Replacing Roses Affected by Rosette Disease

Time after time, designers, landscapers, municipalities, and homeowners overuse certain plants to the point of making them a monoculture, and then an insect or disease comes along and wreaks havoc. We’ve seen it with elm trees, ash trees, and now we are seeing it with landscape roses. Rose Rosette Disease (RRD) is now knocking out landscape roses, particularly in the South. The virus is spread by a tiny eriophyid mite that has an association with multiflora rose, so the disease is likely to intensify throughout the Midwest in states where multiflora rose has naturalized.  At the moment there is no cure for Rose Rosette Disease, so infected roses need to be destroyed and replaced with something other than roses.

Roses infected with Rosette Disease look like they've been sprayed with herbicide

While almost all roses are susceptible to RRD, a few specific landscape rose varieties have been hit particularly hard because of their popularity with landscapers and their use in larger mass plantings. The popular question now is what shrub should be used to replace these roses? First off, we should not replace these infected roses with just one single species or cultivar lest we tempt fate once again. We should be looking at multiple species and cultivars, particularly those shrubs that offer similar characteristics that made these roses so useful and popular in the first place. 

Conceptually, landscapers and designers want shrubs that are bright, carefree, long-blooming or have season-long interest, look excellent in mass plantings, thrive in full sun, and are less than five feet tall. There are a number of shrubs that meet that criteria, and here are some of the Proven Winners® shrubs that fit the bill.

Abelia – Full sun

Long blooming shrubs, many with colorful foliage and fragrant flowers.

               Bronze Anniversary™ - 3-4’

               Ruby Anniversary™  - 4-6’

               Sunny Anniversary® - 3-4’

               Pinky Bells® - 3-4’

               Fairy Dance™ - 2-4’

Ruby Anniversary™ Abelia chinensis

Aronia – Chokeberry – Full sun

Low Scape® Series - A tough native with white spring flowers, glossy foliage, and exceptional fall color.

                              Low Scape® Hedger - 3-5’

                              Low Scape® Mound - 1-2’

Lo Scape® Mound Aronia in autumn

Azalea – Rebloooming – Full sun to partial shade

Bloom-A-Thon® Series - Compact evergreen shrubs with showy flowers that appear in the spring and fall.

Bloom-A-Thon® Hot Pink – 3.5-4.5’

Bloom-A-Thon® Lavender – 3.5-4.5’

Bloom-A-Thon® Pink Double – 3.5-435’

Bloom-A-Thon® Red – 3-4’

Bloom-A-Thon® White - 2.5-3’

Bloom-A-Thon® Double Pink Azalea

Berberis – Barberry – Full sun

               Sunjoy® Series - Tough, easy-to-grow shrubs with colorful foliage. 

          Sunjoy® Cinnamon - 4-5’

Sunjoy® Citrus - 2-3’

Sunjoy® Gold Pillar - 3-4’

Sunjoy® Syrah - 4-5’

Sunjoy® Tangelo - 3-4’

Sunjoy® Series of Barberry

Buddleia – Dwarf Butterfly Bush - Full Sun

Continuous flowering, low-growing shrubs with colorful, fragrant blooms.

               

          Lo & Behold® Series – Dwarf, sterile shrubs that come in a wide range of colors.

Lo & Behold® Blue Chip - 2-2.5’

Lo & Behold® Blue Chip Jr. - 1.5-2.5’

Lo & Behold® Ice Chip - 1.5-2’

Lo & Behold® Lilac Chip - 1.5-2’

Lo & Behold® Pink Micro Chip - 1.5-2’

Lo & Behold® Purple Haze - 2-3’

Lo & Behold® Pink Micro Chip

Miss Series – Semi-dwarf shrubs with vibrant-colored, fragrant flowers.

               'Miss Molly' - 4-5’

               'Miss Pearl' - 4-5’

               'Miss Ruby' - 4-5’

               'Miss Violet' - 4-5’

Miss Violet Butterfly Bush

Pugster™ Series - Dwarf shrubs with large flowers with a wide range of colors.

                    Pugster™ Blue - 2’

Pugster™ Periwinkle - 2’

Pugster™ Pink - 2’

Pugster™ White - 2’

Pugster Blue™ Butterfly Bush

Ceanothus hybrids – New Jersey Tea - Full sun

               Marie Series™ - Drought-tolerant shrubs that thrive in poor soils.

