seed germination of Acer triflorum and Acer griseum

I am interested in the seed germination requirements of Acer triflorum and Acer griseum.

There is information in The Reference Manual of Woody Plant Propagation by Michael Dirr and Charles Heuser (Varsity Press,2006):

Acer triflorum seed is “doubly dormant and when fall planted will germinate the second spring and sporadically thereafter. Seed, unfortunately, is often not sound […] Nine months warm followed by 3 months cold gave reasonable germination. If seed is received dry it may be prestratified for 6 months and then sown. Germination is less than 1% the first year but is very good the second.”

The authors state that with Acer griseum, “the biggest problem is poor seed quality” (between 1 to 8% viability). Also, seed production from an individual tree varies widely from year to year. “Seeds are doubly dormant and if fall planted require 2 years, some germinating the third year and beyond. The pericarp wall is extremely tough and dormancy is caused by a physical barrier as well as internal embryo conditions.” Dirr says that he has cold-stratified seed for 90 days, split the fruit wall to extract the embryos, and planted them in vermiculite with a fair amount of success. Growing this tree from cuttings is considered extremely difficult, and grafting (onto seedling Acer griseum seems to be the easiest propagation method.

Magnolia leaves decay

I have noticed that Magnolia leaves seem to decompose more slowly than other leaves…can you tell me why that might be the case?

There is a lot of anecdotal evidence regarding your observation. Finding information to specifically confirm it is not easy, however. But some facts about plants physiology help, especially in combination with considerations about the conditions required for decay. I referred to Introduction to Plant Physiology (William G. Hopkins, 1995) for most of the information below.

Lignin is a compound that is an integral part of the cell walls of plants. (It is the second most abundant organic compound on earth after cellulose.) Lignin fills the spaces in the cell walls of various plant tissues, providing mechanical strength to the cell wall and thus to the entire plant.

Lots of lignin in a leaf would result in a slow process of decomposition because it is difficult to degrade. That is, it is not easy for bacteria and water (necessary for decomposition) to penetrate the chemical structure of lignin.

Suberin is a waxy substance that is highly hydrophobic (repels water); its main function is to prevent water from penetrating plant tissue. Suberin is found in the outermost layer of the bark (in the dead corky tissue). The cells in this layer are dead and abundant in suberin, preventing water loss from the tissues below.

Suberin can also be found in various other plant structures, including leaves, where it also prevents the movement of water.

So, the combination of a structural function of lignin and the water-repelling characteristics of suberin – in leaves, in this case – is quite helpful in explaining why magnolia leaves decay at a slower rate than other leaves.

An article about composting from University of Florida Extension mentions that magnolia leaves would need to be shredded in order to be usable in compost (or as mulch).

Jade plant care

I have been nursing a Jade plant cutting that dropped off an overwatered and rotting larger plant. It has been thriving in my windowsill for 6 months or so, and has grown a lot already.

In the last week or so, I have noticed a strange white speckling on the upper surface of almost all of its leaves. Upon close inspection, it does not look like insects; it looks sort of like a detergent residue, and if I scrape my nail against the surface of the leaf, a lot of it will come off, albeit with effort.

Do you know whether this is something I need to treat?

I wouldn’t assume the spots are a problem. As the following link to North Dakota State University Extension (now archived) mentions, it might be salt crystals that you are seeing:
“Those dots are salt crystals and can be wiped off with a damp cloth or just ignored because they are not causing any harm to the plant. All water (except distilled) contains some salt. When fertilizer is added to the root system, the plant takes up the nutrient salts with the water. As the water moves through the leaf pores during transpiration, the salts often are left behind on the surface.”

However, if you were to use a hand lens (not just the naked eye) and discover insects, there are resources with information on identifying and treating insect problems on indoor plants.

1. Pest and Diseases of Succulent Plants

2. Washington State University’s PestSense site lists several common houseplant pests, with information about treatment.

Always test any spray on one leaf before spraying the entire plant. Wait a few days after the test spray. Some plants are more sensitive to various soaps or oils.

3. The Northwest Center for Alternatives to Pesticides also has a guide to Growing Houseplants Without Using Pesticides.

planting to stabilize a steep slope

Can I plant groundcovers, shrubs, and trees to stabilize a steep slope?

There are several resources which will help you in
selecting plants to prevent erosion and mudslides on
your slope.

Please note that these articles are merely suggestions and should not be construed as advice. We are librarians, not engineers!

None of our standard books on trees mentions the soil binding quality of tree roots. However, the Miller Library does have very good technical books and articles on slope stabilization. (For example, Slope Stabilization and Erosion Control: A Bioengineering Approach, edited by R.P.C. Morgan and R.J. Rickson, 1995.)

I do want to note one thing that many articles mention: no amount of established vegetation will hold a steep slope if other forces are present that would contribute to a landslide.

The Department of Ecology website has a list of appropriate plants.

