plants as noise buffers

Could you recommend some plants that would be effective at screening out noise from a nearby, busy street? Would bamboo be effective? Any other suggestions?

I have some suggestions for planting and otherwise screening your property from the busy street adjacent to your house. I’ve started with an article by Joel Lerner in the Washington Post that provides good food for thought about this problem. After providing some related information that you may not have considered (#1), I’ve given you a list of plants, most of which are native (#2). Since you have a relatively small area, you will have to plan carefully.

Excerpt from the article:

“A buffer of mixed plants can absorb and deflect sound waves. The mix of plants is important because different types of leaves reduce different types of noises. How much noise control they provide depends on the intensity, frequency and direction of the sound, and the location, height, width and density of the planting.

“Mixed broadleaf plantings at least 25 feet thick and conifers 50 to 100 feet thick can drop noise levels by up to 10 decibels. For year-round noise reduction, plant a mix of evergreens such as arborvitaes, spruces, pines and hollies. To be effective sound barriers, these trees must have foliage that reaches to the ground.

“Deciduous plants are also effective for noise abatement, but only when foliage is present. Like evergreens, these must also have foliage from the ground up to really do the job. Thickets of sassafras and paw paw have been found to be relatively effective for this purpose.

“Include lawn or some other ground cover in shady areas. Turf grass or other low vegetation has a muffling effect on sound, compared with surface areas of bare soil or various paving materials, which are more likely to bounce sounds off their surfaces.”

1. My research indicates that a fence or other solid barrier–massive and thick, such as a brick wall or a berm–provides a more effective barrier to sound than a planting screen.

University of British Columbia Botanical Garden Forums has a discussion on this topic, including this citation:
From the book Arboriculture, third edition, Harris et al., page 138, figure 5-8 caption:
“Thirty meters of trees and shrubs reduce truck noise about as effectively as a similar area of bare cultivated ground. A berm, slope or solid barrier with woody plants would be more effective in absorbing noise (Cook and Van Haverbeke 1971).”

2. You may decide to mask the sound. In addition to music, chimes, and the sound of water in a fountain, you might consider trees that rustle in the wind. You mentioned bamboo, and given your small space, I would recommend a clumping rather than a running bamboo. The frequently asked questions section of the American Bamboo Society website has information about choosing and growing bamboo. Unfortunately, the clumping types prefer sheltered spots and/or shade.
You might consider planting some evergreen trees or shrubs on the edge of the property to shade the bamboo, which could be planted closer to the house (and the rustling sound would be closer to the windows). Or you could plant a running type of bamboo (some can take full sun) in a container or using a barrier.

Evergreen trees and shrubs will provide the most effective barrier. Trees
such as members of the Thuja genus in combination with a fence may be a place
to start, but for more interesting ideas, try visiting the Great Plant Picks website.
You can search with the word ‘hedge’ and come up with a good list of plants that will do well in the Pacific Northwest.

growing under Thuja

I have a large Western Red Cedar (Thuja plicata, I think!) under which grow a few weeds but not much else. I would like to find a low maintenance solution for the ground that won’t do any harm to it. Ground cover? Pea gravel? I worry that the shallow root system can be easily smothered so that adding soil and plants is not a good idea, plus the roots are a dense mat and difficult to dig through. Do you have any ideas or suggestions? What native plants might grow under the tree and how can I get them established?

As you’ve realized, Western red cedars have a dense mat of roots close to the surface. It’s not a good idea to add soil on top of the roots of trees because their root flare should remain above the soil — and even if you did, the roots of cedars would spread into that soil in a short period of time. It’s also important to keep in mind that under natural conditions the ground beneath Thuja plicata is usually bare of other plants.

If the area beneath your tree isn’t in deep shade and has at least some sun, you could plant spring ephemerals, including bulbs. They emerge in spring when the soil has plenty of moisture, then most die back before our summer droughts. They’re not difficult to plant under large trees because you don’t need to dig a large hole for seeds, bulbs, or small bare-root perennials. Good choices are Anemone blanda, Aquilegia (Columbine), Corydalis lutea, Crocus, Galanthus (snowdrops), Iris reticulata, and various kinds of Narcissus, including daffodils. Most tulips are not long-lived in our area. Hardy Cyclamen emerge and flower at other times of the year, but they’re also an excellent choice. Unfortunately, most of these plants are summer-dormant, when you’ll probably be out in your garden, and some self-seed prolifically under ideal conditions. A valuable resource, available for checkout at the Miller Library, is Planting the Dry Shade Garden, by Graham Rice (2011). Some of the plants he recommends will require regular watering under cedars.

