Monday, October 22, 2012

Potassium Feast Follow Up

I'll be completing my sixth and final application of postassium this week.  The canes on my roses are a beautiful dark red; all hardened off for the cold weather to come.

Someone in the U.K. who read my blog raised a valid question on a garden chat site about the level of chloride (salt) being applied to the beds with Muriate of Potash and suggested that perhaps Potassium Sulfate would be a better form of potassium for the roses.  That's a good idea and I will be looking into the availability of Potassium Sulfate next year, if for no other reason to add a little sulfur to my soil.

However, in reality, the level of salts being applied with one tablespoon of Muriate of Potash per three gallons of water is quite small and well within good soil management limits.  Here is an excerpt from an e-mail I exchanged with Dr. Peter Bierman, Professor Emeritus of the University of Minnesota Soil, Water and Climate Department, in February 2011:

" I agree that winter hardiness is one of the most important functions of potassium. The rate you quoted would be about 0.1 lb K2O per plant per year. U of M recommendations for a flower garden for a soil testing low in potassium is 0.4 lb K2O per 100 sq ft., which would be close to that recommendation. So even if your soil tested high in potassium it would be a reasonable amount to apply for winter hardiness insurance and wouldn't be an excessive amount in terms of adding high salts."

Bottom Line:  The "Potassium Feast" has worked for me for 20 years without a problem and falls well within the limits of good soil management.

I would enjoy hearing from others who have tried the "Potassium Feast" this year.  E-mail me:  .

Friday, October 19, 2012


Well, the JBs have found their way into my lawn as grubs, chewing as they went; the spider mites have hopefully gone dormant after our first hard frost here in Minneapolis; and the deer can't do too much more damage, after the roses go dormant.  So, there's nothing else to worry about except winter-protecting the roses, right?  Not!  Now it's time to start protecting the roses from winter's nastiest pest: Voles!

These voracious little rodents are also known as meadow mice, which is a much kinder name than they deserve.  What they do, if you haven't experienced them, is burrow around in the mulch and winter-cover in your rose beds and eat the bark off the roses, right down to the cambium, which, of course, girdles the canes and kills them.  It has happened to me and I had to cut all the plants in one of my beds right to the ground and, in some cases, below ground level to save them.  Thankfully all of my roses grow on their own roots, because otherwise they would not have survived.

Here are a few facts about voles from a North Carolina State University article: 

Characteristics: "Voles are small mammals, commonly called meadow mice, that live in field and shrub habitats. In the wild, voles forage on native vegetation and provide a valuable food source for predators such as weasels, hawks, and snakes. In horticultural plantings, including flower and shrub plantings and home orchards, however, voles can cause damage by eating flower bulbs, girdling the stems of woody plants, and gnawing roots. Plants not killed outright may be invaded by diseases or die from water stress during periods of drought."

Reproduction: "Female voles have a gestation period of 24 days, have an average litter size of 2.8, and produce four to six litters per year. They reach sexual maturity at 37 to 38 days and have a reproductive life span of 15 to 18 months."

That's a pretty amazing, geometric, reproduction rate so it's easy to see how they become an infestation in and around your garden, requiring yearly control, as they have in mine.

Here's the address of the NCSU article if you'd like to read more:

And here's what voles look like:

Vole Control

Fortunately, there are several things you can do to protect your roses from voles. 

Castor Oil: This is the most effective solution I have found.  Voles really don't like castor oil; apparently, from what I have read, it makes them sick, and they avoid an area on which it has been applied.  Mix one or two teaspoons of castor oil (I use more rather than less) and one teaspoon of liquid detergent, per gallon of water, and apply it liberally around the bases of your roses and generally around your rose beds, where the voles might travel/burrow in the winter.  The best time to do this is in late Fall, when the ground is lightly frozen, just before putting your final mulch or leaf cover around your roses. Around here, that would be in mid to late-November.  I mix it in a 30-gallon trash container, pump it out with a sump pump, and apply it with a hose and watering wand, exactly like I do liquid fertilizers and potassium. You can also use a sprinkling can to apply it, if your garden isn't too big. You'll also get a good idea of how castor oil clings to anything on which it is applied if you run your hand around the inside of the trash container or sprinkling can, after you're finished.  It's still clinging to mine, after a full year of using the can to apply other mixtures.

The article below suggests using a hose-end fertilizer applicator and I think that might be a good idea.  The article describes the success a commercial hosta grower in New Hampshire has had with castor oil to protect his hosta fields.

(P.S. There's also an interesting article about controlling slugs on hostas on his website.)

