Docent Guide – October

Garden focus: Woodland (Japanese maples, liquidamber, oxydendron, parraotia, katsura, witch hazels)

Stories to tell:

Why do leaves change colors?

Plants are busy growing all summer long and into autumn. But the dark days of winter are coming. As the days get shorter, trees use this signal to “know” it’s time to begin getting ready for winter.  During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves.

As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green chlorophyll.  The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves to turn this glucose into a red color.  The brown color of trees like oaks is made from wastes left in the leaves.

It is the combination of all these things that make the beautiful fall foliage colors we enjoy each year.

Trees to take note of in Fall:

Japanese Maples (Acer palmatum, A. japonicum, A. shirasawanum)

Many people will tell you that Japanese maples are the most desirable garden trees that exist. This must have something to do with the grace and beauty the trees add to the garden through all four seasons.  Native to Japan, Korea, China, eastern Mongolia and southeast Russia, Acer palmatum has been cultivated in Japan for centuries and in temperate areas around the world since the 1800s. While Acer palmatum cultivars are what is most often referred to as Japanese maple, some may include maple trees from species Acer japonicum and Acer shirasawanum, both of which are native to Japan.  The Lake Wilderness Arboretum’s collection of Japanese maples includes cultivars from all three species.

Japanese maples differ from one another in leaf form, leaf color, overall shape and size. Typical of maples, Japanese maples have lobed leaves with veins spreading out like the fingers of a hand but they are smaller than on a typical maple tree. Acer palmatum leaves have five, seven or nine pointed lobes while Acer japonicum and A. shirasawanum have 9 – 13 lobes.  See the photos below for examples.

Examples of the diversity of A. palmatum leaves

Acer shirasawanum leaf

The leaf color of Japanese maples is usually green or red but the variety within those two colors is wide. Some trees will have remarkable color on their new spring leaves, perhaps fading to another color for summer and then bursting forth with dramatic color in the fall, like Acer palmatum ‘Okushimo’ (W19) which starts with chartreuse leaves in the spring, fading to darker green in summer and turning bright yellow to orange in fall. Some, like Acer palmatum ‘Moonfire’ (W17) and A.p. ‘Bloodgood’ (W19), will hold their red coloring all summer while others may be variegated with white, green, pink or red, such as A. p. ‘Orido Nishiki’ (W30) which blends bright pink, cream and green throughout each leaf. There are even some where the color extends to the bark (A.p. ‘Bihou’ (W17), A.p. ‘Sango-Kaku’ (W17, W26)) which makes quite a show in the winter.

Some Japanese maples can grow up to 20 feet or more in height, while others remain as low shrubs only reaching five feet after many years of growth, such as Acer palmatum ‘Caperci Dwarf’ (W19). Some are upright in form, or pendulous and cascading like our Anniversary maple, Acer palmatum dissectum ‘Viridis’ (W14). This tree was 25 years old when it was planted at the Lake Wilderness Arboretum while the Arboretum was celebrating its 25th Anniversary. That makes the tree 50 years old now.

How did we end up with so many different cultivars of Japanese maple?  These trees are naturally very variable and Japanese gardeners began to collect different forms and produce more from seedlings so that today at least a thousand different forms are known. Many forms were developed in Japan and these have Japanese names, while others were bred in Europe or America and usually have English-sounding names.

Japanese maples are great for the garden because they have few pest or disease problems and are versatile enough to thrive in locations ranging from full shade to full sun. They can be grown in the garden where they are ideal growing under mature, large trees or in containers on decks or small patios. A tree in fall is guaranteed to turn heads and gather admiring looks and the enormous variety of leaf forms, colors, and tree shapes means that no matter what your taste or space restrictions, there will be a tree for you. The Lake Wilderness Arboretum nursery often has a variety of Japanese maples available for sale, so come check them out during one of the Arboretum’s plant sales.



Vine Maples: Acer circinatum

Many people are familiar with Washington’s versatile native vine maple, Acer circinatum, which is popular in both cultivated and natural environments. This handsome species is desired for its dramatic colors and tolerance of sun and shade making an excellent ornamental, especially prized for outstanding fall color. Interesting enough to make a good specimen tree, they also do well as the understory to conifers much as they do in nature.

