Containers can lend a splash of color, brighten a drab corner or create a dramatic focal point in the landscape. The design possibilities are endless, but once the installation is complete, the real test begins — maintenance. With most maintenance contracts calling for weekly visits, keeping container plantings well watered can be a challenge, to say the least.
It starts with design
Thriving potted plants start at the design stage. Keep in mind that the larger the container, the more soil it holds and the more water is available. Do yourself (and your clients) a favor and avoid containers that are less than about 1 gallon. While 4 inches of color might look cute, it will need water on a daily basis or more to thrive.
“Double potting” is a popular technique that will not only conserve water, but will also streamline any plant changes that need to be made. Instead of direct planting into your decorative container, drop the plant in its own pot in the container. You can use Styrofoam pieces to raise the plant. Then hide any mechanics with Spanish moss or other decorative mulches.
Self-watering containers are another great option. They are available in dozens (if not hundreds) of shapes, sizes and prices. If you are handy, instructions are available for making your own.
“We used to do a lot of interior plantscaping in the ’70s and ’80s,” says Jeffrey Bruce, owner and president of Jeffrey L Bruce & Co. LLC. The Kansas City, Missouri-based landscape architecture, planning and urban design firm celebrates its 30th anniversary this year. Among his numerous credentials, Bruce is president of the American Society of Irrigation Consultants (ASIC).
“The Mona system was one of the first self-watering planters,” he says. Instead of drainage holes in the bottom, these containers have an overflow hole on one side. The potting soil sits on a perforated platform directly above a water reservoir. Plant roots grow through the medium and into the water.
In most cases, water is wicked up from the reservoir into the medium. In a way, these containers could be considered a hybrid between hydroponics and conventional pots. Roots grow in the soil and in the water. These can stretch the time between irrigating by several days.
Potting media and water retention
Choosing the right potting media can also help plants thrive. Potting soil usually doesn’t contain any real dirt at all. Instead, it is a mixture of composted bark, peat moss and other organics, often with perlite or vermiculite to encourage drainage.
Other amendments can also help with water-holding capacity. “You could look at some of the hydrogels,” Bruce suggests. Soil hydrogels and the like have been available for decades. These polyacrylamide granules can absorb hundreds of times their weight in water and release it back slowly.
Although claims of water conservation may have been overblown, polymers are actually perfect to stretch the time between watering containers. “You can probably get four or five days of extra watering capacity, depending on your soil type,” Bruce says.
Be sure to hydrate the polymer granules before adding them to the soil. If you add them dry and don’t allow for expansion, they can literally overflow when hydrated, which could lead to a big mess.
A newer product, calcined clay, also holds water well and can help reduce irrigation frequency. The product is like cat litter and is good for drainage and nutrient retention.
Studies at Clemson University showed that using calcined clay in nursery production reduced water use, increased available water for plants and kept plants turgid for days longer than those without. Plus, the soil media was 20 percent lighter — worth looking at for roof garden installations.
Time to water
Now that everything is planted, let’s look at different watering techniques. First and most simply, there’s the “bucket” approach. Simply fill a watering can and go. Sounds simple enough, but you must be sure to wet all the media in the container. This may require more water than you might expect. It will take a bit of practice to learn how much water a particular container will hold before overflowing (a messy situation you want to avoid).
Interior plantscape professionals use a rolling tank on wheels that can be filled and used to hand water many plants before refilling. These are especially handy for large commercial sites with extensive container plantings.
Drip irrigation sophistication
For the utmost in sophistication, drip irrigation is the way to go. Drip systems on automatic clocks can be programmed to irrigate containers as often as necessary, sparing you the aggravation (and expense) if the temperatures soar.
Since systems are low-flow, almost any hose bib can be used as a water source. Drip systems operate the best when a filter and a pressure regulator are installed. Poly tubing can be used to deliver the water to the containers; various emitters and delivery devices are available. “You can use either inline drip emitters, or there are multi-bug drip emitters where you have a hub and add distribution tubing,” says Bruce.
“Spaghetti” tubing can be installed from the poly tubing into one of the container’s drainage holes in the bottom of the pot to help hide the mechanics of your system. “We’ll typically feed through the bottom,” says Bruce.
The tubing can run to the surface of the soil, with drip or mini-sprays installed. The tubing can also be used alone, but will be more prone to clogging than standard drip emitters.
“We tend to use the micro-sprays,” says Bruce. “I like them because we get some foliage washing. We used them for the large containers on the River Walk at Trump Towers.”
When first programming a system, it is critical to monitor the cycle carefully to avoid both under- and over-watering. You might need multiple emitters on some plants or trees in very large containers in roof gardens and other intensely landscaped areas.
Don’t think you can just “set and forget” drip systems. It should be run every time you visit a site, with emitters checked carefully. Sometimes they can miss the target; other times they can mysteriously clog. Just a quick run through the system can save headaches, replacement dollars and your reputation.
Mulch is a container’s friend
As with landscape plantings, mulch can also help slow water loss. Your choice of materials will depend on the design, but ground or shredded bark is a good choice. Interior plantscape professionals often use Spanish moss; its silvery color and great coverage adds a touch of class to any installation.
Other materials can be used as well. Gravels and large cobblestones can be used as design elements and provide added interest.