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Elisabeth C. Miller Library

Archives: Plant Answer Line Q & A

Plant Answer Line questions and answers.

Bonsai care

I was given a 40-year-old Quince bonsai tree and I would like to get some advice on taking care of it. I have a great book called, Bonsai Basics which has given me some insight as to how to take care of it, but I am looking for more information. I was also wondering about getting the tree repotted and the roots trimmed (which needs to happen very soon, as far as I can gather.) The roots have not been trimmed on this particular tree for about 3 years, and it has survived a pretty hard hit of insect and fungus pests.

 

The Puget Sound Bonsai Association has a website with useful information and links to other bonsai-related organizations and information. This is an active group with regular meetings, some lectures/workshops, and a good newsletter.

Nurseries such as Bonsai Northwest, a specialty nursery in South Seattle, often offer classes on bonsai care.

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Clumping bamboo

I would like to have some bamboo planted in my backyard for privacy. However, I am uncertain as to which species will work the best. The planting area will be about 8 feet by 2 feet near a wooden fence. The area does get some sun but is mostly shady. I am looking for bamboo that is fast growing but not invasive. I want it to grow upwardly fast (no more than 30 feet) but I don’t want it to invade my neighbor’s property on the other side of the fence. Could you recommend at least three different bamboo species that would work for this area?

 

In the December 2005 issue of Horticulture magazine, local author Val Easton recommends a number of different clumping bamboos. (You should choose clumping rather than running bamboo for your privacy screen, as they will not be likely to invade your neighbor’s property.)

Here are three recommendations from her article:

Borinda macclureana – hardy to USDA Zone 7 part sun, 12 – 20 feet tall

Fargesia robusta – hardy to USDA Zone 6, dense erect to 16 feet

Thamnocalamus tessellatus – hardy to USDA Zone 7 upright to 16 feet

Local gardening expert Ciscoe Morris recommends Chusquea culeou and several species of Fargesia in his book Ask Ciscoe.

This article from Horticulture Magazine (May 2007) also has a good list of clumping bamboo:

      • Chusquea culeou
      • Fargesia robusta ‘Wolong’
      • Borinda angustissima
      • Thamnocalamus crassinodus

Fargesia murielae

  • Thamnocalamus tessellatus
  • Borinda boliana
  • Chusquea culeo ‘Cana Prieta’
  • Fargesia nitida

You might try the following two nurseries for availability: the Bamboo Garden Nursery and Beauty and the Bamboo.

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Seed exchange programs

Do you know of any plant and seed-sharing sites where I might find some peonies, for example? Or where I might post some stuff I have no place for?

 

Most reliable seed exchange programs require membership, but . . .

PEONIES:
If you are interested specifically in peony seeds, the American Peony Society and the Canadian Peony Society are excellent sources.

You might also consider contacting the Pacific Northwest Peony Society. They are fairly new (est. 1996) and might not have a seed exchange yet, but can be helpful with other information.

DONATING PLANTS:
There are several places locally that list plants for donation.
Plant Amnesty has an Adopt-a-Plant program.
Also, try the Pacific Northwest Garden Exchange at Houzz.

SEED LIBRARIES:
This is a relatively recent phenomenon and many cities now have such programs. Here are some examples:
King County Seed Lending Library
Northeast Seattle Seed Library

SOCIAL MEDIA:
There are groups on Facebook devoted to plant and seed exchanges. Be aware that not all of them are cautious about excluding aggressive or invasive species.

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Controlling mountain pine beetles

What is the latest method of eradication for the mountain pine beetle, Dendroctonus ponderosae, that is rampant in western Canada?

 

In the northwestern U.S., USDA Forest Service states that the focus has shifted from using pesticides to taking preventive measures:
Excerpt:
Control methods have shifted away from direct control (e.g. spraying, felling, burning) and towards prevention of outbreaks. This course of action was chosen after thoroughly exploring direct control measures for nearly a century and arriving at a simple conclusion: They don’t work. It is possible to prevent infestation with penetrating sprays on individual, high value trees such as those in campgrounds and near houses, but they need to be applied before the tree is infected and the cost of such treatments is prohibitive for any large-scale application.

