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Elisabeth C. Miller Library

Keyword: Native plants--Washington

Native plant resources

I’m looking for a good publication on plant communities for my
area, Whatcom County in northwest Washington. We want to encourage plant communities that will do well here, and have about 5 acres to work with. Can you make a suggestion, please?

 

If you are interested in
plants native to Washington, I recommend these two books:

Kruckeberg, Arthur R., Gardening with Native Plants of the Pacific
Northwest, University of Washington Press, Seattle, 2nd edition, 1996.

Pettinger, April, and Brenda Costano, Native Plants in the Coastal Garden – A
Guide for Gardeners in the Pacific Northwest , Timber Press, Portland, OR,
revised edition, 2002.

The Washington Native Plant Society is also a good resource.

If you are interested in plants that will grow well in your area, but are
not necessarily native to Washington State, please check out the Miller Library’s
booklist about gardening in the Pacific Northwest.

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Native groundcovers

I am looking for a native groundcover to grow as a walkway along side my house. It is a shady spot and it would need to be a hardy plant that could be walked on.

Regrettably, there are not any native, shade-loving, walkable ground covers available unless you are interested in mosses. If that is appealing, you can check in the book Plants of the Pacific Northwest Coast by J. Pojar. The following websites may help you find native plants:
King Conservation District

King County Native Plant Guide

Washington Native Plant Society

For information on growing mosses, see the now archived page of “Encouraging Mosses” from Oregon State University, based on the writing of George Schenk.

If your heart isn’t definitely set on natives, there are some good alternatives:

  1. In her book Big Ideas for Northwest Small Gardens, Marty Wingate recommends Mazus reptans. It is semi-evergreen to evergreen with tiny blue flowers from late spring through summer. It takes full sun to part shade and is delicate looking, but takes foot traffic. It requires some fertilizer to stay perky. (Note: I use it in my garden–it is versatile and pretty)
  2. Another source of ideas is the website http://stepables.com/
    Click on plant info, then plant search.
  3. A ground cover that I have found useful (it can take car traffic a couple times a day) is Leptinella gruveri ‘Miniature.’ You’re almost certain to find it at the website above.
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cause of red leaves in rhododendrons

I have some native rhododendrons that have tan or reddish leaves every spring. The red leaves are new leaves, and they are red for about two weeks. They are under some 100 year old Douglas fir trees, and get some shade and some southern light. They were moved to my garden from and altitude of 4000 feet to my altitude of about 1850 feet. What causes the red leaves?

 

New red shoots and bronze leaves are not uncommon in Rhododendrons. In fact, some are grown purposely for their colorful new growth. The creator of Paghat’s Garden, a local website writes enthusiastically of a Rhododendron ‘Hill’s Bright Red’:

“When it is first finishing with its bright red blossoms, it begins producing new leaves, that are at first bright red themselves! …The new red leaves mature to green..”

She also has written specifically about the Pacific rhododendron, Rhododendron macrophyllum.

As to why this coloration sometimes happens, it is possible that the reddish-brown pigment seen in young [Rhododendron] leaves
affords tender foliage some protection from sunburn. This is important because too much ultraviolet radiation can destroy chlorophyll in plant
leaves. Plants avoid getting too much UV radiation by producing red pigments called anthocyanins, which can absorb UV radiation and thus prevent it from damaging other parts of the leaf. Because
the pigment “accumulates in the cell sap, and is usually located in the
epidermal and subepiderma cells,” its presence vividly changes the color of the
leaves (Levitt, p. 294). This, and more information about anthocyanins is available in a book available at the Miller Library called Responses of Plants to Environmental Stresses, volume 2, by J. Levitt (New York:
Academic Press, 1980). In effect, your plants are producing their own sunscreen for the tender new
growth!

You can also find more information about anthocyanin in the article “Nature’s Swiss Army Knife: The diverse protective roles of anthocyanins in leaves,” by Kevin S.
Gould, hosted by PubMed Central.

pruning native roses

What do the experts recommend regarding time(s) to prune the native roses, Rosa nutkana and Rosa gymnocarpa? I am interested in controlling their growth without losing bloom and/or rose hips. Do either or both of them bloom on second year wood?

 

Peter McHoy’s A Practical Guide to Pruning says that the pruning method would follow that of vigorous species roses, which produce flowers on old wood. He says to remove any dead wood in early spring (similar to ‘late winter’).

The Royal Horticultural Society A to Z Encyclopedia of Garden Plants (edited by Christopher Brickell, Dorling Kindersley, 1996) says to prune species roses as needed only, cutting out one fifth to one fourth of the oldest stems. A Pacific Northwest native wildlife gardening source on the web recommends only pruning out dead wood, and otherwise leaving it be.

Since Rosa gymnocarpa is also once-flowering, it should be pruned–if you need to prune it at all–just after flowering.
The following are general guides on rose pruning in the Northwest, from the Seattle Rose Society and Roses for the Pacific Northwest.

lifespan of sword ferns

What is the lifespan of our native sword fern?

The native sword fern, Polystichum munitum, is discussed in local author Sue Olsen’s Encyclopedia of Garden Ferns (Timber Press, 2007). She does not mention the plant’s lifespan except to say that it will suffer and decline with excessive summer heat and humidity (more common in eastern and southern U.S.), and sometimes with long periods of freezing temperatures as well.

Sword fern has a reputation as a tough, long-lived perennial (i.e., returning year after year), and it readily self-propagates from spores, but I have not found any resources which mention the average duration of an individual plant. Most will survive in the Pacific Northwest for many years.

Washington native plants

Is incense cedar native to Washington state? And is the Garry oak native to Kitsap County, Washington?

Although incense cedar, Calocedrus decurrens, grows in Washington State, it is not native. According to the Sunset Western Garden Book (2001), incense cedar is native to south and central Oregon, California, western Nevada, and northern Baja California.

