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Elisabeth C. Miller Library

Keyword: Xeriscaping

Drip irrigation

We are putting in a new garden, and want to install a drip irrigation system to conserve water. The area is full sun. Can you direct us to some information on systems, and offer suggestions on plants?

 

Here is some information from a colleague who has
experience installing and maintaining watering systems on a large
scale (at Seattle Public Library’s sites).

Drip irrigation

  • a sprinkler system using broadcasting spray heads is difficult to
    install and wastes water; they also contribute to fungal diseases
  • these systems also have to be blown out in the fall (winterized)
  • drip irrigation is easy to install

Hints:

  • install after the plants are in, or place parallel lines
    appropriately spaced to provide enough water while allowing for
    plant root zone increase
  • if installed after plants are in, try to encircle the root zones
    of trees and shrubs, allowing for increase in size
  • no need to encircle perennials; they are fine with a line on one
    or both side
  • for such a large area, use more than one zone or there will be no
    pressure (and no drip) at the end of the line
  • use a pressure reducer at the water source or the lines may come
    apart at junctions
  • if on a slope, follow the contours of the slope
  • bury at least 6 inches so settling and soil loss do not expose
    lines–and so lines don’t freeze (no winterizing)–but too deep and
    you can’t tell if it’s working or not
  • draw a picture of the system
  • anchor the line with stakes (they are the shape of croquet
    wickets, but ~ 4″ x 2″) and can usually be purchased with the drip
    line
  • buy “splicing” supplies for breaks: female connectors are easier
    to install and I think Netafim is the most versatile line
  • scheduling: staggering helps (a short watering period followed
    by a long one) and remember that it has to be left on for a long
    time (i.e., 1-2 hours for the long session but not every day)

Seattle Public Utilities offers the plant list and watering
guides linked here:

The Plant List

Smart Watering Guide

Soaker Hoses

Here is a guide to drip irrigation from Washington State University Extension.

I think that the best plant choices for your site in full sun will
be drought-tolerant perennials, shrubs, and trees. Here are links
to resources on selecting plants and maintaining a low-water-use
garden.

Colorado State University Extension features several links on Xeriscaping.

An article on drought-tolerant gardening by Ann Lovejoy.

Here are links to a booklist and a page of resources from the Miller Library.

You may also want to make a practice of mulching the garden to
conserve water. Excerpt from www.greenbuilder.com:

Use a deep layer of mulch in planting beds to help retain
moisture, slow weed growth, and prevent erosion.

The use of mulches on sloped areas along with terracing and
plantings can help prevent runoff and erosion problems.

Examples of organic mulch material include:

shredded bark
wood chips
pine needles
straw
pecan hulls
cotton seed hull
composted leaves
shredded cedar

The depth of mulch needed will depend on the type used. As a
general rule, the coarser the material, the deeper it should be
applied. A 3 to 4 inch layer of bark mulch should be sufficient.
Mulch needs to be reapplied as it decomposes.

The book, Water-Wise Gardening by Thomas Christopher (Simon &
Schuster, 1994), recommends matching the mulch to the planting. For
example, using pine needles around a clump of evergreens enhances
the woodland appearance of the landscape. Using organic materials
(such as compost, bark, pine needles, leaves) as mulch moderates
the access of air to the topsoil, and conserves humus. Mulch
suppresses weeds and keeps the surface of the soil from crusting
over. Ann Lovejoy’s book, Organic Design School (Rodale Press,
2001), recommends compost as the ideal mulch. Finished compost can
be pressed through a fine mesh screen to topdress ornamental
plants, while coarser compost can be used around shrubs and trees.
Compost is a feeding mulch, improving soil texture as well as
nutritional value. Here is what Lovejoy has to say about wood
by-products as mulch: “To a greater or lesser degree, most tie up
soil nitrogen temporarily as they decompose (fresh sawdust uses the
most nitrogen, while coarsely ground wood chips use the least.
Although I never use shredded bark as mulch on planting beds,
many gardeners do. It makes an attractive, deep brown mulch (that)
does not tend to rob nitrogen from the soil.” She cautions against
using thick layers of pine needles (over 2 to 3 inches) which can
get matted down and shed water instead of letting it reach plants’
roots.

Here is information from the University of Georgia Cooperative
Extension, describing the best choice of mulch for a
drought-tolerant garden:

Generally, the best mulch for the landscape is one that is
organic, fine-textured and non-matting. Examples include pine
straw, pine bark mini-nuggets, shredded hardwood mulch or cypress
mulch. Inorganic mulches, such as rock or gravel, are not good
mulches because they absorb and re-radiate heat around the plant
canopy and increase evaporative loss of water from the plant.
Fine-textured mulches, such as mini-nuggets or shredded hardwood,
do a better job of holding moisture in the soil than more porous
coarse-textured mulches.