                              Marie Bleu™ - 2-3’

                              Marie Gold® - 2-2.5’

                              Marie Rose™ - 2-4’                  

         

Marie Blue™ Ceanothus

Clethra alnifolia—Summersweet—Full sun to partial shade

Easy-to-grow native shrubs with later summer, fragrant flowers and yellow fall foliage

             

               Sugartina® Crystalina - 2.5-3’ 
               Vanilla Spice® - 3-5’

Sugertina® Crystalina Summersweet

Deutzia gracilis – Slender Deutzia - Full sun to partial shade

Yuki® Series – Tough, ground-covering shrubs with abundant spring flowers and burgundy fall color.

                              Yuki® cherry Blossom - 1-2

                              Yuki® Snowflake - 1-2’

Yuki Cherry Blossom™ Deutzia

Diervilla – Bush Honeysuckle - Full sun to partial shade

          Kodiak® Series—Tough, native shrubs with colorful spring and autumn foliage.

Kodiak® Black - 3-4’

Kodiak® Orange - 3-4’

Kodiak® Red - 3-4’

Kodiak® Orange Diervilla

Hibiscus syriacus – Dwarf Rose of Sharon or Althea—Full sun

               Lil’ Kim™ Series – Dwarf series from Korea with colorful, long blooming flowers.

                    Lil’ Kim™ White - 3-4’

Lil’ Kim™ Red - 3-4’

Lil’ Kim™ Violet - 3-4’

               PollyPetite™ - 3-4’, a sterile, dwarf hybrid with large, clear lavender blooms

Pollypetite™ Hibiscus

Hydrangea arborescens – Smooth Hydrangea - Full sun

               Lime Rickey® -  4-5’, Attractive green flowers

               Incrediball® -   4-5’, Large flowers emerge green, turn white, and age to green.

               Incrediball® Blush -   4-5’, Large lavender-pink flowers on strong stems.

               Invincibelle® Series – Compact/dwarfs with strong stems and a wide range of colors.

                        Invincibelle® Limetta™ - 2.5-3’

Invincibelle® MiniMauvette™ - 2.5-3’

Invincibelle® Ruby - 2-3’

Invincibelle® Spirit II - 3-4’

Invincibelle® Wee White™ - 1-2.5’

Invincibelle® Spirit II (Two) in our trial fields

Hydrangea macrophylla – Reblooming Bigleaf Hydrangea - Full sun to partial shade

               Let’s Dance® reblooming series—reliable, long-blooming, rich flower colors.

              Let’s Dance® Big Easy® - 2-3’

              Let’s Dance® Blue Jangles® - 3-4’

  Let’s Dance® Diva! - 3-4’

  Let’s Dance® Rave™ - 2-3’

  Let’s Dance® Rhythmic Blue™ 2-3’

Let's Dance® Big Easy™ Hydrangea

Hydrangea paniculata – Dwarf Panicle Hydrangea - Full Sun

               Bobo® - 2.5-3’

               Little Lime® - 3-5’

               Little Quick Fire® - 3-5’

Bobo® Hydrangea

Hydrangea serrata – Serrated Hydrangea - Full sun to partial shade

             Tuff Stuff™ Series – Selected for hardiness and reliable blooming.

Tiny Tuff Stuff™ - 1.5-2’

Tuff Stuff™ - 2-3’

Tuff Stuff™ Red - 2-3’

Tiny Tuff Stuff™ Hydrangea

Hypericum –St. Johnswart - Full Sun

               Sunny Boulevard® - 2-3’, tough, drought-tolerant, and long-blooming

Sunny Boulevard® Hypericum

 Itea virginica – Dwarf Sweetspire—Full sun to partial shade

Little Henry® - 2-3’ A dwarf selection with early summer blooms and excellent orange-red fall color.

Little Henry® Itea

Lagerstroemia – Dwarf Crapemyrtle - Full sun

               Infinitini® Series – Dwarf compact shrubs that flower even if they die back.

Infinitini® Brite Pink – 2-4’

Infinitini® Magenta – 2-4’

Infinitini® Orchid – 2-4’

Infinitini® Watermelon – 2-4’

Infinitini® Magenta

Ligustrum - Privet - Full sun to partial shade

               Golden Ticket® - 4-6’, A non-invasive, non-burning, bright yellow-green foliage.