Another option, also feasible if your area has some sun, is to plant our native Western sword fern (Polystichum munitum). It’s evergreen, so has a presence all year, and is the most sun and drought tolerant of our native ferns. I have a 60 foot red cedar in my garden, and have successfully maintained sword ferns beneath it in partly sunny areas, but not in deep shade, where they’ve died out. However, because they won’t survive our summer droughts in nature under these conditions, I’ve needed to water them about every 3 weeks in order to keep them alive. I’ve planted fairly small plants and watered them more often than that during their first year. If your soil is very sandy, sword ferns might not do well.

If you require a reliably showy solution, staging large planters planted with annuals or perennials, shrubs and/or trees might be best. The plants you choose will depend upon how much sun the area receives. Of course, they’ll need to be watered regularly, but large planters don’t need watering as often as small ones. If your hose-bib is not too far away, installing drip irrigation on a timer will ensure that your plants survive when you’re away from home.

edible galls on sage

I found a reference to a type of edible gall that grows on sage plants in Crete, and is sold as a sweet in markets there. Can you tell me what species of sage that might be, and is it something we can grow in the Pacific Northwest? Will it develop tasty galls here?

It seems very likely that the species of sage is Salvia pomifera. That species name (‘fruit-like’) refers to the apple- or fruit-shaped galls. The webpage of Flora of Israel has a feature article by Professor Avinoam Danin on this type of Salvia that does indeed grow in Crete. He mentions another Cretan species that produces fruit-like gall structures, Salvia fruticosa.

Flowers of Crete (John Fielding and Nicholas Turland, Kew, 2005) describes these two common shrubby sages found in Crete. “They share similar habitats, pine woodland, olive groves, scrub, garrigue, and rocky places,” though S. fruticosa is mainly found in the lowlands, while S. pomifera is more montane. Salvia fruticosa (faskomilo in Greek) is used in herbal tea, but “both species produce globose stem galls, which are eaten raw (including the insect larvae inside) by Cretan children.” (The authors do not say why children–rather than adults?–prefer this treat!)

According to Greek horticulturist and Salvia expert Eleftherios Dariotis, “Salvia pomifera is the one that produces most galls and people like to eat them. Their taste is like a sagey apple and they are crunchy in texture. S.fruticosa produces galls as well, but not as often.”

In the Middle East, there is another species of sage that produces edible galls. Salvia dominica goes by the common name Bedouin peach, or khokh, because the galls it develops are fuzzy like the fruit.

The galls aroused curiosity among plant explorers in centuries past. 16th century French botanist Pierre Belon described them as “covered with hair and sweet and pleasant to the taste. They were collected at the beginning of May and sold by the people of Candie [Candia?] to neighboring villagers.” [Source: The American Naturalist, Volume 52 February-March 1918]

During his travels in Crete, the 17th/18th century French botanist Joseph Pitton de Tournefort came across a sage he called ‘Salvia cretica frutescens pomifera,’ a shrubby Cretan sage that bore apple-like fruit. An article in Saturday Magazine (vol. 16, 1840) mentions his observation of large galls “caused by the punctures of insects; these galls are firm, fleshy, semi-transparent tumours, swelling out from the branches of the plant, and supposed to be produced in the same manner as oak apples, by the puncture of an insect of the Cynips genus. They form an article of ordinary sale in the markets, and are called sage-apples. When preserved with sugar, these apples are regarded as a great delicacy.”

Salvia pomifera will grow in USDA hardiness zones 7-10, and both Salvia fruticosa and Salvia dominica will grow in USDA hardiness zones 8-11. To me, that sounds like potentially marginal hardiness given our tendency for wet (Salvia-rotting!) winters.

I have a feeling that you would not have much luck in attracting the right species of Cynipid gall wasp to Pacific Northwest-grown Salvias. The Aulax species of gall wasp is what causes the galls found on sage species growing in the Mediterranean region. According to the Field Guide to Plant Galls of California and Other Western States by Ron Russo (University of California Press, 2006), the gall wasps which may affect Salvia species in California and other western states are Rhopalomyia species. The galls they form are tubular in shape, and not fruit-like in appearance. There is no documentation on their taste.

native gardens and supplemental watering

I am setting up a native plant garden in Seattle this fall. Since the plants I’m choosing are adapted to our dry summers, is it OK for my landscape to go without supplemental water next summer?

Expect that your new garden will still need some supplemental water next July and August. People often ask why it is necessary to water plants that can grow with just rainfall in the wild. Depending on the situation, though, it can be essential for several reasons. Our city gardens often have hot areas of paving nearby, and soil that’s compacted, sandy, or poor compared to forest or meadow soils. Wild plants spring up from seed or spread underground to where they can find water and other necessary conditions for their species, while the roots of transplants must suddenly support a whole plant in a new environment that is likely quite different than the native plant nursery where they were grown, and may also differ from the conditions for which they are ideally adapted. Climate change is a factor, too.

