The peak of rose bloom in my garden occurs around the last week of April. I consider this an unofficial farewell to spring and the beginning of summer. I say good bye to peonies, iris and pansies and hello to daylilies, hydrangeas and of course, more roses. With the exception of one or two, the roses in my garden are repeat bloomers and will continue to throw out flowers until the first hard freeze in fall.
I’m a rose fanatic and have planted them extensively in my garden. While most of the varieties are fairly carefree I do have a summer regimen that I follow to keep them in tiptop shape.
I give my roses a healthy dose of fertilizer in the early spring to fortify them for their first flush of bloom. I simply use a fertilizer high in phosphorous, which is the middle number on the package. After the first wave of flowers fade I hit them with a second application of fertilizer formulated especially for roses. This will re-energize the plants and promote more roses for those that are repeat bloomers. Through the summer I continue to feed my repeat blooming roses after each bloom cycle.
Black Spot and Powdery Mildew
The biggest headache when growing roses is blackspot and powdery mildew.
Blackspot – As the name implies it starts with a black spot on the leaf. It’s a fungus that certainly diminishes the look of the plant. Now I’ve never had a rose bush actually die from blackspot, but it can certainly cut down on their performance and make the shrubs look pretty shabby.
Blackspot is usually brought on by weather conditions. Sporadic rain followed by humid to hot conditions is the ideal breeding ground for this fungus. The rain soaks the plant, and then the weather heats up and causes the fungus to form on the damp leaves and petals.
If the problem becomes severe, use a commercial fungicide for blackspot and always try to get the plant completely saturated from top to bottom with the spray. Some serious cases of blackspot require several treatments before the fungus is completely annihilated. You should also spray the ground around your roses and put any diseased leaves in your trash, not in your compost.
Powdery Mildew – Powdery mildew is another fungus that reveals itself as a powder-like coating over the leaves.
Rarely will it kill a plant, but some perennials like phlox and shrubs such as lilacs, crape myrtles and roses can be damaged. A heavy infestation of powdery mildew can cause a plant to lose its leaves diminishing its vigor and causing it to not flower quite as much.
If you’re having this problem in your garden there are two approaches you should try in bringing the problem under control. The first is prevention. Remove and dispose of infected plants and leaves by burning them or put them in the garbage to help cut down on the spread. Don’t put infected leaves in your compost because you will just harbor spores for another round next season.
The second line of defense is to take action by spraying. But before using a conventional fungicide, try some of the new safer alternatives. I use a sulfur-based product. Since it’s not a synthetic fungicide, I don’t have to worry about it damaging the environment. Spray your roses about every 7 to 10 days when mildew is a problem.
One home remedy that some people have found useful as a preventative to powdery mildew is using this formula:
1 heaping teaspoon of baking soda
1 tablespoon of summer oil
1/2 teaspoon of insecticidal soap or dishwashing soap
1 gallon of water
It’s important that a plant is well hydrated before applying this solution. Water deeply a couple of days before spraying and don’t spray during the heat of the day.
Black Spot Resistant Roses in My Garden
The time to do any hard pruning of roses is the late winter or early spring before the leaf buds open. But don’t panic, if you didn’t get to cutting back your plants this year. Your plants will not suffer and once the blooms have faded at the end of spring you will have the opportunity to do some light pruning. Not only will this be a chance to reshape and clean up your plants, but with many of the repeat blooming varieties, it will encourage a second round of flower production.
It’s important to realize that not all roses rebloom. Some old-fashioned shrubs types only bloom once in the spring. Cutting the old flowers away on these types will just help the plant look a little better. But for those that rebloom like my favorite ‘New Dawn’ as well as any of the floribundas, polyanthas and popular hybrid tea roses, removing what is left of dead flowers will definitely encourage the next wave of bloom. When you do this it’s important to remove them with sharp pruners, making the cut just above a leaf with five leaflets. By cutting here, when the new bud forms, the stem will be large and strong enough to support it. Another thing I do after I’ve pruned my roses is feed them with a high phosphorus liquid fertilizer.