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Elisabeth C. Miller Library

Keyword: Euonymus

Wings or ridges on tree branches

There are a number of trees in my neighborhood which seem to be abnormal. The branches are changing shape, and instead of being round, they have ridges growing lengthwise along them. It makes the branches look misshapen, almost like elongated stars. It looks unnatural, maybe like a disease. I think the trees are maples. Do you know what could be causing this?

 

There are some trees and shrubs whose branches normally take the form I think you are describing, which is sometimes referred to as winged or alate. I am not aware of maples which do this, so I wonder if perhaps you were seeing sweet gum trees, or Liquidambar styraciflua. According to information from the Mathilda Mathias Botanical Garden in Los Angeles,
“One diagnostic character is the presence of corky wings on young stems. In some cases, wings are due to stimulation of localized phellogens along a stem angle, as in winged euonymus (Euonymus alatus). Wings also occur on young stems of sweet gum (Liquidambar). Longitudinal splitting is the cause of stem wings in certain species of elm (Ulmus.)

Here are more images:
Euonymus alatus
Ulmus alata
Liquidambar styraciflua

According to the book Plant Form: an Illustrated Guide to Flowering Plant Morphology by Adrian Bell (Oxford University Press, 1990), these wings can be part of the way a particular plant grows. The book shows an illustration of metamers (also called phytomers), which are repeated constructional units
(like building blocks) in the plant’s development. From my unscientific perspective, I wondered if the wings might have a leaflike photosynthetic function. I did find an article from the Botanical Gazette from February 1889 (yes, 19th century!) by Emily Gregory which examines this issue. It seems to suggest that the corky wings on the branches may have the function of increasing branch circumference and this may provide the tree with extra protection.

A version of this question and answer appeared in the Spring 2014 issue of the Washington Park Arboretum Bulletin.

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Plants for privacy screens

Could you recommend some plants for a privacy screen that are also narrow? These would be planted in front of a fence in our backyard.

 

Here is some general information on plants for creating a screen.

Trees for Problem Landscape Sites — Screening from Virginia Cooperative Extension

Bet on Hedges by local garden writer Valerie Easton.

Landscaping for Privacy: Innovative Ways to Turn Your Outdoor Space into a Peaceful Retreat by PNW author Marty Wingate.

Here is a list of narrow plants for a screen from local garden designer Chris
Pfeiffer: “Fastigiate shrubs for naturally narrow hedges.” Compiled by Chris
Pfeiffer. 2005.

Zones 5-6:

American arborvitae ‘Rheingold’ (Thuja occidentalis ‘Rheingold’) 5’h x
3’w

Barberry ‘Helmond Pillar’ (Berberis thunbergii f. atropurpurea
‘Helmond Pillar’) 6’h x 2’w

Boxwood ‘Graham Blandy’ (Buxus sempervirens ‘Graham Blandy’) 8’h x 1-1/2′
w

English yew ‘Standishii’ (Taxus baccata ‘Standishii’) 4’h x 1-1/2′ w

Irish yew (Taxus baccata ‘Fastigiata’) 20′ h x 4′ w

Japanese holly Jersey pinnacle (Ilex crenata ‘Jersey Pinnacle’) 6′ h x
4′ w

Japanese holly Mariesii (Ilex crenata ‘Mariesii’) 3′ h x 1-1/2′ w

Zones 7-9, in addition to the above:

Dwarf yeddo rhaphiolepis (Rhaphiolepis umbellata Gulf GreenTM) 3-4′ h x
2′ w

Heavenly bamboo ‘Gulf Stream’ (Nandina domestica ‘Gulf Stream’) 4′ h x 2′ w

Japanese euonymus ‘Green Spire’ (Euonymus japonicus ‘Green Spire’) 15′ h x
6′ w

 

You might also consider installing a trellis to increase the height of
the fence, and then growing an evergreen vine such as Clematis armandii,
evergreen hydrangea (Hydrangea seemanii), or star jasmine
(Trachelospermum jasminoides).

This link is also helpful (scroll down to
“Evergreen Vines” and look for appropriate height and light requirements).

You could grow bamboo, but I would recommend growing it in a container,
or a series of containers, as you do not want the roots to spread. I have
seen an effective bamboo screen between two houses growing in a long
rectangular lined wooden trough (lined with bamboo barrier). Some species
of bamboo are more tolerant of partial shade than others. Look for a
clumping, rather than a running, bamboo (like Fargesia) to be on the safe
side.