Loropetalum – Dwarf Chinese Fringe Flower—Full sun to partial shade

Jazz Hands® Series—Selected for healthy growth and attractive flowers and foliage.

Jazz Hands® Bold – 5-6’

Jazz Hands® Dwarf Pink – 1-3’

Jazz Hands® Dwarf White – 1-3’

Jazz Hands® Mini – 1’

Jazz Hands® Variegated – 4-6’

Jazz Hands® Bold and Mini

Physocarpus – Dwarf Ninebark - Full sun

Dwarf selections with colorful foliage and a high level of mildew resistance.

  

Festivus Gold® - 3-4’

Tiny Wine® - 3-5’

Tiny Wine® Gold – 3-5’   

Potentilla – Bush Cinquefoil - Full sun

Happy Face® Series - Tough, free-flowering native shrubs with a range of colors. 

Happy Face® Pink Paradise – 2-3’

            Happy Face® Yellow – 2-3’

HappyFace® White - 2-3’

Happy Face® Yellow Potentilla

Spiraea - Spirea - Full sun

Double Play® Series – Attractive spring foliage color and superior flowering.

                        Double Play® Artisan® - 2-2.5’

Double Play® Big Bang™ - 2-3’

Double Play® Blue Kazoo® - 2-3’

Double Play® Candy Corn™  - 1.5-2’

Double Play® Gold – 1.5-2’

            Double Play® Painted Lady™ - 2-3’

            Double Play® Pink – 2-2.5’

                        Double Play® Red™ - 2-3’

Double Play® Blue Kazoo® Spiraea

Weigela - Weigela - Full sun

Sonic Bloom® Series – Continuous flowering in a range of flower colors.

Sonic Bloom® Pearl – 4-5’

Sonic Bloom® Pink – 4-5’

Sonic Bloom® Red – 4-5-

Wine Series™ – Early summer flowers and attractive burgundy foliage.

Fine Wine® - 2-3’

Spilled Wine® - 2-3’

Wine & Roses® - 4-5’

Sonic Bloom® Red Weigela

How did Your Hydrangeas Bloom this Year?

So how did your Hydrangeas bloom this year?

One the most common questions I get, is "Why won't my Hydrangea bloom." Of course they're talking about the beautiful species called Hydrangea macrophylla (Big Leaf Hydrangea).

.... [Not sure what type of Hydrangea you have? Click here]

This plant is extremely popular because it is the most colorful of all the species. This plant can be categorized into two main groupings: Mopheads (snowballs) and Lacecaps. The Mopheads are large round clusters of sterile flowers and the lacecaps are flat heads composed of both fertile and sterile flowers. The mopheads are the most popular because we tend to love the gaudy. The lacecaps are gaining in popularity and are considered by many, including myself, to be even more beautiful because of their delicate looking nature.

The key message here is that Hydrangea macrophylla is it sets its flower buds in the fall when night temperature fall below 60F/16C. Thus the flower buds must survive the winter if they are to mature into big beautiful flowers the following summer. [We call this blooming on old wood.] This is the crux of the problem - a hard winter, an early fall freeze, a late spring freeze, or untimely pruning will damage the flower buds and result in a loss of flowers.

So what is a person to do if they want to be successful with Hydrangea?

1) Understand how and when to prune

Big Leaf Hydrangea does not require much pruning once established, but proper pruning is critical if expect to see flowers.

The best time is in early to mid-July. Prune back any non-flower stems back to about six inches from the ground. This helps to produce short stems which keeps the next crop of flower buds close to the ground where they can be more easily protected from winter damage. It is critical that you cease pruning by the end of July. This allows time for the new flower buds to form and harden off prior to winter.

2) Shut the plants down before winter

Hydrangeas will continue to grow as long as there is ample water, fertilizer and warm weather. Later season growth is tender growth and more prone to winter injury, so useful to shut the growth down before winter comes. In late summer and fall, stop fertilizing and cut back on the water. Don't worry if the plant looks severely wilted, just provide enough water for the plant to survive. This will slow down the growth, help to induce flower bud formation and make the plant less susceptible to an early freeze.

3) Mulch and Protect

In late fall, mulch the base of your plant with six to ten inches of bark or peat moss. This will protect the buds on the short stems (the ones you pruned in July). Apply the mulch after the onset of cold weather but before the temperature falls below the teens. This mulch will be removed or spread out in the spring after the danger of frost has past.

