City Gardener

The plants in the greenhouse of the University of Minnesota Conservatory, all 3000 of them, are now well into the growing season. The sap is rising and new growth is bursting up the stems. All this tender new plant material is a feast for plant-eating insects. Mealybugs, scale insects, thrips, and other species are multiplying in numbers by the day. If not kept in check, the result would be withering leaves from the insects, and sooty black mold which thrives on their poop. To combat these many critters there are tools to reduce, but never eliminate, their numbers. Today, my chore as a volunteer at the greenhouse is to use a simple soap solution and a sharp spray of water to physically knock the insects off from the surfaces of the leaves. It took me about 3 hours to treat one bench of plants; there are approximately two-dozen benches in the collection, spread across 4 different climate-controlled rooms. Especially in the growing season, it takes dedicated persistent effort to keep the...

What could possibly go wrong? Today at the U of M Conservatory Greenhouse where I volunteer, I was assigned the task of watering the plants in two of their four large rooms, the rooms for tropical and subtropical plants. These two rooms house hundreds of threatened and critically endangered plant species. The finger test The time honored finger test: insert your finger up to the first knuckle or two into the soil of any plant pot, if it feels dry water the soil thoroughly, if it feels damp leave it alone - don't drown the plant roots. It sounds like a mom-ism , but there truly is a sweet spot for dampness of the soil in a plant pot. Too dry and the plant withers; too wet and the roots rot. Basic energy economy of all plants Above the soil surface, plants makes sugar:  Sun's Energy + CO2 + Water  =>   Sugars + O2 Below the soil surface, roots use the sugar: Sugar + O2  =>   CO2 + Water + Energy to absorb nutrients and transport of water for the leaves and ...

 It is an adolescent instinct to make everything in life about yourself. For example, at the university greenhouse where I volunteer, two staff members have recently been promoted to new positions. I thought, initially, that it would be a fine idea to give them farewell cards that I made. As a personal touch the cards would feature one of my own photos of forget-me-not flowers, with its implicit message. I intended to include inside the cards a packet of forget-me-not  seeds. Clever, no?  I could even make it seem more inclusive of everyone in the department if I wrote a comment saying forget-us-not  rather than forget-me-not . What could be more friendly than the presentation of these pretty blue flowers?  I'll address the problem with my thought further below. But, put that aside for the moment and let's carry on with the plan. Forget-me-not flowers (the photo taken on our recent visit to Muir Woods, CA) Due diligence To ensure the flower seeds were going to b...

Surprised by the unexpected arrival of springtime this year, I suddenly recognized the opportunity to revive the balcony garden of our apartment. For the past two years the balcony has laid fallow, because I was out of town for weeks at a time. This summer, I'm here for the duration of the growing season and the balcony garden is back with a vengeance. The advantage of grasses I've  previously described my choice of plants for the balcony. But to summarize, the space is often challenged by intense afternoon sun and heat - sometimes up to 125F - reflecting off of the glass windows; the wind up here on the 13th floor can tear apart any plant stem that isn't firmly staked; and the entire balcony is steeped in deep shade until 1:00 in the afternoon when the direct sunlight slips past the edge of the balcony ceiling. Grasses offer the advantage of being tolerant to drought, adapted to wind, and easy to manage. I like how they soften the hard edges of the cityscape. Because this...