Spotting damage on the perennials that you’re working so hard to grow can be frustrating, but don’t overreact. Perennials are a tough bunch. Problems may be due to the environment or to pests.
Don't worry too much about a few holes in the leaves; it won't affect a plant's vigor and probably isn't noticeable at ten paces, anyway.
Environmental damage often creates symptoms that look very much like disease or insect mischief. Determine whether any of the following conditions may be responsible for your flowers’ ill health:
Air pollution: Some flowers are sensitive to smog. Their leaves may appear bleached or distorted. If you live in an area where smog is a problem, ask a local nursery person to recommend resistant varieties.
Chemical damage: Use herbicides on cool, still days to prevent spray from accidentally drifting onto your flower beds. Swimming pool chemicals can also damage plants. Symptoms of chemical damage include distorted and twisted stems and foliage, browning in an even pattern over the whole plant, or irregularly-shaped brown spots.
Drought: Too little water causes plants to become warped, stop growing, and develop brown tips or yellowing leaves.
Fertilizer burn or fertilizer deficiency: Too much fertilizer can actually kill a plant. Shortages of any of the essential plant nutrients can cause stunting and leaf discoloration.
Freeze damage: Frost can blacken the most exposed parts of the plant. Hardy perennials usually grow back after freeze damage, but, just to be safe, protect plants from unseasonable cold spells by temporarily covering them with old sheets or blankets. Don’t use plastic — frost goes right through plastic.
Inadequate sunlight: When a flower isn’t getting enough light, it turns sickly pale and its stems become long and spindly. If you plant in a shady area, choose shade-tolerant flowers.
Poor drainage: Flowers that are too wet become yellowish or brown, wilt, and eventually die. Plant flowers that are tolerant of wet conditions or improve the drainage in your flower bed.
Salts: Salt can occur naturally in the soil or ride on salt-ridden breezes, if you live near the ocean. Cars can also splash salt onto your garden when roads are salted in the winter. When salt concentrations build up, your flowers can become stunted and brown. The cure is to rinse the soil with plenty of fresh water.
Sunscald: When shade-loving flowers are getting too much sunshine, they become pale all over and then may develop papery patches or dark, irregular burns. Move the plant to a shadier location.
Transplant shock: A recently moved flower can go into a real sulk and wilt badly. Provide temporary shelter from the sun and wind until the plant recovers and has settled into its new home.
If you think that insects are eating your flowers, you first you need to identify the suspects. Don’t panic when you look over the following list. Most insect infestations are localized — you aren’t likely to ever get to know all these pests, unless you move around quite a bit. Insects also have good and bad seasons. You may be thoroughly plagued by leafhoppers one year but not find a single one the next.
The following list describes the most common insect pests of perennial gardens.
Aphids: Often, the first indication of aphid infestation is an odd twisting and distortion of the foliage.
Beetles: Many types of beetles eat perennials; many other types eat bugs. If you catch them in the act, you can tell the difference.
Caterpillars: Usually, butterfly caterpillars are big, brightly colored, and travel alone. You may decide to look the other way when one of these critters inches by. Other types run in packs and do a great deal of damage munching on leaves and flower buds. Still another type of caterpillar, called borers, tunnel destructively through stems or roots. Cutworms are soil-dwelling caterpillars who cut off whole young plants at ground level.
Leafhoppers: These insect Typhoid Marys carry a disease called aster yellows, which does particularly nasty things to flowers.
Leaf miners: Leaf miners are tiny fly maggots that tunnel in leaves, resulting in tell-tale trails.
Mealybugs: Furry little white, oval-shaped critters, mealybugs would be cute if they didn’t do so much damage and multiply so rapidly.
Spider mites: As their name implies, spider mites are actually tiny arachnids, not true insects. Usually, the first hint of a spider mite invasion is a mottled bronze tint to the foliage. A closer look reveals traveling dots about the size of the period at the end of this sentence.
Thrips: If your flowers turn brown and are distorted and streaked with silver, tiny thrips are the culprit.
Weevils: Beetles with long snouts, weevils often drill holes in flower buds, so the flowers don’t open properly, if at all.
Whiteflies: Small, snow-white whiteflies suck plant juices and reproduce at lightning speed. Symptoms of whitefly attack are mottled and yellowed leaves.