4) Grow Varieties that Bloom on both Old Wood and New wood [rebloomers]

Within the last ten years, varieties have been developed that make buds in both the fall [typical], and during the summer [atypical]. Or putting it another way, they flower on both old and new wood. This means that even if the flower buds are injured in the winter, new buds and flower will form the next summer. This is great news for those of us who live in cold climates.

The cultivars 'Endless Summer', Let’s Dance Moonlight, Let’s Dance Starlight, and 'Forever and Ever' have the ability to bloom on old and new wood alike. These are great selections for the Midwest where it is hard to get Hydrangea to bloom. 'Endless Summer' was the first rebloomer to hit the market, while the Let's Dance series is the newest generation of rebloomers. The Let's Dance series has superior flower color, overall substance and thicker, glossier leaves. They are also less likely to die to the ground in the winter.

Now I know that many people were disappointed with the Endless Summer Hydrangeas this year.

We had a long warm spell in late winter followed by weeks of freezing weather that knocked many Hydrangeas back to the ground. As a result, the old wood buds were killed, and we lost the early-season flowers, even on the rebloomers.

Keep in mind that, even with these new varieties, you get a much better flower display if the old wood buds survive the winter. Sure, if your plants die back to the ground in the winter, you will still get flowers, but they appear later in the season and there are typically fewer flowers overall. So - it still pays to prune properly, keep the buds close to the ground and protect these buds with mulch.

- Another Tip for Rebloomers Like Endless Summer -

If your Endless Summer dies back to the ground in the winter, forcing growth will deliver more flowers and sooner. Endless Summer and other rebloomers have to put on a certain amount of new growth before they will make new buds and flower. So it pays to give these plants extra fertilizer and water to push the growth. Miracle Grow once a week after any danger of frost does the job.

For some people, rebloomers are not the best choice.

If you live in a mild climate where big leaf hydrangea blooms reliably there is no advantage in growing rebloomers. You lucky people have a wonderful array of varieties to choose from, many with superior foliage and flowers. For example - consider the new dwarf cultivars sold under the CITY LINE series. These compact plants form a neat compact plant that is covered with blooms. They also have very vivid flower colors.

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(If you live in a very cold area consider Hydrangea paniculata (Limelight, Pinky Winly, Little Lamb and Quick Fire) and Hydrangea arborescens (Invincibelle Spirit and Incrediball. There are many great new vareities and they are pretty much fail proof.)


----------------Back to Hydrangea macrophylla

Flower color - How to change Flower Color

Another interesting attribute of this plant is that its flower color may change depending on soil p.H.. It is not the p.H. itself that changes the color, but it is the availability of aluminum ions that directs the color. Aluminium has greater availability in acid soils thus the blooms turn blue in acid soils. If the soil is either basic [alkaline] or high in phosphorous, the aluminium is tied up and flowers tend to be pink. The degree of color change is dependent upon the amount of aluminum ions available and the cultivar itself. It should be noted that if you are growing in a container your soil mix you may not have much aluminum availability even at low p.H. levels. Aluminum sulfate treatments would then become necessary to get blue flowers. If you fertilize your plants be aware that you will tie up the aluminum with high levels of phosphorous.

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Plants that Impress

It's the last day of January, and there is over a foot of snow on the ground here in Michigan, but spring is almost here. I say this because we turned on the heat in our greenhouses today. We are waking up our plants, so we can start propagating. 

Last year, I didn't post all that much, and I'm going to blame it on Covid. The pandemic had such a strong impact on the nursery business, and we've been incredibly busy trying to keep up with the demand for plants. My Delta account is full of cancelled tickets because I did not go to Italy, Germany, Korea, or the Netherlands as I had planned. On the positive side, I did spend more time in our trial garden, R&D greenhouse, and breeding fields evaluating plants. Today I want to share with you some of the plants that impressed me the most. Hopefully you'll see something you like, and the spring and summer photos will warm you up until spring arrives for real. Enjoy.