Once a mountain pine beetle outbreak begins to spread, it can be stopped by thinning the stand ahead of the edge of the outbreak. This is because outbreaks expand on a tree to tree basis where the incoming beetles switch their attacks from a recently attacked-stem to the next largest tree. More importantly, infestations can be prevented by thinning stands before crown closure, an operation that not only increases the vigor of the residual stand, but also prevents the spread of an outbreak if individual trees have been attacked.

Mountain pine beetles are a natural part of western ecosystems, and for this reason will never be completely eradicated (nor should they be, as they serve to create small stand openings which are important for biodiversity of both flora and fauna). As such, the death of a few trees on your property doesn’t necessarily mean an epidemic is getting started; check your trees for root disease symptoms. To maintain mountain pine beetles at their normal levels, predisposing factors for outbreak must be removed. Some of these, such as environmental stresses, are not possible to control. However, many stresses are related to stand management practices. First and foremost, two situations need to be addressed: root disease centers and overstocked stands. More details about treatment for root disease centers have been given in other WSU Cooperative Extension “Forest Health Notes;” in summary, they need to be identified and planted with resistant species. Overstocking causes trees to compete for water, light and nutrients, and thus weakens their defenses against bark beetle attack. To minimize stand stresses and maintain vigorous growing conditions, stand managers should: (adapted from Berryman: Forest Insects, 1986).

Natural Resources Canada has a task force on the mountain pine beetle. You might want to contact them for the latest update. Go to their mountain pine beetle website and follow the links for additional information, including how to contact CCoFI.

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Sumac in za’atar

What species or variety of sumac is used in the spice mix called za’atar? I googled it after reading about it in a Lebanese cookbook written by Mary Laird, but the recipes all just say “sumac berries with salt spray left on them!” Are there different versions of the spice mix in Israel and Arab countries?

 

There are many variations of za’atar–Syrian, Lebanese, Israeli, Palestinian, etc. I’m going to go off on a bit of a tangent from your question about sumac, because the identity of the main ingredient of za’atar is a bit complicated.

One primary difference, these days, between Israeli, Palestinian, or Jordanian za’atar, and za’atar made anywhere without plant protection laws is that the picking of Origanum syriacum (the main ingredient of za’atar) is prohibited in Israel, the West Bank, and Jordan because it is an endangered plant, and there’s a hefty fine if you’re caught harvesting it in the wild. (Sources: Gil Marks, Olive Trees and Honey 2005, and “A political ecology of za’atar” by Brian Boyd in Environment and Society, 2016).

The word za’atar means ‘hyssop,’ as in the common name for Origanum syriacum, rather than Hyssopus officinalis, which would be too bitter to eat. (Marks says that the plant mentioned in the Hebrew Bible–the Torah–is ezov, which is hyssop, but again, those bible writers weren’t necessarily botanists, so they are believed to have meant O. syriacum.) For more discussion of biblical botanical confusion, see Old Dominion University’s page on bible plants.

Gil Marks’s recipe for za’atar is as follows:
1/4 c. brown sesame seeds
1 c. Syrian oregano (aka white or Lebanese oregano) or alternatively [if you’re not a lawbreaker]: 2/3 c. dried thyme and 1/3 c. dried wild or sweet marjoram
2-4 T ground sumac or 1 T lemon zest
1/2 tsp table salt or 1 tsp kosher salt (optional)

My handwritten recipe which is probably from Claudia Roden’s Book of Middle Eastern Food, 1968, says:
1 cup dried thyme
1 cup sumac
1/4 cup cooked, dried unsalted chickpeas finely pulverized
3 T. toasted sesame seeds
1 T. marjoram
2 T. salt
Bear in mind that Roden is from an Egyptian Jewish family.

There are probably countless regional variations. The za’atar we used to get in a twist of paper from the bread vendors in Jerusalem’s Old City seemed to have very little sumac–it was mostly something like oregano, thyme, sesame seeds, and salt.

And now, back to sumac! Here’s a link to an article on sumac in HaAretz by Daniel Rogov (a cookbook author and food writer). He doesn’t say which species of sumac is the edible one, but most powdered sumac is from Rhus coriaria.

