Category Archives: Trees and Shrubs

woody plants, trees and shrubs

Rhododendron diversipilosum ‘Milky Way’

Rhododendron diversipilosum 'Milky Way'

Image courtesy of Briggs Propagators

We thought you might enjoy the subtle charm of this hardy little known Rhododendron (perhaps nomenclature is its problem) . Commonly called Labrador Tea, formerly classified in the genus Ledum, and then later named R. tomentosum, there’s been obvious confusion when gardeners are seeking information. ‘Milky Way’ is a superior clone selected by Steve Hootman. In mid April, it produces trusses of small white starry flowers, which allude to its cultivar name. Fine textured evergreen foliage is small narrow and olive green.

Rhododendron diversipilosum ‘Milky Way’ is quite cold hardy, growing well in zones 3-6. It can take poor soil conditions but will be happiest if given a well drained soil with humus and regular moisture in sun or partial shade. Plants grow to 3′ in height and up to 5′ in width. It would be a great addition to a rock garden planted with early spring Narcissus, Hellebores and Veronica ‘Georgia Blue’.

Spirea thunbergii ‘Ogon’

Spirea thunbergii ‘Ogon’, in fall

Had to include this plant portrait now because this baby’s fall color is on fire! We had wanted to portray Spirea thunbergii ‘Ogon (a.k.a ‘Mellow Yellow’) in a blog post last spring, but there are always so many plants vying for our attention at that time of year. Not that this Spirea doesn’t. As a matter of fact, it is one plant we never tire of, and include it in many of our landscape installation projects.

Unlike most Spirea, this species has narrow willow like foliage that emerges a bright lemon yellow in early mid spring. White flowers adorn the arching branches just prior, and as the leaves unfurl. Although they are sweet enough, they aren’t why you should grow this shrub. Grow this Spirea for the texture and color the foliage provides year round, and which as you can see here, is an especially grand finale of volatile color in November.

Spirea thunbergii ‘Ogon’ is hardy to minus 20F (zone 5), and grows quickly to a height and width of 4-5′. It’s very happy in full sun, but grows well in partial shade, and seems to withstand poor dry soil conditions without hindering its performance. Like all Spirea it can be cut back hard in the spring if you choose to keep it shorter, but you’ll sacrifice the flowers. We could go on and on about which plants to use in combination with ‘Ogon’, but the list is practically endless. May we suggest Acanthus spinosus, Fothergilla ‘Blue Shadow’, Japanese maples of any form, Geranium ‘Rozanne’.…..(we could go on and on).

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Fothergilla x ‘Blue Shadow’

With Halloween just weeks away, it’s fitting that we take a look at a very colorful Witch Alder. The Witch Alders, as you may guess, are closely related to Witch Hazels, and are native to the southeastern US.  They are multi season plants, with honey scented white bottle brush flowers emerging in early spring (just before and as the plants leaf out), plus attractive form and outstanding fall color. One we are pleased to be growing is Fothergilla x ‘Blue Shadow’ notable for the lovely glaucous blue foliage it displays all summer.

Fothergilla x ‘Blue Shadow’ was discovered by Gary Handy of Boring OR, when he noticed this very blue leaved sport on another fine cultivar, Fothergilla ‘Mt Airy’. It’s a vigorous but compact grower, with an upright habit at first, then becoming thicker with age, and finally achieving 5-6′ in height and width. ‘Blue Shadow’ grows well in full sun or partial shade, prefers a reasonably moist but well drained slightly acidic soil, and is quite hardy in zones 4-8. It can be used as a focal point, or planted en masse at the edge of a woodland. So many plants would make great companions. For spring interest, pair with dwarf Rhododendrons; for summer, Hydrangea quercifolia ‘Peewee’ , and for fall the golden Leucosceptrum  and Carex ‘Blue Bunny’ to compliment ‘Blue Shadow’s technicolor display.

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Heptacodium miconoides

Our theory is, if a plant looks fantastic in the September garden, it merits attention. And if it has winter interest, grows quickly to a reasonable size and is easy to keep happy, then you should absolutely consider finding a spot for it. As I was driving though our little town of Dartmouth the other day, I had to pull over when I saw a picture perfect candidate of such a plant, Heptacodium miconoides, gracing a small streetside garden.

