City Gardener

For the past five years it has been a distinct pleasure to volunteer my time at the Conservatory and Botanic Collection  at the University of Minnesota. Within those greenhouses I quickly learned there are many dangerous plants. For example, imagine having to relocate the pot of a 5-foot 30 pound cactus covered in 2-inch needles sharp enough to pierce almost any glove. As another example, imagine dividing and repotting an agave measuring 4 feet in height and diameter, with leaf edges as sharp as any knife blade. Many Euphorbia from Africa evolved to fill the same niche as American cacti The Desert Biome room at the greenhouse, filled with dangerous plants Despite all the dagger-like thorns and razor-edged leaves, these plants must still be cared for with regular watering, re-potting, pruning, and cleaning. Because the plants are precious, they must not be damaged in the process. But still, the slightest inattention might result in a painful skin puncture or laceration. Working with...

A large contingent of students and staff was gathered when I arrived for my volunteer shift at the Conservatory Greenhouse at the University of Minnesota on the St. Paul campus. The crowd was on hand to help with the gentle felling of the largest plant in the greenhouse, decades old and 30+ feet tall. Native to the island of New Caledonia in the South Pacific, this fern -- S phaeropteris intermedia the largest of all tree ferns -- has been happily growing in the tropical room of the greenhouse for a number of years, to the point its fronds are brushing up against the glass ceiling panes of the roof.  Tree fern fronds brushing against the roof of the U of M greenhouse Rather than cut the tree down and lose the specimen, the staff decided to try to save the tree. The process would involve cutting off the top half of the tree and reinserting it into a new space in the soil of the greenhouse floor. Months of planning and preparation A well-known technique was used, referred to as ai...

It has been a sincere pleasure for me to volunteer a few hours a week at the University of Minnesota Botanical Conservatory. After many visits over the last few years, exactly none of those days have felt ordinary or repetitive. If there is a routine , it is that the botanic diversity of the collection - with over 3000 species - is displayed in a spectacular way each day. The Conservatory is located on the St. Paul campus, and is free of charge and open to the public during typical weekday hours. For instance, today most of my allotted time was spent in just one of eight rooms, the room that houses the tropical collection. The chores included pruning, re-potting, spraying, sweeping, etc. As I moved through the room, in every direction, there seemed to be a stunning plant pleading to be admired.  After the chores were complete, I had the opportunity to go back and photograph some of the beauties that surrounded me while working.  Dendrobium tangerinum , Papua New Guinea Dendr...

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...

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...

I didn't know that the cardboard palm - Zamia furfuracea - is a cycad. It isn't a palm tree (don't judge me, I'm not a botanist). But it also doesn't look like the other more familiar types of cycads with their fluted upright palm-like fronds. I didn't know it is said to be the second most commonly cultivated cycad, after Cycas revoluta . I didn't know this plant is unrelated to the common ZZ plant - Zamioculcas zamifolia - although they have a similar appearance. Before today I didn't know any of these things, but now I am happy to have learned them. From the parking lot I walked to the U of M Conservatory greenhouse in near-zero F weather. Stepping into the tropical spaces was a joy of its own. But being able to learn new information and experience new procedures was a compounding factor. Joy squared. During my 3-hour volunteer shift, my initial task was to clean the parasite critters (mealybugs and scale) from the stems and leaves of the cycad, Zami...

Whether in our homes or workplaces, we all have a routine for cleaning things. But often apart from our routine, there are those hard-to-reach places where dust or other bits collect. Over time, the buildup of debris can be a shock when the existence of these neglected spots is finally realized. Today at the U of M Conservatory greenhouse, where I am a volunteer indoor gardener, I spent my 3-hour shift reaching into out-of-the-way spaces to sweep, rinse, or wipe away fallen debris. I focused my efforts on the public area of the conservatory where new guests are more likely to see dusty surfaces that have escaped recent routine maintenance. A similar form of untidiness is the sudden realization that a particular plant has grown immensely since the last time you noticed it. The leaves have overspread the space and blocked much of the sun light for everything below. It is time to prune away the excess. My task for today included pruning the largest plant in the collection, a tree fern nat...