Proper Irrigation Grows Healthy and Vigorous Plants

The cold spells we are having this winter are not too bad. Around the city and in my garden, the damage that I see from the chill is minimal; most people would not even notice it.

I have added photos of heliconia that are growing and blooming in my garden to this article. Just a few years ago they would have been cold-damaged with burnt foliage, but that certainly is not happening now. These heliconia are actively growing and producing gorgeous inflorescences, the colorful structures that hold the flowers.

In my garden I never use commercial fertilizers, since I have created – and continue to create – a very healthy soil profile that includes well decomposed organic matter. The limiting factor in my garden for growing healthy and vigorous plants now is irrigation.

The organic matter that I added over the years was from spreading a thin layer, maybe two or three inches thick, of mulch from a commercial tree chipper throughout the garden a couple of times a year. I always let the first layer of mulch completely decompose before adding another. Now I only use the leaf litter from the trees, palms and shrubs that falls naturally to decompose and add to the soil profile.

The added organic matter serves several purposes. It creates a biologically active soil profile that supplies nutrients to the plants; organisms in the soil profile assist in protecting plant roots from pathogens; and, very importantly, it retains soil moisture that the plants can use. Organic matter will increase the water holding capacity of the soil. This is really important to consider when trying to determine how often you need to irrigate your garden.

Believe it or not, at the Parrot Jungle and at Jungle Island we only irrigated the entire landscape once a week, even the lawns. Each irrigation event put out from 3/4 to 1 inch of water. I actually measured the amount of water per hour by placing buckets throughout each irrigation zone so I knew how long to run the sprinklers, which were turned on and off by hand.

Once the timing was figured out, I placed the sprinklers on a schedule and staff or myself would turn the sprinklers on and off. In most instances we had the water supply capacity to run two or three zones at a time.

I am often called upon to inspect recently developed properties to determine why plants and trees are not growing well in the landscape. By far, except for really poor pruning to trees and palms, I find dysfunctional irrigation systems to be a very serious issue.

Landscape areas are often built up above adjacent walkways or driveways so the grade is sloped. Rainwater or irrigation water immediately runs off onto the sidewalk or driveway, leaving almost no water to penetrate the soil. Plant and tree roots which may be more than 1-3 feet below the soil surface begin to dry out and die. I find this to be very common on newly built and landscaped sites. This is a design failure.

You know those fancy pop-up sprinklers that all your shrubs were planted next to? I’ll bet that the shrubs were allowed to grow taller than the sprinklers so that when the sprinklers turn on their spray is blocked by foliage. None of the water gets to the plants. I see this all the time. This is another design and maintenance flaw.

How often have you seen sprinklers running and the wind blowing all of the water into the street or away from the plants that need to be irrigated? This is a really common issue. Yet another design failure.

Mature trees, or even smaller newly installed trees, need a lot of attention in particular, because these are major investments for a property. Mature trees that have been in a landscape for years without irrigation do not need added irrigation. I have seen where fancy irrigation and landscape designs were added to mature trees only to eventually cause serious fungal issues to those trees.

But newly installed trees and especially large mature trees that have recently been relocated need close attention irrigation-wise for them to become established or reestablished. I have too often seen large, relocated trees die due to poor irrigation measures, and of course no one followed up to review the irrigation, so the trees are lost.

I have found large mature trees that were kept flooded, so the tree roots died due to anerobic conditions. I have also found trees with large root balls only serviced by two or three bubblers, or sometimes a single bubbler (bubblers are laid on the ground and the water passively runs out of them). The water that comes out of the bubblers goes straight down and does not spread throughout the large root ball, thereby drying out the entire root mass.

Thoughtful irrigation is key to growing a lush landscape. The heliconia will thank you.

Jeff Shimonski is an ISA-certified arborist municipal specialist and a retired director of horticulture at Parrot Jungle. Contact him at jeff@tropicaldesigns.com.