Heptacodium miconoides, or “Seven Son Flower” is relatively new in cultivation here in the US, having come ashore from China in the 1980’s. It bears attractive green foliage, resembling peach leaves, and finally in late summer and early fall, it produces panicles of fragrant, jasmine scented white flowers, which last for a couple of weeks, after which showy rosy red bracts remain. The common name “Seven Son Flower” refers to the 7 branches of blossoms of each panicle. We acquired our first specimen as a plant dividend at the Arnold Arboretum’s Fall Plant Sale in 1989. To our delight, it grew quite quickly, putting on as much as 3′ in a season. We learned after a bit that Heptacodium wants to be a multi stemmed shrub, unless pruned to one or several strong leaders. Our preference was to show off the handsome exfoliating bark, so we removed all but the strongest 3 trunks. If you would prefer to have a single trunk, select a young plant and stake one stem for straight growth.

Heptacodium merits attention for its adaptability to a variety of soil conditions, including soils that remain dry for some time, although occasional supplemental watering wouldn’t hurt. It is tolerant of salt spray, making it useful near the seashore. Other big plusses: Heptacodium is deer resistant, and the butterflies and bees absolutely love the blossoms. Provide it with lots of sunshine. Pruned as a small tree it can be the focal point of a small garden, or planted en masse it would make a showy hedge. It’s perfectly hardy in zones 5-8.

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Lespedeza thunbergii ‘Gibraltar’

Bush clover in blossom waves
without spilling
a drop of dew
—- Matsuo Basho

If you had to choose one plant to fill your late summer garden, you might consider the lovely Japanese Bush Clover, Lespedeza thunbergii ‘Gibraltar’. This selection was discovered by the accomplished plantsman, Bill Frederick, at Gibraltar, one of the duPont family estates in Wilmington, Delaware.  We have to admit ‘Gibraltar’ is a big show-off, quickly growing to 5-6′ tall and in just a few years occupying an 8-10 sq. ft. area quite easily. It loves a sunny spot and is hardy in zones 5-9.

 Lespedeza thunbergii ‘Gibraltar’ is in the legume family, and this means it does not require a rich soil, but prefers one that is a lean and well drained. To manage its size and form, you should cut the woody stalks hard to the ground in early spring. This may seem alarming at first, but Bush Clover blooms on new growth and  the full height will be attained by mid summer. A bevy of cascading branches adorned by an abundance of purple pink pea blossoms will add eye catching color from late August through September.

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Albizia julibrissin ‘Summer Chocolate’

Purple Mimosa TreePerhaps the most asked about plant in our garden right now is this purple leaved silk tree or mimosa, with it’s stunning chocolate purple fernlike foliage. The followup question is often, “but is it hardy” to which we answer, “yes, but…”. (Recommended hardiness zones are zones  (6b) 7-10, and our garden is definitely zone 6a.)

This is the scoop based on our experience. Albizia julibrissin ‘Summer Chocolate’ is a fast growing ornamental tree or large shrub, introduced to the US market roughly 10 years ago. True, it is less hardy than the more common green leaved forms. In 2005, our first attempt to establish this tree failed. We didn’t site it well.  We planted ‘Summer Chocolate’ in a spot where we thought it would look outstanding, but alas, it was the lowest spot on our property and the soil remains too wet there over the winter.  Initially we were resigned to growing it as a container subject, but were reminded by the old adage: if a plant doesn’t grow well in one spot, try another, and then another.

Good drainage usually is key in wintering over borderline hardy plants. We planted the next specimen in well drained soil in front of a south facing stone wall, and are now enjoying this beauty for the 3rd year in a row. It did get some die back after the winter of 2009-2010, but broke growth along the lower trunk and quickly grew to 6′ that year. We won’t expect it to reach full height or width, and don’t really care.  Tropical appearing chocolate colored foliage with a shrublike habit suits us just fine.

Those of you in milder winter areas (zones 7-10) can expect this tree to reach 20′ in stature and spread, with silky pink puffs of flowers in summer.  Gardeners in zones colder than 6 might consider growing ‘Summer Chocolate’ as a stunning container specimen. The plant, pot and all, can easily be moved into an unheated garage or other protected spot once it goes dormant in late autumn.

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Viburnum plicatum ‘Summer Snowflake’

Viburnum 'Summer Snowflake'There are many good Viburnum selections on the market, but this cultivar of Double File Viburnum  gets high marks from us. It is laden with white lacecap blossoms in early June, like all the rest, but this particular form continues to produce blossoms on new growth all summer into fall. It is especially striking in autumn, when the white blossoms are set off  by foliage that takes on wine tones.