Growing Bamboo
in Georgia

Running and Clumping Bamboos

Bamboos for hedges or
tall privacy screens

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plants for narrow planting areas

I am redoing the narrow planting areas (2-3′ wide) on either
side of our 20′ long entry. Garages from next door townhouses butt up
against the outer edge on each side, causing morning sun and afternoon shade on one
side, and vice versa on the other side. I have picked out some
euphorbias, heucheras, and carexes which should do well. I’m wondering
if I should have some taller, more dramatic plants to offset these and if
you have any suggestions of ones which might work. Also, any bulb ideas
would be appreciated.

 

Have you considered putting up trellises on one or both sides? Then you
could grow vines which require little width, but still have the
advantage of height. You could also grow taller plants (maybe some
grasses like Miscanthus or even a well-restricted–using root
barrier–Bamboo) in containers, and keep them shaped to suit the narrow
space. Some shrubs and trees are naturally narrow or fastigiate in growth
habit.

Here is a list of narrow plants compiled by local garden designer Chris
Pfeiffer, c2005. Some will be too wide for your planting area, but you
might want to research those that fit the site.

American arborvitae ‘Rheingold’ (Thuja occidentalis ‘Rheingold’) 5’h x
3′ w

Barberry ‘Helmond Pillar’ (Berberis thunbergii f. atropurpurea ‘Helmond
Pillar’) 6’h x 2’w

Boxwood ‘Graham Blandy’ (Buxus sempervirens ‘Graham Blandy’) 8’h x 1-1/2’w

English yew ‘Standishii’ (Taxus baccata ‘Standishii’) 4’h x 1-1/2’w

Irish yew (Taxus baccata ‘Fastigiata’) 20’h x 4’w

Japanese holly Jersey pinnacle (Ilex crenata ‘Jersey Pinnacle’) 6’h x
4’w

Japanese holly Mariesii (Ilex crenata ‘Mariesii) 3’h x 1-1/2’w

Dwarf yeddo rhaphiolepis (Rhaphiolepis umbellata ‘Gulf Green’) 3-4’h x
2’w

Heavenly bamboo ‘Gulf Stream’ (Nandina domestica ‘Gulf Stream’) 4’h x 2’w

Japanese euonymus ‘Green Spire’ (Euonymus japonicus ‘Green Spire’) 15’h x
6’w

There are also a good number of tall perennials you might try, such as
(for your afternoon sunny side) Helenium, Verbascum, Baptisia,
Eupatorium, and bulbous plants like Allium and Eremurus, and for your
shadier morning sun side, Macleaya, Digitalis, Filipendula ulmaria,
Anemone x hybrida, Actaea (formerly called Cimicifuga), Lilium martagon, Thalictrum, and Veronicastrum.

There are many excellent gardening books you could consult for ideas.
Since you have a small, narrow space, I highly recommend local garden
writer Marty Wingate’s book, Big Ideas for Northwest Small Gardens
(Sasquatch Books, 2003). You are welcome to visit the Miller Library,
where you can do further research and also borrow books.

plants to form a small tight hedge

Can you all give me some recommendations for plants that will form a tight hedge? I want a fast growing plant that does not get more than 2-3 feet tall and 2-3 feet wide. I do not want boxwood. Evergreen with glossy leaves is preferable; flowers do not matter to me.

 

I collected some information from websites and a couple of books for you. I am making one other plant suggestion, and it is the last item.

Euonymus japonicus ‘Microphyllus’

Text

Images

Ilex crenata ‘Northern Beauty’ is described on the website of Great Plant Picks

Ilex glabra ‘Shamrock’

See Missouri Botanical Garden for information and an image.

Osmanthus delavayi

This can be grown as a dense hedge. It can reach about 8 feet, but takes pruning well. Evergreen and attractive all year. Small, oval, tooth-edged leaves. Fragrant tiny white flowers in spring. Here in Seattle it can take the full sun but partial shade is okay too.

Great Plant Picks is a local organization with information about plants that do particularly well in the Pacific Northwest.

shade tolerant and low maintenance groundcovers

What is a good way to deal with a gravelly area with a lot of shade? Are there good groundcovers that would be low maintenance? Can the plants grow right in the gravel, or do I need to do something to the soil?