, ,

water-wise gardens in Washington state

Where in Washington State can I find examples of public gardens designed to be drought-tolerant xeriscapes?

There are Master Gardener Demonstration Gardens around the state, such as Riverfront Park Demonstration Garden and others in Wenatchee. There is also a WaterWise demonstration garden in Woodinville.

There is a water-wise garden in the Bellevue Botanic Garden.

There is a native plant garden maintained by the Tacoma Garden Club at Point Defiance Park.

Seattle Tilth maintains several demonstration gardens, including the Good Shepherd Center in the Wallingford neighborhood in Seattle and Bradner Gardens Park at 29th Ave. S. and S. Grand Street, in south Seattle. While not exclusively xeriscapes, their gardens employ water-saving techniques.

drought-tolerant container planting

Our neighborhood has a small planter area at its entrance. There is no water supply to this area, but a nearby resident is willing to water occasionally. The soil contains much clay. We would like to plant a few drought-tolerant annuals to add color and supplement the more permanent shrubs–such as boxwood–planted in the area. Can you recommend some plant choices? How could we amend the soil to best hold water during the upcoming dry months? Would a commercial product such as “Quench” be of any value, in addition to organic mulches?

I found the following article by Nikki Phipps on GardeningKnowHow.com about drought-tolerant container planting. Here is an excerpt:

“…many plants not only thrive in containers but will tolerate hot, dry conditions as well. Some of these include annuals like marigolds, zinnias, salvia, verbenas, and a variety of daisies. Numerous perennials can be used in a xeriscape container garden such as Artemisia, sedum, lavender, coreopsis, Shasta daisy, liatris, yarrow, coneflower and more. There is even room for herbs and vegetables in the xeriscape container garden. Try growing oregano, sage, rosemary, and thyme. Vegetables actually do quite well in containers, especially the dwarf or bush varieties. There are also numerous ornamental grasses and succulents that perform nicely in containers as well.”

This Brooklyn Botanic Garden’s 2001 article provides a list of drought-tolerant plants for containers.

I had not heard of Quench, but since it is cornstarch-based, it is certainly preferable to the hydrogel and polymer products which are more widely available. I found an article by garden writer Ann Lovejoy in the Seattle P-I (June 3, 2006) about Quench. Here is an excerpt:

With pots and containers, mix dry Quench into the top 12 inches of potting soil in each pot and top off with plain compost. Few roots will penetrate deeper than a foot, so it isn’t very useful down in the depths of really big pots unless you are combining shrubs and perennials.

I would not recommend hydrogels or polymers as a soil amendment. Professor Linda Chalker-Scott of Washington State University has written about these products and their potential hazards. Here is a link to a PDF.

You could consider applying a liquid fertilizer (diluted seaweed-fish emulsion would work) to your containers once every week or two during summer. Here is an excerpt on some general information on container maintenance, from a no longer available Ohio State University Extension article. Excerpt:

“Once planted, watering will be your most frequent maintenance chore, especially if you are growing plants in clay containers. On hot, sunny days small containers may need watering twice. Water completely so that water drains through the drainage hole and runs off. Water early in the day.

“If you incorporated a slow release fertilizer into the potting mix, you may not need to fertilize the rest of the season; some of these fertilizers last up to nine months. You can also use a water-soluble fertilizer and apply it according to the label directions during the season.

“Mulch can be applied over the container mix to conserve moisture and moderate summer temperatures. Apply about one inch deep.

“Depending on the plants you are growing, you will need to deadhead and prune as needed through the season. Monitor frequently for pests such as spider mites. Pests usually build up rapidly in containers.”

Garden Tip #96

Ready for a truly drought tolerant garden? Plant hardy cactus and succulents. The only requirement for these plants is perfect drainage. Hardy succulents can die of rot in our winter wet. Overcome that challenge by building raised beds and mixing plenty of gravel and sand into the planting hole. The book Cacti and Other Succulents by Keith Grantham and Paul Klaassen (Timber press, $34.95) reports the following plants are good candidates for growing outside in the Pacific Northwest:

  • Cacti
    • Echinocereus triglochidiatus (hedgehog cactus)
    • Opuntia humifusa (prickly pear cactus)
    • Coryphantha vivipara (pincushion cactus)
  • Succulents
    • Delosperma cooperi (ice plant)
    • Calyptridium umbellatum (pussypaws)
    • Yucca
    • Agave paryi
    • Lewisia cotyledon
    • Sedum
    • Sempervivum.

Garden Tip #17

Ready to trade in that thirsty boring lawn for a wildflower meadow? Do a bit of research first with British gardener Christopher Lloyd’s book called Meadows (Timber Press, $29.95). Lloyd dispels the myth of a maintenance-free meadow without dampening the reader’s enthusiasm for creating a flowery, drought-tolerant lawn alternative.
Additional wildflower information is available online: