Neil Sperry

Pondering some of the bigger landscape questions

Leaves on lawn
Leaves on lawn

Some questions leave gardeners scratching their heads. Their answers may not be predictable, yet we know they’re important. Let’s list a few of them and poke around at their solutions.

“Why does my neighbor’s St. Augustine do very well beneath his live oak trees, while mine does not? What do I need to add?”

Perhaps nothing over which you have much control. Subtle differences in amount of sunlight make a huge difference in whether St. Augustine lives or thins. We watch this happen in our own yards as our trees grow larger. The grass is thick in full sun, and it becomes thinner and thinner as we approach the trees’ trunks. Live oaks cast extremely heavy shade, and they do so year-round, so it’s quite common for St. Augustine to fade away beneath them.

Perhaps your neighbor’s trees are pruned slightly higher off the ground, or perhaps the sun hits their grass at a stronger angle in the afternoon. For whatever the reason, there is a very small difference. It’s best that you deal with your own situation and not compare. You may need to start thinking about changing over to a shade-tolerant ground cover.

“How far back can I trim my shrubs? They’re way too tall and they’re blocking my windows. When should they be pruned?”

There is no one pat answer for this. It depends on the types of shrubs involved. It also depends on whether this is the first time you’ve pruned them to reduce their size, or maybe the 19th. Plants run out of steam after they are penalized time after time. But most of all, it depends on what percentage of their normal mature height you’re going to allow the plants to attain.

If you’re trying to keep 15-foot shrubs such as redtip photinias at 4 feet tall, you’re on a time bomb. Eventually you’ll wear them out. However, to attempt some type of meaningful answer, you can usually trim shrubs back by 20 to 25 percent without fear of damaging them. Late winter is the best time to do so.

“I just moved into a house that has been empty for two years. It has no lawn to speak of. What can I do? I don’t want a mud pit all winter.”

Sow ryegrass as soon as you can. Annual ryegrass seed is less expensive, but you’ll have a more uniform stand that will require far fewer mowings if you use “perennial” rye. Both types die out when temperatures begin to climb into the 90s. Prime time for planting your permanent lawn grass comes in late April, May and early June, so the timing works out perfectly.

“What is the best perennial for a bed where I’d like color most of the growing season?”

Step carefully. You’re about to hit a trap. Perennial gardens are lovely, but they must be planned precisely. That’s because almost all perennials bloom one time per year and for only two or three weeks. You must plan for a succession of blooms that will involve perhaps 10 or 15 different types of perennials.

Start with daffodils, thrift and the other spring bloomers, and work your way through summer to Mexican bush salvia, fall asters and mums in the autumn. Annuals, by comparison, may be colorful for four or five months. Sure, you have to replant them seasonally, but overall they will probably be less work. Perennial gardens are beautiful, but only because their gardeners plan them in great detail.

“My live oaks have big roots that look like they’re going to pop the sidewalk 8 feet away. Can I remove them? How and when? What other options do I have?”

Trees’ roots are quite near the surface of the soil. After all, that’s where rainfall hits and that’s where decaying tree leaves release their nutrients. As the tree grows larger and larger, the roots expand up and out of the soil. That’s true for all trees, but most notably live oaks. It’s best not to fret, but to let them develop. They’re completely natural parts of the trees’ growth processes.

If you must remove one or more roots to save walks, drives or the foundation, fall is the best time to do so. In the interest of your tree, you may want to involve a certified arborist to be sure the job is done properly.

“What is the very best thing to do with tree leaves as they fall? Should I grind them into the grass like we do our grass clippings, or should I bag and remove them?”

For most of the year you can simply mulch fallen tree leaves back into the soil. They will add much-needed organic matter and nutrients into the ground. However, for a couple of weeks in late fall, leaves will accumulate in excess. Even if you mowed daily, you would still be adding excessive amounts of rapidly decaying organic matter into the soil. Bacteria that break that organic matter down would tie up nitrogen, and your lawn could be yellowed in the process.

I’d recommend bagging the clippings during those two or three weeks and using them in the compost or as a loose mulch in shrub beds.

Neil Sperry hosts “Texas Gardening” from 8 to 10 a.m. Sundays on WBAP/820 AM. Reach him during those hours at 800-288-9227. Online: http://neilsperry.com.

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