If it’s pure gravel, you can just make a border (with rocks and/or wood, preferably non-treated) and fill it with 9-12″ of soil. (No need to remove the gravel.) You buy soil by the cubic yard, so to figure out how much, multiply the length (feet) x width (feet) x depth (.75 or 1), then divide by 27 to get the number of yards. One yard of soil is 3′ x 3′ x 3′, or 27 cubic feet. My guess is that you need less than a yard, but it settles.

You can save money by buying the soil in bulk. Otherwise, you have to buy it by the bag, and they might come in cubic feet. If there is only some gravel, you may be able to get by with the soil/gravel mix that you have. See how much hardpan there is by digging around a little.

If you have lots of weeds in the gravelly area, try mulching the whole area with a thick layer of wood chips (freely available from arborists) Smothering weeds depends upon complete darkness more than anything.

Once you’ve done that, you can plant right away. Here are some plant suggestions. I’ve
included links to pictures, but you can always find more on Google images or
the Missouri Botanical Garden’s PlantFinder.

  1. Lobularia maritima, known as sweet alyssum: You can plant seeds of this and it will come up this year. It’s best to mix it with something else, since it dies down in winter (but self-seeds vigorously and will return). The white seeds the fastest (year to year), but it’s nice to mix with purple. Both varieties smell good and attract
    beneficial insects.
  2. Fragaria x ananassa ‘Pink Panda’: A strawberry-potentilla hybrid that grows fast and spreads easily, is good weed suppresser, and blooms twice a year with pink flowers. This is an excellent groundcover, will probably be evergreen.
  3. Pachysandra: This plant is evergreen, and though it is not as fast growing as some groundcovers, it does spread.
  4. Hardy Geranium spp.: Geranium x oxonianum ‘Claridge Druce’ is a variety that spreads well. Another good variety is Geranium endressii ‘Wargrave’s Pink’; in particular, it seeds itself well. Geranium macrorrhizum has many cultivars, a pleasant scent, and self-seeds readily.
  5. Galium odoratum: Also called sweet woodruff, this plant is prettily scented, probably evergreen here, and spreads fairly rapidly. It produces white flowers in early spring, and it would be particularly good to mix with something taller, like Geranium species.
  6. Oxalis oregana: This native plant looks like a shamrock, and though it is slow to establish, once it has it’s very
    tough and spreads. If you don’t get the native Oxalis oregana be careful, as the other species are very aggressive.
  7. Euonymus spp.: These woody groundcover plants are evergreen, and come in lots of varieties like
    E. fortunei ‘Emerald ‘n’Gold’ and ‘Emerald Gaiety’. Do be sure to get a groundcover and not a shrub version of the plant. ‘Emerald and Gold’ is the most robust choice.
  8. Convallaria majalis: Also known as lily of the valley, this is a vigorous (aggressive!) groundcover.
  9. Maianthemum dilatatum: Called false lily of the valley, this native plant is a good choice for shade groundcover.
  10. Polystichum munitum: The native swordfern (or another fern species) might work. P. munitum is basically evergreen, though you might need to cut out some dead fronds in late winter, and makes a good mix with something else. Other deciduous ferns are higher maintenance.

There are also a couple of plants to avoid!

  1. DON’T plant Aegopodium podagraria ‘Variegatum’: Commonly called bishop’s weed, and frequently used as a groundcover, this plant is very invasive.
  2. DON’T plant Lamium galeobdolon (formerly known as Lamiastrum), either: Yellow archangel is very invasive in Pacific Northwest forests.

shrubs and low trees that will grow in the shade

Can you suggest some shade shrubs/low trees that could be used in the bottom quarter of a huge, years-old pile of yardwaste and branches that is now a 20 foot cliff? I have started with some Vinca minor in the lower part but could use some ideas of some things to plant that might get 15 feet tall, evergreen, and grow in woods/shade or sun through trees.

The closest list I could find to meet your needs is one of evergreen shrubs that will grow in shade:

Japanese aucuba – Aucuba japonica vars.

common boxwood – Buxus sempervirens

camellia – Camellia sp.

gilt edge silverberry – Elaeagnus x ebbingei ‘Gilt Edge’

Euonymus – Euonymus fortunei radicans

Japanese aralia – Fatsia japonica

drooping Leucothoe – Leucothoe fontanesiana

Oregon grape – Mahonia aquifolium

Burmese mahonia – Mahonia lomariifolia

longleaf mahonia – Mahonia nervosa

holly leaf osmanthus – Osmanthus heterophyllus vars.