Given the wide variety of shapes, sizes, and colors observed in the wild, and the popularity of the tree in landscaping, it is not surprising that several cultivars of Acer circinatum are now available in nurseries. These cultivars have been propagated vegetatively from naturally occurring variations found in the wild. The beauty of a cultivar is that you always know what you are going to get (they are all identical to the original plant). Accordingly, while you still enjoy the benefits of a native plant, you can now buy a vine maple that will have the specific shape, size, and color that you want. The Smith Mossman garden features a native vine maple right next to the water feature and 15 different cultivars throughout the garden.  The cultivars vary in foliage color (yellow, burgundy, green), colored bark (red, green, yellow) and size (2 feet tall up to 18 feet tall).

Maple Valley has close ties to the vine maple as the city was once known as Vine Maple Valley. The area was settled in 1879 by three men who were improving a trail and brought their families in. When a name for a future community was proposed, the names Vine Maple Valley and Maple Ridge were suggested. A vote was taken by writing the names on slips of paper and placing them in a hat. Vine Maple Valley won by 2/3, but the word “vine” was later cut by the post office because it made the name too long.


Paperbark Maple:  Acer griseum  (in meadow by gazebo & in W02 near gazebo)

The paperbark maple (Acer griseum) stands out for its exfoliating copper orange to cinnamon reddish/brown bark which peels into large curls which remain on the tree rather than falling to the ground. But this tree also stands out in the fall because of its showy orange to red fall color. This handsome Chinese native with an oval to rounded crown and open habit and upright branching typically matures to 40’ tall. It becomes distinctive and elegant with age and makes an excellent tree for small properties, deserving a location where its ornamental features can be appreciated.


Sourwood: Oxydendron arboreum  (W03 by gazebo)

On Arbor Day 1981, an Oxydendrum arboreum, commonly called a sourwood tree, was planted near the gazebo. This deciduous tree is native to the eastern United States and is most commonly found on rocky wooded slopes in the Appalachian Mountains, often growing in combination with other heath family members (e.g. azaleas and rhododendrons) that share the same acidic soil preferences. In the wild, it may grow to 50-60’ tall but in cultivation, it typically reaches 20-25’ tall. The Arboretum’s tree has suffered some damage to the top from winter storms and has marred its straight, slender trunk and narrow oblong crown. But keep an eye on this tree around summer when you’ll start seeing its waxy, lily-of-the-valley-like, white flowers. The flowers are quite attractive to bees. And then in the fall the leaves, which have a sour taste and thus its common name, will turn crimson red. The spent flowers contrast well with the red fall color and provide continuing ornamental interest after leaf drop into winter. The multi-season interest of this beautiful flowering tree makes it a great specimen for lawns, patios, shade gardens or open woodland areas.


Sweetgum: Liquidamber styraciflua  (planted for Arbor Day 1984 along NW edge of meadow)

Fall is the best time to appreciate the sweetgum tree (Liquidamber styraciflua), a medium-sized to large tree native to warm temperate areas of eastern North America and tropical montane regions of Mexico and Central America. It is recognizable by the combination of its five-pointed star-shaped leaves and its hard, spiked fruits. The rich dark green, shiny leaves generally turn brilliant orange, red, and purple colors in the fall. The reds and yellows compare to that of the maples (Acer), and in addition it has the dark purples and smoky browns of the ash (Fraxinus). Sometimes people confuse the sweetgum with a maple because of the five-pointed leaves but they are easily distinguished from Acer by its glossy, leathery leaves that are positioned singly (alternate), not in pairs (opposite) on the stems.

Another way to distinguish Liquidamber from Acer is the hard, spiked fruits which started as non-showy flowers in April-May. The flowers then give way to the infamous gum balls which are hard, spherical, bristly fruiting clusters to 1.5” in diameter. The gum balls mature to dark brown and usually remain on the tree through the winter. They can create clean-up problems during the winter and spring as the clusters fall to the ground which cause unsightly litter but can also cause human safety problems (e.g., turning an ankle by accidentally stepping on a cluster).

