Some Roses Like It Hot
This is an updated article I wrote for The American Rose The Magazine of The American Rose Society edition July/August 2014 to now include Illinois Roses
How hot is too hot for roses?
Moving from Texas to Illinois in June of 2011 I thought I was saying good-bye to mind numbing days of counting the days of temperatures over 100, water restrictions, and days without rain. Then the summer of 2011 the entire nation faced a 100-year drought and record heat. Even though I had had enough of Texas heat it seems I had packed up Texas weather and taken it with me to the rolling cornfields of Central Illinois. The summer of 2011 was also a 100-year draught across much of the nation proving once again a message that rosarians can convey to each other and those new to growing roses. Roses are resilient and can withstand very hot temperatures as long as they are watered regularly. Click to read: Killer Texas Summer Shatters Heat Drought Records.
Fast forward June 2016!
Here’s the Question I was asked to answer for readers of American Rose Magazine July/August edition 2014
Question: Do you think its better to “use canopies or individual coverings for roses during extreme heat conditions or let your roses sulk in the summer heat”?
There’s more than one answer to the question:
When roses (and virtually any other plants) reach the point of excessive water stress, they don’t “feed,” nor do they try to grow. They simply try to remain alive. That’s why even when you’re watering daily with what feels like excessive water amounts, many rose bushes will begin shedding their leaves to reduce their water stress. With less leaves and they don’t “sweat”, transpire it through the foliage. That slows and can literally stop the flow of sap from the roots upward, so no food is taken in. Nature demands balance. Even in times of extreme heat I have seen my roses continue to remain beautiful with just smaller blooms and less frequent bloom cycles. Roses seem to go into almost a dormancy state to conserve energy and water.
Answer: For the purpose of this article I chose to let my Roses swelter in both N. Texas and now Central Illinois heat with protection in mind to identify heat tolerant roses that perform better under extreme heat and low water conditions.
Here’s ways that we can continue to grow good roses and preserve our plants and maintain water restrictions. In extreme heat like the DFW area I recommend protection and filtered light as protection from the unending heat rather than canopies if possible and here are a few tactics I employed in N. Texas while growing over 200 roses there. I had hybrid teas, grandifloras, floribundas, miniatures, shrubs, David Austin Roses, Large Flowered Climbers, and Knock-Outs.
- Select roses suitable for a hot climate. I have a list of modern roses that I have proved can survive extreme N. Texas heat for 20 + years. And you can also plant OGR’s that are adapted to heat, those in existence before 1867. The beauty of these roses lie in their heady fragrance and can include Hybrid Perpetuals, Teas, Chinas, Hybrid Musks, Bourbons and other Classes like these. Avoid using antique roses bred for colder climates such as the Kordes Roses and Rugosas.
- Just as dark colors retain heat and light colors keep us cooler, lighter-colored roses can hold up to extreme heat better than dark reds, and oranges do. Plant darker colored roses where there is some protection or perhaps less than full sun. Choose some white, light-pink and pale yellow roses that seem to hold up better to extreme temperatures.
- The elevated beds I put in in N. Texas allowed me to put in a laser cut drip irrigation watering system. I watered deeply and at the base of the plant, not directly on the leaves of the plant. I set timers to water very early in the morning not ever during full sun. During times when water restrictions were in place we could use the hose and I deep watered allowable amounts and my roses did just fine. Remember that dehydration during summer months can put your plants in peril. If you have an irrigation system in place be sure that it’s set to water at least 2 inches of water per week, and does not water directly on the leaves of the plant during full sun. This is difficult to determine when you take into consideration factors like wind, temperature and type of soil. So you may want to purchase a moisture gauge for your rose garden.
- Fertilize from two weeks to 30 days prior to when you expect hot weather to reach and maintain temperatures near 98F. Organic fertilizers and soil amendments are far less likely to burn your plants even during sustained high temperatures. For those of you living in zones where temperatures really start to warm up in late-February, this is a time to begin fertilizing. Then fertilize monthly until mid-May when temperatures start to rise. You really have to watch carefully your fertilizer to water ratio during the hottest months. That should be your signal to start reducing your fertilizing until late in the summer.
- Shredded hardwood mulch retains moisture and keeps the soil cooler; I use layers of hardwood mulch over Canadian Sphagnum Peat Moss that I add each season.
- Plant roses with protection from afternoon sun and be sure they still receive at least 6 hours of direct morning sunlight.
- Roses love to grow in largely organic soil with good drainage. To grow the best roses in summer heat, plant your rose in a deep hole that drains well. Water regularly and deeply, In Texas my roses in the front yard had indirect afternoon sun with the dappled light of oak trees I planted that grew to be mighty shade providing oak trees, and this provided a canopy of well-needed cooling shade cover.
You can use a shade cloth cover if that is aesthetically acceptable to you. Don ‘t plant roses next to a South or West facing wall, especially stone or brick because the stone holds heat that can also burn your plants and will reflect too much heat. My roses that I planted and added stones along a path held heat late into the evening on a hot summer day due to absorbing qualities of the stone and I could see these roses suffered from the excessive heat of the stone, the roses with grass next to them were far cooler. Don’t forget that layers of mulch help to keep the soil cool. Spraying off the roses in the evening helps to cool your plants and wash away spider mites but never spray during direct sunlight.
My Susan Fox Top Ten List from my Texas & Illinois Garden Garden
- Julia Child, F
- Francis Meilland, HT
- Sugar Moon, HT
- Pretty Lady Rose, HT
- Bolero, F
- Easy Does It, F
- Take It Easy, S
- Pumpkin Patch, F
- Watercolors Home Run, S
- Europeana, F
I also thought I would ask Minnesota Rose Gardener Jack Falkner about heat in the a northern climate and here’s what Jack had to say:
“Folks are often surprised to hear that we get a lot of hot weather in Minnesota in the summer. It’s not at all unusual for us to see temperatures upwards to the high nineties and 100, along with very high humidity. That’s when I wash my roses at mid-day to cool them down. Syringing is also the best thing you can do to control spider mites. You can use any kind of nozzle that delivers a sharp stream, but I use a spider mite blaster that shoots a high-pressure fan of water up from the bottom of the plants and they love it. An added advantage is that I get pretty wet in the process, which makes me feel like a kid running through the sprinkler on a hot day.” ~ Jack Falkner