Grevillea and cold damage

I have a Grevillea victoriae that I bought 2 years ago. It’s about 2 ft tall and is in a pot with bagged soil and sand added for better drainage. It hasn’t bloomed much, but it was trying. This year it has a lot of frost damage, and I’m not even sure it’s alive.

When can I expect to see new growth? Should I prune off the damaged areas and cross my fingers?

The usual rule of thumb about winter-damaged plants is to scratch the surface of a branch or stem with your fingernail to see if there is green underneath. If there is, that is a good sign. Then, you should give the plant until late June or early July to show signs of resurgence from the damage. I will include below an entire newsletter item on this topic from Plant Amnesty’s Cass Turnbull:

January 2009 e-mail newsletter: Is Your Frozen Shrub Dead? by Cass Turnbull

“After an extraordinarily cold winter in Western Washington, many garden owners will want to know what to do about the damage to many of our not-completely-hardy shrubs. With many of our broadleaf evergreens, it’s common for their leaves to turn brown or black and eventually fall off. The plants themselves are probably still alive. To check, use a hand-pruner blade to peel back a little bit of the “skin” to see if the cambium layer just beneath is alive (green) and not dead (brown). If alive, it’ll probably flush out with a new set of leaves. So don’t panic if you shrub looks dead. Wait and see. How long? By June you will have an answer.

“By then, those that can put on a new set of leaves will have done so. If you can’t stand the sight of the stricken brown shrub until June, try running your hands along the branches to knock the brown leaves off. Then, the plant might seem to be deciduous, not dead. By the end of August, the final report will be in. Freezing weather sometimes does internal damage that doesn’t show up until after the stress of the summer “drought”. A shrub may look okay through June and July, but then, while it is pumping H2O like crazy trying to keep up with the heat demand in August, some portions can collapse, and you will see die-back. (The non-scientific explanation is my own and may be a little, well, anthropomorphic.)

“Many evergreen shrubs, such as escallonia, that suffer freeze damage, will die from the tip back. These shrubs respond well to radical size reduction which in this case means big ugly cuts to the point of green wood. The plants will “break bud” just below your cuts and many new green-leafed shoots will rather quickly grow out to hide the cuts and provide you with a “new” plant by the end of the growing season.

“Often, (for example, in the case of choisya), branches will split, break or splay flat to the ground due to snow loading. Get your loppers out and whack everything back to 4″ to 6″ off the ground. Yes, it’s really Okay. I promise. I have done this thing many times. As soon as the growing season begins, the majority of cut plants will spring into action. As the renovated shrubs grow up, it is advisable to pinch them back every so often, to encourage branching and thicken them up. ‘Pinching’ means a very light heading, just nipping the end bud of each branch with your fingernails or hand-pruners.”

You may find this link to a Northwest grower of Grevilleas of interest, too.

On another topic, I’m curious about the mixture of potting soil and sand you are using for your Grevillea victoriae. If you were to add sand to most Seattle-area garden soil (which tends to be clayey), you would end up with poorly draining concrete-like soil. I would assume that potting soil which already has perlite or something similar in it for drainage and would not need an addition of sand. Are you planning to move the shrub into the garden at some point? This is a substantial shrub–the mature ones I’ve seen are at least 6 feet tall by the same width. If you can find a place in the garden for it, it might fare better. As you probably know, plants in pots tend to be more vulnerable to extreme cold.

on selecting Cladrastis

I am trying to help my neighbors select trees for their front garden. The trees will be in a parking strip that doesn’t have any structures near it or any overhead lines and it is on the north side of a fairly large 2-story house. We live in an old neighborhood with very large, grand trees. One tree I thought might be a contender, which is approved by the city (Portland, OR), is Cladastris kentukea. My only concern is that the seed pods might be messy. The neighbors themselves were thinking of aspen (nostalgic for them, as Coloradoans), but I didn’t think this was a good idea. What do you think?

I checked in a few places, and the main thing that might be disappointing is that in the Pacific Northwest, Cladrastis kentukea doesn’t flower reliably (although that solves the small trouble of seedpods, I guess!). Local tree expert Arthur Lee Jacobson says the following, in his book Trees of Seattle (2006):
“In nature this is an uncommon, even endangered species. It has been recorded to 87′ x 23′ x 96′ wide, and has reliable bright yellow or even yellow-orange fall color. Its heartwood is also deep yellow. Uncommon in Seattle, Yellowwoods are unreliable as flowering trees: their white flowers appear full force in some Junes, but are absent or weak in most years. They have no other faults except a branching habit prone to breaking up; careful pruning can help with this.”
(The Seattle-dwelling specimens of this tree which Jacobson lists are between 23-60 feet tall by 4 to 8 feet wide)

Below are links to information and images, from Oregon State University. This tree looks glorious when it flowers! Provided the spot is well-drained, and has no history of verticillium, to which Cladrastis is susceptible (see the link from SelecTree below for details), it seems like a great choice.

OSU

SelecTree

As an argument against aspen (Populus species, usually P. tremuloides in our area), Arthur Lee Jacobson mentions that they tend to sucker from the roots. The SelecTree site mentions twig and dry fruit litter, high allergen count, and numerous pest and disease problems.

lifespan of sword ferns

What is the lifespan of our native sword fern?

The native sword fern, Polystichum munitum, is discussed in local author Sue Olsen’s Encyclopedia of Garden Ferns (Timber Press, 2007). She does not mention the plant’s lifespan except to say that it will suffer and decline with excessive summer heat and humidity (more common in eastern and southern U.S.), and sometimes with long periods of freezing temperatures as well.