So, my immediate question, after reading the article, was: Where the heck do I get castor oil?  I did some research on-line and found that you can order large quantities of castor oil, enough to last you for many years, relatively inexpensively, but I also found that buying more than you need for one year at a time is a mistake, because castor oil has a very short shelf-life once its container has been opened.  So, the best place I have found to buy just the right quantity of castor oil is Wal-Mart, in their health and beauty area.  Look in the laxative section, because that's what it's used for and, come to think of it, that's probably why it works on the voles! 

Rodent Baits:  Killing voles is desirable, before they over-run you, but this is a touchy subject because rodent baits can also affect other animals, like neighborhood cats and dogs.  The common rodent bait that you find in most stores is an anti-coagulant poison, which, when eaten a couple of times, stays in the intestines, causes massive internal bleeding and kills the animal.  I used it in my rose beds for years, without thinking, until about five years ago when we got a new kitten and he managed to find a mouse or vole that had eaten it, in among the winter-protected roses.  I will save you the terrible details, but it resulted in a very large emergency veterinary bill to save this humane society kitty and, fortunately, he is still with us (but he used two or three of his nine lives on that one).

After that experience, I went to work researching what other non-coagulant rodent baits might be on the market, and I found one.  The brand name is "Eraze", made by Motomco, the same company that makes the anti-coagulant baits.  The active ingredient in this one is Zinc Phosphide, which is nonetheless a poison, but acts in a different way, killing small animals immediately after ingestion.  There are conflicting opinions on this, but an article by Michigan State University indicates that it is less lethal to larger animals, such as cats and dogs, because their normal reaction after ingesting it would be to regurgitate it rather than digest it.  There is no question that it would kill any animal if eaten in sufficient quantity, but it apparently is less dangerous because it kills the rodent and dissipates rather than staying in the animal as the anti-coagulant does, thus potentially transferring to another animal or predatory bird (owl or hawk) that might eat the dead or dying rodent, as we believe our kitten did.  Note that Motomco also makes a similar product labeled as mole bait that uses Zinc Phosphide, so if you can't find Eraze, you can use the mole bait (check the label to be sure).  Other companies also offer Zinc Phosphide under different brand names.

Most important is how you use the bait.  The most common way of putting it in the rose beds is to use a tin can lying on its side alongside or between the rose bushes.  The can should be covered with leaves and/or protected in other ways (such as fencing) so that neighborhood animals can't get at it.  I also use the large, black, "Tomcat" poison dispensers that are usually found in warehouses or barns.  I put a couple of bricks or heavy stones on top of each container because animals like raccoons try to get the bait out of them by tipping them on their sides.  I also put a securely anchored cylinder of  24" fencing around each container to keep other animals away.

There is another device for dispensing rodent poisons that is made of L or T-shaped PVC piping buried in the winter protective leaf and mulch cover.  This method is used extensively in the University of Minnesota Landscape Arboretum rose gardens and is discussed in detail in the following article from the University of Missouri.  The article also deals specifically with Zinc Phosphide as the vole bait of choice and displays a graphic of the PVC dispenser, right at the end of the article.  I will leave you with that article for your perusal:

Bottom line is that in every winter I have either used rodent baits, applied castor oil, or both (as last winter), I have not had vole damage to any of my roses.  The one winter that I did nothing I had severe damage.  So, lesson learned: you need to do something to protect your roses from voles.

E-mail if you have any questions to: .

Saturday, October 6, 2012

Overwintering Potted Roses in the Garage

I contend that, if you want to learn anything about winter-protecting roses anywhere in the world, ask someone in Minnesota.  Historically, Minnesotans have experienced some of the harshest winters in the lower 48 states and that has given rise to the most unique ideas of winter rose protection you will find anywhere (witness the "Minnesota Tip").  I always chuckle when I read nationally published articles about winter protecting roses in zones 6 or 7, earnestly describing their "harsh" winters.  I grew up in zone 6 (Detroit) and all we ever did was rake leaves around our hybrid teas, with never a winter-kill problem.  Obviously not so in Minnesota, despite the fact that our winters have gotten significantly warmer in the last ten years or so. We're feeling a lot more like zone 5 than zone 4 these days.  (See my blog post: Climate Change in the Rose Garden:  ).

The members of the Twin Cities Rose Club (TCRC) are a bunch of smart northern gardeners and some of the best rose-growing ideas get published in the TCRC Newsletter, month-to-month.  A recent article by my friend Chris Poppe really caught my eye and I asked her if she would let me pass along her excellent article "Over-wintering Roses in the Garage" to the readers of the Minnesota Rose Gardener blog.  She enthusiastically agreed, so here we go.  Chris is a recently retired teacher from the Minneapolis Public School System; a smart lady with a beautiful rose garden on a small lot in Minneapolis (hey, she even grows broccoli alongside her roses)!  She's also the program chair of the TCRC.

