Sub-irrigation: The Best Interiorscape Investment
For many of you, this will be an expanded version of the almost daily postings I’ve been writing to the major interiorscape forums, Interiorscape.com and GreenChat, for many years.
Now, the folks at NewPro Containers are giving me the opportunity to expand on the topics, issues and questions we discuss on the fly each day online with regular blog posts on their revamped website. So let’s get down to the business of helping you grow and manage your interiorscape business.
Those of you who know me know that I’m very opinionated. My opinions are usually based on three things: my thirty-five years of experience in the green industry, my own research based on my biology and horticulture education, and the opinions and feedback of the many knowledgeable, experienced, generous people in our industry with whom I speak on a regular basis. And it’s my considered opinion that the best investment you can make in the horticultural end of your interiorscape business is sub-irrigation.
Over the years, I’ve watched as the various sub-irrigation (“self-watering”) technologies have evolved, from the earliest, primitive systems (wick-and-platform setups) through the more modern yet flawed “passive” drop-in systems such as Jardinier, Ollie Plant Sipper System (formerly known as Mona Plantsava) and Everlife and then evolving to the present-day favorites, Lechuza and Controlled Watering systems, as well as an entirely new take on this technology, the Joey Pouch.
There’s no shame in a wick-and-platform system. The object of the game is to deliver irrigation water to plants to supplement or replace traditional top-watering. This can be anything as simple as strips of decay-resistant synthetic fabric (e.g. “cap-mat”) inserted up into the drain holes in a nursery pot and a block of styrofoam board supporting the pot above the water reservoir inside the watertight container, to proprietary products such as Sippers.
In fact, virtually every type of subirrigation system that’s ever been marketed operates on some variation of the wick (capillary action). The pros of a wick subirrigation setup are low cost, quick installation and changeouts, and customization; you can create a reservoir as large as you like by placing the wick and riser inside of a watertight container. The cons include constantly wet medium due to the wick’s inability to do anything beyond, well, wicking water from the reservoir until none remains. This can be a problem for plants that don’t like constantly “wet feet”. Another drawback is that large volumes of standing water that become contaminated with organic runoff from growing media may eventually produce foul odors and mold growth, two client concerns that must be top priorities when choosing a subirrigation method. But for simple applications such as high-moisture-use plants (e.g. Spathiphyllum), wick systems are elegant and cheap solutions.
The transitional designs for sub-irrigation (Ollie, Jardinier and Everlife) are all variations on the theme of wicking, but they employ custom-designed hardware to achieve the effect.
Ollie Plant Sipper System
Ollie Plant Sipper Systems (formerly known as Mona Plant Systems) consist of interconnected modules or tanks that serve as water reservoirs. These are particularly useful for bed plantings or large built-in planters and stand-alone containers that will hold large specimen plants or densely-planted gardens. Water is wicked into the medium from the tanks as the soil dries, making this a “passive” sub-irrigation method similar to wicks.
Jardinier subirrigation containers consist of a nearly watertight cylindrical container with a wick platform and fill tube that drop inside, and into which the individual plants are planted. Perlite is used as the wicking material, occupying the “capillary legs” of the inner platform below water level in the reservoir at the bottom of the container. There is a row of tiny aeration holes located on an overhang just above this reservoir, allowing air into the medium even when the reservoir is full.
Everlife works in an almost identical manner, but dispenses with the perlite in the capillary legs in favor of whatever planting medium is used (I personally adapted our Everlife inventory to the Jardinier setup, using perlite to prevent direct contact of the medium with the water in the reservoir). Because the Everlife system was essentially a sealed system when filled with water, the technician had to be very careful not to “top off” the reservoir before it was empty, or risk root rot due to waterlogging.
Present Day Favorites
Fast-forward to 2014…we currently have at our disposal two very different subirrigation technologies.
Lechuza, a division of the Playmobil company in Germany, manufactures stylish polyresin planters with a decided European look in various shapes, heights, sizes and finishes that may be used as stand-alone decorative containers or outfitted with the patented Lechuza subirrigation system. This method uses a finely ground aggregate called Lechuza Pon as the wicking material at the interface between the planting medium and the reservoir, and it includes a float gauge to assist the technician in determining when to refill the reservoir, but it is essentially the same type of passive subirrigation system as those discussed previously. Its main advantage is the integration of subirrigation with the decorative planter, which can be a cost-saver for mid-priced interiorscape installations.
Finally we come to what I consider the two most advanced techniques for subirrigating plants. The Controlled Watering system from Tournesol Siteworks (originally known as Natural Spring) consists of a series of self-contained “smart” subirrigation units whose water-dispensing properties are controlled by a sensor built into each container. The walls and floor of the container comprise the reservoir, and water is added through a fill port at the top of the container, secured by a rubber stopper.
Controlled Watering Systems
The sensor consists of a length of plastic aquarium tubing running from a hole on the inside wall of the unit into the planting medium, with a plug at the end that regulates the flow of water from the reservoir by means of vacuum pressure. When the tip is wet, it effectively stops the flow of air into the space above the water in the sealed reservoir; when it dries, vacuum is broken and water is released through tiny weep-holes inside the bottom of the unit, wetting the medium until it reaches the sensor tip (by capillary action, of course), which absorbs the moisture and again “shuts off” the flow of water to the medium by means of the vacuum pressure effect. While this system has a pronounced learning curve and must be rigorously supervised during the training period for each technician, it is, when properly installed and maintained, probably the single best method for growing, maintaining and reducing the costs of replacing plants in almost any light conditions you will encounter.
And last but certainly not least is the newest member of the toolkit, the Joey Pouch, marketed by TOPsiders, Inc. When Barb Helfman sent me some samples of this product to try, I was understandably skeptical. When she told me to wrap the rootball of my “guinea pig” plants in this thin sheet of gray, porous foam material and then fill my decorative cachepot halfway with water, I thought she was kidding! Everything I’d ever learned about root physiology and plant pathology told me that my poor little Stromanthe ‘Triostar’ would become a blob of rotten mush within a week or two, but to my astonishment, it has flourished in that same “pouch” for almost three years now, right on my desk at the nursery. This technology is a by-product of research done for the aerospace industry and takes advantage of the material’s unique property of nearly perfect aeration and drainage, allowing the plant’s roots to be submerged in water yet grow and thrive almost indefinitely. Truly a modern engineering marvel!
The many benefits of Sub-irrigation
The benefits of subirrigation are myriad: longer maintenance intervals for plants on the systems; dramatically lower plant failure and replacement rates; significantly improved plant health, performance and aesthetic quality; and fewer worries about service access problems to plants installed in conference rooms, executive offices and hot, sunny locations that used to take a high toll on our plant inventories. The costs are not insignificant; a Controlled Watering Insert may cost as much as the plant that you install in it. However, subirrigation should not be looked at as a cost center so much as an investment in time-savings, plant savings and client satisfaction with lush, long-lived plants. Especially for smaller ‘scapers with limited personnel assets, this appropriate technology can be the best partner your interiorscape business will ever have.
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