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Plant Answer Line Question

Keywords: Weed control, Equisetum, Lonicera, Geranium, Cistus

What does "horse grass" look like? According to Ciscoe, it can't be gotten rid of and I want to see if this is what I have.


I wonder if you are referring to horsetail, or Equisetum, which is a very persistent weed.

Wikipedia has a picture, and here is another from CalPhotos

Here is an article on Field Horsetail and Related Species from Oregon State University Extension.

Here is what Ciscoe Morris said about this plant in the Seattle P-I (April 29, 2006):

"Hands down, horsetail (Equisetum arvense) is the worst weed you can get in your garden. If you've got it, just be glad you weren't gardening in prehistoric times. Back then, horsetail grew to 90 feet tall and you were in danger of being stepped on by a brontosaurus while weeding.

The worst thing about horsetail is the speed with which it returns to make your life miserable after you weed it. No matter how great a weeding job you do, it will be back, practically to full size, within a week!

Do what we did at Seattle University. Plant a mix of shrubs, ground covers and fast-growing perennials that are thick and tall enough to hide the horsetail. Shrubs that hide horsetail include Cistus (rockrose) Lonicera pileata (privet honeysuckle) Lonicera nitida (Box honeysuckle) and rosemary. My favorite perennial to hide horsetail is the prolific hardy Geranium oxonianum 'Claridge Druce.' It will seed all over your garden, but new seedlings are easy to remove in spring. These drought-tolerant plants look great in their own right and because they are so thick and tall, no one will see the hoards of horsetail growing within."

Washington Toxics Coalition recommends controlling it by persistently hand-pulling or hoeing the above-ground growth as soon as it appears. This will weaken the plant over time. It does die back over winter, when you could cover the affected area with black plastic (for a duration of 2 years), but even this may not be entirely successful.

An article by Irene Mills in the Fall 2008 issue of the Northwest Perennial Alliance's Perennial Post says that pulling, digging, and covering with black plastic are a waste of time. The author recommends keeping an eye out in April for emerging spore-bearing stalks, and cutting these off and disposing of them in the garbage. She suggests improving the soil texture (improve drainage, add organic matter, increase soil fertility, and in some cases increase soil pH). She recommends this guide called "Controlling Horsetail" from Swanson's Nursery, originally published in Gardens West by Carol Hall.

Date 2017-12-09
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Plant Answer Line Question

Keywords: Native plant gardening, Nandina domestica, Cistus

My landscaper has planted several Cistus marked Cistus x purpurea. He said it was a solid colored [pink/lavender] flower without spots at the base of petals. I have spent hours searching for a photo, all photos that refer to purpurea are spotted. They also are referred to as orchid rock rose. Once there was a picture of a unspotted shrub, referred to as Cistus and next to it was a spotted one that had the purpurea label. Can you shed some light?

Also planted is Nandina domestica "Royal Princess." There is hardly any information available on my search for this. It appears to be pretty, but I did read that outside of Seattle, some nurseries on the west coast stopped selling it. Should I anticipate a problem with this plant ? I also read that in some eastern states Nandina domestica is invasive.


Here is what I found on the web page of the Royal Horticultural Society. The correct name is Cistus x purpureus. It has deep pink flowers with burgundy blotches at the base of the petals.

The Cistus website (a British site), in addition to its gallery of pictures of different species of Cistus, has some information about misnamed plants, which may be what you and your landscaper encountered.

Here is information from The National Gardening Association about Nandina domestica 'Royal Princess.'

Here is an excerpt from San Marcos Growers site:

Nandina domestica 'Royal Princess' (Heavenly Bamboo) - This is an upright growing shrub to 6 to 8 feet tall has very lacy foliage. Pinkish white flowers bloom in clusters at the ends of branches in the late spring and summer followed by a heavy set of red berries ( notably heavier than most Nandina cultivars). The foliage turns to burgundy in spring and later a orange-red in fall. Branching stands stiffly upright unlike typical Nandina domestica and the foliage has a much finer texture. Plant in sun or shade. Tolerates fairly dry conditions but looks better when given water occasionally. It is hardy to about 10 degrees F.

Nandina is widely grown in our area, and so far has not exhibited the invasive properties it has in the Southern U.S. Several cultivars are listed on the Great Plant Picks website, which is created by local gardening experts, so I am assuming there should not be a problem with growing it here. If you are still concerned about it, the main way it becomes invasive is from the berries setting seed and spreading. You could plant native ornamentals in its place, if you wish. Here are links to information about native plant landscaping:

Washington Native Plant Society
King County's Native Plant Guide

Date 2018-09-12
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Garden Tip

Keywords: Sarcococca, Plant cuttings, Salvia, Lavandula, Propagation, Rhododendron, Gaultheria shallon, Penstemon, Holly, Cistus, Ceanothus

Make new plants by taking softwood cuttings. Cuttings Through the Year, a booklet published by the Arboretum Foundation(available for sale at the Washington Park Arboretum gift shop) suggests which plants to propagate month by month and how to do it. A few September plants include: Rock Rose, Salal, Lavender, Holly, Penstemon, evergreen azaleas, Sweet box, Salvia, California Lilac and many others.

For a tutorial on taking softwood cuttings go online to a Fine Gardening article complete with clear color photos: www.finegardening.com/propagate-your-shrubs-softwood-cuttings

Date: 2006-10-23
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