Rugosa roses disease resistance

My favourite roses are Rugosas, since they are ideal to grow in a Zone 3 climate I have mostly lived in. I’ve grown many cultivars over the past few decades in several Canadian cold and warm geographical locations.

This year I had a bumper crop of Rugosa seedling from my breeding work in 2016. Cultivars used included ‘Hansa’, ‘Snow Pavement’, ‘Aylsham’, ‘Schneezwerg’, ‘Caroyal’, ‘Jens Munk’, ‘Apart’ and ‘Carlos Dawn’.

I was surprised at the lack of disease resistance (powdery mildew and blackspot) in most of the seedlings. Only a few were worth keeping for future evaluation. For example, three ‘Hansa’ x ‘Caroyal’ seedlings, which had large leaflets. A couple of ‘Schneezwerg’ seedlings (staminate parent undetermined yet) were okay, too.

One ‘Hansa’ x ‘Juns Munk’ seedling was totally clean and had attractive, shiny green foliage. Flowers were nothing special though, just single and a light pink in colour. Interestingly, in late October when the other Rugosa seedlings had turned a fall colour the foliage of this seedling didn’t.

Obviously, I’m going to focus on using ‘Jens Munk’ in the future to breed with other Rugosa cultivars. Also, with ‘Fru Dagmar Hastrup’, one of ‘Jens Munk’ parents, which is likely responsible for the disease resistance of the latter cultivar. Of course, ‘FDH’ has very attractive foliage and perhaps it’s this feature that contributes to disease resistance to its descendants.

I note the Rugosa ‘Claire Laberge’, while the flowers are nothing special, the foliage is disease resistant. ‘Jens Munk’ is one of its parents (the other is ‘Scabrosa’).

From this experience, it resulted in me having far more appreciation for the rose breeders who developed Rugosa cultivars that are commonly grown today because of their good disease resistance.

Hi Paul!!

I love rugosas and think it is wonderful the advances you are working towards with them. Over the years I’ve cut back working with them due to space constraints, etc., but I have more space now in the new house and should do some more with them. It is sure sad to see disease take many of them down. It seems here in the Twin Cities ‘Hansa’, ‘Jens Munk’, and many Pavements get black spot pretty badly. ‘Fru Dagmar Hastrup’, ’ Scabrosa’, and ‘Blanc Double de Coubert’ and a few others have stood up. I wish you the best in your efforts and look forward to your beautiful future hybrids.

I should mention a couple of years ago I discovered an apparent Rosa rugosa x R. woodsii shrub growing about 50 metres from a Rosa rugosa planting on an old homestead in the Rainy River region of N.W. Ontario. This Rugosa hybrid was growing on a disturbed site where a small bridge had been constructed over a small creek many years ago. In close proximity of this Rugosa hybrid are populations of Rosa woodsii and Rosa acicularis (perhaps only one shrub). Tentatively, I’ve named it ‘Stonebridge’ (large rocks support the bridge on both sides of it).

Interestingly, the foliage of this Rugosa hybrid has the deepest green colour I’ve ever seen of one. It’s also very disease resistant. Single, medium pink flowers are prolifically produced and therefore the shrub sets many hips. I’m thinking it might have potential to use in a breeding program for rose hips. For this purpose It’s likely I will first cross it with ‘Fru Dagmar Hastrup’ and ‘Scabrosa’. But it also might be worthwhile to use with ‘Carlos Dawn’ (very good hip producton) and Rosa blanda ‘Riches’ (very good hip production). The use of the latter cultivar perhaps has the potential to substantially reduce stem prickles in the progeny, which of course is ideal for shrubs developed for rose hip production.

Hi Paul, I love Rugosas too, but working with then here on the Eastern Prairies is not that easy or successful. Most Rugosas, if they survive, do not thrive. I think because of the high pH on our soils. Rugosas become chlorotic, which effect their ability to make through our winters.

A few years ago, I took a trip to the Maritines. I was surprised to see Rugosa roses growing every where.
Some had escaped cultivation and were growing on the sheltered bays in Peggy’s Cove next to the sea.
They were covered with blooms and healthy.
Here’s one of my attempts at working with Rugosas. Martin Frobisher is a decendant of Scheezwerg.
2017-11-26 17.54.32.jpg
2017-11-26 17.55.02.jpg

I like rugosas. I, too, have problems with chlorosis in my pH 7.5 soil. We are right on the edge of the prairie, and rugosas sometimes work and sometimes don’t around here. Crosses with modern polyploid roses give interesting results, albeit with a lot of sterility.