Sword fern has a reputation as a tough, long-lived perennial (i.e., returning year after year), and it readily self-propagates from spores, but I have not found any resources which mention the average duration of an individual plant. Most will survive in the Pacific Northwest for many years.

on the toxicity of Azaleas to cats

Are azaleas poisonous to cats?

Azaleas are indeed a problem for cats and other pets. See this link from Purdue University’s Veterinary Program.

Excerpt:
“These ornamental shrubs aren’t commonly nibbled on but they can cause fatal heart problems in dogs, cats, and pet birds. Signs to watch for are similar to that of the yews and include weakness, fainting, salivation, difficulty breathing, vomiting, and diarrhea.”

According to the Handbook of Poisonous and Injurious Plants, 2nd ed., by Lewis Nelson et al. (New York Botanical Garden/Springer, 2007), all Rhododendron species, including Azaleas, contain grayanotoxins in their leaves. Honey made from the flower nectar would also be toxic.

Betula jacquemontii and their susceptibility to pests

I am a professional landscaper in the Portland area. I am wondering if Betula jacquemontii have much of a problem with aphids or other pests. Everything I read says they do, but since this tree is one of the Great Plant Picks, I wonder if that’s not the case.

There is certainly the potential for aphids with this type of birch. I don’t think all the plants listed in Great Plant Picks are necessarily immune to problems, more that they can serve a particular purpose in the landscape. Betula utilis var. jacquemontii is also susceptible to bronze birch borer, according to Oregon State University.

University of British Columbia Botanical Garden Forums includes a discussion of the merits (or not) of this tree, including this comment from Seattle-area gardening expert Ron Brightman:

“Silver birch is customarily Betula pendula. It grows large and is an aphid magnet in my area. Betula utilis jacquemontii does not produce the same elegant weeping habit. But the clone commonly sold here displays stark white bark. Mine became infested with what looked to be the same leaf miner that can be quite abundant on native stands of B. papyrifera north of here. Finding the effects of the miners tiresome and this not being a rare tree here, I cut it down. Since native paper birch trees are abundant around Vancouver I would wonder if you might end up with the same problem.”

Here’s another link of interest, from Washington State University. It mentions that “this tree is susceptible to bronze birch borer, a wood boring beetle that will girdle the trunk. Aphids can be problem on the foliage. Excrement from aphid feeding can leave the ground sticky beneath this tree.”

Jacquemontii birch is common as a street tree in Seattle, and as the neighbor of a row of three of these birches, I can say that so far they appear relatively pest-free (I’ve seen a hint or two of sticky aphid honeydew on the leaves ), but they make voluminous leaf and bark litter which blows into my garden. I keep thinking the bark is wastepaper (grocery receipts, etc.). It looks great on the trees, but is a minor nuisance when blown far and wide.

the fruit infesting Spotted Wing Drosophila

Could you tell me more about a new type of fruit fly that is supposedly infesting fruit here in the Pacific Northwest? Which fruit are affected?

The fruit fly is called the Spotted Wing Drosophila. It is known to affect strawberry, raspberry, blueberry, plum, peach, cherry, and grape. Oregon State University has created an information clearinghouse about this pest. Here is their information for home fruit growers. Washington State University has also devoted several web pages to this fly. Here is their Integrated Pest Management information, excerpted below (SWD stands for Spotted Wing Drosophila):
“Monitor for SWD using traps. […] These vinegar traps are for monitoring purposes only and will not provide control of SWD. Remember, chemical control is not necessary if SWD is not present.
Composting fruit will likely not be effective at destroying maggots and pupae.
Remove infested and fallen fruit. Destroy or dispose of infested fruit in a sealed container.
Management recommendations are currently being developed for this pest. For the time being, good sanitation practices should be used.”

Whatcom County Extension has clear, basic information for home gardeners as well. Since this insect is a relatively recent invader in the Northwest, information is constantly being adjusted and research is ongoing.

distinguishing between mosquito larvae and tadpoles

I’ve been noticing creatures in my garden pond that I’m hoping are not mosquito larvae. How can I tell the difference between mosquitoes and tadpoles? I wouldn’t mind having frogs, but I don’t want to breed mosquitoes!

The following may help you tell the difference between mosquito larvae and tadpoles.

Mosquito (note their hairy appearance):
New South Wales Mosquito Monitoring image 1

Tadpole (note their smooth sides):
University of Richmond biology professor W. John Hayden’s photos

If you are concerned about mosquitoes in your pond, there are a number of preventive steps you can take. Mosquitoes are less likely to thrive in moving water, so you may want to install a submersible pump. Washington State University Extension provides information for homeowners on West Nile virus prevention and mosquito control. Here is an excerpt:
“Manage weeds; keep vegetation short around water. Adult mosquitoes are attracted to dense, tall vegetation around water.
Remove unnecessary floating structures or debris from ponds. Mosquitoes are often found around floating debris.
Keep drains, ditches and culverts clean to allow proper drainage.
Consider stocking ornamental or permanent, self-contained ponds with insect-eating fish, such as goldfish.
Shape pond edges to a shelf or steep slope. Mosquitoes prefer shallow pond edges.”

grafting pears

Can I graft an Asian pear onto Anjou rootstock?

Anjou is a European pear variety, and European pears are the species Pyrus communis, which is not an acceptable rootstock for Asian pears, according to a Pacific Northwest Extension publication by Robert Stebbins on “Choosing Pear Rootstocks for the Pacific Northwest.” Here is an excerpt:
“Asian pear trees require rootstocks that impart a high state of vigor. No Pyrus communis rootstocks are vigorous enough for most Asian pears, with the possible exception of the most vigorous Old Home x Farmingdale clones.

Asian pears require vigorous rootstocks such as P. betulaefolia or P. calleryana. Unfortunately, their cold-hardiness isn’t well-known.”

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.