Great gardens are built on great soil

It's almost a tautology, or at least a cliche, to say all great gardens are built on great soil. But when looking at a plant what do we see? We see the parts above the ground and think that is all there is to the plant. But the aerial parts depend almost entirely on roots for water and essential elements; and, the roots depend on their surroundings...the soil. The soil has to contain the correct amount of minerals, water, oxygen, etc. If any one of these requirements aren't just right, a particular plant cannot grow well in that particular soil. Of course, different plants have adapted to different types of soil: dry sandy soil, wet clay soil, richly organic soil, or soil that is so inorganic that it's essentially chalk (yes, some plants prefer to grow in chalky soil).

With those general comments about soil in mind, today my assigned task involved mixing ingredients to produce a soil used to support the majority of the tropical plants in the Conservatory's collection. Although this task can be dusty and physically demanding, the quality of the work is important for the success of every plant in the greenhouse.

The Conservatory has a staff workroom situated between the public hallway and the collection's greenhouses. It is in this room where much of the plant work happens: repotting, pruning, seed collection and planting. The room is usually buzzing with activity and chatter. Often, there are tour groups walking through, adding to the busy atmosphere. Around the walls of the room are several large, wheeled bins containing various soil mixtures adapted to particular types of plants.

Today, the bin containing soil mix #1a is entirely empty. This soil mix is especially suited to tropical plants due to its organic fiber base and well-draining properties. When wet, it feels like very coarse and damp coffee grounds. Since the collection has thousands of tropical plants, this mix is the most commonly used, and the most likely to be in short supply.

The greenhouse manual says of soil mix #1a "this mix is intended for typical terrestrial plants. It holds water well, never goes hydrophobic, but drains freely. Many plants in the collection can be potted in this mix." The recipe has changed slightly with the varying availability of the ingredients, but currently includes coconut coir, gravel-size pumice stones, and sand in a ratio of 3:2:1.

I gathered my trusty tools, buckets, and gloves and marched off to the storage room where the ingredients for the mix are kept. Along with my tools, I rolled the empty bin from the workroom to the store room to reduce the number of trips back and forth. I was happy to see all of the soil ingredients needed for the job were present in the storage room, except for the supply of pumice stone. The bag of pumice was almost empty. Additional bags of pumice are stored in the basement of the building, on a pallet down a long dark hallway. The bags weigh about 50 lbs. To make it easier to carry, I lifted the bag up on my shoulder, like a stevedore lifting a sack of flour or grain. I carefully hiked up the stairs and down the long hall to the storeroom where I arrive puffing like an old steam engine. I made another trip for a second bag, but got smart and used a two-wheel hand-truck for part of the trip.

Once I had all the ingredients on hand, I started by pouring 10 gallons of pumice stones into the bottom of the bin. A cloud of white gritty dust rose up into the air of the small storage room. Luckily I had an N94 mask in my pocket which I quickly donned to keep the stone dust out of my lungs. Next, I added 15 gallons of slightly damp coconut coir. I then used a long-handled spade to roughly mix the ingredients before adding the final layer of sand. Since the sand is quite heavy, I added 5 gallons of sand and again spaded the mix until the consistency seemed uniform. The weight of the sand will likely cause it to distribute toward the bottom of the bin, for this reason it is recommended to be added on top as the final layer before mixing.

After returning the now-full bin of soil mix to the workroom, the storeroom looked a bit like a hurricane had hit, with dust and sand covering part of the floor. Also, I had depleted the supply of coir and sand. I had to find replacements, so the next person to make the mix had enough on hand to do the job. For the sand, I used a 5 gallon pail and rolled the hand-truck down a long hall to a pile of sand the size of a small room. I filled the pail 3 times, ensuring enough sand to last for a while in the storage room.

To replace the coir supply, I found dehydrated and compressed blocks, each weighing several pounds. They are suitable for shipping, but hardly useful for potting in this form. To be useful, the coir had to be rehydrated and broken up into coconut fibers. Using a rubber mallet and chisel I pounded apart the compressed coir, laying the fragments in a large tray. I filled the tray with water, allowing the fibers to soak up the water. I used my rubber-gloved hands to break up the fragments into fibers.  Eventually, the fibers expanded to about 5 times their original volume.

Finally, more than 2 hours after having started, the soil bin had been refilled in the workroom, and the supply of ingredients in the storeroom had also been topped up. The supply was ready for a new batch to be mixed at some point in the next few weeks. I swept the sandy and dust coated floor, tidied my tools and buckets, and returned them to the workroom.

Although after working only two hours or so, I felt tired and my hands were quite sore, as if I'd kneaded several batches of bread dough. Still, I felt satisfied with the accomplishment of adding to the effort to keep the Conservatory functioning. I like a job that has a well defined beginning, middle and end. Today, I got it at the greenhouse.