It sounds like Frau Dagmar will be a good one to use. Mine were just planted. Henry Hudson has given me interesting results. I’ve also used Belle Poitevine, just because I have it and it sets hips. It seems like Belle Poitevine seems to lend a bright vivid pink color when crossed with other medium pink roses, which is odd. Both Belle Poitevine and Henry Hudson don’t set every hip when pollinated…perhaps 30% of pollinated hips stay on to maturity. My Hansa, for some reason, NEVER sets hips whether OP or pollinated. Strange that other people have good luck.

One thing I like about rugosas is their fast hip ripening time. I think I’ve pollinated them as late as early August. When I’m craving more pollinating but it’s just too late I can still slap some pollen on rugosas.

I have an OP seedling of Caroyal (I’m pretty sure, kinda lost track) that reblooms. Caroyal itself is non-recurrent. It seemed to accept pollen readily, so I made up a kitchen sink blend of pollen from this or that rose and pollinated this seedling heaviliy this summer. Lots of seeds. I will have a tendency to select against seedlings with pure rugosa leaf types, wise or not, just because I’m so interested in the hybrids.

Breeding with Rugosa’s can seem daunting at times. Those which set seed usually germinate quickly and easy but the pleasure of seeing a lot of seedlings can be quickly be turned when the seedlings develop vigour and disease problems. The Fru Dagmar Hastrup plants I use for seed parents, were exposed to chromosome doubling compounds (Trifluralin) as seedlings just germinated. This caused a lot of distortion of the plants growing tip and foliage. I am not sure if the doubling was complete , but the results shown from emerging hybrid seedlings suggest some benefit, has occurred. As a simple hybridizer I feel they have contributed an extra set of rugosa chromosomes to pair up within the newly developed hybrids giving rise to a more healthier, vigorous and fertile offspring.

Below are photographs of seedlings developed from these FDH (T) seed parents. The first is three variations of FDH(T) x R.tunquinensis.
S2 T17 T4jpg.jpg
S2 T17 T2.jpg
S2 T17 T1.jpg

The next three of the FDH(T) are. The seedling of Ann Endt (T) probably has R.woodsii in it as seed parent showed some R.woodsii characteristics, the seed came from Joe B.
S2 T132.jpg
S2 T106.jpg
S2 T82 T2.jpg

This last seedling is FDH(T) Type 3 x Apache
S23 T144 T2.jpg

Thanks for the pics, Warren.

If the FDH(t) x Ann Endt and x R. nitida seedlings end up being sterile that will indicate that the the FDH(t) might be a tetraploid.

Hi Warren,
Those are some very healthy Rugosa seedlings. Do you keep them in pots? Doesn’t this retard the maturity?
What is the pH of your soil?

I read a paper by Prof D Byrne saying if the chromosomes of a diploid species were doubled, and that if the autotetraploid offspring were to be used in an breeding program with another diploid species, it would have that extra set of chromosomes to pair with, making the offspring of those two different species types, fertile. I feel that is what has happened here. I will soon post pics of the vigour to show the height achieved for these 2017 seedlings, remember we are still in late Spring here.

Hi Chuck:

Thanks Chuck. They are kept in pots at the moment because of the lack of space in my garden beds, if they were to have been planted out, the growth would be a lot bigger than that shown. The pH I am not sure of, but I would say acidic due to the large amounts of organic material present in the potting media. Last year I grew some OP seeds from the FDH(T) Type 1, they were kept in 6"pots and took 9months to flower, with these species hybrids I probably wont see anything for over a year.

This information accords with the trial and error I’ve experienced in my garden over the years! The Rugosas that I ended up keeping in Minnesota have also done well in Georgia–no difference in disease, though I think the long hot summers are a little tough on them. Hmm, maybe I should water more? Fru Dagmar Hastrup, Blanc Double de Coubert, Belle Poitevine, Magnifica, Wasagaming, Will Alderman, and Ann Endt are the best for health and fertility. Rosa Zwerg and Jens Munk have also been good here. Therese Bugnet is a good seed parent but gets a sort of leaf crud as the season wears on. Roseraie de l’Hay is pretty good but does get a little blackspot. I have grown many other varieties but ultimately gave them away when we moved because they were either infertile (though fine garden plants–Polareis comes to mind) or too prone to disease. All the seedlings tend to be spindly at first, but I attribute this to the fact that they are diploids. They are remarkably tough. They will often outgrow mildew, but they won’t outgrow blackspot so I cull for that first.

Does anyone have experience using Muriatic acid as an agent to lower the pH of irrigation water
for watering roses? Especially Rugosa roses? What could be the benefits and pitfalls?

I’ve never used muriatic acid in watering. It is a really poor buffer (no capacity at all), so it will be hard to control pH achieved by adding a particular amount. Will depend a whole lot on whether you water has carbonate and sulfate in it. I know you can buy it at a hardware store cheap. I would prefer to use something like ferrous sulfate which acidifies soil when the iron (fe) is bound to stuff in the soil. If your water is alkaline though, the Fe will precipitate as rust in your watering container if left very long. If the soil pH is your issue, it will take an incredible amount of watering with dilute added muriatic acid to ever lower the pH. Alum (aluminum sulfate) is often used, but I don’t like the aluminum very much. That’s why the iron sulfate is my choice. Pine or oak leaves will acidify soil. So does addition of nitrogen fertilizers. Agronomists worry about this one which is why adding lime is important in many places.


