber and not break, which is a good testament for strength. This is a good urban tree characteristic.
Read More "American Hornbeam Cultivars – Carpinus caroliniana: Native Flame®, Palisade®, Ball O’ Fire™, & Rising Fire®"
Maples have been widely planted in the urban landscape because they are so tough and tolerant of the urban environment. Not that we need even more maples on our tree lists, but if you are growing them or are planting more, you should know how the various forms and cultivars compare to each other. The Urban Sunset® Maple, Acer x platanoides ‘JFS -KW187’ 27545 is a close relative of the Pacific Sunset® and Norwegian Sunset® maples, relatively new maples that are so popular these days. The most significant difference between these three is that the Urban Sunset® has a more narrow growth habit than the others. Pacific Sunset® and Norwegian Sunset® maples can become incredibly wide.
Urban Sunset® Maple is noted to produce consistent red or burgundy fall color. They are relatively easy to transplant. They grow very fast, but usually do not exceed 35 to 40 feet tall by about 20 feet wide. From my experience, they appear to be drought tolerant and show none of the sagging leaf characteristics of red maple that looks pathetic during dry summers. The shade under mature specimens is so dense that turf will struggle. A ground treatment of arborist’s chips and woodland adapted groundcover plants and ferns is the best option. Read More "Urban Sunset® Maple – Acer truncatum x platanoides ‘JFS-KW187’ 27545"
The swamp white oak, Quercus bicolor, is as tough a drought tolerant, wet soil tolerant, broadleaf work horse of an urban tree as you might ever see. It may not have some of the bright fall color characteristics of some of the other newer cultivars, but this Midwest native should be on your street tree and open space tree list. It has a broad and strong branch structure with the potential to become a relatively care-free urban tree. The swamp white oak can be susceptible to a number of potential diseases and insect pests, most of which are not too significant in the Pacific Northwest. Read More "Swamp White Oak, Quercus bicolor"
In place of a tree profile this quarter, I’ve compiled an update of what we have observed about the performance of different species. Over 60 trees have been reviewed here and we have learned a lot of helpful information for tree selection and management. Remember, these are my observations, limited to these specific trees grown in western Washington. Your conditions and results may vary. Consider: Read More "PNW Tree Profiles September 2017 Updates"
Cultivars of Parrotia persica have been mentioned in past articles but the Persian Spire™ upright ironwood, ‘JL Columnar’ P.A.F., merits its own profile. Discovered by John Lewis of JLPN Nursery in Salem, Oregon in 2013, he likely first noted its strong upright growth. He then found that the foliage was finer with a narrower leaf than the common ironwood. Read More "Persian Spire™ Upright Ironwood, Parrotia persica ‘JL Columnar’ P.A.F"
Linden trees, especially American, Tilia americana and littleleaf, Tilia cordata, have been widely planted in urban areas because they are drought tolerant, durable and beautiful, and thrive is some of our toughest locations. However, aphid infestations on these lindens can be incredibly messy and a real nuisance. The “honeydew” under a street tree can appear as if it rained just beneath the canopy. Except in this case, the shiny area you see is sticky like glue, excretions from the aphids. This glaze of honeydew can be horrible for cars, sidewalks, and outdoor furniture.
A perfect solution to avoid this malady is to select a close relative, the silver linden, Tilia tomentosa, which does not attract aphids. As the species name implies, tomentosa is used to describe a woolly coating on the leaf formed by the tomentose hairs. Apparently, it is the hairs or woolly coating on the leaves that repel the little critters. So, there is no need to blacklist all lindens because of the aphids. Read More "Silver Linden Tilia tomentosa"
There are technically only a few trees that come close to the small tree category for utility planting these days, maturing at less than 15 feet tall. There are even fewer that are narrow and this short. The new Emerald Spire® crabapple, Malus x adstringens ‘Jefgreen’ fits the bill. Maturing at no more than 15 feet tall and 6 feet wide, this is truly a small tree. It has shown remarkable winter hardiness and solid disease resistance as far north as Manitoba for over 10 years, making it a zone 2 plant. Did you hear that, Alaska? Read More "Emerald Spire® Flowering Crabapple Malus x adstringens ‘Jefgreen’"
The magnificent Princeton elm, Ulmus Americana ‘Princeton’ is the ideal tree to plant where large soil volume and above ground space is available. This is a true American elm, not a hybrid, but selected from a specimen around 1922 and developed by Princeton Nurseries. It has a proven record of Dutch elm resistance and longevity on the street. Ironically, the Dutch Elm Disease that decimated most elm trees in the US was not introduced into the US until about 10 years later, and Princeton elm trees planted before this time are still around today. This selection is also resistant to the elm leaf beetle but may be susceptible to phloem necrosis and wet wood. Read More "Princeton Elm, Ulmus americana ‘Princeton’"
The large and fragrant flower of the common lilac is a fondly held memory and experience for many of us. Most often planted as a shrub, lilacs have also been grown in tree form for some time. However, they are not used as often as they should as a tree. In addition to the more familiar shrub forms, there are tree forms of this plant. As we get better at selecting small maturing trees for use in smaller spaces, tree lilacs Syringa reticulata and S. pekinensis are definitely ones to consider.
Tree lilacs are relatively small, at most about 20 to 30 feet tall and 15 to 25 feet wide. Leaves are opposite, single, entire, broad-ovate, 2 to 5 and half inches long and about half as wide. Leaves are dark green on top and grayish green and reticulate (netlike pattern) on the bottom. The undersides might also be glabrous or slightly pubescent.
Spring growth appears to be fresh, clean, and balanced. Newly emerging leaves have a wine colored hue, turning green as they expand.
Read More "Tree Lilacs, Syringa Reticulata and S. Pekinensis"
Not long ago, I wrote of three Parrotia Persica cultivars worthy of note for your street tree list: ‘Ruby Vase,’ ‘Vanessa,’ and ‘Persian Spire.’ I have just come across another to add to this list, Golden BellTower™.
A friend and local tree grower, Ken Christianson at Chrishaven Trees in Burlington, Washington, discovered this tree nearly 24 years ago; unlike many new tree varieties, this one has a pretty good history and performance record. Ken describes the ‘Golden BellTower’ as more reliably upright and columnar than some other Parrotia cultivars. It appears to be a moderate to fast grower, reaching 30 feet tall and up to 10 feet wide in about 25 years. Many other trees claim those mature dimensions but do not always live up to them, usually growing wider with age.
If you are unfamiliar with the Parrotia, you may mistake the leaf for a witchhazel, not really a stretch since they are both in the Hamamelidaceae family. And although the straight species of Persian ironwood has been a favorite for many, it was limited for urban use because of its relatively broad and unruly form. The arrival of new cultivars with more reliable form like ‘Golden BellTower’ have changed the game.
An unusual feature from the other narrow cultivars is the gold to apricot fall color, lending “golden” to its name, BellTower. It should be noted that fall color can vary considerably because of regional soils, and climate. From my experience, I have seen fall color vary from spectacular to incredibly boring on the same tree from year to year depending on seasonal weather. This selection apparently leans towards the yellow spectrum with more reliable color each year.
Read More "Golden BellTower™ Columnar Ironwood PPAF Parrotia Persica ‘Chrishaven 1’"