Additionally, there are a number of books with
information on the subject. Vegetative Contribution
to Slope Stability at Magnolia Park (by Kathy Parker, 1996)
recommends Oregon grape (Mahonia), which she suggests
for gentle slopes.

Other smaller plants she lists are:
Polystichum munitum (native sword fern)
Vaccinium ovatum (evergreen huckleberry)
Symphoricarpos albus (snowberry)

Larger shrubs in her list:
Alnus rubra (red alder)
Philadelphus lewisii (mock orange)
Sambucus racemosa (red elderberry)

Small trees:
Acer circinatum (vine maple)
Amelanchier alnifolia (serviceberry)
Corylus cornuta (hazelnut)

For steeper slopes, Parker says that they may not be
good candidates for vegetative rehabilitation unless
you put in some kind of structure. She says that Jute mats can be used in conjunction with native seed, mulch, and shrubs, if carefully anchored. She also mentions a Weyerhaeuser product called Soil
Guard.

Steep Slope Stabilization Using Woody Vegetation (by
Leslie Hennelly, 1994) has a plant list, as well as a chart which indicates plants used to control erosion, the degree
of the slopes, and the rate of success in resisting
erosion.

Two titles which focus more on the garden design
aspect of planting on a slope are
Hillside Gardening : Evaluating the Site, Designing
Views, Planting Slopes (by William Lake Douglas, 1987) and
Hillside Landscaping (by Susan Lang and the editors
of Sunset Books, 2002).

diseases affecting fir trees

Can I attempt to diagnose a diseased tree online? We’re getting more brown spots on our grand fir and I would like to try to figure out what is wrong.

You can attempt it, but you will not know for certain based solely on a comparison of symptoms. You can certainly get an idea of what the potential problems could be. Try the Pacific Northwest Plant Disease Management Handbook online—it has excellent photos. Search for fir.

There are several possibilities with brown spots as symptoms, especially:
*needle casts (there are 3 kinds)
*rust
*web blight
*current season needle necrosis
*shoot blight
*Grovesillea canker
*interior needle blight

The best way to diagnose a problem is to bring photos of the affected tree along with samples (if you can reach them) to your local county extension agent or Master Gardener diagnostic clinic.

programs on horticultural therapy

Do any colleges or universities in the Seattle area have programs on horticultural therapy?

At one time, Edmonds Community College offered a certificate in therapeutic horticulture but they do not any longer. You can find other programs available around the U.S. on the website of the American Horticultural Therapy Association.

The University of Washington doesn’t offer a horticultural therapy program, though there may be individual courses through the department of Landscape Architecture. Professor Daniel Winterbottom specializes in “ecological urban design and the role of restorative/healing landscapes in the built environment.” The Miller Library has a good selection of books and articles on the horticultural therapy, including information about making raised beds, appropriate tools, gardening for the differently abled, and the like. This booklist will give you an idea of the resources available. For information about library hours and directions, go here.

sources for native plants in the PNW

Where can I buy plants native to the Pacific Northwest?

The Miller Library website has information on sources for native plants – see the section on finding northwest native plants.

Below is a list of nurseries close to Seattle:

1. MsK Rare and Native Plant Nursery (and lots of NW natives) in Shoreline

2. Washington Native Plant Society plant sales and native plant and seed sources

3. Woods Creek Wholesale (and Retail) Nursery in Monroe, WA

King County’s Native Plant Guide has a list of sources, as does PlantNative.

diseases that affect peony plants

I planted some peony bulbs last year and they grew nicely until they reached about 10 inches high. One was in the ground, and the other is planted in a medium sized pot outside. The one in the ground is now dead, and the other one is not looking good. It gets dark spots on the leaves, and then the leaves die. Can you help?

Without additional details, it is difficult to say what may be wrong with your peonies. The Penn State Extension has information on different diseases that can affect peony plants. What you describe sounds somewhat like peony leaf blotch or measles, as shown in Iowa State University’s Plant Pathology webpage on peony diseases. Here is an excerpt:
“Peony leaf blotch is also known as measles or stem spot. Warm, humid weather provides optimal conditions for infection by the causal fungus, Cladosporium paeoniae.

The leaf spots are glossy and purplish-brown on the upper sides of leaves. On the lower sides, spots are chestnut-brown. Infection is generally more pronounced at the margins of outer leaves. Leaves may become slightly distorted as they continue growing.

Fungal infections on young stems first appear as elongated, reddish-brown streaks. As plant growth continues, infected tissue near the crown may darken and become depressed. Stems on the upper portion of the plant may show individual, raised spots.
To manage peony leaf blotch, cut the stems at ground level in the fall or early spring. Rake the area before new shoots appear. Fungicides are available to help control the disease, but must be used in combination with other management practices. Also, providing good air circulation and avoiding wetting the leaves when watering can help reduce disease severity.”

