River birch and root damage potential

A landscaper planted a River birch next to our house 9 years ago. The roots are everywhere. We heard that this is one of the worst trees to plant next to a house. We have a basement. What should we do?

River birch (Betula nigra) is rated as having moderate root damage
potential by the Urban Forest Ecosystems Institute.

The following, from University of Saskatchewan’s “Guide to Birch Trees,” supports what you have heard about planting this tree near a structure, but takes the approach that it is not good for the tree, rather than a danger to the foundation. Excerpt:

“On a healthy birch, the roots will spread to a distance of at least twice
the tree’s height. This means that the roots of a mature tree may cover
an area about one third the size of a football field. To permit proper
root spread, trees should be planted as far as possible from any
obstruction that may interfere with root development. Sidewalks,
driveways, patios and building foundations will all limit root
development. Where a tree is growing on heavy soils, aeration holes will
help maintain root vitality.”

Tree roots are not likely to infiltrate a solid foundation, but if there
are cracks, it is certainly possible, and if tree roots expand
sufficiently over time, they may begin to exert pressure on the
foundation. However, birch roots are shallow, as indicated in this USDA
Forest Service guide to growing birch trees.

It is not a good idea to plant any tree right next to a house, if only
because the tree will undoubtedly require pruning to keep it out of the
way of windows, doors, and so forth. If you like the tree and would like
to move it to a better spot, you should consider contacting a certified
arborist. Here are links to referral services.

Plant Amnesty

Pacific Northwest Chapter of the International Society of Arboriculture

diseases affecting beans

I have grown runner beans in the center of England for
several years, with good crops and healthy plants, but this year my
plants have some sort of disease. The leaves have brown spots which seem
to spread along the leaf veins and then over the whole leaf. Some plants
are still producing healthy beans, but on some plants the beans have shrivelled
and turned yellow. I don’t know if these are the same plants with the
worst leaf problems as the plants are tangled together too much. I have
looked at various websites, but am not sure that any diseases shown
correctly match my problem. I would be very grateful if you have any
idea as to what it is and how to deal with it.

While I cannot diagnose the problem remotely, your description does sound
quite a bit like anthracnose, which is a fungal disease. According to The
Organic Gardener’s Handbook of Natural Insect and Disease Control by
Barbara Ellis (Rodale Press, 1996), this disease thrives in wet, humid
conditions. You would see leaves with dark streaks, and black petioles
and veins on the underside of the leaves. If this is indeed the problem,
plants may be sprayed with sulfur, or you can seek out resistant
cultivars next time around (‘Espada,’ ‘Marbel,’ Morgane,’ and ‘Rocdor’
are a few).

On the other hand, the yellowing of the seed pods sounds more like
bacterial blight, also encouraged by warm, damp weather. If your plants
are not forming any new pods, remove and destroy them. Next time you
plant, be sure there is adequate space between plants, and perhaps
rotating the crop to a different location might help.

Just to give you some basis of comparison, here are links to sites with
information about diseases affecting beans:

Cornell University Vegetable MD Online

University of California, Davis Integrated Pest Management

Royal Horticultural Society lists several problems affecting runner beans. There is a fungal disease of broad beans called chocolate spot which sounds a little like what you describe.

how poisonous are poinsettias?

Just how poisonous are poinsettias? My mother lives in a nursing home, and the director just confiscated nearly 200 potted plants that were donated to residents for the holidays. I think he overreacted. Do you agree?

I agree with you. It is a fact that poinsettias (Euphorbia pulcherrima) are in the Euphorbiaceae family, and the sap of plants in this family is irritating to the skin and eyes. However, it seems highly unlikely that people would be exposed to the sap of these plants, and it would take eating large quantities of leaves to become seriously ill. It’s not a good idea to eat the leaves of most indoor plants, in any case.

There is information about the degree to which poinsettias are poisonous on the following sites:

It’s possible the director of the nursing home was alarmed by a recent news story about a local woman who went to the emergency room after weeding in her garden and getting Euphorbia sap in her eye. There is a big difference between stationary houseplants which one mainly looks at without touching, and the aggressive and weedy Euphorbia species one pulls from the garden (only with gloves and goggles)!

on planting Darwin tulips

Will my Darwin hybrid tulips come back every year?

In his book Ask Ciscoe (Sasquatch Books, 2007), local garden expert Ciscoe Morris suggests planting Darwin and Empress hybrid tulips 12 inches deep (rather than the often recommended 6 inches) so that the bulbs will be less likely to divide and the squirrels less likely to dig them up.

Ann Lovejoy says much the same thing…plant tulips 10 inches deep, in a sunny spot, and in well-drained soil, and some are likely to return for several years. (See Seasonal Bulbs, 1995, p.16)

on glossy-leaved fringe trees

Which varieties of fringe tree have glossy leaves? I am especially interested in a comparison between C. virginicus and C. retusus.

More than one variety of fringe tree (Chionanthus) is described as having lustrous leaves. According to Michael Dirr’s Dirr’s Hardy Trees and Shrubs (Timber Press, 1997), Chionanthus retusus has “3- to 8-inch long, lustrous dark green leaves,” while C. virginicus has “3- to 8-inch long leaves [which] vary from medium to dark green, with various degrees of gloss.”

If you wish to see images, you can search Google images with the different species names. Oregon State University’s online guide to Landscape Plants has good detailed images and descriptions of these two species of Chionanthus.

lists for invasive and noxious weeds

Can you provide me with an extensive list of resources for checking whether a plant is invasive or a noxious weed?

