a case of the slime flux

I have a client whose Clematis I just renovated. The client called to say the ends of the cut stems were frothing! What could be causing this?

My best guess (and it is only a guess, since I am basing it solely on your description) is that it could be slime flux. According to the Royal Horticultural Society, “pruned stems may fail to reshoot and ooze a sticky substance–this is known as slime flux.” To confirm this theory, ask the client if the frothy ooze was pinkish orange in hue, and if it had an unpleasant odor. Here is more about this problem from the Daily Telegraph’s garden advice column by Helen Yemm excerpted below:
“This is not so much a disease as a condition that affects some trees and shrubs in spring. Bacteria enter the plant through cracks in the stem – which may well be caused by a combination of adverse weather conditions – and then attack the sap as the plant springs into action early in the year.

Slime flux is often fatal but it depends where the damage is. Everything above the oozing wound will certainly die and should be cut down. However, the plant may well shoot out from below and recover.

Slime flux will not spread to other plants as diseases do, nor will it contaminate the soil like clematis wilt. However, its occurrence would indicate that, for some reason, the general growing conditions in that part of the garden have become unsuitable. If you do lose your clematis, then perhaps it would be a better idea to plant a new one in a less exposed spot.”

primroses and common pests

I have grown primroses both in Seattle and in South Everett. The first time the plants looked like the leaves were being eaten, and then when I pulled one of the almost-eaten plants out of the pot, most of the roots were gone. When I cleaned out the pot, I found many little white grubs in the dirt. It happened again in my new location. I am mystified, as I grow them in pots on a second floor balcony. What could be causing this and is there a way to grow primroses without this happening?

I wonder if the problem is in the potting soil. Were you using the same batch each time? It might be worth experimenting with a new brand of potting soil to see if you have the same or different results.

Also, you could try purchasing your plants from different sources. The ones you have now may have come to you from the nursery already infested.

There are a number of pests that afflict Primula. Of the culprits listed on University of California, Davis’s Integrated Pest Management site, weevils might be a possibility, as their larvae (grubs) live in the soil. The recommended treatments include parasitic nematodes and trapping of adult weevils. Here is more on this pest, from the Connecticut Agricultural Experiment Station.

differentiating between Beesia deltophylla and Beesia calthifolia

What is the difference between Beesia deltophylla and Beesia calthifolia?

In her book Gardening with Woodland Plants (Timber Press, 2007), Karan Junker says the following about Beesia:
“It is normally represented in cultivation by the species B. calthifolia. Apparently embossed veining enhances the flossy, leathery, heart-shaped leaves. Upright spikes of starry white flowers are produced from midspring into summer. Beesia deltophylla is similar.”

In American Nurseryman, vol 194, no. 12 (2001), p.66, Beesia deltophylla is described as a Dan Hinkley / Heronswood introduction grown from seed collected in Sichuan Province in 1996. “Airy, white, 1-foot racemes that appear in May through July; produces corpulent rosettes of glossy, deep-green, heart-shaped leaves up to 5 inches long.” Under the heading of how this plant differs from other species or cultivars, it simply says “durable, evergreen perennial.” It clumps but does not colonize, has a moderate growth rate and prefers light shade, and a well-drained but moist site.

Beesia deltophylla has fewer teeth and less texture, according to this article by Robbie Blackhall-Miles in The Guardian (May 1, 2014):
“A little later [after George Forrest discovered and named Beesia cordata–what we know now as B. calthifolia], Frank Kingdon Ward discovered a second species of Beesia in Burma which was named Beesia deltophylla. Very similar to B. calthifolia, this plant only has about 15 teeth on each side of its leaf as opposed to B. calthifolia’s 50, and lacks the interesting texture in its leaves. To this day, the two species are confused in cultivation.”

Here is more on B. calthifolia, from Flora of China. This site differentiates between the two species in terms of the veining on the leaves.

shade tolerant rhodie

Do you have a recommendation for a particularly shade tolerant rhodie? I have dappled shade, but also some areas of fairly deep shade. I’m in the Portland, OR area.

Generally speaking, rhododendrons are tolerant of shade, but need some light if they are to produce flowers. According to Rhododendrons in America by Ted Van Veen (Binford & Mort, 1969), “the larger the leaf, the more shade required … In the Pacific Northwest … most varieties look their best if they have about one-third shade when the sun is warm.”

