Fill lawn’s low spots with same type of soil

Q: My hybrid Bermuda grass lawn is flat , yet it seems bumpy when I mow. Can I get it as flat and smooth as a putting green? Should I fill these low spots with sand or something else?

A: This climate can produce high-quality hybrid Bermuda grass. If you need to fill low spots in the lawn, then fill them with soil similar to the existing soil . I would not use pure sand to fill in these low spots.

You can level a lawn by taking the high spots out with a straight-nosed shovel. You can do a lot of damage to hybrid Bermuda. It will come back but you should create this damage when it gets hot, not now.

Use the same plants taken from high and low spots to plant in the bare spots you repaired. They will root easily in bare soil during the summer months. Add some fertilizer and extra water to speed up the repair.

This putting green (if that is what you want to do with it) will never have the same type of ball roll as an Augusta National putting green because it is not built the same way. The best putting greens are constructed along engineering specifications outlined by the U.S. Golf Association .

Once you have your area level, you should then aerate, fertilize and top-dress your green on a regular basis .

If you don’t have one, you will need a greens-type mower. This will be a reel mower, not the rotary type. Greens are mowed about three-eighths of an inch high . To maintain this height, you must mow daily in the summer. Mowing frequently makes the grass “tight” and helps keep weeds out.

Bermuda grass will start to have an inferior look if you don’t dethatch the lawn. An advantage of overseeding Bermuda grass in the fall is that this process requires dethatching or opening up the turf for better seed-to-soil contact to improve germination. If the area is small, a hand dethatcher is adequate and gives a great upper body workout.

Aerating is important but if you do not dethatch Bermuda grass, you will have problems with color, texture and just plain looks of the grass. If you don’t overseed in the fall, then you should dethatch it. Dethatch your lawn before cold weather hits so it has a chance to recover and fill in. I would dethatch any time it is actively growing fast.

Bermuda grass can handle that kind of stress in the heat. Cool-season grasses such as tall fescue cannot and must be dethatched in the spring or fall; fall is preferable, around mid-September to mid-October.

Q: I have some well-established rose bushes in our front yard that are 15 years old. Five years ago we converted to desert landscaping and the landscaper put about 3 inches of small rock in the area containing the roses. They seem to be healthy, although the density and beauty of the blooms was weaker last year. I’ve been using liquid Miracle-Gro. Is there a better liquid fertilizer, or should I consider pulling the rock away from the bases and fertilize through the soil?

A: Miracle-Gro is a good fertilizer for roses but I would add a separate iron fertilizer as well. Go to the nursery and get a 1 pound canister of iron EDDHA. You should be using this with roses once a year in the early spring along with your regular fertilizer application.

Each rose should get about 1 teaspoon of iron now (January-March) in a once-a-year feeding. I suggest that you add another application of Miracle-Gro this month and a third application in September for fall flower production.

You also should consider increasing the amount of water applied at each watering. A sign of drought is a reduced growth and smaller leaf sizes.

The rock in the landscape has dramatically changed the microclimate of your yard to be much hotter for more months during the year. You will probably see a change in your flower production cycle. They will produce better in the winter but not as well in the warm and hotter months.

Q: Do nitrogen-fixing plants such as trumpet vines and locust trees provide significant nitrogen to nearby plants? For example, the Bermuda grass lawn surrounding the locust or the iris and daffodils in a flower bed anchored by a trumpet vine.

A: No they don’t produce enough for our high expectations in landscapes and gardens. Nitrogen fixers supply enough to help themselves to make sure they can reproduce and make seed. Nitrogen-fixing plants have bacteria living in tangent with the plant (called “symbiosis”).

These bacteria live in nodules or bumps on the roots in close contact with the air in the soil. They are capable of taking nitrogen from the air and converting it into nitrogen available to plants and animals. The extra nitrogen produced by these bacteria spill over to the plant and add extra nitrogen fertilizer.

The objectives (if I can put it in human terms) of plants and humans are different. Plants want to survive and reproduce; they compete with other plants for their niche. In nitrogen-poor soils, nitrogen fixers, such as legumes, take nitrogen from the air and supplement what they can’t get from the soil. In nitrogen-poor soils, legumes are fantastic competitors. In nitrogen-rich soils, they are not.

The human expectations for plants that we care for are far greater than plant expectations. We want beauty and lushness from landscape plants and we want a good production of food from our legume crops, all of which require high levels of nitrogen.

The nitrogen needed to meet human expectations is far greater than the nitrogen needed to meet plant objectives. So for this reason we need to fertilize nitrogen-fixing plants with added nitrogen so that these plants meet our objectives.

The basic rule of thumb I use is the question, “Do I want my plants to meet what they consider to be adequate (reproduction and beat out the competition) or do I want them to do more than that?”

Most people want their plants to do far more than successfully reproduce. On the other hand, some people are purists and want a native look or, for philosophical reasons, prefer that the plant produce what it can from its environment and live within the plant’s expectations.

There’s nothing wrong with that as long as you are aware of the end result. If you want lushness or greater production, then add extra nitrogen.

The general rule of thumb you can follow is that many nitrogen-fixing plants manufacture only about 25 percent of the nitrogen that they need to meet our expectations. You can treat legumes just like any other plant and feed them extra nitrogen to get a better production but they may produce little to no nodules on the roots.

So to answer your question with a short-winded response, no, they will not produce enough nitrogen for surrounding plants if your expectations are high.

Bob Morris is a horticulture expert living in Las Vegas; he is on special assignment in Balkh Province, Afghanistan, for the University of California, Davis. Visit his blog at xtremehorticulture.blogspot.com.