Preventing Diseases in Your Plants

Veteran gardeners know the best disease treatment is prevention.  There are some things you can do no matter what outdoor plant you are growing that make it harder for plant diseases to attack your plants.

Sanitation

The most important way to prevent plant diseases is to practice good sanitation.  Sanitize your gardening tools at the beginning of each gardening day.  Wash dirt off the tools, then wipe them with rubbing alcohol, including all the nooks and crannies and the handle.  Rinse and dry the tools well. 

Sanitation also refers to removing dead plants promptly.  Do not compost diseased plants as that will spread the disease.  Put them in the trash.  For vegetables, remove all the spent plants at the end of the season.  Keep windfall fruit picked up.  Both pests and diseases can overwinter in vegetable debris.  Keep animals out of food crops, including chickens.

Purchase From Reputable Dealers

As with anything, you get what you pay for.  Do not purchase plants and seeds unless you know the place where you are shopping has a good reputation.  Many diseases are spread by seeds, so buy only certified disease-free seeds.  Do not purchase plants that look wilted or unwell.

Rotate Plants

If you grow vegetables, rotate your crops each season.  Rotate by families.  For example, if you grow tomatoes in an area one season, do not plant anything from the nightshade family in that spot for three years.  Some people do not have a big enough garden to effectively do this, but if you can, rotate your crops.

If you have a plant die, do not put another plant of the same or closely related species in that spot until you are sure the disease is not soil borne.  For example, if a peach tree dies of cotton root rot, planting another susceptible tree such as another fruit or nut tree, ash, cottonwood, elms, figs, or a sycamore tree will probably result in the death of that tree, too.  Plant a tree that is resistant or immune to cotton root rot instead.

Plant At Ideal Time

Plant different plants at the best time to maximize their potential.  If possible, plant bare root plants in late fall or early spring so they can become established before the summer heat.  While you can plant a container grown plant at any time of the year, it is better to plant them in the fall so their roots can get established before the cold.

Plant Properly

When you plant something, dig a hole that is twice as wide as the root ball and a foot deeper.  Do not put fertilizer in the bottom of the hole because it will burn the tiny root hairs off the roots.  These are the part of the root that takes in water.  To plant your tree or shrub, have someone hold the tree at ground level.  Fill in the dirt from the hole under and around the tree to make it stand up straight.  Water to settle the soil.  Fill more soil into the hole until full.  Water and repeat until the soil does not sink any more after watering it.

Mulch

Mulch helps stabilize soil temperature and soil moisture.  It blocks weeds and helps protect trees and shrubs from lawn mower and string trimmers.  The mulch should ideally be three inches deep.  Leave a three-inch zone around the trunk free of mulch, then put the mulch from there to the edge of the dripline.  As the tree grows, the mulch should be extended with it.  You can use a low growing ground cover like Virginia creeper or creeping phlox instead of mulch, but don’t leave bare ground under the tree.  Mulch helps keep soil borne diseases from spreading by putting a layer between the plant foliage and the soil.

Don’t Overcrowd Plants

When installing a new landscape, the temptation is to plant things close together, so the landscape looks fully grown now.  The problem is that when the plants grow, they are too close together.  Air cannot circulate around them, so the foliage doesn’t dry after a rain, setting them up for a fungal problem.  The neighboring plants compete for light, water, and nutrients.  The plants are not able to grow to their potential.

Water Properly

Watering sounds easy enough, but some watering practices increase the chance your plants will get fungal infections, soil borne diseases, and other problems.  Most ornamental perennials need about an inch of water a week.  In hot climates, they may need to be watered twice a week.  Watering deeply once or twice a week is preferable to watering a little every day.  Plants that are watered deeply grow good roots that reach down into the soil.  Not only does this let the plants reach water that is deeper in the soil, it helps stabilize the plant so it doesn’t blow over as readily.

When you water, try to get the water in the root zone without getting the plant wet.  Fungal infections need about eight hours of wetness to take hold.  If you do not get the foliage wet, it makes a fungal infection less likely.

Drip irrigation is the gold standard for watering, but a soaker hose works, too.  Always water before ten o’clock in the morning.  This leaves the whole day for wind and sun to dry any water you might get on your plant.  If you do have to use overhead sprinklers or a water hose, make sure the area where you water is mulched.  This keeps soil with fungal spores from being splashed onto the foliage of your plant, where it can cause a problem. 

In the winter, plants need less water.  You do still need to water them, however.  Watering early in the day will give the water time to soak in before it gets freezing at night. 

Don’t Overfertilize

Most native plants do not need much fertilizer.  They have evolved to live in the soil in your area.  Plants from elsewhere, fruit trees, nut trees, and vegetables need fertilizing.  When fertilizing, follow the directions on the label of the fertilizer.  Many people feel that if a little fertilizer is good, more is better.  This just isn’t true.

Too much fertilizer can burn your plants and can even kill them.  Too much nitrogen encourages plants to put on lots of new growth.  Many pests and diseases love tender new growth.  In addition, too much new growth can make it hard for the roots to bring up enough water for the plant’s needs.  Fertilizing too near cold weather means all that new growth will freeze and die back, potentially injuring the plant.

Remove Diseased Plants Promptly

Many plant diseases are contagious.  The best way to protect your plants is to promptly treat any plant disease that is treatable.  If the disease is too severe or is viral, pull the plant up and discard it in the trash.  Do not compost diseased plants or you will spread the disease when you spread the compost.

Plants that are native to your region have usually developed resistance or immunity to the diseases that frequent the area.  They are usually able to tolerate common pests in the area, too.

Ask Question

TN Nursery staff are happy to answer any gardening questions you may have.  Give us a call at 931.692.7325 and we will help you find the perfect plant.