Choosing a roof or wall plant palette (Groof)
Groof recently did a search for the best resources available today related to the plant selection for green roofs and walls in cold climates. The following is a look at our favourite excerpts from articles we think offer the most value about the topic - for the full article, click on the link provided. Enjoy the read!
Colder climates
Canadian Landscapes: Plants and Flowers That Survive the Winter | JRL (robertlandscapes.com)
if you’re a Canadian resident, consider adding gorgeous plants and flowers to your landscape design that survive (and thrive) throughout harsh Canadian winters.
While some plants can survive winter, others will die.
Cold-resistant perennials and other plants survive the winter in a resting stage underground.
Other plants, such as trees and shrubs, are hardy enough to survive the winter above ground.Here are some of the best flowers that will either grow or survive underground in fall and winter.
RED TWIG DOGWOOD
CAMELLIA
HYSSOP
CONEFLOWER
LILY-OF-THE-VALLEY
SIBERIAN IRIS
‘PURRSIAN BLUE’ CATMINT
CYCLAMEN
Check out these hardy yet beautiful winter plants to find your newest outdoor eye candy.
WINTERBERRY
SNOWBERRY
FIRETHORN
JAPANESE YEW
BOXWOOD HEDGE
ENGLISH BOXWOOD
SIBERIAN CYPRESS
HOSTA
PERENNIALS
PEONY
MONARDA
VEGETABLES THAT YOU CAN GROW THROUGH THE WINTER
Broccoli
Ornamental Cabbage & Kale
Collards
Swiss Chard
Spinach
Lettuce
Potatoes
10 Winter Plants That Will Thrive in the Cold Weather - CNET
There are actually several plant species you can count on to survive through the winter season.
Making sure your landscaping is planted with hardy plants is one way to make sure you'll be greeted by greenery after the winter
Choosing plants that are adapted to your climate isn't difficult and takes just a bit of know-how. There are more than enough plants to choose from and, if you shift all of your landscaping to these perennials, you'll save money and time each year.
To help people determine that, the US Department of Agriculture has divided North America into distinct areas based on average minimum temperatures called USDA hardiness zones. TL;DR: The lower the number, the colder it's likely to get in that zone.
Local gardeners and nurseries can share firsthand knowledge of what works in your area and what's doomed to fail. A local expert might have a better grasp on microclimates and unique gardening challenges in your area. Temperature isn't the only factor when it comes to healthy plants: soil type, moisture and sunlight all play a role, too.
Plants that can survive extra-cold winters
Rhododendrons
Daffodils, crocuses and tulips
Hostas
Bleeding hearts
Irises
Daylilies
Lilacs
Hydrangea
Sedum
Blueberries
While native plants are often pitched as being good for wildlife, including pollinators, they can also be very pretty. Even if you just want a good looking set of flowerbeds, native plants can get you there while weathering winter after winter.
Top 17 Hardy and Cold Tolerant Perennial Flowers - Gardening Channel
If you live in a colder climate, you probably don’t want to dig around outside, in the cold to add a little color to your yard. But by planting perennials, you can avoid the whole planting process! Plant cold-tolerant perennial flowers once, and they’ll return year after year.
If you’d like for your yard to brighten up, even while the temperatures are still cold, consider the following flowers as a nice addition for your landscape:
SIBERIAN IRIS
YARROW
NEW ENGLAND ASTER
LILY OF THE VALLEY
SEDUM
CORAL BELLS
PEONY
HELIOPSIS
HOSTA
BEE BALM
CONEFLOWER
BAPTISIA
WILD COLUMBINE
LADY’S MANTLE
BUGLEWEED
CATMINT
HOLLYHOCK
Green roofs, cold winters, and dealing with drought - Construction Canada
Intensive vegetated roof systems are thicker and can support a wider variety of plants, but are heavier and need more maintenance than extensive assemblies, which are covered in a light layer of vegetation. Either way, it is important to ensure the right plants are being used for the project. (Along with the usual roofing concerns, such as waterproofing and structural capabilities.)
green roofing consultants often suggest selecting the plant material native to the project’s locale. This helps avoid unnecessary plant death by way of establishment and/or if the flora is being transported from far away. Native plant species have also already been adjusted to that particular location’s climatic conditions, making it easier for them to get established quickly.
The plants traditionally chosen for vegetated roofs tend to be hardier species that can be grown almost anywhere; they do not require a specific combination of soil material, with some even thriving out of stones. They also need very little water.
While design/construction professionals need not be botanists or horticulturalists, having a background understanding about the subject can be invaluable when working with others to ensure the ideal green roof is being specified. The information shared about the mechanisms of drought and cold adaptations of plants in this article will help engineers and architects designing a green roof understand what type of plants are suitable that are cold-, heat- and drought-tolerant.