Excerpt:
“Now before we get too far into this, let us make it clear that edible sumac is not to be confused with Rhus glabra which many people know by its common name ‘poison sumac,’ which causes severe itching and skin reactions when touched. Those who have lived in North America are probably familiar with this annoying plant which is a cousin of Rhus toxicodendron (poison ivy).

“In preparing edible sumac, the hairy coating is first removed from the berries, which are then ground to powder-like consistency and used by many in the same way that lemon juice and vinegar are used in the West. The spice is probably at its most popular when making mixtures of za’atar…”

Here is additional information about sumac from Gernot Katzer’s Spice Pages.

For another discussion of za’atar and its ingredients, see the Food-Condiments section of this site from a Society for Creative Anachronism member–it gives you an idea of the diverging opinions about the constituent ingredients.

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Safety of bat guano

My local nursery is selling bags of bat guano, and enriched compost that includes it. What is it good for, and is it safe to use? The company describes all their products as organic.

 

No matter what is in your compost, it is always a good idea to wear a dust mask when opening bags of soil amendments, and when spreading them in the garden. A mask will help protect you from breathing in airborne fungal spores.

Bat guano is used as a fertilizer, and provides supplemental nitrogen, according to this information from Oregon State University. It contains about 12 percent nitrogen. The ratio of N-P-K (nitrogen-phosphorus-potassium) is approximately 8-5-1.5.

A recent news story on National Public Radio highlighted the human health risks of exposure to bat waste (guano) in caves in Borneo. Both world travelers visiting bat caves and local harvesters of guano may be at risk of contracting very serious viruses, unless they take precautions (masks, gloves, and scrupulous hygiene). In parts of the United States (particularly the Ohio and Mississippi River valleys), there is a fungus called Histoplasma that is found in soil which contains bat or bird droppings. Gardeners who wear masks when digging in affected areas can avoid contracting
histoplasmosis.

Bat and bird guano are allowed as soil amendments “with restrictions” imposed by the U.S. Department of Agriculture. They must be decomposed and dried according to the USDA Organic Regulations requirements for raw manure. I recommend contacting the manufacturer of the products and asking them about where they obtain their bat guano, and whether they meet NOP (National Organic Program) and OMRI (Organic Materials Review Institute) standards. You can also ask about their veterinary and phytosanitary certificates for these products, and whether they make certain the guano is harvested sustainably and without harm to the bats and their ecosystem or to the health of harvesters (particularly in countries without strong worker protection laws).

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Growing edible plants in galvanized containers

Is it safe to use galvanized containers (in this case a large
galvanized tub like the kind used for watering livestock) in which to
grow root vegetables, herbs, etc? I’ve seen some sites sell these for this
use, but there are also some postings referring to the potential for ill
effects of anti-rust coatings.

 

You may want to consider both what goes into the galvanizing process, and what could be leaching out of containers as the coating wears down over time.

Here is information on the process of galvanizing from the American
Galvanizers Association. Excerpt:

“What are the steps in the galvanizing process?”

  1. Pre-inspection – where the fabricated structural steel is viewed to
    ensure it has, if necessary, the proper venting and draining holes,
    bracing, and overall design characteristics necessary to yield a quality
    galvanized coating
  2. Cleaning – steel is immersed in a caustic solution to remove organic
    material such as grease and dirt, followed by dipping in an acid bath
    (hydrochloric or sulfuric) to remove mill scale and rust, and
    finally lowered into a bath of flux that promotes zinc & steel reaction
    and retards further oxidation of the steel… (steel will not react with
    zinc unless it is perfectly clean).
  3. Galvanizing – the clean steel is lowered into a kettle containing 850
    F molten zinc where the steel and zinc metallurgically react to form
    three zinc-iron intermetallic layers and one pure zinc layer

Based on the above, one concern would be whether the zinc would be
harmful. Zinc is one of many nutrients needed by plants, but I couldn’t
hazard a guess as to what effect the zinc from the coated steel would
have, if any, or whether the galvanizing process involves other
substances.

