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The Honolulu Advertiser
Posted on: Saturday, June 5, 2010

HAWAI'I'S GARDENS
Some parting advice on home lawn care


By Jay Deputy

As someone once said, "all good things must eventually end." And so it is with the weekly Hawai'i's Gardens column. On behalf of the other contributing columnists, I extend our fond aloha.

As a parting offering, I've decided to give you my version of a quick guide to home lawn care.

Establishing new lawns. My best piece of advice is do a good job of soil preparation. Soil amendments such as compost and fertilizer and weed elimination are the most important.

The warm-season grasses used in Hawai'i are planted from seed or vegetatively by sod or sod pieces (plugs, sprigs and stolons). See my May 8 article for more information.

Be careful if you buy grass seed. Some garden shops carry a mixture of what is advertised as "shade grass." This is a mixture of cool-season grass such as Kentucky bluegrass, fescue and rye, which do not survive the warm Hawai'i climate. Susan Owen at Ko'olau Seed (239-1280) is your best source of information for any lawn, pasture and ground cover seeds.

Fertilizing. Turf grass needs more nitrogen than other ornamentals or food crops. Always look for fertilizer formulations that contain a high percentage of N nitrogen (the first of the three numbers on the front of the bag). Slow-release forms of nitrogen last longer, give a more even growth rate, and are less likely to burn the grass if too much is applied at one time. Information on the amount of slow-release formulation can be found in small print in the "Analysis" part of the label on the back of the bag. The higher the percentage of slow-release N, the better. When using slow-release N fertilizers, use 1 1/4 pounds of nitrogen per 1,000 square feet of lawn with each application.

All turf grasses do not require the same amount of fertilization. Most home lawns with Bermuda grass or one of the paspalums will benefit from one application every six to eight weeks during the spring and summer months. All of the zoysia varieties, El Toro, Z3 and Emerald, will do fine with an application once every 12 to 14 weeks. St. Augustine can be maintained with an application twice a year and centipede grass only once a year.

Fertilizer requirements will vary with soil type. Sandy soils should be fertilized at lower rates but more often. It is better to under-fertilize than to overdo it. Too much nitrogen makes the grass grow faster, which means more mowing and thicker thatch build-up. You can apply iron for a fast green-up without the increase in growth rate. Several granular and spray-on products are available in garden shops.

One final precaution always use a rotary spreader when applying fertilizer and water well immediately after.

Watering. Irrigation schedules depend a lot on your soil type. Sandy soils drain quickly and do not hold much reserve water. During hot summer days, it may be necessary to water every day. The water should be on long enough to soak the soil to a depth of at least 12 inches. Short watering periods will result in shallow rooting and greater chance of damage to the grass.

Clay soils have a much greater water reserve but often do not drain well and runoff is much more likely. The rule of thumb here is to water less often but for longer durations. Once every two or three days usually works well. Again, soaking the soil to a depth of 12 inches is the goal for each watering. If water begins to run off before enough has been applied, use a split watering cycle. If 30 minutes is required to give enough water for one cycle, use two separate 15 minute cycles for that zone. Typical clay soils will require about two inches of water to wet to a depth of 12 inches. One inch of water requires about 600 gallons per 1,000 square feet.

Mowing. Follow the one-third rule. Mow often enough so that you do not remove more than one-third of the blades with each mowing. Each grass species has its own recommended mowing height range. The best results usually come from keeping the mowing height near the middle of the recommended range. Bermuda grass, paspalum and Z3 and emerald zoysias are best mowed at one-half inch to one inch. El Toro zoysia can be maintained from 1/2 to 1 1/4 inches, centipede at 1 1/4 to 2 inches and St. Augustine at 2 to 3 inches. Mowing heights below one inch require a reel-type power mower; above one inch a rotary mower is needed.

Unfortunately, I'm out of space. I have enjoyed corresponding with many of you who read this column.

The CTAHR website is a great source of information for landscape and many other horticultural and agricultural topics: www.ctahr.hawaii.edu/site/BrowsePubs.aspx