How to Fortify Your Roses Against the Cold

– Posted in: Roses

Jack Falker is a rose enthusiast who gardens in Minnesota. Minnesota–in case you don’t have the USDA Hardiness Map memorized–is entirely a cold climate state, consisting of Zone 3 and 4. (Okay, there is a teeny bit of Zone 5 in the most recent map, but still.) One can’t grow roses in Minnesota without knowing how to grow them in a cold climate, and Jack grows a lot of roses.

Jack gives his roses a potassium feast every fall, starting six weeks before the first hard freeze. (He started this year on September 16th.) He first read about this in a rose book by Suzy Bales, and had the concept confirmed by a retired soil science professor, who assured him that “… winter hardiness is one of the most important functions of potassium”.

Jack Falker applying the potassium feast to his roses.

Jack mixes the “potassium feast” in a 60-gallon trash can, and uses a sump pump to apply the mixture to his roses. Photo: Mary Eileen

He dissolves one tablespoon of muriate of potash into three gallons of water, and gives each rose a gallon for each of those six weeks before they go dormant. As Jack says, “Potassium blocks the growth-promoting effects of nitrogen and phosphorous, thereby hardening the canes in time for winter.” As the canes become more hardened, they start to turn red, as you can see in the photo at the very top of the post that Jack supplied. I have been intrigued by this and was eager to try it on my roses. There was only one thing that stopped me:

Where do I get muriate of potash?

Jack gets his from farm supply stores, and “I define a farm supply store as a place that sells bulk fertilizers to farmers, not someplace that sells bird-seed to bird watchers,” he says. I called my local Tractor Supply and Agway, and neither of them had something by that name. Well, what exactly is muriate of potash? Turns out it’s potassium chloride, plain and simple. Maybe if I had asked for it like that, those stores would have told me they had it. But in the course of researching exactly what it was, I discovered Amazon sold it in four pound bags. Problem solved!

I’m getting started a few weeks later than Jack, and I’m not sure I’ll get six weeks in, but some is better than none. And I’m going to mix it up in my trusty Rubbermaid watering can, and not in a 60-gallon trash can as he does. I think I’d have to grow a lot more roses to make a set-up like that worthwhile. And I’ll make sure to wear old clothes, as he says the mixture stains red, though it eventually washes out.

If you live in a cold climate and love to grow roses, Jack’s Minnesota Rose Gardener blog is required reading. He has a lot of good advice on winter protecting your roses.

About the Author

Kathy Purdy is a colchicum evangelist, converting unsuspecting gardeners into colchicophiles. She would be delighted to speak to your group about colchicums or other gardening topics. Kathy’s been writing since 4th grade, gardening since high school, and blogging since 2002.

Autumn is a second spring when every leaf is a flower.

~Albert Camus in Albert Camus quotations

Comments on this entry are closed.

John Boles October 30, 2014, 5:38 am

Great post Kathy , beautiful roses, thanks for the information will have to try it out

Ian October 15, 2014, 2:48 pm

It’s always great to see people thumbing their nose at the climate and gardening however they want. There are so many different plants and flowers that can thrive in a cold climate as long as you know how to take care of them – more people should take advantage!

Rachel October 10, 2014, 10:08 am

Good Afternoon Kathy,
I really enjoy your blog and all the different post you bring to the table. This one in particular stuck in my mind due the fact that I work for an Organic fertilizer company called OceanGrown, Inc. We are focused on reintroducing all 90 elements to plants using mineralized pure ocean water to fertilize them rather then harsh chemicals. The two added minerals are nitrogen and potassium. Plants, fruits and vegetables all prosper when using our products from receiving all the nutrients the earth was intended to give them. I believe, jack and yourself would love and benefit from our products. you can visit our website at and let me know if you would be interested in us sending you a sample trial of our products you can blog about! Thanks for your time and thank you for your blog and reaching out to us fellow gardeners! God bless

PaulP October 10, 2014, 3:57 am

I love planting roses and it’s a good thing I stumbled upon in your blog post regarding fortifying roses. I will try you advices Kathy and I will check out Jack Rosarian Blog as well. Thanks!

Joanne Toft October 7, 2014, 7:10 pm

Ok – we are on the edge of frost now as Minnesota moves into October. Is it worth it for me to try this? I only have a few roses because they die off so easily. What do you think – so I give them a dose?

Kathy Purdy October 7, 2014, 7:42 pm

Joanne, even after the first frost, roses don’t go dormant right away. Jack says to give them six doses, until a hard freeze (25F). So I gave them their first dose yesterday and will try to do so weekly for all of October. I may not get all 6 doses in, but some is better than none, I figure. But this is my first year doing this and is something of an experiment.

Donna@GardensEyeView October 7, 2014, 9:51 am

I will definitely check out his blog and look at doing this next fall…my fall gardening is limited still.