Let's Dance Sky View™ reblooming hydrangea

With each passing year, the genetics on our reblooming Hydrangea macrophylla keep getting better and better. Let's Dance Sky View hydrangea is one of the best yet. When we trial reblooming hydrangeas, we cut our plants back hard in that fall and once again in the spring. We do this to simulate untimely frosts. We also trial them for multiple years outdoors to make sure they'll bloom reliably in our harsh Michigan climate. If they bloom here, they should bloom anywhere. As you can see from the photographs below, Let's Dance Sky View excelled in both our trials, blooming nicely after being cut back as a container or having been frozen back in our field. When treated with aluminum sulfate or grown in acid garden soil, the flowers are an attractive sky blue color. 

Plants on the left were cut in fall, and the plants on the right were cut back again in spring.

Let's Dance Sky View hydrangeas flowered well after freezing back to the ground in 2020 and 2021.

'Viva Polonia' and Happy Jack® Purple Clematis 

So many consumers are disappointed by clematis, and it's not their fault. We set out to change that. You may not know it, but most clematis varieties on the market are selected for their flower size and how they perform for the grower, while we select ours based on garden performance. 'Viva Polonia' and Happy Jack Purple offer the very best in terms of garden performance. Here you can see how they looked in our trial garden last summer. Simply amazing! 

'Viva Polonia' clematis in our test garden 

Unique reddish-pink, star-like flowers on 'Viva Polonia' clematis

Happy Jack Purple is always looking happy and healthy.

Happy Jack Purple climbing on a Quick Fire hydrangea 

Puffer Fish™ Hydrangea paniculata

Puffer Fish™ hydrangea is a new selection developed at North Carolina State University that will be at retail in a year or so. Think of it as a super-sized Bobo hydrangea. Just like Bobo, it has full, lacy blooms from top to bottom, but the blooms are much bigger. The flowers open pure white and remain white until they transition in fall to a light green. It's also quite distinct in that new flowers continue to produce at the tip of the panicle, making it look as if the puffer fish flowers are spitting a bit of water. Puffer Fish has been a standout in all our trials. 

Puffer Fish hydrangea in our trail garden

At full bloom, it's hard to see the foliage on Puffer Fish.

An easy-to-identify bloom, Puffer Fish blooms spit a bit of water.

Wine & Spirits™ Weigela

We evaluate a lot of Weigela breeding each year, and one of the plants that shone was Wine & Spirits™ weigela, a new variety developed by Megan Mathey. What I love about this selection is its fresh greenish-white flowers. I've never seen this color before, and it just makes the flowers almost glow against the backdrop of their dark foliage. Growers and retailers will appreciate how well it looks in a container in the spring, and gardeners and landscapers will love how it looks in the landscape. Its unique flower color and overall flower power made it a standout in all of our trials. 

The greenish-white flowers of Wine & Spirits weigela appear to glow. 

A standout Weigela in our container trials

With lots of flower power, it lights up a garden even more than Wine & Roses.

Mr. Mustard™ Sorbaria

When we trial a new variety, we compare it to similar plants on the market, and if it's not better, we pass on the plant. Mr. Mustard™ Sorbaria sorbifolia was clearly brighter and more compact than 'Sem' and the others. The plant is at its best in spring when it is flushing, showing off its feathered hues of red and yellow. While other selections burn or get ragged by mid-summer, Mr. Mustard Sorbaria passes inspection with its clean green foliage and cherry-red fruit. Be aware this species sends out runners in loamy soils and should only be planted in areas where it is contained. Plant in an isolated bed, or keep it contained by growing it in a decorative container. It's plenty hardy and will overwinter just fine. Its white, conical summer blooms look a bit like astilbe and are wonderful for attracting pollinators. This is a tough, hardy plant that performs wonderfully when in the right location.

Mr. Mustard is a colorful container plant. 

At its best in spring, Mr. Mustard is colorful and compact.

In the summer the foliage turns to green, as opposed to brown like 'Sem.'

Sting™ Thuja occidentalis 

I am partial to columnar plants, so it is no wonder that Sting arborvitae captured my heart and imagination. This seedling selection of 'DeGroot Spire' that I sowed out some 15-18 years ago has remained exceedingly slim and attractive. Hardy and heat tolerant, use it as an exclamation point, or go all in and plant it in rows down each side of a road, like the Italians do with their narrow Mediterranean cypress, Cupressus sempervirens. Sting Thuja is a fun tree that is only limited by your imagination. 

Make a statement with Sting arborvitae, the super narrow Thuja occidentalis. 

Sting arborvitae in our test garden

That's all for now. Join me soon when we'll take a look at some new and exciting plants specifically for the South. Until then, stay warm.