Snip off any spent roses. Allow as many leaves to remain as possible. Extra foliage protects the canes from sunburn and provides more tissue for photosynthesizing and nutrient production. If dead blossoms are left behind, they signal the bush to start making seeds (rose hips). We don't want the plant to expend energy on seeds and reproduction, but rather put forth more foliage and prepare for more blooms when the temperatures cool.
Extending the Life of Rose Bouquets
Although not as prolific as spring and fall, roses still produce blossoms in summer. To enjoy them in a bouquet, cut early in the morning before they open up fully. Use a sharp pruner and make a clean cut on a slant. Use a floral preservative or make one with 1 pint of regular Sprite or 7-Up (not diet) mixed with an equal amount of water plus 1 teaspoon of bleach.
Don't Fret Half-Moons on Foliage
You may see carefully cut semi-circles on the edges of rose leaves and other smooth foliage, such as bougainvillea. This is the handiwork of leafcutter bees who use the material to construct narrow, tubular nests. These bees do no harm to the plant. They do not ingest the foliage, so applying any sort of insecticide is worthless. Bees are excellent pollinators, so be happy they are visiting your area!
Fertilizing Roses in Summer
There are varying schools of thought on fertilizing roses in the summer. Some rosarians recommend allowing them to rest during the heat. Others suggest using a slow-release fertilizer at the start of summer. These products usually last about 90 days. Another possibility is to continue feeding every 6 weeks but use fertilizer at half-strength. I prefer using organic fertilizers, such as fish emulsion or alfalfa meal, because they have a low concentration of nutrients and must break down further in the soil before being absorbed by roots. Both of these characteristics make it unlikely they will cause root burn.
Hose Off Spider Mites
Roses seem to attract spider mites, especially if the foliage is dusty. Spider mites love dusty conditions! They are easy to control with regular blasts of water from the hose. Inspect the bushes daily, looking for tell-tale webbing and sometimes a rusty, dusty look. Examine the undersides of leaves. Many spider mites are a rust color. Spray early in the morning before the sun gets too hot. The humidity from the water will help the plant. Spray underneath the foliage as well. Don\'t spray late in the day, as moist conditions at night promote fungal diseases.