The book The Edible Container Garden by Michael Guerra (Fireside, 2000)
says the following:

“Galvanized buckets are increasingly popular but don’t use them for
ericaceous or acid composts.” (This would be a compost which is
lime-free. Usually soils in the Pacific Northwest tend to be acidic. I
don’t know from your message what part of the country you live in, but
this might be something to consider as well).

Another issue is that the metal containers will probably heat up quickly,
meaning that your plants might need more attentive watering.

Los Angeles County Cooperative Extension offers the following information, in an
article on trace elements and urban gardens. Excerpt:

“Cadmium is a contaminant of many manufactured products containing zinc.
Any zinc plating or galvanizing operations and galvanized metal
containers sometimes used in horticulture and gardening operations are
potential sources of cadmium.”

I certainly don’t think you want to grow vegetables in a cadmium-laced
container. In situations where there is any doubt about safety, I would
recommend growing ornamental plants in the tubs, and growing edibles in
untreated wood or clay pots.

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Encouraging blooms on Hydrangeas

Help! We live in North Bend and have several Hydrangeas. I have a large Annabelle that
has never bloomed properly. Is there some special care or
fertilizing that I can do to encourage normal blooms on these
plants?

 

Here is some information on how to improve flowering, from the U.S. National Arboretum:

Excerpt:

“There are three possibilities for lack of flowering among the hydrangea
species. The first two too much shade and improper pruning apply to
all hydrangeas, while the other weather-related damage to flower buds applies primarily to the bigleaf hydrangea.

“While most Hydrangea species benefit from some shade, too much shade can
reduce flowering. This is particularly true of panicle hydrangea, which
is the one Hydrangea species that grows well in full sun. If you have a
hydrangea that used to bloom well but now flowers only sparsely, evaluate
whether the growth of nearby trees has reduced the amount of light that
reaches the hydrangea. If so, you may want to consider moving the
hydrangea to a sunnier location.

“Improper pruning can also reduce flowering in Hydrangea. Since bigleaf
and oakleaf hydrangeas flower on previous year’ s growth, potential
flowers buds would be removed if the plants were pruned in fall, winter
or spring. Panicle and smooth hydrangea flower on this year’s growth, so
pruning them in early summer would reduce or eliminate flowering for that
year.

“The most common reason for lack of flowering in the bigleaf hydrangea is
unfavorable weather. Most H. macrophylla cultivars flower primarily on
previous year’s growth. Weather conditions that damage aboveground parts
of the plant can reduce flowering. Damaging weather conditions include
early fall freezes that occur before the plant is completely dormant,
extremely low winter temperatures, and late spring freezes that occur
after the plant has broken dormancy. In USDA Cold Hardiness zone 6 and
warmer, which is the recommended growing area for H. macrophylla, the
most common of these unfavorable weather events is late spring freezes
that damage tender new growth. This is particularly true in the
southeastern U.S., where ‘see-saw’ temperatures are very common in the
spring.

“Bigleaf hydrangea responds quickly to warm temperatures in late winter
and early spring by breaking dormancy and producing new leaves.
Unfortunately, these spells of warm weather are often followed by periods
in which temperatures reach well below freezing. The severity of the
damage caused by these freezes depends on how many of the buds had broken
dormancy. If a substantial portion of the buds on a stem were actively
growing, the whole branch may die. For some cultivars, the loss of the
aboveground part of the plant will completely eliminate flowering the
following summer. The plant will produce new buds from the base of the
stems, but stems produced from these buds will not flower in these
cultivars.”

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Hollies for the Puget Sound area

We are planning a 30′ x 100′ planting bed to screen a metal building
and have been thinking about using a variety of holly for the background evergreen tree in this bed. Do you have any recommendations for varieties that do well in the Puget Sound area and are as pest free as possible, and yet have good color, berries and form. Setting has: sun, good soil, irrigation if needed and no height restrictions.

 

The local resource, Great Plant Picks, recommends the following hollies:

  • Ilex aquifolium ‘Ferox Argentea,’ or hedgehog holly. Note that this clone
    does not produce berries, which is considered by some to be a positive
    attribute, as berries can lead to nuisance plants sprouting in the
    garden.
  • Ilex crenata ‘Convexa’ (convex-leaf Japanese holly)
  • Ilex crenata ‘Mariesii’ (columnar Japanese holly): this is a female clone
    whose flowers will develop black berries if pollinated.
    Great Plant Picks offers more information and images.

