By Nancy Louwman, Rideau 1000 Islands Master Gardener

Choose the best roses for your garden

• Check the recommended zone hardiness for the variety you are purchasing. Will it survive where you live? The Kingston area is designated as Zone 5a-6a on the Natural Resources Canada Map, depending on where you live. The United States Department of Agriculture Map’s zones are different- zone 6 here may be zone 5 there. Check which zone map is being used for the roses you are buying. Palatine Roses, for example, uses the USDA zones for their roses, so a zone 6 hardy rose may not survive here. Be aware that factors other than zone appropriateness may affect your rose’s survival: soil type and drainage, snow cover, wind exposure, and rainfall, all play a part in the health of your plants.

• Look for own-root roses when possible for colder climates. Most roses commercially available are grafted on hardier multiflora rose rootstock. In a severe winter, with dieback to the ground, these roses may regrow with suckers from the rootstock rather than the grafted rose. Grafted roses in a zone 5 garden should be planted with the graft union 5 cms below the soil level for winter protection. 

• Roses may be purchased either potted or bagged from garden centres, or ordered bare-root from rose growers. Potted roses are best planted in the spring or early summer, and bagged roses best in early spring. Both need to be well-watered in the first season. Palatine Roses in Niagara-on-the-Lake ships bare-root grafted roses for late fall planting. These are the healthiest roses for the first season as roots are well-developed by the following spring. Corn Hill Nursery in New Brunswick ships bare-root own-root roses in the spring. By season two, these roses are thriving in my garden.

• If possible, use the American Rose Society ratings in their handbook which can be purchased from the ARS and includes invaluable information for choosing the best roses .  

• Choose the roses with the growth habit you want. The rose’s classification (Hybrid Tea, Floribunda, etc.)  as well as descriptive information you can find online will both help. Do you want a hedge rose, a climber for a fence or arbor, a large shrub for the back of a border, or a miniature for the front of a border? 

Try  Dave’s Garden and Help Me Find Roses when looking for more than the rose’s classification. 

Both are used for entirely different purposes.

• The genetic makeup of the rose can provide you with invaluable information about growth habit and hardiness. Many species roses, beautiful in their own right, have been used to hybridize hardier, more vigorous, varieties which are resistant to disease and pests. Some hybrids have been grouped for the Canadian market because they are fully hardy and disease-free if grown in the right conditions, like the Canadian Artist Series, the 49^thParallel Series (fully hardy and disease-resistant), and the Canadian Explorer Roses. 

These hardy species roses can serve as examples of parents of beautiful garden roses for our area

Rosa rugosa is a top-rated ARS (9) species rose native to Northern China, Japan, and Korea, where it grows in sand dunes along the coast. It and its hybrids are therefore more salt-tolerant and survive drier summers than many other thirstier roses.  Rosa rugosa is a dependable repeat bloomer, has beautiful large hips, and is extremely hardy to Zone 2 as are many of its hybrids. The following roses are a just a few of the many excellent rugosa choices for Ontario gardens because of their parentage. Like their parent, they also spread by suckers, so do well in large areas where they can spread.

‘Roseraie de l’Hay’, France, 1901, Z2 double, fragrant, deep mauve flowers, 2 m tall, ARS rating 8.7

‘Therese Bugnet’, Saskatchewan, Canada, 1950, Z2, double, fragrant, pink flowers, 1.5- 2 m tall, ARS rating 8.3 

‘Blanc Double de Coubert’, France, 1892, Z3, double, fragrant, white flowers, 1.5 m tall, ARS rating 8.1 

‘Foxy Pavement’, Germany, 1987, semi-double, fragrant, pink flowers, .75 m tall, no rating as yet

‘William Baffin’, Canada (Explorer Series), 1983, Z3, small double, bright pink flowers, 3m tall, ARS rating 8.3

Rosa spinosissima syn. pimpinellifolia , also called the Scots rose, a species native to the British Isles, northern Europe,  and western Asia, has an ARS rating of 8, and is hardy to Z3. Many of its hybrids are tough, hardy, plants with ferny foliage, and usually very fragrant, profuse spring blooms. Two excellent roses in this family are ‘Stanwell Perpetual’ (pictured below), England, 1836, Z3, small fragrant double white flowers, 1m tall. ARS rating 8.4, and ‘Golden Wings’, USA, 1956, Z4, large, single, fragrant, yellow flowers, 1.5-2 m tall. 

Roses are classified generally according to growth habit and origin

• Old (Antique) garden roses are pre-1867 and include many ancient roses with unknown origins, and some species roses. While most old European roses within this group are not hardy here, we can grow many Alba, Gallica, and Moss shrub roses. They are non-recurrent, very fragrant, and well worth a place in our gardens. Canadian rose growers offer several within these groups for bareroot shipment. Many species roses are single flowered (usually), non-recurrent, have lovely hips, and are hardy here including Rosa rugosa (ARS 9), R. spinossisima (ARS 8.4), R. setigera (ARS 9), R. rubrifolia (ARS 8.8), and R. virginiana (ARS 8.6).

