Zoning Landscapes for Water Conservation and Ease of Management

Zoning Landscapes for Water Conservation and Ease of Management

It’s hot! It’s dry! I’m writing this in early spring, but like any of us who have lived in Texas for even a few years, we know that July and August in our great state will be brutal. You can be assured the thermometer will be in the 90s and probably several times reach over 100 degrees during these two months. The absence of rain is common for several weeks. That combination puts a big stress on our landscape plants and on our water bill.

We typically don’t think about water conservation until we are forced to conserve due to dwindling reser-voirs and receding aquafers. Hopefully this summer won’t be too extreme, but now is as good a time as any to think about how we can have an attractive and functional landscape without risking the health of our plants during summer extremes while keeping our water bills in check.

A large part of my professional career was with the Texas A&M AgriLife Extension Service, and one of the issues we focused on was water conservation. In the 1980s we promoted the principles that make up the nationally known xeriscape program. But that name often had negative connotations (like “Zero-scape”), which conjured up images of landscapes of cacti and rocks. That’s not what the term was intended to convey, but it was hard to overcome that mistaken perception.

In the 1990s, the Extension Horticulture group with Texas A&M adopted most of those water-conserving concepts but wrapped them up under the banner of “Earth-Kind” landscaping. Both promote several principles that, when combined, result in not only water savings but also healthy and environmentally friendly landscapes. One of those recommendations highlights zoning your landscape to maximize water savings, while still having a beautiful yard.

Basically, zoning means arranging and combining your plants based on their water needs. An extreme example is to not plant bananas and Texas sage (Leucophyllum) in the same bed because meeting the water needs of the banana would most likely kill the Texas sage.

When designing water-requirement zones, we can divide them into three general areas. There can be a zone devoted to plants which require regular watering to look their best. Then you can create a zone consisting of plants which might need occasional watering (after they are well established) during a prolonged dry spell. Finally, you can have a zone for established plants which can get by on natural rainfall and need no supplemental watering, even during a drought.

I realize most of you reading this probably already have an established landscape and have no intention of doing a total renovation to make it more water-wise. I also know that with the recent years of plant-stressing weather events, many plants may still be hanging on by a thread of life, or some just look terrible and need replacing. When planning on replacing or renovating the landscape, keep the thought of grouping plants to-gether by water needs as you begin to repair or replace.

The first zone, where plants need regular water to look their best, might be for annual flowers, water-sensitive ferns, hydrangeas and other plants which do best with consistently moist soil. Turfgrass also fits in this category, though personally I only water a few times during the summer. I like to think that this zone would be made of smaller beds that are close to the house or in high-visibility locations. These beds would be easily watered either by hand or by a separate zone on your irrigation system.

I’ve seen many yards where potted plants dominate the areas close to the home. A popular trend is to use large containers with a mix of plants to create a mini-garden. Taller “thriller” plants grab your attention, while “spiller” and “filler” plants create an impact. These plants can be perennials or annuals. A convenient and water-thrifty way of maintaining these pots is with micro-sprinklers or drip emitters, hooked up to a timer so that the plants never suffer from getting too dry.

The occasional watering zone can be for a wide variety of shrubs and perennials that, once established, should be able to get by with only an occasional watering during extended dry periods in the summer. The key here is, “once established.” All plants need careful attention the first year or two after planting to ensure that their roots have expanded beyond the original planting area and that these roots are now expanding into the surrounding soil to make use of available soil moisture.

For sure, most shrubs and trees preferably should be hand-watered as the soil dries out the first summer, replenishing soil moisture several inches deep within the original root ball and also in the surrounding soil. Don’t keep the soil too wet, however. Roots need the oxygen that exists in the spaces surrounding the tiny soil particles. If the soil stays saturated, oxygen is excluded in those tiny pore spaces, and then the roots will not grow well in that environment.

What kind of plants might fit in this zone? Plants that tend to wilt in the summertime when the soil dries out are candidates for this zone. I live in Tyler, where a variety of plants that do best in acidic and well-drained soils thrive. Azaleas, camellias, gardenias, Japanese maples are some of the common plants that come to my mind when thinking about that type of zone. Hydrangeas would also be candidates for this zone. Their large leaves can lose a lot of moisture through transpiration during the dry months of summer.

Many perennial flowering plants (recommended for Texas landscapes) and ornamental grasses will do nicely in landscape beds after they have been in the ground for at least a year. These too should be hand-watered during the first summer to help them get established well. After that, they should be fine with only an occasional watering during dry spells.

Locations for plants that can get by on natural rainfall ideally would be farther from the home and sources of irrigation water. Plant types might be shrubs and trees planted for privacy, windbreaks, sound “barriers” or shade cover. Most shrubs with waxy leaves, such as hollies, get along quite well without regular watering after establishment and can thrive on rainfall alone. Think of some of our native hollies, such as yaupon, possumhaw and American holly. Agaves, yuccas and many, but not all, native plants are also obvious candidates for the no-irrigation zones.

Most trees, once established, will withstand a typical summer dry spell. Of course, there are exceptional years when Texas experiences several months with no significant rainfall and excessively hot summer temperatures. In such instances, even our “rainfall-only” zone plants would benefit from an emergency watering to help them keep going and minimize their stress.

For all zones, the most important step you can take is to apply a sufficient layer of mulch in beds and around young plantings. Apply any organic mulch several inches deep. An ideal mulch is composed of a mix of large and small pieces. Large pieces allow air to filter to the lower areas and thus more effectively inhibit weed-seed germination. Smaller pieces help reduce soil-moisture loss through evaporation. Weeds and grass compete for soil moisture, and mulches are a key feature for reducing weed germination and growth.

How deep should a mulch be? It depends on the type of mulch. Coarse-textured mulches can be safely applied at least four-to-six inches deep. For finer mulches, perhaps only about three inches deep. A key thing to remember about organic mulches is that they do break down. On the one hand, as they decompose, they improve the soil underlying the mulch. On the other hand, as they decompose, they lose their weed-suppression and moisture-retaining benefits. So, topping with fresh mulch every year will help maintain optimal benefits. There is no need to remove existing mulch before applying a new layer. I have been using arborist woodchips for many years. They are free, usually readily available in most parts of Texas, and help achieve all the above benefits.

Whether you are planning a new landscape, creating some new planting areas in an existing yard or replacing old, stressed and damaged shrubs or trees, keep in mind their water needs. Avoid placing plants with low-water needs in the same beds with plants that require regular watering. Your plants and your water bills will both benefit.

By Keith Hansen
Smith County Horticulturist, Emeritus
Texas A&M AgriLife Extension Service
Owner, East Texas Gardening