A great book that can help you with planning and maintaining landscapes with our native plants is April Pettinger and Brenda Constanzo’s Native Plants in the Coastal Garden. The authors emphasize the importance of siting your native plants well, in communities of plants that are suitable for the conditions you have. Their list of plants for dry places may be helpful to you if you are still choosing plants.

the fragrant beverage-producing willow

There’s a type of willow used traditionally in Iran to make a fragrant beverage. In Farsi, it’s called bid, and I think it’s also known as musk willow. I need to know what the species is, and I wonder if it will grow in the Seattle area.

Most sources I consulted confirm that musk willow or bid is Salix aegyptiaca. Encyclopaedia Iranica says “bid” is a general term for the genus Salix, but does identify “musk willow” as Salix aegyptiaca. The online version of W.J. Bean’s Hardy Trees and Shrubs: Temperate Woody Plants in Cultivation says the following:
“Native of S.E. Anatolia, S.E. Transcaucasia and N. Persia; introduced to the Botanic Garden at Innsbruck in 1874 by Dr Polak, doctor to the Shah of Persia, and in cultivation at Kew five years later. At one time a perfumed drink was made in Moslem lands from its male catkins, which were also sugared and eaten as a sweetmeat, and used for perfuming linen. For these it was cultivated from Egypt to Kashmir and central Asia, so the epithet aegyptiaca is not so inappropriate as it would otherwise seem to be.”

Salix aegyptiaca is featured in the February 2016 issue of the Royal Horticultural Society’s publication, The Garden in an article entitled “Willow the wish” by David Jewell. Since the article recommends it for gardens in England, where the climate is similar to ours here in the Pacific Northwest, it will probably thrive here in Seattle as well.

rose gall and the scotch broom gall mite

I work on a restoration site and this fall I have been noticing weird fuzzy growths on many of the Nootka roses (Rosa nutkana) growing there. Do you know what is causing this? And is it related to similar strange growths on all of the Scotch broom? In the case of the broom, it actually kills them completely—they turn brown or black, and their roots are pretty much non-existent, which makes them very easy to uproot (which is what we are trying to do). I just don’t want to lose the roses or other desirable plants on the site.

What you are describing on the roses sounds like mossy rose gall (Diplolepis rosae). Washington State University Extension’s HortSense page says that these galls which are caused by cynipid wasps will not harm the host plants. You could picky them off the roses, but that seems impractical in a restoration site, and besides they are fairly benign and attractive curiosities. The particular species of cynipid wasps which cause it are unlikely to affect plants which are outside the rose family.

Your other question about dying Cytisus scoparius (Scotch broom) is especially interesting. I think what you are seeing on those browned and blackened plants is also a gall, caused by the Scotch broom gall mite (Aceria genistae). This insect is apparently on the cutting edge of controlling invasive broom. According to this informational page from University of California Statewide Integrated Pest Management Program, the mite was first seen on broom plants in Tacoma, WA and Portland, OR in 2005. It has since spread through the Pacific Northwest. An abstract of an article entitled “The Scotch Broom Gall Mite: Accidental Introduction
to Classical Biological Control Agent?” (J. Andreas et al.) appeared in the 2011 XIII International Symposium on Biological Control of Weeds. Studies are underway to see if the mite affects non-target plants such as lupine. For now, you can rejoice in the fact that the mites are curbing the growth and reproduction of the broom, and making your work a little bit easier!

overwintering tuberous begonias

Will Nonstop Begonias overwinter here in Seattle and do well in subsequent years? Mine are in a north-facing shaded area with good soil drainage.

According to the Sunset Western Garden Book (2007), it is possible but not always easy to overwinter tuberous begonias such as the ‘Nonstop’ series. Most people use pots and bring them into a cool, dry, dark environment (such as a garage) for the winter. Others put tubers in the ground but dig some in fall to overwinter in a cool shoebox full of sand. Sometimes they can survive our Seattle winters in the ground, but that is not a sure thing. For example, neighbors of mine lost their last winter despite a blanket of mulch they hoped would protect them. Freezing weather kills them, and the damp soil doesn’t do them any good either.

growing and caring for citrus indoors

I have a Eustis limequat, and it’s producing flowers. Should I be taking a brush and dusting pollen from one bloom to the other? Also, I’m growing it inside. Do I need any additional lighting? I have fluorescent lights as well as full-spectrum UVA/UVB lights that I can use. Someone told me I’d need to get really pricy calcium lights, or something similar.

All the resources I’ve found suggest that citrus flowers are self-pollinating with a very few exceptions. However, your limequat (x Citrofortunella floridana) is growing indoors, so pollination assistance from you will help. Alabama Cooperative Extension, in a publication no longer available online, describes citrus as generally self-fruitful.

Excerpt:
“With the exception of Clementine tangerine and certain tangerine hybrids such as Orlando tangelo, citrus trees are self-fruitful and do not require cross-pollination. Thus, self-fruitful types of citrus can be grown as single trees. Cross-pollination requires that two or more varieties bloom at the same time. Some varieties will not cross-pollinate each other. Satsuma and navel do not produce viable pollen and thus cannot be used for that purpose.”