• Hybrid Teas, long-stemmed exhibition roses, originally were hybrids of tender China roses, and were therefore not hardy here. Many Hybrid Teas today, however, have been bred for colder climates. Check the rose’s parentage when purchasing a Hybrid Tea if it was not bred for northern climates. Winter protection is advised for this group. Floribundas, which resemble Hybrid Teas, have smaller flowers in clusters. Again, be sure the Floribunda you are buying is Zone 5 hardy. Winter protection is still advised. There are many hardy Hybrid Teas and Floribundas for this area.

• Most climbers are not fully hardy in zone 5 and therefore require protection along the canes and at the ground from our cold winters. The best roses to train as climbers are Kordesii hybrids in the Canadian Explorer group like John Davis (pink, ARS 8.8) and Henry Kelsey (red, ARS 8). New Dawn (light pink, ARS 8.4) is an older climbing rose hardy here with some winter protection.  

• Shrub roses include a wide variety of sizes, and include many highly rated, fully hardy roses for this area including the Canadian Explorer Roses, Canadian Artist Series roses, Parkland roses, the 49^th parallel series from Vineland, Ontario, some David Austin English roses, Drift, Knockout, and Oso Easy landscape roses, and the older Hybrid Musk roses like ‘Ballerina’  (pink, single, ARS 8.5). Below, in order, are the pink Hybrid Musk rose ‘Ballerina’, the red Parkland rose ‘Hope for Humanity’, and the Canadian bred rose ‘Navy Lady’. 

Questions and answers

What is the best way to manage Japanese beetles?

Japanese beetles overwinter in lawns as grubs which feed on the roots of grass.  Replacing traditional lawns in your yards is one way to help. Handpick from affected plants, drowning the beetles in a mixture of dish detergent and water. When dealing with large quantities, pheromone traps can be effective when placed approximately 30 feet downwind from the beetles. Commercial treatments include neem oil and pyrethrin, but both are harmful to other insects in your garden. Try some antique roses which bloom earlier than the beetles emerge in a zone 5 garden; once-blooming, they have finished flowering by the time you see Japanese beetles. 

What are recommended companion plants for roses?

To deter pests, underplant roses with aromatic plants like garlic, rue, lavender, thyme, golden oregano, sage, catnip, hardy geraniums, wormwood, alliums, marigolds, and dianthus. Be careful to choose lower growing varieties to allow good air circulation around your roses.

What are your recommendations for aphid control?

I use a garlic or insecticidal soap mix if the problem cannot be mitigated with a quick spray from the hose. Check online for the recipes. I rarely have problems, though, probably because of the companion plants I use. Trap plants such as nasturtiums planted at a distance from your roses will attract the aphids away from your roses.

An old climbing rose over an arbor has dead looking 1” canes in part of the plant, while other parts are in bloom. How should we approach pruning this?

There are some excellent demonstrations of pruning on YouTube. Prune the dead canes out at the base, and any weak, diseased, or crossing canes to allow air circulation through the rose. Pruning a non-recurrent rose takes place after the rose has finished blooming; a reblooming rose should be pruned in spring when the forsythia blooms. In subsequent years I would prune out old woody canes to promote new growth.

Do you have any suggestions to manage a green caterpillar eating buds on my roses.? Could this be the same caterpillar as the one on my bee balm nearby? (It is not a cabbage moth)

Buds are normally attacked by the small white larvae of the rose midge. From mid-May to the first week in July, roses are also attacked by the rose slug sawfly larvae which are small green caterpillars.  I would hand pick the green worms and feed them to the birds, and treat the plant with an environmentally-friendly product like Safer’s BTK if hand picking was not effective in controlling the problem.

An old climbing rose starts out well in spring, but every year by July the foliage is eaten by something (full of small holes). The gardener is never able to see the insect responsible. The rose is 6 ft at its tallest point. At times she cuts it back severely because it is eaten so badly. She has had this rose for 15 to 20 years (takes it with her when she moves). It is once blooming and in more than 6 hrs. of sun. When is it best to spray, before the damage is done or when signs of the damage become visible?

The damage may be caused by rose slug sawfly larvae and/or rose chafer beetles. Both are active from mid May to the beginning of July. Spray at the first sign of damage, and repeat after a rain. The sawfly larvae pupate in the soil beneath the rose, so treating or removing and replacing the soil beneath the rose can break their life cycle. Two species of sawflies produce two generations or more in one season, so the problem won’t go away after a spring treatment. Rose chafer beetles’ grubs overwinter in the soil beneath the rose, so a similar soil replacement will help as well.

Can you share the recipe for a garlic solution to use for insects?

Peel and crush several large cloves of garlic and let sit in one liter of water for a day. Boil for 10-15 minutes, cool, strain with fine cheesecloth, and use in your hand sprayer. I have also added 1/2 tsp. cayenne pepper to this mix with good results.