Here is a list of helpful resources:

Washington State Noxious Weed List from the US Department of Agriculture

State noxious weed list and schedule of monetary penalties from the Washington State Legislature

Class A, Class B, and Class C

Washington Department of Ecology (aquatic plants)

Washington Invasive Species Coalition and their GardenWise handbook

King County Noxious Weed Lists

National Invasive Species Lists

Plant Conservation Alliance Alien Plant Invaders list

Invasives in British Columbia

The lists which are national in scope are useful too, as some plants not
yet officially listed as invasive here may still be plants to watch out
for.

There are a great many books on this subject. A recent one, co-authored
by a faculty member here, is Invasive Species in the Pacific Northwest edited by P.D. Boersma, S.H. Reichard, and A.N. Van Buren; Rebecca L. Gamboa, photo editor.
University of Washington Press, c2006.

fast-growing shrubs for privacy

I will be having a very overgrown, rarely pruned laurel removed from my back garden. It has been, if a monstrosity, an effective visual screen. The bare area that it leaves is appproximately 40′ in length, is atop a rockery, approximately 3′ high, and will look up into the neighbor’s back hillside, while they peer down at us in dismay. Can you suggest one or several fast growing, shrubby plants or suitable trees that will act as an attractive visual screen? I do not want bamboo.

Here are a few ideas:

Morella californica

Thuja occidentalis ‘Smaragd’

Osmanthus delavayi is also a good choice, but it doesn’t get quite tall
enough–my own hedge, which is pruned at least twice a year, is about 8
feet tall, so if I really let it go, maybe it would be 10-12 feet.

Juniperus scopulorum ‘Wichita Blue’

Juniperus virginiana ‘Manhattan Blue’

Viburnum tinus

Ceanothus would also be striking, with blue flowers, but you’d need to
find the tallest possible species, and they tend to be short lived.

You could plant a mixed hedgerow, which would allow you to include some of the flowering plants you prefer. King Conservation District has more information on hedgerows.

usage of sawdust as mulch

We recently had a large blue spruce tree cut down and had the stump ground. Would the resulting sawdust be a good mulch for roses?

Also, what is your opinion of using a pre-emergent herbicide for weed
control in our rose bed?

Sawdust has high carbon content and may rob soil of nitrogen and moisture. It is also recommended for acid-loving plants and may be problematic for roses. There may also be compaction problems with sawdust, so it may need to be combined with other mulching materials to improve water penetration. Sawdust also decomposes slowly and compacts (Source: Mulch It! by Stu Campbell, Storey Communications Inc., 2001).

You may also be interested in two articles by Linda Chalker-Scott. In Wood chip mulch: Landscape boon or bane, she discusses the pros and cons of wood chip mulch. She also comments on sawdust in an article called The Myth of Pretty Mulch.

If you had spruce chips, they would be fine for mulching roses. Avoid
letting mulch touch the main stem; the goal is to pile it on the root
system away from the stem. You can remove it in the spring, or at least
be sure that it’s not too deep. While mulch protects from cold in the
winter and drought in the summer, if it’s too deep, water cannot get to
the root zone of the plant.

I would recommend that you avoid chemicals, as I find that you have to pay more attention when you use them than if you just wander through the garden now and then and pull all the weeds you see.

Pre-emergent weed controls never provide complete weed control. The most important thing to do is weed the area first, as pre-emergents only control weeds that have NOT sprouted. And if you have lots of seeds in the soil, don’t expect weed killer to eliminate them all. If water is required, beware of too much water (i.e., rain) that can wash away the herbicide.

Rather than use a chemical, I would weed the area now and then apply mulch. In addition to protecting the roots and soil, the mulch will suppress weeds, possibly until spring. You will have to watch for weeds that do sprout and be sure that you don’t let them go to seed. Otherwise, you will set yourself up for lots of future weeding. Chemicals don’t really help in situations like that, as you have to time their application perfectly. Hand weeding and mulching–well timed–can work better than any herbicide.

best time to fertilize rhodies, azaleas, and roses

Is it okay to fertilize my rhodies, azaleas, and roses in September? I missed
doing it in August.

Generally speaking, it is best not to fertilize your shrubs after mid-summer. The tender new growth that results is susceptible to frost, disease, and insects just at the time of year when the plant is beginning to shut
down. This is also true of roses, which are even more tender and susceptible than rhododendrons and azaleas.

An article by Terri Richmond (British Columbia) on the American Rhododendron Society website, entitled Fertilizing Rhododendrons the Organic Way supports the practice of fertilizing in spring. (Keep in mind that azaleas are in the same genus as rhododendrons.)

Oregon State University Extension suggests that budbreak in spring is a good time to fertilize roses, just as new growth is beginning. Stop fertilizing in late summer. Oregon State University also weighs in on fertilizing rhododendrons (if needed, in spring shortly after flowering, and preferably with organic fertilizer).

lack of flowers in star jasmine vines

I bought an established, white star jasmine perennial vine one year ago. I was told I could plant it in an extremely large pot and expect to enjoy blooms for about 3 years, but it has not bloomed, nor does it have any buds. It has no pests or blight of any kind. It gets full sun in the morning and partial during the day, and full again in late afternoon. It has always had sufficient water. What’s wrong? When do they normally bloom? Was I given inaccurate information?

I am assuming the star jasmine is Trachelospermum jasminoides, as shown in this image from Missouri Botanical Garden.

Failure to flower can be due to a number of causes, as described in this link from University of Vermont Extension.

My top guesses for what may be causing the lack of flowers would be exposure to
severe cold in the winter, or over-fertilizing with a nitrogen-heavy fertilizer.
The light exposure you describe sounds fine for this plant. In the Pacific
Northwest, it flowers mainly from spring to early summer. This link to
a Seattle garden writer’s site has cultural information appropriate for this
region (I don’t know where you are writing from).