We inject sulfuric acid at times to neutralize the very high alkalinity (which is a separate metric from pH) of our water. Straight battery acid works, which is available from auto parts stores in 5 gal containers. Run through an injector such as a Dosatron or Dosmatic and into a tank.

For watering seedlings I have used powdered citric acid, checking pH with high-resolution testing strips. Once the pH starts to move significantly it is a good indication you’ve neutralized the alkalinity of your water, which is the main thing you need to do.

For outdoor plants growing in the soil, we’ve had amazing results greening up chlorotic rugosa roses using SoyGreen, a farm fertilizer that is a chelated iron product. Dramatic greening in a short period of time. Not sure if this would be a good idea to use for container-grown roses over the long term, but it would sure help if used once in a while.

Thanks Joe for the battery acid idea, which I presume is conc sulfuric. I would have recommended that if I’d thought it was available to general consumers. I guess we need to distinguish between soil and water. I never worry about our water which is all treated to city specifications and has some of both calcium and magnesium plus sulfate and carbonate. But not too much of either or it would leave hard water films on things.

Depending what the soil has in it in the way of clays and organic matter, Epsom salts (magnesium sulfate) might work too to lower soil pH some. And it is often used to increase basal breaks in HT roses. When the Mg binds to clay it releases the sulfuric portion to lower soil pH. Gypsum (calcium sulfate) has a similar effect. Both help unclod the clay soils around here, which contain a lot of swelling clay, which means it is short of cations like potassium, calcium and magnesium. Potassium as the sulfate or chloride salt is useful as a plant nutrient if the soil is low in potassium. It also gives off the chloride or sulfate when binding to soil, or taken up by plants. So any of these could lower soil pH. But probably none so cheap as the battery acid.

If I were worried about the soil, I’d have the state testing lab run an NPK analysis, + pH and CEC, before taking on major work. I’d rather add 100 lb/sq yd of composted leaves and yard waste and dig it in. that’s a lot of organic matter. Really helps around here.

I moved into my new home last winter and had the water tested. The well water was ~200 for alkalinity. The target is less than 100. I did the math with some of the free online calculators through one of the state extension services for greenhouse growers and in the end use 1ml of concentrated sulfuric acid per 5 gallon bucket. I got the acid easily shipped to me and it is affordable from this site: Sulfuric Acid [sa950] | DudaDiesel Biodiesel Supplies I try to be very careful with it and make sure I put the bit of acid into the filled bucket of water versus water being poured into acid (Larry can explain why better than me). The rose seedlings grew great this spring- better than with my St. Paul city water. For rugosas in the greenhouse, this is what I’ve done. I’ve added a bit of finely ground sulfur (available in garden centers) with the soil before planting and even with the high alkalinity water on campus at times, they still looked good for well over a year in pots. I should measure the amount better and do a soil test to see what the pH is for curiousity sake, but I haven’t and the rugosas have looked very nice.

I have not had a lot of success in obtaining healthy rugosa F1. It may be what I’m using as the other parent that might be the problem. I don’t know. I tried ‘Nijveldt’s White’ 2 seasons ago as a seed parent with a yellow patio rose type that descends from First Impression as the pollen parent (Larry Davis’ 13-1), and had two seeds germinate mid summer this season. One plant is extremely tiny, lacking vigor, and the other has grown to about 10" tall this first season. Leaves on the larger one show some rugosa influence and disease resistance has been very good so far. My thoughts were to try something that wasn’t straight rugosa but rather having other species mixed together.

One other rugosa hybrid that I have germinated from seeds from OP Baby Love. One F1 has rugosa type leaves and is completely disease free so far. I’m looking forward to seeing what this one looks like next season and hoping for a bloom…yellow flower would be awesome. The likely rugosa hybrid that bees or wind contributed pollen from is Ruglauca. Ruglauca is (Rugosa #3 × R. glauca) x OP and has excellent disease resistance. I may cross Ruglauca with ‘Nijveldt’s White’ ,since both are diploids, and see where I can go from there.

I found this yesterday a seedling of a Fru Dagmar Hastrup (T) Type 1 X R.tunquinensis, as you can see the foliage is quite healthy and for a seedling produced this year it has developed a cluster of flower buds. It is around 5 months old and close to 2ft high. The water here comes from the river but sometimes they add bore water which tends to be saline, and for that reason my young seedlings are watered with rain water, I collect in two 5,000 gallon tanks.