How To Water Lawns in Summer
Tom Ingram: Ask A Master
Gardener
Sunday, August 18,
2019
Q: It’s been so hot outside. How do I know how
much I should be watering my lawn? JB
A: Keeping our growing things alive in July and
August can be a challenge in Oklahoma. However, there are some general
guidelines that can help.
If your lawn is
primarily Bermuda (or another warm-season grass), it needs about 1 inch of
water per week this time of year, while fescue (or other cool-season grasses)
need about double that or 2 inches of water per week.
Whenever we tell
someone this, the next question is typically something like, “Then how long do
I run my sprinkler to get an inch of water?” The answer to that question
necessitates you doing what we call a “simple irrigation audit.”
For a simple
irrigation audit, you are going to need nine collection cups, a pen, paper and
a calculator (most of us will probably need a calculator). Collection cups can
typically be purchased from an irrigation supply store or you can use clean
metal cans that might previously have contained tuna, cat food or perhaps
tomato paste. You will get the best results if all your collection cups are the
same.
If you choose cans,
you can use a ruler and a fine-tip permanent marker to mark the outside of the
cans in ¼-inch increments. Or you can just measure the collected water by
sticking a ruler directly into each collection can.
To collect your
measurements, place your nine collection cans about 8 feet apart in something
close to a 16-by-16-foot grid. For best results, do this in one sprinkler zone
at a time.
Next, let your
sprinkler run over your collection grid for 20 minutes. After the collection
period is over, measure the amount of water in each of your collection cups,
add up the total amount collected (now it’s calculator time), and divide the
total by nine because you were using nine collection cans. This will give you
an average amount of water your collection grid area received in 20 minutes.
So let’s assume your
average measured amount was ½ inch. This means for every 20 minutes your
sprinkler system runs, your turf will be receiving a ½ inch of water. If you
have Bermuda grass, which needs 1 inch of water per week, you are going to need
to water twice that amount, or 40 minutes per week. You can split this up into
two watering sessions per week of 20 minutes each.
If you have a fescue
lawn, which needs 2 inches of water per week, the math says you would need 80
minutes per week, which can be split up into two watering sessions of 40
minutes each. This would not be a total for your yard, just for that zone. As
you can imagine, each zone is going to be a little different, so for complete
accuracy, you would need to repeat the process for each zone.
Performing this simple
irrigation audit will likely end up saving you money, as most of us
overestimate the water needs of our turf and end up “pouring money down the
drain.”
Garden tips
·
August is a good month
to start more crops in your fall vegetable garden. Bush beans, cucumbers and
summer squash can be replanted for another crop. Beets, broccoli, carrots,
potatoes, lettuce and other cool-season crops can also be planted at this time.
·
Discontinue
deadheading roses by mid-August to help initiate winter hardiness.
·
Irrigated warm-season
lawns, such as Bermuda and zoysia, can be fertilized once again; apply 1 pound
nitrogen per 1,000 square feet this month. Do not fertilize these grasses after
the end of August. Do not fertilize tall fescue lawns in summer; fertilize in
late September after it cools and again in November.
·
Make a note on your
calendar that our free Fall Lunch & Learn classes will be starting Sept.
17. You can find more information and topics on our website
.
