What is the single most important factor in the short-term and long-term success of a new planting? If you said proper watering, you're right. (You might also be using context clues from the title of the post, but the important part is that we got to the right answer.) Why is water so important early on? Newly installed plants don't yet have extensive root systems like more established plants, so they rely on the moisture present in their original root ball. Balled and burlapped trees and shrubs face greater initial stress because they lose substantial root mass when they are harvested for planting. Even drought tolerant species will need a little help at first if you expect them to survive long enough to become the low-maintenance rock stars you want. As new plants grow and root out into the surrounding soil, they become stronger and more resilient to changes in moisture levels. But be careful - there is such a thing as too much water, especially in the slow-draining clay soils common in the Indianapolis area. Also be aware that just because the hose is running, it doesn't mean that the right amount of water is going to the right place. Follow these instructions to make sure your new installation is happy and healthy.
When to water
Dig into the soil 2-4 inches with your hand or a trowel. If the soil feels damp, don’t water, but check the soil daily to see if it's dry. Soon you will be able to observe that the daily temperature, natural rainfall, and the look of the plant will help you judge if it is time to again test the moisture in the soil. If it's 90 degrees in July, and it hasn't rained in three weeks, a new tree or shrub might need to be checked twice per week, while perennials should be checked every 2-3 days. If it's 60 degrees in April and it has poured rain for a week, you should be fine checking once per week at most. Eventually, you'll learn what your property needs, and you may not need to dig into the ground often at all.
How to water
When the soil is dry, water the plant slowly and deeply. This means you should water at a rate that allows all the water to be absorbed without running off. Leaving the hose running on full blast at the base of a tree won't help much because the water will run off instead of soaking into the soil. Instead, leave the hose on a trickle within the root ball of a tree or shrub.
Periodic deep watering is better than frequent shallow watering because it encourages the roots to grow deeper and further, and so it prepares the plants to be stronger and more resilient after you stop supplemental watering.
Fifteen minutes of gentle hose watering in one spot should be enough for a shrub or very small tree. For larger trees, water the tree for a total of 30-45 minutes, moving the hose once or twice to make sure the root area is evenly covered. Tree irrigation bags can be helpful in the short run if you know you'll forget to water a tree. Follow the instructions provided with the bag to make sure you're providing the right amount of water for the size of your tree. In very hot, sunny weather, tree bags can actually hurt your tree by trapping heat and humidity against the bark. In these conditions, consider removing the bag entirely or at least taking it off between fillings.
Annuals and perennials don't need to be watered as deeply as trees and shrubs since their roots are shallower. A sprinkler or a hand-held hose nozzle works well. 20-30 minutes is usually enough time for a sprinkler on perennials, 10-15 minutes for annuals. When hand-watering, I like to slowly move over the area in 15-30 circuits depending on how dry the soil is. Annuals will need water more frequently than perennials, because we focus more on growing those for a showy display above ground rather than a durable root system below ground.
Keep in mind that all these numbers for watering frequency and duration will change depending on soil type and moisture. When in doubt, check the soil in the way we described above.
Water newly planted trees and shrubs throughout the first year from spring until late fall. Trees benefit from an additional season of watering, especially if they were planted late in the year. Perennials are usually safe to stop watering after 2-3 months, but keep an eye on them. Annuals should be watered all season long. Temporary irrigation can be installed for the first few months or the first season so you don't have to worry about checking the soil. Ask us about this option if you are concerned about your ability to keep your new planted watered properly. Water plants in subsequent years when they look wilted.
Water between late evening and early morning to reduce water loss through evaporation (but don't wait until evening to water if a plant is wilting now!)
Avoid watering foliage when possible. This can cause fungal and bacterial leaf spots on some plants, especially roses.
Frequent light watering is only acceptable for annuals
Wilted leaves can come from too much water as well as from too little water. Always check the soil, especially in containers without drainage.
To cover one square yard of soil with water one inch deep will take approximately 6 gallons of water. To do the same over one square foot of soil will take 2/3 gallon of water.
A soda straw sized stream of water will take approximately 15 minutes to produce 6 gallons of water
A thick layer of mulch will help conserve moisture. Just make sure you apply extra water so that the soil still gets soaked to a depth of a few inches.