Flatlands too boring? Tips for building hills, valleys into your North Texas landscape

Builders go to a lot of trouble to level the land before they start pouring foundations. That’s fine for the concrete, but it’s not much fun when you start daydreaming about hills and valleys and beautiful places in nature. It’s also not good when heavy rains just sit there and accumulate until they start oozing in through the doors.

So, there come times when you decide to build hills and cut valleys. We’ll call them “berms” and “swales” so we sound like we know what we’re doing. How do we get started, and how do we proceed to succeed? I’ve been watching this for decades and I’ll give you a few of my observations.

▪ Establish the need. Why are you doing it? Are you building a berm to gain a bit of privacy or for deadening street noise? Perhaps it’s just to give you a slope on which you can display a bank of colorful perennials.

▪ At the other end of the spectrum, a swale is most often used to divert water away from the house. Think of it as a shallow drainage ditch, perhaps only 1 or 2 inches deep and several feet across, and yes, you’re right — your eyes may not even perceive the grade changes, they’ll be so gradual.

▪ These changes in terrain should look like they’re part of the neighborhood. They need to blend in. You don’t want them to look like some giant wall or aqueduct that was constructed with heavy machinery. Berms may not need to be more than 12 or 16 inches high, or in a large landscape a bit taller, but 10 or 15 feet wide. Once again, the change in elevation will be subtle and graceful – all in proportion.

▪ It’s just a personal thing for me, but I like to compare berms to hillsides in nature, and you’ll rarely see trees growing along the highest points on the hills. That’s not where the water accumulates. It’s down the sides of the slopes and at the bases. For that reason, I get uncomfortable when I see people planting trees as if they were monuments across the tops of their berms. There’s a large planting of bald cypress trees in a commercial planting I pass frequently, and another planting of columnar Italian cypresses punctuating the tops of their hills. In a word, those look “weird.” Or “unnatural.”

▪ Skilled landscape planners work beautiful stone, preferably of a type that’s native to the area, into the sides of their berms, much as you’d see in a hillside wash. And you’ll see attractive dry streambeds constructed as swales. In both cases, however, you have to keep it all simple. You walk a fine line before it looks gimmicky. You might want to get professional help if you’re uncertain.

▪ Groundcovers are a nice way to cover a berm. For decades Asian jasmine has been that plant, and it’s still a great choice. More recently, however, many people have switched over to purple wintercreeper euonymus because of its better winter hardiness. It also tends to root into the soil better, plus it gives nice seasonal change in leaf color from dark green in summer to maroon all winter long. In shaded areas regular mondograss (monkeygrass) is excellent at holding the soil and giving a soft, pleasing texture.

▪ Your swale needs to empty its outflow into a safe place, preferably a city storm sewer nearby. Monitor the elevations carefully as you design things to be sure you’re not going to be aiming runoff toward your house or your neighbor’s garage. You can also install grates and sub-surface drains to carry a great amount of water away in a hurry, but this really is a job for a professional — someone with a transit and the experience of having done this before.

▪ It’s nice to have flowering annuals on a berm, but I’ll continue to warn you to keep the berm simple. You don’t want to draw too much attention to the fact that you have a grade change in your garden. Plus, it will be a bit harder to get a rototiller back onto the hill to work up the soil each time that you replant it. My preference is to have an odd number (3-5) of large decorative pots near the base of the slope. I grow my annual color in them. It’s much easier to change color in pots than it is to rework the soil.

You can hear Neil Sperry on KLIF 570 AM on Saturday afternoons 1-3 p.m. and on WBAP 820 AM Sunday mornings 8-10 a.m. Join him at www.neilsperry.com and follow him on Facebook.