Ilex aquifolium (the species) is now considered an invasive plant in our
area. The Tacoma News Tribune published an article on this topic, with suggested alternatives. Excerpt:

“Just don’t plant English holly (Ilex aquifolium), the species with the
dark, glossy leaves and bright red berries that most people picture when
they hear the word ‘holly.’ This non-native species has become invasive
here and isn’t recommended for home gardens (see box for more
information), so leave it to the professional growers.
But that still gives gardeners about 400 species of holly to choose from,
and many can be seen at the Washington Park Arboretum in Seattle, which
has the second-largest holly collection in the U.S.
‘Our U.S. native Ilex opaca (American holly) and its many cultivars are
underutilized and in many cases better ornamentals than (the) Ilex
aquifolium counterparts,’ said David Zuckerman, horticulture staff
supervisor at the arboretum, which is part of the University of
Washington Botanic Gardens.”

Like American holly, some hollies have the ‘traditional’ holly look,
while other holly species display different charms.
One of Zuckerman’s favorites is the deciduous Ilex verticillata. Although
the plant’s oval leaves drop in the fall, ‘the berries persist through
winter and can really liven up the winterscape,’ he said.
Japanese holly (Ilex crenata) is a family of ‘quite handsome shrubs’ with
small evergreen leaves and black berries, Zuckerman said. These hollies
look more like boxwood than holly, and lend themselves to hedging and
topiary. ‘I really enjoy some of the whimsical dwarf-forms,’ he said,
such as Sky Pencil, which grows 6 to 8 feet tall but just 12 to 18 inches
wide, adding a vertical accent to the landscape.

When adding holly to the garden, remember that hollies are dioecious and
both male and female plants are needed for the female to produce berries,
Zuckerman said. Good companion plants for evergreen hollies include
deciduous choices like witch hazel, lindera (spicebush) and corylus
(filbert), Zuckerman said. And Asian plants such as Japanese maple and
bamboo can partner well with the more formal-looking Japanese hollies, he
said.

I wonder if you might also consider other plants which have colorful
fruit but are less likely to become invasive. This article,
from local website Rainy Side Gardeners, lists a few possibilities, like
Arbutus, Gaultheria, Mahonia, Skimmia, Nandina, and Sarcococca.

Crocosmia planting and care

I just received about 20 Crocosmia lily bulbs, fresh out of
the ground. I’m new to the species, and don’t know that much about
gardening in general… Should I plant them now or wait until spring?
Should I cut the foliage or keep it? I’d almost rather wait until spring
to plant these, as I’m considering moving in the next few months and want
to take them with me, but what is the best way to keep them over the
winter? Also, can I plant them in a pot (how deep should it be) or do
they need to be in the ground?

 

Crocosmia is in the plant family Iridaceae, and is related to Gladiolus
but not lily. You may find this general information on Crocosmia from
Washington State University useful.

As far as when to plant them, since it sounds like you have entire
plants, not just the corms, you can certainly try putting them in the
ground. If winter temperatures do not go below 10 degrees, they will be
fine without protection. The leaves tend to start looking scraggly in the
fall and you can either leave it as is, or cut the spent flower stalks back. If you were just planting the corms, it would be best to do this in spring.

I’m assuming these plants have finished flowering,as it is mid-October. According to British gardener Alan Titchmarsh, you can “cut back flowering stems to near ground level in November, but leave evergreen foliage to provide winter protection, removing it in early March. In cold gardens, lift corms in October.” (Source: author’s webpage, 2007)

Since you are moving, you may want to put the plants in containers just
for transport, and then plant them into the ground in your new location.
This plant might work in a permanent container if the pot were large and
fairly deep (at least 16 inches), with excellent drainage (or else the
corms will rot). These are tall (2 1/2 to 3 feet), spreading plants, so
planting into the garden is probably best.

If all else fails, you can always start afresh by purchasing and planting
new corms in the spring.