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Search Results for ' Green roofs (Gardening)'

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Keywords: Native plants--Washington, Green roofs (Gardening), Sedum

PAL Question:

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?

View Answer:

I highly recommend the information booklet entitled Green Roof Manual from a local group, the Pomegranate Center. It has a list of Sedum to be used as green roof material, and a bibliography that will also be helpful.

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

Season All Season
Date 2008-02-07
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Keywords: Green roofs (Gardening), Native plants

PAL Question:

I am trying to select plants for a green roof on Lopez Island. I would like to use some native plants, and not have to do too much weeding. Can you help me?

View Answer:

The Miller Library has a booklist on green roofs which includes weblinks. With respect to weeds, as a former professional gardener I don't believe there is a "maintenance-free" garden. However you may be able to come up with a freely seeding grass (Festuca ovina var. glauca comes to mind) that would do well and look good with other plants.

Regarding Pacific Northwest native plants (i.e., grasses), I recommend using a native plant book (such as Pojar and MacKinnon's Plants of the Pacific Northwest Coast) and searching for those which suit the conditions of the site. You may also find King County's native plant guide useful, as it is searchable by site requirements. Washington Native Plant Society offers a similar plant selection guide. There are also native species of Sedum.

The book Green Roof--a Case Study by Christian Werthmann (Princeton Architectural Press, 2007) evaluates green roof plants and planting techniques, and includes observations regarding soil depth, the factors affecting desiccation (i.e., metal edging and the planting medium/size of the plants used), and density considerations. Here are some of the conclusions of the case study:

  1. p.69-insects and other invertebrates need >6" of soil to survive the cold; drought tolerance increases with soil depth; probability of seed germination also increases with soil depth
  2. p.76-erosion control (bird repellant?) made from a degradable straw mat (such a mat may be useful for preventing birds from pulling up the plugs)
  3. Plants: p.95-sweet fern Comptonia peregrine-not too vigorous, suffered from weed infestations
    p.96-prickly pear Opuntia fragilis-did well
    Phlox subulata, Silene caroliniana-did well
    Sedum telephioides, S. lanceolatum, S. stenopetalum-suffered from heat, drought, and birds-these were replaced with European sedums (S. album, S. reflexum, S. spurium, S. cauticola, S. sexangulare, S. floriferum, Sempervivum tectorum, Orostachys boehmeri) and not planted as plugs but as larger plants that started in the green roof substrate (reducing transplant shock)
    p.100-mixed prairie perennials with sedums (in 6" soil), which filled in when perennials died-the architects note that there is no record of prairie plants doing well on green roofs, therefore the backup with succulents-they also note that metal roof edges speed up desiccation
    Perennials included ice plant (Delosperma nubigenum; my note: be careful about this, as it's a noxious weed in California and if it spreads by seed, it might become a problem on Lopez); flameflower (Talinum calycinum); Eragrostis spectabilis; Allium schoenoprasum; Allium cernuum; Bouteloua gracilis; Elymus virginicus; Achillea millefolium; Tradescantia bracteata; Solidago nemoralis; Artemisia ludoviciana; Coreopsis verticillata; Asclepias tuberosa; Rudbeckia hirta
    p.105-in 3" soil with nearby metal (and thus an overheating issue), they used proven sedum species; heat from metal can be reduced by using aluminum (proved cooler than wood)
    p. 108-conclusions: use a combination of indigenous plants with "successful green roof performers"-thin soil and high light "even overtaxed the hardiest succulents"-soil depth and temperature extremes made a big difference; even a slight difference in soil depth in a harsh environment can mean the difference between success and failure-continuous care and maintenance in the beginning is important for success-plugs grown in peat moss were less successful, since completely dried-out peat moss repels water-dense plantings (and/or rapidly spreading plants) important because bare soil gets hotter than soil covered by a plant

Season All Season
Date 2008-06-28
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June 24 2013 12:55:25