Early info about the size of this plant reaching only 4-6′ was inaccurate. In our garden our specimen quickly reached 8′ tall, and as much in width. We’ve pruned our ‘Summer Snowflake’ to have a single leader with a more open habit. Plant ‘Summer Snowflake’ in good well drained soil where it will receive 6-8 jours of sun.  Birds love take cover in it’s branches. Deer find them unappealing for the most part.

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Indigofera amblyantha

Indigofera amblyanthaIt’s time to love pink, and how can anyone say no to a flowering shrub that produces upright racemes of soft pink pea blossoms from late spring right through fall. Indigofera amblyantha, commonly known as Chinese Indigo, is a member of the legume family, so it fixes its own nitrogen from the soil and thus is a candidate for poor soil conditions. It asks for full sun and good drainage, and is hardy in zones 6-9. It wants to be a multi branched shrub but we have seen it charmingly pruned to a single leader (to appear as a small tree). In zones with severe winters, Indigofera amblyantha may get winter die back, so we suggest that if you try this pruning treatment, do so on plants located in a sheltered spot and consider it as an experiment. Then again, should die back occur, you can always enjoy this plant as the bushier shrub it is more inclined to be.

Attractive companion plants for Indigofera amblyantha are Calamintha nepetoides, Euphorbia ‘Blue Haze’ and Sedum ‘Maestro’.

Ilex verticillata

December is the perfect month to enjoy this eyecatching deciduous holly whose brilliant berries, clustered on bare branches, provide splashes of color to the early winter landscape. Commonly called Winterberry, this North American native is found in the wild from Nova Scotia to Florida, usually growing in low lying areas, since it doesn?t mind wet feet. It is nonetheless adaptable to many soil types and will be happy enough in dryer locations. A large number of clones have been selected for their eventual stature, as well as for variation in fruit color and size.

As you probably know, the genus Ilex is dioecious, meaning there are different male and female flowering plants, and they have to tango for fruit set. Take note that there are earlier and later flowering selections of Ilex verticillata and it is a good idea to plant a male counterpart that blooms at the same time as the female clone.  Some of the earlier blooming female clones such as ‘Red Sprite’, ‘Berry Heavy’ and ‘Berry Nice’ should be pollinated with the male clone ‘Jim Dandy’. Use ‘Southern Gentleman?’, a late-blooming male pollinator for ‘Winter Red’, ‘Winter Gold’, ‘Capacon’, ‘Sparkleberry’ and the other later blooming girls.

Ilex verticillata waits until fall to become a star when the berries begin to color, so it is best sited in a spot where it does not have to be commanding all season long. Remember Winterberry does sucker, but this can be useful where you want to create a screen to attract wildlife. A number of years ago, we used it in repetition behind one of our beds that borders a wet area, and the planting now provides us with a bounty of branches for cutting.  Eventual plant size is dependent on which cultivars you select, and they range from 3-4′ to 12′ or more. Plants enjoy sunny or partially shaded exposures, soil that is acid to neutral, and are hardy through zone 4.

Cornus sanguinea ‘Arctic Sun’

Cornus s. 'Arctic Sun'You won’t pay much attention to Blood Twig Dogwood in spring and summer. The ordinary green foliage is attractive enough, but it does not sing “Here I am!”. It’s not until autumn, when Cornus sanguinea ‘Arctic Sun’ starts to make music in clear apricot tones with the changing fall foliage. Colder temperatures transform its green branches into stalks of vibrant yellow, orange and red which glow in an otherwise increasingly dull landscape.

‘Arctic Sun’ (a.k.a. Cornus sanguinea ‘Cato’) is a compact clone of Blood Twig Dogwood, reaching only 4-5′ tall as opposed to 8-10′, and this size is useful in smaller gardens. It thrives in average to moist soil in full sun or part shade, is deer resistant, and is hardy in zones 4-7, which means it will take temperatures to minus 30F, but probably won?t be happy in mild winter climates. We recommend planting ‘Arctic Sun’ in a location so that the dazzling winter stems can be viewed from an inside perch, perhaps where you sit with your morning coffee, or where you might pass by as you enter and leave your home. You’ll enjoy the show all winter, and may even be inspired to cut a few branches for decoration.

One thing you should note is that the best color on twig dogwoods is displayed on young wood. Every two or three years you should “stool” yours plants in early-mid spring. Stooling is a simple pruning technique where you cut back the entire shrub to about 6′ above ground. The new growth will provide a more colorful display when late fall and winter arrives.