But the question everyone wants to ask about the sweetgum tree is “why is it called sweetgum?” Well, in the earliest known published record of the tree, it is described as a large tree producing a fragrant gum resembling liquid amber, and so the genus name Liquidamber. Today, the gum obtained from genus plants has been used for a variety of purposes, including chewing gum, incense, perfumes, folk medicines and flavorings.


Katsura: Cercidiphyllum japonicum (NW edge of meadow)

The katsura tree, native to Japan, stands out for its delicate heart-shaped leaves that offer an array of color throughout the year. In spring, the leaves emerge reddish purple, changing to a subtle blue-green as they mature. In the fall, they change again to glowing shades of yellow and apricot. As if this was not enough, the leaves also produce a scent in the fall that resembles burnt brown sugar or cotton candy.

Katsura trees are often multi-trunked with a dense, rounded habit that typically matures to 40-60’ tall in cultivation. It is grown for its beautiful shape and attractive foliage. There are two cultivated varieties that are worth noting: the weeping katsura (Cercidiphyllum japonicum ‘Pendulum’) which grows 15 to 25 tall and wide and the Red Fox Katsura (Cercidiphyllum japonicum ‘Rot Fuchs’) which grows as an upright oval about 30 feet high and 16 feet wide with bronze purple spring foliage that turns a bronze-green in summer. The fall color is orange-bronze.


Persian Ironwood: Parrotia persica (W20, W25)

The Persian ironwood, native to northern Iran and southern Azerbaijan, is an uncommon, drought-tolerant garden tree prized for its striking autumn color and the exfoliating bark that develops on mature specimens. It is a small tree, growing 20-40’ tall, with leaves that emerge reddish-purple in spring, mature to a lustrous, medium to dark green in summer and change to variable shades of yellow, orange and red in fall. Bark of mature trees exfoliates to show green, white or tan patches beneath and provides good winter interest.


Maidenhair Tree: Gingko biloba (in the meadow)

Gingkos put on a spectacular yellow show in fall. Considered living fossils because they are the last survivors of tree varieties that grew worldwide 200 million years ago, gingkos are related to conifers but have fan-shaped leaves rather than needles. The leaves resemble those of the maidenhair fern, thus the common name: maidenhair tree. Trees often have an umbrella shape and can grow 80 feet tall, though many stay only half that height.

Shrubs to take note of in the fall:

Witch hazels: Hamamelis

What distinguishes witch hazels (Hamamelis) in the plant world is that flowers, fruits, and next year’s leaf buds can manifest simultaneously on the plant, in fact, the name Hamamelis means “together with fruit.” But around the Pacific Northwest, this genus of flowering shrubs may stand out for other reasons.

Around here, winter sometimes comes in February. Some years this might mean snow, others it could be cold and sunny, and others dark and dreary. But February also means the arrival of the witch-hazel flowers. The spider-like flowers with strappy petals come in an assortment of cheerful yellows, from pale yellow, bright lemon yellow, golden yellow to orange or copper tones. These bright, cheerful colors are just what we need in the wintery days of February.

Then, in the fall, witch hazels can put on a show when their handsome oval green leaves, sometimes downy on the underside, take on golden-yellow shades before shedding to the ground.

The genus Hamamelis is made up of four species, two native to the United States (H. virginiana, H. vernalis) and one each from China (H. mollis) and Japan (H. japonica). The most popular American species (H. virginiana) is found over a wide area of the Eastern states, reaching as far west as Texas, and in Canada, from Ontario to Nova Scotia. Hamamelis vernalis, commonly known as the Ozark witch hazel, is limited in its distribution to the Ozark Plateau of Missouri, Oklahoma, Arkansas, and Louisiana.

The popularity of witch hazels jumped once the two Asian species were crossed to produce the sturdier Hamamelis x intermedia hybrids. Hybridization of these species has been going on since the 1930s at places like the Arnold Arboretum at Harvard University. The first cultivar to be named was ‘Arnold Promise’ in 1963, followed by ‘Diane’ in 1969, both of which can be found in the Woodland Garden.

