IPM: Growing Hemp on the Green Roof Panels Has Proven Successful

It is time to install this year's FAMU Pilot Project Florida x Hepius variety of hemp plants.

Shallow, extensive green roof panels ready for x Hepius hemp plants

Last year the x Hepius thrived in the shallow planting trays. Rainfall and irrigation water are collected and recycled. We use a special, non-organic planting medium designed by the University of Central Florida's engineering department. Organic nutrients are mixed with irrigation water and delivered via drip irrigation.

Growing hemp on the green roof panels last year proved to be a successful experiment. The x Hepius variety growing in the green roof panels were shorter and exhibited a significantly more compact growth habit than the x Hepius plants growing in the ground level garden soil.

One huge advantage of growing hemp on a roof is that there are significantly fewer caterpillars and other pest insects who crawl up the support walls to reach the hemp. Additionally, any aggressive bugs that make it up to the roof are prime targets for hungry birds.

The x Hepius variety produces significant amounts of aromatic terpenes on flower buds without any detectable level of THC. Last year I noticed the living roof x Hepius plants filled the garden air with a complex scent of citrus and spice.

I prefer shallow green roof systems because I prefer creating shallow but wide root architecture patterns so that our Florida hemp plants can better survive tropical storm wind patterns. Shallow root architecture is not necessarily better than deep, intensive planting systems but they are my preference having worked with coastal and hurricane resilient green roofs over the decades.

As mentioned above, not all green roof systems are shallow such as these.

Green roof systems can be classified based on their depth into extensive, semi-intensive, and intensive systems. Shallow or extensive green roofs, often referred to as "eco-roofs," are the simplest and lightest type. They are typically used on residential, commercial, and small-scale buildings for their ease of implementation and maintenance. Here are some key points to understand about shallow green roof systems:

1. Depth and Weight: Extensive green roofs have a shallow growing medium, typically ranging from 1/2 to 6 inches in depth. The shallow depth makes them relatively lightweight, adding approximately 15-50 pounds per square foot, including plants and saturated growing medium. This makes them suitable for a variety of building structures without requiring significant structural reinforcement.

2. Plant Selection: Due to the shallow depth, the types of plants used in extensive green roofs are those that are drought-tolerant, wind-resistant, and can thrive in shallow soil. These often include succulents (like sedums), herbs, grasses, and some types of wildflowers.

3. Water and Nutrient Requirements: The plants used in shallow green roof systems are typically adapted to harsh conditions and require minimal irrigation and nutrients. This is ideal for conserving water resources and reducing maintenance requirements.

4. Installation and Maintenance: Extensive green roofs are typically easier and less expensive to install compared to their intensive counterparts. They also require minimal maintenance, primarily in the form of periodic weeding and checks to ensure the roof's waterproof membrane is intact.

5. Environmental Benefits: Like all green roofs, shallow systems provide many environmental benefits. They can help reduce the heat island effect, improve air quality, manage stormwater runoff, provide habitat for wildlife, and enhance a building's thermal performance, potentially saving on heating and cooling costs.

6. Aesthetic Value: Extensive green roofs can improve the visual appeal of a building, providing a lush, green space in urban environments that are often dominated by concrete and other hard surfaces.

Despite their many benefits, extensive green roofs aren't suitable for all situations. They require a waterproof and root-resistant roof membrane to protect the building, and while their maintenance needs are relatively low, they still require some care to stay healthy and attractive. Lastly, not all plant species will thrive in the shallow growing medium, limiting the plant diversity compared to intensive green roofs.