Dappled shade should be fine for most rhododendrons, but deep shade might mean that you end up with a non-flowering shrub. Look for large-leaved species or hybrids. These are sometimes referred to as elepidotes (generally, this term refers to hybrids with large leaves and flowers that grow in relatively large clusters).

Below are just a few examples of the hundreds of species and hybrids available. (Images and information from Oregon State University are included)

R. catawbiense

R. macrophyllum

Marjatta hybrids

Here is a list of Proven Performers for Oregon, from the American Rhododendron Society:

(These are the recommended large-leaved cultivars from the Portland Chapter:)

‘Blue Peter’
‘Cynthia’
‘Lem’s Cameo’
‘Mardi Gras’
‘Mrs Furnival’
‘Odee Wright’
‘Taurus’
‘The Hon. Jean Marie de Montague’
‘Unique’

magnolia tree root systems and damage potential

Does a magnolia tree root system cause cracking on the house foundation if planted too close, especially on clay soil?

What kind of magnolia are you growing? Is it deciduous or evergreen? Is it large species or one of the smaller varieties?

According to SelecTree, a website of the Urban Forest Ecosystems Institute, most Magnolias have a low root damage potential. A few, such as Magnolia delavayi, are rated as moderate. I am not an arborist, so I cannot conclusively tell you that a Magnolia will not be problematic for the house foundation. However, it is always a good idea to plant trees far enough away from structures so that you do not have to do a lot of pruning to keep them from conflicting with windows, entryways, the roofline, etc. From what I have read, most tree roots that harm foundations are not themselves causing the cracks, but are exploiting preexisting weak points in the foundation. Roots do expand in size as the tree matures, and they do seek out water to some extent, depending on the type of tree.

Below are some links to information that may be useful to you.

North Dakota University Extension (no longer available online)
Excerpt:
“How close to the home should trees be planted?

Large trees such as ash, hackberries, maples, lindens and oaks should be kept at least 20′ from the foundation. Medium sized trees such as buckeyes, honeylocust and little leaf linden – 15-20 feet away and small trees such as flowering crabs, mountain ash and Canada red cherry – 10 feet from the foundation.

Do tree roots actually crack the foundation?

No, the wetting and drying of the clay soil causes the initial cracks. After these have developed, tree roots will grow into the cracks for moisture.”

A personal essay on tree roots and foundations, from Renegade Gardener,a garden blogger

International Association of Home Inspectors
Excerpt:
“Tree Roots and Foundations

Contrary to popular belief, InterNACHI has found that tree roots cannot normally pierce through a building’s foundation. They can, however, damage a foundation in the following ways:

Roots can sometimes penetrate a building’s foundation through pre-existing cracks.
Large root systems that extend beneath a house can cause foundation uplift.
Roots can leech water from the soil beneath foundations, causing the structures to settle and sink unevenly.”

on low hazard pesticides

I heard somewhere that the fungicide Rose Pride was less toxic to beneficial insects than plain baking soda. Is this true? I’d like to continue to use it in my garden.

Rose Pride is the chemical Triforine. I was not able to find any articles which suggest it is safer for beneficial insects than baking soda. Pesticides Action Network’s Pesticides Database indicates it is toxic in varying degrees to some forms of aquatic life. It is on the PAN List of “Bad Actor” pesticides, which means it belongs to a group of pesticides classified as most toxic (because they are known or probable carcinogens, reproductive or developmental toxicants, etc.). The Extension Toxicology Network also has a profile for this pesticide. Here are excerpts:

“In the United States, triforine is marketed for use on almonds, apples, asparagus, blueberries, cherries, hops, ornamentals, peaches and roses. Triforine is a ‘restricted use’ pesticide (RUP) with an EPA toxicity classification of I (highly toxic). Check with specific state regulations for local restrictions which may apply. Products containing triforine must bear the Signal Word ‘Danger’ on their label.

Triforine and the formulated product Saprol are considered of low hazard to honeybees and to the predatory mite Typhlodromus pyrii. It is also of low hazard to earthworms at recommended dose rates.”