Some of the more popular and commercially available witch hazel cultivars that can be found in the Woodland Garden are:

  • ‘Arnold Promise’. Lemon yellow, sweetly fragrant flowers that appear in late winter to early spring. Its fall color, in shades of yellow, orange, and red, is unusual among yellow-flowered cultivars. (W27, W29, W30)
  • ‘Diane’. The deepest red flowers of any cultivar, appearing in midwinter. Named after the daughter of famed Belgian growers Robert and Jelena de Belder. (W32)
  • ‘Jelena’. Features luxurious copper flower colors, blooming in early to midwinter. (W29)
  • x intermedia ‘Pallida’. This highly floriferous, citrus-scented yellow-flowered beauty is actually found in the Arboretum’s Perennial Garden instead of in the Woodland. Look for it in the center of the garden, the bright yellow flowers or buttery fall foliage help make it a standout. (P08)
  • ‘Westerstede’. Lovely primrose yellow flowers that are elaborately curled and crimped. Blooms in later winter. Golden yellow fall foliage. (W30)

Other cultivars that can be found throughout the Woodland Garden are:

  • ‘Orange Beauty’. Orange-flowered form that blooms in late January through March. Yellow, orange and red fall foliage. (W32)
  • ‘Ruby Glow’. Dull red to pale coral-violet flowers with yellow to orange-red fall foliage. (W32)
  • ‘Sunburst’. Bright lemon-yellow flowers. (W02, W04)
  • mollis ‘Goldcrest’. Sweetly-scented golden yellow flowers tinged with maroon at the bases of the petals. (W27, W30)
  • vernalis ‘Amethyst’. Lavender-purple flowers with grey-green foliage that turns brilliant scarlet in fall. (W34)

Given the winter appeal of witch hazels, finding a good site in the garden is worth some time and thought. Flower color and scent will be a factor in your decision but the shrub’s mature shape and winter silhouette should also be considered. In a home garden, you might want to plant one where it can be viewed from indoors. A background of evergreen shrubs will help show off the plant’s delicate and colorful blooms, especially the yellows. In a woodland garden, consider the amount of sunlight that will reach the plants. Witch hazels do best under deciduous trees, which allow winter sunlight through their bare branches. If the witch hazels are too shaded by evergreens that can become straggly and have fewer flowers.


Smoke Tree/Bush: Cotinus coggygria (W21)

Starting in May, the smoketree’s (Cotinus coggygria) purple foliage branches are tipped with large, smoke-like plumes of flowers. The actual flowers are very ineffective since they are extremely small and yellowish in color. What we actually enjoy as “flowers” are minute hairs along the structure of the panicle inflorescence. These small, fibrous hairs vary in color from a cream, to pale green, to pink or vivid red—depending on the cultivar. This plume of colored hairs creates a smoky look that lasts from May until fall. The purple or blue-green, oval-shaped leaves provide great fall color, with leaves turning yellow, red and purple.


Oakleaf Hydrangea: Hydrangea quercifolia

Oakleaf hydrangeas (H. quercifolia), with their lobed, oak-like, dark green leaves are native to woodlands of the Southeastern United States. Their pyramidal panicles of white flowers, that can be up to 12” tall, age in color from creamy white to pink and by fall are a dry, papery rusty-brown. Oakleaf hydrangea leaves turn rich shades of red, bronze and purple in the fall and persist in winter accompanying the persistent dried flower-heads. Oakleaf hydrangea and Panicle hydrangeas are the only hydrangeas with cone-shaped flower clusters; all the others have their flowers in ball-shaped or flat-topped clusters. The bark on Oakleaf Hydrangeas have attractive cinnamon-tan-orange bark that shreds and peels in thin flakes. The Woodland Garden has two oakleaf hydrangea cultivars, Hydrangea quericifolia ‘Munchkin (W03), a compact grower, and Hydrangea quercifolia ‘Snowflake’ (W04), which has intricate blossoms that resemble magnified snowflakes.