City Gardener

It is springtime for plants in the greenhouse, including aquatic plants which are adapted to having their roots always damp or entirely submerged in water. Before plants get too far into the new spring season, now is a good time to address the overgrown roots from last season. One option for an overgrown plant is to divided it into two parts; or, the root ball can be cut down to a smaller size; or, more simply, a plant might be moved into a larger pot. Today, I was directed to use all three techniques for some of the aquatic plants. Umbrella sedge Cyperus alternifolius   A clean tank and water, with repotted plants at the far end With the plants removed from the tank for repotting, it was an opportunity to replace the murky water in the open tank. But, it is not only the tank water needing to be replaced. The majority of the dirty water sits in a large reservoir below the tank. A pump in the reservoir pushes water up into the tank to find its way back down through drain holes. Over...

How do plants do it... ...some stand-off-ish plants have figured out how to keep their distance from each other. They have evolved clever adaptations - sharp elbows - to keep their neighbors away. This behavior is important for survival, especially in the desert where plants compete for water.   I have noticed this phenomenon especially when I've been on a plane flying low over the desert. Where there are plants, they are uniformly distributed but not touching each other. They don't form clumps. They seem to know how far apart to grow. How is that? Why is it these desert plants don't form clumps? They weren't planted this way on purpose (Palm Springs, CA). It seems so obvious to me now that I recognize what is going on, but it took me a few years of hiking in the desert to be mentally conscious of how widely separated, but yet uniformly distributed in the landscape many plants seem to be. How is it that plants are able to keep what appears to be a relatively uniform dis...

Tens of thousands of native California fan palms ( Washingtonia filifera)  rise over the gardens and streets of Palm Springs. The fan-like leaves flutter and wave as the trees gently sway in the desert breeze. If a plant could be described as elegant, this plant would certainly be one. Delicate fibers peel away from the leaf blade as they age, giving the palm part of its name, filifera . The advantage of the fibers to the plant is uncertain; however, the fibers were used by the indigenous Cuhuilla tribes for tools and fabrics. It is no accident the city is named for the palm. For centuries the native Cuhuilla residents were vastly outnumbered by fan palms. For the Cuhuilla, the plant became an important resource for their tools and shelters. Even today, I wouldn't be surprised if the number of palms outnumber the residents of the current modern city. Bird's eye view over old Palm Springs neighborhood; fan palms are everywhere. In their native environment, the palms grow best al...

Finally, after three years... my plant vines have grown and spread to be green wall that I had hoped for. I'm not sure it would have taken as long if the plants were in a more humid, sunny climate, et cetera. But given our indoor Minnesota location - even with a southwest exposure - the vines have needed that amount of time to climb the six feet from the base to the top rungs of the metal grid supporting them. The result has been worth the effort. And to be honest, I didn't have to wait three years to begin enjoying the green wall. The vines were already attractive when only half way up the trellis. A metal grid is filled with mix of Epipremnum aureum cultivar "Marble Queen", Epipremnum aureum aka golden pothos, and Philodendron Brasil . Architecture of the green wall The initial intent of the project was to grow a green wall, in an apartment, that could be moved around to be able to clean underneath, and also to provide a mobile room divider for our open-plan loft....

The assignment for my four-hour volunteer shift at the University of Minnesota Conservatory greenhouse was clearly listed on a whiteboard, with my name attached. Since most of the tasks involved working with strings of overhead cables or air tubing, much of my shift was spent at the top of a ladder. Vining plants are limited to only a few of the many benches in the greenhouse. Steel cables are strung above the benches to support their growth. Because many plants grow in a small space, part of the challenge is to untangle and separate the vines so that they don't strangle each other. Not many of the vines are blooming at the moment, as it is winter. However, Thunbergia grandiflora is producing a few lovely blue flowers (its tendrils grow clockwise, hence the common name Bengal clockvine). It's a popular houseplant, but it has become an invasive weed in parts of the world, like Australia, especially around waterways. Thunbergia grandiflora; notice small brown scale insects sucki...

Today, I returned to volunteer at the University of Minnesota Botanical Conservatory for another shift. It was once again a pleasure to roll up my sleeves and continue the never-ending task of cleaning insect pests off the plants. My assignment was limited to a small area: a bench holding about two dozen plants. Each one had to be inspected for pests, cleaned with soapy water, and sprayed with a solution of essential oils to deter further infestation. While working, I couldn't help but wonder about the efficacy of spraying the plants with clove and spearmint essential oils. Do they really work as well as synthetic pesticides, which are specifically designed to kill insects? How much credible literature supports the use of plant oils as insecticides and repellents? And do they work against all insect pests, or only certain species? A brief search in Google Scholar produced thousands of articles spanning many years, addressing the use of essential oils in agriculture. It's defini...