My comment would be that “low hazard” is not the same as no hazard, and since there are many other areas of concern with this highly toxic product, it would be best to find an alternative. Locally, the Woodland Park Rose Garden converted a pesticide-dependent landscape to an organic one, and the roses look better than ever. (See an article about the garden from the Seattle Times.) Many gardeners are learning to live with a bit of black spot on their roses, and manage the disease by maintaining good garden hygiene. Don’t leave fallen leaves on the ground. Give your roses good air circulation, and keep the leaves dry when you water your plants. Mulching with wood chips can help, too, since they may prevent water from splashing up onto the leaves.

When deciding whether to treat a garden problem with pesticides, the “Precautionary Principle” provides an important perspective:
“When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically.”

fungal growth on trees

I have a 50-year-old Italian plum tree. The limbs have oyster-shaped growths on them. These growths will not come off–they are hard. Is it a fungus or disease? Or is the tree just getting old?

Hard fungal growths on trees are called conks, a type of bracket fungus, and they are not a good sign. According to The Sunset Western Garden Problem Solver, these growths “indicate a hazardous condition from decay inside.” Usually by the time they are seen, decay inside the tree is substantial and you may need to get an arborist’s help to keep the tree from breaking and dropping branches, and to assess whether it is a danger to structures or people. The Pacific Northwest Chapter of the International Society of Arboriculture provides a listing of local certified arborists. You can also get an arborist referral from Plant Amnesty.

on Cape fuchsia and tree fuchsia

I live in the Western Cape of South Africa. I’d like to plant a Cape fuchsia near a wall in a small garden. Can I do this without concern that the roots will lift the wall?

What we call Cape fuchsia over here is a shrubby perennial, not more than 4 feet tall in most cases. Its Latin name is Phygelius. It does tend to spread around the garden, and it is not easy to dig up its root system, but perhaps you may be talking about a different plant in the same family, Halleria lucida. Here it is sometimes called “tree fuchsia.” According to Pitta Joffe’s book Creative Gardening with Indigenous Plants: A South African Guide, Halleria lucida “has a non-aggressive root system,” so it is unlikely to damage your wall. Keep in mind that the mature size is about 6 meters in height and up to 5 meters in breadth, so planting it too close to a wall may not be ideal in the long run. Pitta Joffe highly recommends the tree because it attracts sunbirds and canaries with its nectar and many other birds with its fruit.

dwarf tree fern plant culture and care

I recently purchased a plant which the grower referred to as Blechnum gibbum, or dwarf tree fern. I have searched many databases including the BBC, IPNI, and fern societies. Ultimately, I would like to discern the accurate, current name for the plant and plant culture and care information for in-home.

I confirmed the name Blechnum gibbum on the Royal Horticultural Society’s website, as well as in Sue Olsen’s Encyclopedia of Garden Ferns (Timber Press, 2007). For now you can safely assume that Blechnum gibbum is the correct, current name for the plant commonly called dwarf tree fern. It is a member of the family Blechnaceae, native to Fiji, and commonly grown as a houseplant in North America.

According to The New Houseplant Expert by D.G. Hessayon (Sterling, 1991), tree ferns require a temperature range between 60 and 70 degrees Fahrenheit (over 75 is a problem), an east or north facing window (or some shade in a hotter exposure), moist air (misting ferns can help with this), regular watering (particularly in spring and summer), and repotting so that the crown is not buried and the pot is not overly full of roots. The House Plant Encyclopedia by Ingrid Jantra (Firefly Press, 1997) says much the same thing, adding that temperatures below 54 are also a problem and that a light feeding once a month is helpful.

cedar wood chips and allelopathy

We’ve taken down some big cedars and chipped the branches. I’ve heard that cedar mulch can damage plants. What is your take on this? I already put it around some choice pines and some viburnums, but I could move it if need be.

Washington State University Extension horticulturist Linda Chalker-Scott has written about this very issue, and her scientific research on the subject says that cedar (both Thuja and true Cedrus) wood chips are not allelopathic (toxic) to plant tissue. Here is the article.

This author has further information on the general benefits of wood chips as mulch. Here is a newer Washington State University factsheet on the subject.

Allelopathy, Mulching, Wood chips