It’s cold outside. All plant life is covered in centimetres of the white stuff and our hopes of fresh garden vegetables are months away. In this cold-weather season, don’t you just crave a good, fresh mushroom? No? Well, if you lived in the Townships during the first part of the 20th century, the mushroom, along with leaf lettuce and rhubarb, was among the limited locally-grown produce available from Slack’s greenhouses in Waterloo through the winter months.
In the 1890s, Thomas Slack built the first of the company’s greenhouses in Waterloo on the family’s property. At the time, his aim was to grow a variety of vegetables and flowers for the local market. Later on, in 1912, the business was taken over and expanded by his sons Charles W. Slack and Fred A. Slack. As part of their expansion of the business, they purchased land near to the Canadian Pacific Railway line for the construction of new greenhouses, which facilitated the delivery of the large amounts of coal and fertilizer needed to keep vegetables growing in the cold winter months. More specifically, the coal was used to create steam that was then pumped into the greenhouses to maintain the temperatures needed to grow their produce.
Into the 1910s, the brothers had built nine greenhouses and were growing flowers, plants, and vegetables for the garden market. A newspaper advertisement appearing in February 1929 listed lilies, sweet peas, lettuce, rhubarb, mushrooms, tomatoes, and cucumbers among their products, with lettuce, rhubarb, and mushrooms being the items available at that time of year. In addition to lilies, Slack’s also grew chrysanthemums and carnations for market.
Over time, however, the Slack Brothers focused increasingly on mushroom production. In a 1946 Maclean’s Magazine profile of Slack’s mushroom business, it was highlighted that, with 16 miles (26 kilometres) of mushrooms, Slack’s was the 5th largest producer of mushrooms in the world. Why mushrooms, you may ask? Unsurprisingly, profitability is the short answer. The longer answer is that in the 1920s, the demand for leaf lettuce – one of Slack’s key crops – was overtaken by demand for iceberg lettuce, which caused the prices to plunge.
Seeing the possibility in mushrooms, Charles and Fred Slack began to shift their production to mushrooms, gradually phasing out or scaling down their other products. In 1936, Charles bought out Fred’s interests in Slack Brothers (one article notes it was so that Fred could pursue the mushroom business in Europe) and eventually the company would become known as Slack’s Waterloo Mushrooms. Similar to other food producers of the time, Slack’s published their own collections of recipes which focused on the mushroom, featuring titles such as “Le gourmet touch” and included recipes for dishes that included mushroom and asparagus parfait and hot mushroom sandwiches.
The risk the Slack Brothers took when they first set out to expand their mushroom business paid off but was not without its hurdles. In 1938, a hail storm in Waterloo shattered upwards of 4,000 panes of glass on their greenhouses. In the 1940s, a fire in their heating system threatened the whole crop and one year, for reasons no one ever figured out, not a single mushroom came up.
At its height, Slack’s was producing eight million pounds of mushrooms annually and employed around 300 people. In 1983, however, Slack’s was forced to close its doors and lay off their employees when the Bank of Montreal withdrew the company’s credit privileges. This was followed by a few ventures to bring the mushroom business back to Waterloo over the years but it was essentially the end for the King of the Mushroom.