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The Honolulu Advertiser
Posted on: Saturday, April 3, 2010

HAWAI'I'S GARDENS
Soil preparation key to healthy lawn


By Jay Deputy

Q. I have a seashore paspalum lawn that my dad and I started from stolons about two years ago. One of things that I didn't do was till the yard before planting. My grass grew out OK, but there were patches in the lawn where it just didn't grow well.

Lately my grass is pretty stagnant. I cut my grass pretty low and I noticed that it is just not coming back like it used to. I have mossy spots in the lawn in areas where the water runs to the front of my house, and the grass has never really taken where there is the most shade. I also noticed that there are little black bugs that are crawling inside the grass. I currently use hydroprill fertilizer and throw it on four times a year. Isn't this the time of year when lawns start getting green and growing well again? I was wondering if it was time for aeration.

Jason, Mililani Mauka

A. It is always best to do as much as possible to prepare the soil before planting anything, especially grass. This is the best chance you have to till and add amendments that can make a significant improvement. At this point, the soil may be getting compacted and not draining well, particularly in the areas that are getting mossy where the water runs to the front of the house. This is actually algae which likes wet, compacted, shady areas. Core aeration followed by a top dressing of compost will help to improve the drainage. You might also try to divert the runoff.

Shade is always a problem in lawns. Seashore paspalum can withstand some shade but does best in full sun. There is not much you can do about constantly shady places such as under the shade of the eaves of the house or in narrow side yards shaded by buildings or hedges. Mowing a little higher and less fertilizer in these areas can help some.

Seashore paspalum does best when mowed at less than one inch on a regular basis with a good reel-type power mower. This will help to keep the thatch at a manageable thickness. Check to see if your thatch (the brown, stemmy growth between the soil and the green leaves) is more than three-quarters of an inch thick. If so, it is time to de-thatch, which requires a special type of mower called a verticutter. They are available at most garden rental shops. As you mentioned, this is the time of year that the grass is beginning to grow faster after the winter months and is the best time to start major renovation chores such as verticutting, aeration and any re-planting.

You are using a good fertilizer. The main thing to look for in a lawn fertilizer is the amount of nitrogen (the first of the three numbers on the bag). The higher the number, the better value you are getting but even more important is the amount of slow-release nitrogen. Look on the back of the bag for the total analysis information. The higher the percentage of slow-release forms, the better.

Do not over-fertilize; paspalum does not need a lot of fertilizer once it is established. Too much will result in more rapid growth resulting in greater thatch buildup, not to mention having to mow more often. Heavy thatch can also become a nice home for insects. Always use a rotary spreader to apply fertilizer. Throwing fertilizer by hand results in uneven distribution and usually results in areas that get too much (causing brown burned spots) or too little, giving the lawn an uneven coloration.

And, finally, your bug problem. Lots of little black bugs, or insects of any type, can mean trouble. These bugs you have are probably of the sucking type. They can cause the lawn to look brown and dried out. They can be controlled with an occasional treatment of a broad-spectrum systemic insecticide. Systemic insecticides are absorbed by the leaves and roots and spread through the entire plant. They remain effective for several months. Be very careful to keep them away from any edible plants, including fruit trees. There are many products available at most garden shops. I prefer a product called Merit, which can be spread as a granular, in combination with any number of products that contain the active ingredient called acephate, which are diluted with water and sprayed.

Jay Deputy has retired from the University of Hawai'i and is now a professional landscape consultant and state administrator for the Certified Landscape Technician Program, sponsored by the Landscape Industry Council of Hawaii. Got a lawn care or turf question? Reach him at deputy@hawaii.edu.