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The Homeowners Column
Good Gardener Equals Good Waterer
State Master Gardener Coordinator
To be a good gardener you have to be a good waterer. The when and how of watering is as mysterious to novice gardeners as the attraction to reality TV is to me. The dynamics of good watering include an understanding of the interrelationships of weather, plants and soil; and of course the trial and terror of killing a few plants. However I can assure you with some practice you will get better at knowing when to hose 'em and how to grows 'em. August often heralds in a dry period. So how long can our plants last before they literally "bite the dust" from lack of water? As one of my horticulture professors was fond of saying, "It all depends".
As a general rule garden plants need about an inch of water a week, but that depends on soil type, plant species, and if the plants are well established. Clay soils tend to stay wet longer, but are harder to rewet once they turn to pottery. It takes about one half gallon of water per square foot to get an inch of water. Plants such as ferns and hydrangeas need more water than prairie plants. Any plants flowering or setting fruit such as tomatoes need more water than carrots or sweet potatoes. Anything planted this year including plants listed as drought tolerant and any trees or shrubs planted over the last two years need extra water. New plantings and containers often need water daily.
new trees purchased as balled and burlapped should be watered with one gallon
of water per diameter inch of trunk every 5-7days if rain is not adequate. For
example a 2-inch diameter tree should be given 2 gallons. Trees and shrubs
purchased in containers will need to be watered more often, perhaps daily,
depending on temperature and wind. Container plants are usually grown in
soilless mixes which tend to dry very quickly even once planted. Tree watering
bags such as Treegators® are a great way to water new trees and a good visual
reminder for us. Established trees (more than 3 years in present location)
should be watered once a month during dry periods. Apply water at the dripline,
not at trunk.
Any recently planted lawn grass will need more water than more established lawns. With established lawns it depends on whether you want the lawn to stay green or just alive. Cool season grasses such as Kentucky bluegrass naturally go dormant when it gets hot and dry. Once they are dormant, it's best to leave them there during hot dry periods. Cycling between green-up and dormancy drains plant reserves. A dormant lawn may not look as nice, but is less prone to insect attacks. The lawn greens up once cooler, wetter weather returns.
The common question is how much water is enough to keep the lawn alive? Applying at least 1/3 inch of water every 3 weeks should be enough to maintain moisture in the crowns and roots for turf to survive. Use empty tuna fish cans in area covered by sprinklers to determine how long the sprinklers need to run. Remember to mow lawns higher in summer between 2.5 to 3.5 inches and avoid applying nitrogen fertilizer during hot, dry conditions. Limit traffic on a dormant lawn. Water in morning to reduce disease problems and lessen water loss due to evaporation.
Use soaker hoses to efficiently water landscape plantings. Check soil after half hour of soaking to determine proper watering period. An inch of water will wet an average of 6-15 inches of soil, depending on soil type.
Conduct triage when deciding what gets watered. Check out our local UI Extension website http://web.extension.illinois.edu/cfiv as well as the state website http://web.extension.illinois.edu/state for more information about all things gardening.