The Washington Native Plant Society does not include Garry oak, Quercus garryana, on their list of plants native to Kitsap County, but this tree will grow there.

A list of plants native to Kitsap County

More information on Garry oak at this link

Both of these links are part of the Washington Native Plant Society website.

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.

Sedum as a green roof material

I am trying to find a Sedum expert to help figure out better uses for this plant as a green roof material. Can you help point me in the right direction? Also, are there native Sedums?

Here is a list of the books the Miller Library has on this subject, including the following titles:

  1. Planting green roofs and living walls by Nigel Dunnett and Noel Kingsbury (Timber Press, 2004)
  2. Ecoroof: questions & answers by Portland Environmental Services (Portland, Or. : Environmental Services, 2004)Note: Portland’s Ecoroof Program is a cooperative effort of the Bureau of Environmental Services and the Office of Sustainable Development. The program promotes ecoroofs by researching ecoroof technologies an providing information and technical assistance to community members.
  3. Green roofs: their existing status and potential for conserving biodiversity in urban areas by Ecoschemes Ltd (Peterborough: English Nature, 2003)

An article by Jessie Keith from The American Gardener (March/April 2005, pp. 38-41) mentions different types of Sedum appropriate for a green roof, which I will list here:

  • Sedum album ‘Coral Carpet’
  • Sedum ‘Green Spruce’
  • Sedum lydium
  • Sedum rupestre (syn. S. reflexum)
  • Sedum sexangulare
  • Sedum spurium ‘John Creech’
  • Sedum telephium ‘Matrona’

You might also want to speak with someone at the Cascade Cactus and Succulent Society of Washington State.

There are some Sedum species native to the Northwest.The Sedums that are native to the Pacific Northwest, according to
The Encyclopedia of Northwest Native Plants for Gardens and Landscapes by Kathleen Robson, (Portland, OR: Timber Press, 2008) include:

  • Sedum divergens Cascade stonecrop
  • Sedum laxum Roseflower stonecrop
  • Sedum oreganum Oregon stonecrop
  • Sedum oregonense Creamy stonecrop
  • Sedum spathulifolium Broad-leaved stonecrop
  • Sedum stenopetalum Wormleaf or narrow-petaled stonecrop

Two additional species are listed in Plants of the Pacific Northwest
Coast, edited by Jim Pojar and Andy MacKinnon (Richmond, WA: Lone Pine Publishing, 1994):

  • Sedum integrifolium Roseroot
  • Sedum lanceolatum Lance-leaved stonecrop

Philadelphus lewisii habitat and care

What is the specific habitat of the Philadelphus lewisii (wild mock orange)?

What does this plant need from the habitat in order to survive?

What range does the Philadelphus lewisii grow in?

What family is it in?

What other plants does it often grow around?

What specific habitat does it need?

Where does it grow?

Is it an annual or a perennial plant?

Philadelphus lewisii is a Northwest native, a common shrub east and west of the Cascades. According to Trees and Shrubs for Pacific Northwest Gardens, 2nd edition by John A. Grant and Carol L. Grant, it will “thrive in almost any garden soil in either full sun or partial shade, and are of the easiest possible culture. The hybrids respond noticeably to generous cultivation , fertilizer, and water. (It belongs to) the group of summer-flowering shrubs that are best pruned immediately after flowering.\”

Philadelphus lewisii is a deciduous shrub (in other words, it is not an annual and, although it has a long life span, it is not like an herbaceous perennial that completes its life cycle and starts over the next spring–it is a woody deciduous plant which loses its leaves in winter). (Source: The Royal Horticultural Society A-Z Encyclopedia of Garden Plants, edited by Christopher Brickell; Dorling Kindersley, 1996).

Here is a link to a page from the Washington Native Plant Society about Philadelphus lewisii and its habitat.

It is a Northwest native (state flower of Idaho), and grows throughout Western North America (from British Columbia south to Oregon), southern Europe, and eastern Asia.

The genus Philadelphus grows in rocky woods, semi-desert, and open areas in wet forest. In gardens, it prefers loamy soil and moderate sun.

The genus Philadelphus belongs to the Hydrangeaceae family.

plants for restoring wetlands

I am an Ecologist with Adopt-A-Stream Foundation, a non-profit stream restoration organization. I am creating a planting plan for a golf course in Snohomish County. My constraints: Low-growing native shrubs with extensive root systems to help filter out the golf course irrigation water before it enters the stream. Willow would be an obvious choice, but it would grow too tall and out of control. I was looking at such species as Snowberry (Symphoricarpos), Nootka Rose (Rosa nutkana), Salmonberry (Rubus spectabilis), etc. It would have to be a FAC+ (streams and wetlands). Any thoughts?

FAC+ is a wetland indicator status term meaning “Facultative,” i.e., more likely to occur in wetlands but also found in non-wetlands.

I found a list in Restoring Wetlands in Washington Publ#93-17 and picked out the FAC-identified ones, eliminating all the tall trees and shrubs. Symphoricarpos (Snowberry) would be a good option, but Rosa nutkana (Nootka Rose) and Rubus spectabilis (Salmonberry) get too big for your purposes. A different rose I could recommend is Rosa gymnocarpa (Baldhip Rose). Many of the following recommendations are grasses of one sort or another. (See the USDA Wetland Indicator status definitions.)

Allium geyeri (non-native) FACU

Athyrium filix femina FAC

Carex aperta (non-native) FACW

Carex stipata FACW

Deschampsia caespitosa FACW

Juncus effusus and ensifolius FACW

Ledum glandulosum FACW

Sambucus racemosa var. melanocarpa FACU

Spirea douglasii FACW

You might also try the Snohomish County Conservation District website.