Posted by Gary Mueller - Rose Expert on 9/2/2016 to Fertilizing & Watering Tips
Below are general guidelines for fertilizing most types of roses.
Best Growing Conditions
Roses prefer a well-drained but moist soil that is rich in organic matter. The Knock Out and other low-maintenance shrub roses aren't as finicky about organic matter as are hybrid tea roses. As with so many other types of plants, roses do not like a constantly soggy or wet soil, which can lead to root and foliar diseases. They grow best in a mildly acid to neutral soil ranging from 6.0 to 7.0 on the pH scale. Most average garden soils fall between a pH range of 6.0 to 7.0.
Testing Soil pH
Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. If you're unsure about the pH of your soil, or whether or not it's suitable for growing roses, it's a good idea to test the soil in the planting area. You can quickly test soil pH with an inexpensive soil pH tester probe. To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil or using compost as mulch can also help to increase acidity and maintain acid soil conditions.
Learn More: What is Soil pH and How To Adjust It?
Feeding Tips and Instructions
At planting time
When planting a new rose during the growing season, I always mix in some compost or some aged compost at a 25% ratio to the native soil. Then, after planting, I fertilize with a mild, slow release natural or organic fertilizer. Follow the application instructions on the label.
Fertilization of established roses
Low-maintenance shrub roses: I feed my shrub roses in late winter or very early spring, and then as needed throughout the season. I usually use a specialty rose food. Some rose foods have built-in systemic insecticides. Follow application instructions on product label. Cease fertilization about 60 days prior to the average first frost date in your area.
Tea roses and other hybrids: I feed my tea roses, floribundas and climbers in late winter or very early spring and then every 6 weeks or so with a rose food containing systemic insecticide. Additionally, about every two weeks I water around the base of the plants with a solution of water soluble fertilizer. Never apply liquid fertilizers directly to the foliage of roses.
How To Water Rose Bushes
Watering your roses is as important as feeding them, and it can sometimes be a tricky thing. During the hotter months of the year, roses may need almost as much water to stay healthy as people do. That being said, low-maintenance shrub roses and dwarfs don't require as much water as the hybrid teas.
There are quite a few things that must be considered before you water your roses:
As might be expected, roses need more water during warmer weather than colder weather. Heat makes the soil dry faster and the roses become more thirsty. Keep an eye out for new growth that begins to wilt. This is a sure fire indicator that your rose needs water.
On the other hand, too much watering can lead to root rot and other damaging diseases. Roses like moist, but well-drained soils. They do not like their roots to stand in constantly soggy soil.
Always provide water at the base of a plant. Water that stands on foliage too long can sponsor the development of powdery mildew, black spot and other diseases. That being said, Knock Out Roses and other low maintenance roses are much more resistant to black spot.
A light coat of mulch at 1 or 2 inch depth around your roses can help to retain extra moisture and suppress weed growth.
Other Helpful Tips
In regions that experience colder winters, where temperatures dip below freezing, stop fertilizing roses about two months before the average first frost date in your area. Promoting new growth during winter can lead to freeze damage.
Avoid fertilizing roses when they are under stress from extreme heat or drought. Doing so can cause damage to leaves or buds. It is be best to simply provide additional water during prolong periods of drought.
With the exception of a few roses that will tolerate more shade, most prefer full sun to light shade. Keep in mind that morning sun is a must to dry dew from the leaves.
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