Here's her article, along with some very good "how-to" pictures:

Over-wintering Roses in the Garage
by Chris Poppe
Every year, as I pile potted rose bushes (sans the pots) into the trench where I bury my tree roses, I wish that I could just leave some of them in their pots for the winter and save myself a lot of work.  But, that would only mean that I’d have a lot of dead, potted roses come Springtime.  So, I dig and bury until they’re all covered. 

Then, last year I went to the open garden offered by John and Char Turek at their farm in Chaska.  John has over 300 rose bushes in his garden - about 90% of them grown in pots.  Every Fall, John gives them all a good watering, cuts them way back and moves them to an insulated, but unheated, part of his barn, where they rest for the winter and emerge to grow and bloom another year.  Some of John’s roses are 5-10 years old and have lived in pots all their lives. 

That got me thinking.  Where and how can I replicate John’s storage area?  Living in the city, I have no barn, but I do have an unheated but sort-of- insulated garage.  Hmmm.   It’s a double garage and I have only one car, but it’s also the winter home of all my outdoor furniture (tables, chairs, glider, settee, etc), garden decorations, potting bench, lawn mower, wheel barrow, bicycle, etc. etc. etc.  Along the East side and into the SE corner, I have an old wooden picnic table which serves as a storage area for a lot of the folding furniture.                                                                             

I decided to build my winter rose shelter in that SE corner, so I shoved the picnic table about 3 feet to the North and lined the back and floor of the space with foil-faced, roll insulation.  I wedged a piece of 1” foam insulation into the space along the back wall of the garage, put another piece of foil insulation on the opposite “wall” and put a second piece of foam on the floor on top of the foil, so the pots would be separated from the floor.

The picture below shows the the start of the enclosure-building, with foil on the back wall and extending across the floor, a piece of foam insulation on the right wall and, although you can't see it, another piece of foam on the floor under the foil insulation.

Below is the enclosure as it was being constructed. The curved piece of foil will become the left side wall of the enclosure.

After watering the pots and cutting the canes back to about 10 inches, I wrapped  foil around each pot and made a small “hat” to put over the canes. Below is one of the pots ready to be put into the enclosure. The pot itself is wrapped in foil and I made a little cap of taped-together foil to cover the canes themselves.

 I pushed the pots into their insulated box, packing them together as tightly as possible. Then, I put another long piece of foil over the top of the space, tucking and taping it into place.   

When Spring came, I opened my  storage area to find that all four Hybrid Tea roses were already beginning to leaf out!

I then moved the pots out into the garden. Here is the wintered-over rose bush enjoying its first sunshine in more than five months

My "wintered-over" plants have grown and bloomed all summer.  Below is "Love's Kiss" in full bloom in mid May.

This fall, I’m going to try to winter over several more.  Give it a try in your storage shed or garage. This might lead you to a whole new program for growing roses!   

                                                                                            Chris Poppe

Editor's note:  Chris doesn't mention that one of the important things she is doing by enclosing her potted roses in foil insulation packages is not only to keep them insulated, but also to keep them in complete darkness throughout their dormant period.  Also, she mentions watering them before enclosing them.  I have read that watering the plants, but not soaking them, is the right way, which I'm sure is what she did.  At some point, perhaps half way through the dormant period, you can open them a bit and add a little more moisture, so they don't completely dry out.

I have used a similar, though less sophisticated, method, putting my pots on the wood floor of my trailer (i.e. off the concrete floor of the garage) and covering the whole trailer with a canvas top.  My garage is insulated and heated, so I am able keep them right at, or just above, the freezing point.  Another TCRC member, Millie Hisey, just puts her potted roses in the back of her pickup truck (which has a camper top), puts the truck in the garage, and goes to Arizona for the winter.  So there are several ways of doing this, but I think Chris' method is the slickest I've seen.

I'm sure Chris will be glad to take your questions.  Simply leave a comment/question at the bottom of the blog page, and I will pass it along to Chris.


Tuesday, October 2, 2012

Follow-up on Potassium Feast and Air Layering

Here are a few pictures showing current results of my previous posts on the Fall Potassium Feast and Propagating Roses by Air Layering.

As I mentioned in my article: Potassium - A Special K-Ration Feast For Your Roses: , after a few weekly applications of liquid potassium, the canes and stems of the plants start turning red, as they harden off on their way to dormancy.  I made my third application (of six) yesterday and here are a couple of pictures showing how my roses (Earth Song) look at the half-way point in the process:

Note how red the stems are becoming, as the potassium moves into the plants; also note the edges of the leaves and the vivid color of the flowers.  After the final three applications, this becomes even more noticeable.  I think it's quite beautiful.

Second, here is an update on the status of my air-layered maidens pictured in my article: Propagating Roses by Air Layering: .

As you can see, they have grown quite a bit in the last couple of weeks.  They are sunbathing for a couple of hours this afternoon, from their usual spot in a shaded cold-frame on the north side of my house.