English laurel – Prunus laurocerasus ‘Mount Vernon’

Japanese skimmia – Skimmia japonica

evergreen huckleberry – Vaccinium ovatum

nannyberry – Viburnum lentago

Source: The Pacific Northwest Gardener’s Book of Lists, by R. & J. McNeilan, 1997, p. 46-47

 

managing mildew on Euonymus

I am considering using Euonymus ‘Green Spire’ for a hedge. My experience with Euonymus japonicus is that every year it seems to get mildew and drop leaves. Is this likely to happen with the ‘Green Spire’ as well? Do you have any suggestions about how to treat the mildew or avoid it?

 

‘Green Spire’ is a variety of Euonymus japonicus. This plant can suffer from a fungus, Oidium euonymus japonici, which occurs only on Euonymus japonicus, and is found wherever the host grows. Clemson University Extension says that fallen leaves and heavily affected branches should be disposed of. Plant in a sunny site which is not overcrowded, and do not water from above.

According to University of California, Davis’s Integrated Pest Management site, variegated forms of Euonymus are less susceptible to mildew. Preventive measures are the first step, but if your plants already have mildew, this resource lists less toxic fungicides, such as Neem oil, jojoba oil, baking soda spray, potassium bicarbonate, and biological fungicides: “With the exception of the oils, these materials are primarily preventive, although potassium bicarbonate has some eradicant activity. Oils work best as eradicants but also have some protectant activity.”

Powdery mildew and Euonymus

Have you heard about a problem with Burning Bush
(Euonymus alatus) getting a mildew this year? The
leaves have turned yellow green with small spots of
lighter yellow discoloration.

 

Powdery mildew is a common and usually not life-threatening
problem with Euonymus. Make sure the plant has good air
circulation, and be sure to clean up and destroy fallen
leaves which are infected. However, the symptoms of this
fungal problem would be whitish coating on the leaves, rather
than yellowed leaves. This makes me wonder if it is a
different problem such as scale (which is actually an
insect). Check and see if there are small bumps on the leaves
or stems. Scale can cause yellowed leaves. If your plant has
a small infestation, you can try scraping the scales off with
your fingernail, prune out the most infested parts of the
plant, and then apply dormant oil to the trunk and branches
before growth starts next spring, or apply superior oil
during the growing season. There are also other fungal and
bacterial problems that could be causing the spots.

See this fact sheet from Penn State for more on Euonymus scale.

Here is an archived link to additional information, which comes from
University of Illinois Extension. Excerpt:

Burning bush (also called Winged Euonymus): Euonymus alatus

Cold injury – Winter injury may be caused by very low
temperatures as well as drought stress. With excessively low
temperatures, the moisture in the cells freezes (due to
chemical compounds in plants, moisture freezes at various
degrees below freezing). Drought stress already has resulted
in limited moisture in the plant cells. Dry, freezing winds
during the winter reduces the moisture level even farther,
often resulting in dead plant tissue. Diseases can help
magnify or increase susceptibility to winter kill. Nectria
canker kills the sapwood tissue thus reducing or even cutting
off moisture to tissue further out on the plant. Winterkill
also makes plants more prone to infectious diseases and
insect problems.

Dieback/canker – See bridal wreath spirea. In addition
Botryosphaeria dothidea will infect and kill for similar
reasons.

Winged euonymus scale – Lepidosaphes yanagicola occasionally
occurs in the southern half of Illinois on burning bush. It
is an armored scale. And will attack several trees as well.
This scale can cause premature leaf drop, branch die back and
cause the plant to become more prone to winter injury. It is
found between the “wings” – the bark ridges. It does not move
to the plant’s leaves. The scale over winters as an adult and
lays its eggs in June. Eggs may be laid for up to a month.
Mating occurs before frost.

Euonymus scale – Unaspis euonymi – females are black and
males are white. The scale causes the foliage to develop
yellowish green spots. Heavy infestation results in early
foliage drop and often stems are killed. Eggs survive by over
wintering in the female body. The eggs hatch about early June
in Northern Illinois. Crawlers emerge and move onto new
growth or can be blown by wind to other plants.

Since I cannot diagnose the problem remotely, it makes sense
to take plant samples to a Master Gardener Clinic.