Green Roofs - Living Architecture Monitor - Winter 2012 - (Page 19)

ally do not grow true-to-type if grown from seed. Thyme requires regular irrigation after installation until it establishes. It can’t take the level of drought and abuse that sedums can. Although it is a very tough plant in the right environment, and is moderately tolerant to foot traffic, it can also be finicky. I kill trays of thyme regularly if I am careless with water, heat, or fertilizer levels. Thick bushy plants can suddenly develop a bald spot in the middle, even as the outer fronds of the plant are green and healthy. On some roofs, the thyme fills in thickly and never looks back, and sometimes it wants to die and replanting will not help. Some aspect of the growing media or moisture level is usually the reason for Thyme doing poorly. It may be related to the lack of nutrients, pH, or moisture holding capacity and the microbial community that develops accordingly. All of these are possible interrelated factors. Although one can broadly say that thyme likes full sun and well-drained growing media of average to poor fertility and moderate pH between 6 and 7, that pretty much describes all green roof media. Yet not all media is the same, and thyme performs differently on different roofs. A high or low pH, soggy or crispy growing medium, or poor fertility, can contribute to its demise. For an intensive green roof with richer growing medium and more moisture retention, I wouldn’t hesitate to use plenty of thyme. On an extensive roof with tougher conditions, I would be conservative with its use until it establishes and shows that on this particular roof, thyme is happy. It wants 6 inches of media to perform reliably, although of course climate affects that. Like most plants, there is a degree to which you can predict a plant’s performance, and a degree to which you have to wait and see what a given roof and plant palette will do. LEFT & MIDDLE: Thymus serpyllum (creeping thyme) RIGHT: T. pseudolanuginosus (wooly thyme) Images provided by: Marguerite Wells Plants have their own opinions which they will voice, like it or not! Thyme is a familiar garden plant in either upright or creeping habit, useful for aesthetic, medicinal, and culinary purposes. Its use on green roofs and walls is likely to continue since it is a beautiful, aromatic, and fairly reliable creeper, and its use in the kitchen is always appreciated. A few basic species are carried by many nurseries, and a few nurseries that specialize in herbs carry a much wider range of species and cultivars with varied flower color, aroma, height, and spread. Marguerite Wells, MSc, Owner Motherplants LIVING ARCHITECTURE MONITOR / WINTER 2012 / 19

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Winter 2012

Green Roofs - Living Architecture Monitor - Winter 2012
From the Founder
New Kid on the Green Roof
New Incentives for Green Roofs
On the Roof with Ben Flanner
Award Winning Green Roof and Wall Projects Represent!
Awards of Excellence Profiles
CitiesAlive 2012 – Building a Legacy of Outstanding Performance in Chicago!
Recognizing the Pioneer that was Malcolm Wells
Green roof and wall performance standards volunteers required!
Plant Profile: Thymus
Project Profile: Green Wall Maintenance Madness
GRP in Focus: Mary Ann Uhlmann
Project Profile: Healthy Haven for Community Members
A Positive Outlook for Urban Greening of Vacant Lots
A Green Space is a Clean Space
The Ambassador Program
Professional Calendar
New Corporate Members
GRHC Buyers Guide
Back to Planning’s Roots

Green Roofs - Living Architecture Monitor - Winter 2012