I looked at several of our books on growing citrus to see if they mentioned any special lighting needs, and Success with Citrus Fruits by Sigrid Hansen-Catania (Merehurst, 1998) simply says that your artificial light source needs to provide 12 hours of light a day, if you do not have a position for the plant near a sunny window. She mentions “specially adapted fluorescent tubes which you can fix to the ceiling about 8-16 inches above the plants,” though she mentions it in the context of providing adequate light during winter months.

University of Missouri Extension has a general article on indoor lighting for plants.

Here is an excerpt from an article (no longer available) from Purdue University Horticulture specific to citrus: “Citrus foliage can adapt to the relatively low light levels typical of our homes. However, if flowers and fruit are what you’re after, you’ll need to give the plants as much light as possible. If natural light is inadequate, you can supplement with artificial lights. A combination of cool white and warm white florescent lights placed close to the plants will help, as will the special ‘grow lights’ that emit the wavelengths of light most important for plant growth. (…)

If citrus is kept indoors year-round, the plants will likely need a bit of pollination assistance when they do flower. Use an artist’s paintbrush or cotton swab to transfer pollen from one flower to another.”

The good news is that I don’t think you need to invest in any additional expensive lighting systems!

pruning and propagating Dracaena

My indoor Dracaena is getting too tall. I’d like to prune it, and maybe use the cuttings to start new plants. How do I do this?

You should be able to do both tasks. The Complete Houseplant Survival Manual by Barbara Pleasant (Storey, 2005) says “when plants become too tall, cut off the cane at any height. New leaf clusters will grow from just below where the cane was cut. You can cut sections into 6-inch pieces and root them like stem cuttings.”

You might also find this discussion from University of British Columbia Botanical Garden’s online forum useful.

Here is more information, from University of Florida, which describes how pruning will result in two or more branches forming where the pruning cut was made: “Cut one or two of the stems to a point where new foliage is needed.”

on growing tea plants

I am interested in growing tea plants. In particular, I am interested in these: Cyclopia intermedia (honeybush), Aspalathus linearis (rooibos), and Citrus aurantium (bergamot). Also, do you know which local nurseries might sell these plants?

For the first two plants, I consulted Cape Plants by Peter Goldblatt and John Manning (Missouri Botanical Garden, 2000). Cyclopia intermedia and other Cyclopia species (Honeybush) grow in southeast and southwest Africa in what is called “mountain fynbos” regions. The climate is similar to that of Mediterranean areas, so if your climate has wet winters and dry summers, there is a chance you may be able to grow this plant. The South African Honeybush Tea Association has more information about this plant as a source of tea.

Aspalathus linearis, or Rooibos, is found in South Africa from the Bokkeveld Mountains to the Cape Peninsula. The website PlantzAfrica has information about it that suggests it is not often grown in home gardens: “This is thought to be due to the difficulty in propagation by seed or root cuttings and in providing the optimal growing conditions for the plants. In order to grow Aspalathus linearis successfully, seeds must first be scarified and then planted in acid, sandy soils.” The Plants for a Future Database suggests that this plant would not grow with much success in a colder, wet winter climate.

The bergamot which is used to flavor Earl Grey tea goes by the botanical names Citrus aurantium, C. aurantium subspecies or variety bergamia, and Citrus bergamia. According to Purdue University’s New Crops web page, this tree is a native of Southeast Asia: “The sour orange flourishes in subtropical, near-tropical climates, yet it can stand several degrees of frost for short periods. Generally it has considerable tolerance of adverse conditions. But the Bergamot orange is very sensitive to wind and extremes of drought or moisture.” See also the following from University of California, Riverside’s Citrus Variety pages. The tree grows well in Italy and North Africa, but it may not do very well in the Pacific Northwest.

Of these three plants, the only one for which I found a nursery source (in California, not locally) on Plant Information Online was the bergamot Citrus. You may want to call your favorite local nurseries to ask if they ever carry this plant, but I suspect that most will not, as it is not likely to succeed in our climate. You might have better luck growing familiar herbs like chamomile and mint which can be used for tea. You could also make green, black, and oolong tea from the leaves of Camellia sinensis, a plant which will thrive here in Seattle, and should not be too difficult to find. According to Keith Possee, who manages the UW Medicinal Herb Garden, offers the following advice:
“The trick is to pick only two leaves and a bud in the spring flush of growth. If we lived in the tropics, home tea growers could be picking tea most or all of the year, but 48 degrees north latitude is not ideal.” The most important step to learn is how to roll the leaves. Keith recommends this University of Hawaii Extension document entitled Home-Processing Black and Green Tea by Dwight Sato, et al.