All around town the roses are finally in bloom! It's been a rough year for roses with an early fall freeze and a late spring freeze. Not all roses were able to survive the extreme weather. For those roses that made it, here are some tips to keep them healthy during the heat of summer. An excellent resource is “Growing Roses in Colorado” published by the Denver Rose Society. There is a wealth of information on their website as well as a calendar of events.
If you want to stir up the conversation among rose growers, just bring up the topic of fertilization. There are many different opinions and lots of advice – and no real consensus on what is the best fertilizer for roses. Do some research: there are balanced rose foods, chemical fertilizers and organic fertilizers. A soil test will provide you valuable information about what ingredients need to be added to your soil. The first fertilization happens in spring, soon after pruning. Continue fertilizing every 4-6 weeks, with your last fertilization in mid-August. Be sure to water your roses well before and after, and don’t be tempted to over-fertilize. In this case, more is definitely not better. If you have newly planted roses, go easy on them this year. Don’t fertilize at the time of planting – wait until you see new growth or the first bloom.
Watering
In general, roses are thirsty plants. Your summer watering regime will need to change with the weather, and will be influenced by your soil amendments, amount of sunlight received and drainage. The best way to determine whether your roses need water is to get down and dirty in the soil. If the top 2-4 inches of soil are dry, it’s time to water. Roses benefit from deep watering, down to 18”. A rain gauge can help you determine how much water you need to apply to achieve deep watering. Overhead watering can contribute to some rose diseases, so if you use that method, be sure to water early in the morning to allow the leaves to dry out before evening. Watering the soil with a bubbler or hose wand helps reduce the problems of wet leaves.
Mulching
Mulching your rose bed will help reduce soil temperature in the summer, conserve moisture and reduce the growth of weeds. Like fertilizers, there are many choices. Choose mulch that compliments your landscape, won’t blow away and won’t compact easily. Black plastic film is not recommended, but other non-organic mulches like gravel may be appropriate for your garden. Organic mulches will decompose slowly and enrich the soil – an added benefit. Apply your organic mulch to a depth of 3-4 inches. Straw is not recommended because it may contain weed seeds. Dried grass clippings can be applied in thin layers – but only if they have not been treated for weeds.
Deadhead!
Roses, like many other flowering plants, benefit from deadheading – or cutting back the spent blooms. On roses, cut back the cane to the point where it is pencil-thick, or to the place where the next 5-leaflet leaf occurs. Cut at an outward-facing eye to keep the plant from growing inward. Apply a cane sealer (I use Elmer’s glue) to the cane to help reduce insect damage at the point of pruning. And use sharp, clean pruners; shaggy cuts are an invitation to disease and damage.
Most pest problems are managed best when caught early. Prevention of pest problems and disease starts with good horticultural practices. Clean up dropped leaves and blooms and prune out infested branches. A fantastic resource for managing insect problems is Whitney Cranshaw’s publication “Rose Insects – What are They Doing?” downloadable at: http://www.denverrosesociety.org/education/Cranshaw_RoseInsects.pdf
So go out there and make the world more beautiful by planting some roses!
So go out there and make the world more beautiful by planting some roses!
