sprinkler1How much and how often should you water your grass? When is the best time to water? Those sound like pretty basic questions, but the answers aren't always so simple.

Turfgrass irrigation and watering needs depend on many factors ... like the kind of grass you have, your mowing height, and the irrigation system or sprinkler you use. Plus, of course, what Mother Nature does and doesn't dole out.

Also, what's your soil profile like? Have you added organic matter ... ever? I wish there were simple, foolproof, silver-bullet answers, but there are just too many factors to make it that easy.

So, today we'll rehash many of my suggestions for lawn irrigation. And, as always, if you your question isn't addressed below, please give me a call at 713-212-KTRH (5874) on GardenLine this weekend and we'll tackle it on the air.

Even if you think you know how often you should irrigate, take a moment to go over these points. While we had a nice soaking rain last Monday, you can't always count on similar downpours during our hot July, August and September.

My basic irrigation schedule takes into consideration temperatures and rainfall:

Normally, turf and landscapes in this area do fine with 1-1½ inches every seven days when daytime temperatures are in the 70s and 80s. As daytime highs hit 88-92, you can probably up that to 1-1½ inches every four to five days. When temperatures exceed 93 consistently (normally July-August), you should probably water every two to three days. And during 100 degree days, it's possible some lawns will need irrigation every other day. That may be a problem during irrigation restrictions, and that's why it's important to have great soil under that grass.

Your soil is ultimately the most critical factor. Clay or sandy soils that are not well-enriched with organic matter definitely need more water because they dry out quicker. When was the last time you added a good organic top dressing? If it seems some of your neighbors don't run their sprinklers as much as you, they may have more organic matter in their soil. Rich, organic soil doesn't happen overnight, though ... enriched compost, humates or soil activators need to be added consistently each year.

sprinkler2Talk to anyone who's done that on a continuing basis, and they'll likely tell you they water the lawn maybe once a week, even when temperatures are in the 90s.

The type of grass you have is also very important. St. Augustine needs the most water, Bermuda the next most, and Zoysia far less than the previous two.

As for when to water, I've always recommended early in the morning. That's when water pressure is best, there's almost always less wind to evaporate the moisture, and the turf will get a store of water for the warm day ahead. If you have automatic sprinklers, schedule them to run between 4 and 9 a.m. If you don't have an automatic system, start the water when you first get up. If you water at night, you run the risk of suffering fungal diseases like brownpatch. Watering in the early evening or at night is probably okay until our nighttime temperatures get back down in the 60s — that's definitely when you should get back on a morning schedule. Temps in the 60s are an open invitation to brownpatch when and where there is too much moisture available.

How do you determine how much time it takes for your system to put out that inch to inch and half of water? Place an empty tuna or cat food can at the farthest point in the spray pattern. When it fills up, that's how long it takes. Depending on the system, it can take 15-45 minutes.

There is one caveat to all of the above. Newly sodded lawns need to be watered on a daily basis during the heat of the summer. Keep the mud wet under the root zone so it will break down and allow the roots to establish in the soil below. Don't drown the new sod ... just keep it moist enough to soften the soil and help the roots grow down

By the way, if you don't have an automatic sprinkler system, what kind of sprinkler heads are you using? In the summer, you should be using impact sprinklers or lower trajectory sprinklers. Oscillating sprinklers (the ones that throw water straight up and slowly wave back and forth) are the most wasteful because of the intense evaporation summer brings.

Remember: when you're watering wisely, you're saving money. According to the Texas Water Development Board, as much as half of all outdoor water use in the warmer months is wasted because of poor watering practices. This can have quite an impact on your water bill, since 50-80 percent of our water consumption during those months is used outside. It just makes common sense to use this valuable resource more efficiently to save both water and money.

Also, if you aren't mowing as tall as your lawn mower will allow, make the change today. Tall grass in good soil develops deeper roots which draw a larger volume of deep moisture, requiring less supplemental irrigation. Simply put, taller grass blades, especially in St. Augustine lawns, reduce evaporation and shade the soil.

Finally, I often get asked about using buffalo grass in Houston-area lawns because it does so well in very arid climates. Here's the irony: in Houston, we get way too much rain for it to succeed. Buffalo grass thrives in areas like West Texas where annual rainfall can be less than 20 inches per year. If we get another tropical system shoving in from the Gulf, we can get 20 inches in less than two months around here.

PHOTOS: Fabrice Florin creativecommons.org/licenses/by-sa/3.0/