How To Prevent Disease On Annual Flowers And Perennial Plants
There's nothing more disappointing to the flower gardener than planting a garden bed or container garden of beautiful annual or perennial flowers to then watch a fungus or disease lay the plants to waste. 

When planted properly, in the right soil, provided preferred light, and watered and cared for properly, most plants will have few if any serious disease problems. That said, even when everything is done right there can be disease.


Plant selection is important. When selecting different types of plants that will be planted to grow closely together in the same garden bed, make sure to choose plant types that share similar soil moisture and sunlight requirements. Simply put, you don't want to mix moisture-loving plants with plants that prefer life on the dry side, or plants that prefer sun with plants that like life on the shady side. Too, make sure you select plants that have demonstrated tolerance to disease - especially if you garden in a hot and humid climate.

Let them breathe.  Rather than overcrowd plants in a flower bed or container garden for instant gratification, space plants properly. Overcrowding prohibits good air circulation, which is necessary to keep plants healthy and free from disease. Too, as the growing season progresses, overcrowding causes competition with the roots for soil space, which can increase the need for water and nutrients and cause plants to decline.

Keep a watchful eye. With the exception of powdery mildew, which appears as a white powdery substance on the surface of leaves, if a disease happens to pop up on a plant growing in your garden bed or container garden, or a leaf is damaged, remove any infected foliage and discard immediately to stop any spreading of disease throughout the entire flowerbed.

If a plant(s) looks diseased or discolored, check soil moisture. More annual and perennial plants become diseased and die (or are killed) due to improper watering than anything else. The rate of water loss and thus the need to water your plants depends upon air temperature, light levels, and other factors including the type of plants you have. Thus, it is hard to set a strict watering schedule. 

Water right. If possible, water plants at the base to avoid splashing water on leaves. Water or irrigate plants in the early to mid morning hours. Doing so at this time of day allows any water that might splash on foliage to dry before the heat of the day. Avoid watering plants in the late evening or at night as this can cause development of harmful or deadly fungus and other -plant diseases.

Know the requirements of your plants and use the "touch method" to evaluate soil moisture and the need to water, or not. Press the tip of your finger down about an inch or so into the soil. A cool, damp feeling indicates there is still adequate moisture in the soil and a dry feeling indicates that you should water. If you have a lot of house plants, consider getting a water moisture meter to test soil.

Avoid over-watering! Over-watering plants is the number one cause of death. Allow the soil in garden beds and containers to dry out a little before watering. 

Spray if necessary. If you've seen a disease, and had to remove some plants or plant parts, it can be helpful to spray a fungicide to prevent further spread of the disease. For disease prevention on annual bedding plants and perennials I use neem oil, which can also be used on fruits, vegetables, ornamental plants and trees, and roses to prevent black spot, rust, leaf spot, and powdery mildew. Neem oil also works to control many harmful insects as well. 

IMPORTANT! Because neem oil is not a contact killer it does not harm beneficial pollinating insects, only killing the insects that actually ingest plant parts. That said, whenever spraying flowering plants, to avoid killing beneficial insects spray in the very early morning or very late evening hours when pollinating insects are not active.

Homemade Recipes for Treating Fungal Diseases

Mix two tablespoons of baking soda into a quart of water. Pour into a spray container and spray affected areas. Repeat this process every few days until problem ceases.

Powdery Mildew: Mix equal parts milk and water and spray on infected plants. Three treatments a week apart should control the disease.

Insects and Fungal Diseases: Combine one tablespoon of cooking oil, two tablespoons of baking soda and a few drops of Ivory soap into a quart of water. Pour into a spray container and spray foliage.