Perennials
Divide perennial flowers such as hosta, Oriental poppy, lily, daylily, ornamental grasses and bearded iris.Prune all summer flowering shrubs once the blooms are finished. The heat and humidity will encourage plant diseases, check your plants for any diseased foliage and remove it.
Fertilize
Fertilize summer- flowering bulbs but stop fertilizing perennials, trees and shrubs.Don’t feed your lawn with a high nitrogen fertilizer now as this will encourage lots of new growth which is easily damaged by autumn weather. Lawn growth slows down in the summer so raise the cutting height of your lawn mower. Continue to feed tomato plants with a tomato fertilizer.
Pruning
Deadhead bedding plants and perennials to encourage them to flower in fall and to stop them from self seeding. Deadhead lilies. Cut back herbs now to encourage a new flush of leaves before frost. Trim lavender plants after they flower to keep them healthy. Give hedges a final trim before they stop growing.
Tomatoes
To prune, remove the suckers by pinching them with your fingers. Remove yellow leaves from plants. These leaves use up more sugar than they actually produce. The best time to prune is early morning on a dry day.
Take photos of your garden if you want to rearrange things next year. Enjoy the summer!