There are other possibilities, including peony blight, also known as Botrytis blight. The Royal Horticultural Society discusses this problem:
“Peonies collapse at soil level and the stem bases are covered in grey mould. In a severe attack the leaves are also affected and the plant may be killed or so badly weakened it fails to sprout again next spring. Infections also occur frequently behind the flower buds just before they open.

This is a disease that affects both herbaceous and tree peonies. It is caused by a fungus (Botrytis paeoniae) related to grey mould (Botrytis cinerea), which may also attack peonies in a similar way.

Wilt is encouraged by high humidity which builds up around dense clumps of peonies. Increase the circulation of air by thinning out overcrowded shoots. Also avoid over-feeding, especially with nitrogen-rich fertilisers, which encourages lush, disease-prone growth.

Cut out all infected stems well below soil level, as soon as you notice them. Don’t put infected material in the compost bin but burn it or put it in the dustbin, preferably in a sealed bag. If whole plants are badly affected lift and destroy them in their entirety along with the soil surrounding the roots. This total destruction is essential as the fungus can produce black resting bodies (sclerotia), which survive for long periods in the soil ready to re-infect new peonies.

There are no fungicides available to amateur gardeners at present.”

I recommend taking plant samples to your local county extension agent for diagnosis.

a variety of hydrangea called ‘Miss Belgium’

I am attempting to find detailed plant information on a variety of hydrangea called Hydrangea macrophylla ‘Miss Belgium’, and can find very little in my plant books and online. Do you have any suggestions? Some of the details I am looking for are flower shape and size, plant habit, height & spread, and foliage details.

I found some information about Hydrangea macrophylla ‘Miss Belgium’ in Glyn Church’s book, Hydrangeas (Cassell, 1999):

An excellent pink in alkaline soil or in containers. The plant is ideally suited to pot and tub culture as it stays small and compact (3 ft.) and the rounded heads tend to be tiny, keeping the flowers in proportion to the bush. Its free-flowering habit and healthy nature are its good qualities. It is not the best plant for acid soils as the flowers will be a strident purple-blue.

There is a photograph of ‘Miss Belgium’ in Corinne Mallet’s Hydrangeas: Species and Cultivars (vol .1).

Heritage Hydrangeas’ website (no longer available) has this description: “Bright magenta-red on neutral soils or purplish blue on acidic soils, the centre of each floret is always white. Impressive flowers on a compact shrub.”

sowing and growing Magnolia seeds

I have a Magnolia wilsonii in my garden, and this year there
is a definite profusion of seed that followed a long flowering season (I’m collecting more every day). What is the best way to sow and grow these?

According to the American Horticultural Society’s Plant Propagation,
edited by Alan Toogood (DK Publishing, 1999) you can collect fresh seeds
in the fall, and thoroughly clean them (the book recommends using a
fungicide to prevent rot or damping off). To extract the seeds, gather the
ripe cones and dry them until the fleshy fruits come away. Soak them in
warm water with liquid detergent for a couple of days to remove the outer
coating. Once softened, drain the water. Remove any flesh still attached,
and dry the seeds with tissue. Sow fresh and overwinter in a cold frame,
or mix with moist vermiculite, sand, or peat, and store in a plastic bag
in the refrigerator for 2 months before sowing. Seedlings may be
transplanted the following summer, and put back in the cold frame for a
second winter.

Another method is to stratify the seeds for 3-6 months at 41 degrees
Fahrenheit, sow under cover in spring with bottom heat (68 degrees) for
germination to take place in about a month. It will take plants grown
from seed from 3 to 10 years to flower, but some species take much
longer.

Texas A & M University’s horticulture department has an article on starting Magnolia from seed. The article focuses on Southern magnolia, but should still be relevant. Here is an excerpt:
“The seeds should be collected as soon as possible after the fruit is mature which is usually mid-September or early October. The cone-like fruit should be spread out to dry for several days until they open. The seeds can then be shaken from the dried cone or fruit.

“If the seed is to be kept for any length of time, the red pulp should be allowed to dry enough to lose its fleshy character, placed in sealed containers and stored at 32 to 41 degrees F. If stored over winter at room temperature seed will lose its viability. The seed should be cleaned before planting or stratifying. To remove the fleshy seed coat, soak the seed overnight in warm water. Remove the seed coat by rubbing against hardware cloth or window screening. After cleaning, the seeds should be sown immediately or stored for 3 to 6 months at about 40 degrees F and planted in the spring. An excellent way to stratify seeds is to use a polyethylene bag and place alternating layers of a moist medium such as a sand and peat mixture and seeds in the bag. Tie the top of the bag and place in a refrigerator at about 40 degrees. The medium should be just moist enough to stick together but not so wet that it will drip if squeezed by hand.

“Whether sown in the fall or stratified in the refrigerator and sown in the spring, the seeds should be covered with about l/4″ of soil and mulched to prevent drying. Seedbeds should be kept moist until germination is complete. Partial shade should be provided the first summer for seedlings.”