The critical knowledge of rain capture and storage plays an important role on plant survivability on a non-irrigated roof as well. This author has been asked frequently by architects about how long the plants on a vegetated roof live. Many times, manufacturers have to provide a survivability certificate on the type of plants being used on a particular roof and their watering requirements, with information if they are drought-tolerant and can survive in heavy rainfall.
For decades, green roofs have been planted with sedums (e.g. Sedum album, S. acre, S. kamtschaticum, S. rupestre, and S. spurium), but there are few publications on the flora’s basic physiology and water use efficiency. Most sedums are Crassulacean Acid Metabolism (CAM) plants, which means they survive through a photosynthesis method that has carbon dioxide (CO2) fixed by an enzyme (i.e. phosphoenolpyruvate carboxylase [PEPC]) during the night to form malic acid that is stored in the plant cell vacuoles, keeping the stomata closed the next day.2 In other words, CAM plants are characterized by their water use efficiency, making them ideal for rooftop environments where they are unlikely to be frequently tended to by a landscaping team.
Transferring mature and well-established plants on a roof is more beneficial for survivability than planting young seedlings.
Lack of research regarding planting options and managing green roof survivability in Canadian climatic conditions means this is a topic not yet widely explored. However, over the last decade, various North American universities are undertaking work to study the suitability of plant species using both native and non-native species for Canada’s colder environment.
Cold stresses include severely low temperatures, strong winds causing desiccation, ice, and pathogens. Some types of plants adapt to these situations and become tolerant; others remain sensitive and eventually die after a certain exposure period. The most common adaptive feature of cold tolerance or overwintering is cold acclimatization with which plants are able to tolerate freezing injury.15 Cold acclimatization involves a number of molecular changes associated with taking care of the membrane functions at low temperatures.Generally, cold adaptation is defined as plants that survive temperatures as low as −40 C (−40 F) during winter. The freezing of the liquid inside the plants is a serious threat as the freezing of water present in the soil. It causes imbalance in the mechanisms involved in transporting water/nutrients to different parts of the plants.
When winter is about to set in, it becomes critical to ensure the green roof will not be saturated with water—any excess water should be drained out as it can damage the plants when ice is formed. If this is not taken into account, when the snow melts, plants may not revive completely, leaving patches of dead plants on the otherwise-green roof.
This information can be useful to design/construction professionals in regard to pre-winter maintenance. The specifiers can have information available explaining how to protect the plants from getting subjected to freeze-thaw cycles—essentially instructions not to water, remove any excess water, and avoid ponding.
People working for the green roof industry have a huge task ahead of them to understand the effects of cold and drought on the mechanisms of growth and development of sedum plants.
a general knowledge about plants and their mechanisms helps in understanding why a green roof may not be able to establish itself in adverse and harsher climatic conditions.
Although sedums are considered the most tolerant of plants, like any other living species they are subject to limitations after a certain threshold. It is essential now to investigate the undiscovered fundamental principles of drought and cold tolerance of sedums plants. The information is important for the growers mainly to have a clear idea when planting sedums in terms of survivability culminating into better production enhancing yield, which will be economically beneficial in the end.
Hardiness Zones in Canada (gardenia.net)
Canada's plant hardiness map provides insights about what can grow where. It combines information about a variety of climatic conditions across the entire country
These are the 21 best plants for cold weather climates | HappySprout
The earth is categorized by five different climates. They are tropical, dry, temperate, continental, and polar. The majority of the United States is in dry, temperate, and continental. A cold-weather climate would be considered continental and would range from zones 1 to 4.
For inside the home, there are many plants that can survive and even thrive in lower light and shorter day situations. The biggest hurdle with indoor plant care during the winter is moisture.
Cold tolerant:
ZZ plant
Snake plant
Aglaonema
Clivia
Jade plant
Christmas cactus
Succulents and cactus
Frost resistant:
Pines and Evergreens
Japanese Yew
Blue spruce
Browns Yew
Cotoneaster
Bushes and hedges:
Boxwood hedge
Cypress topiary
Thread-Branch cypress
Ligustrum
English boxwood
Winter Jasmine
Holly bush
Trees:
Camellias
Japanese Maple
Star Magnolia
With a little research, you can find a plant to suit your needs, even if it’s cold outside.
The 15 Best Cold-Weather Plants That Can Withstand Harsh Winter Temps | Hunker
However, winter is arguably the season when people rely most on nature to provide a reminder that life continues. Plants can survive winter's worst cool weather and thrive, and so will we.
When you consider adding plants that will survive winter weather, knowing your hardiness zone is of top importance. If you pick plants that thrive in your hardiness zone, they are very likely to survive your normal winter freezing temperatures.
GROUND COVERS:
Tricolor Caucasian Stonecrop
Golden London Pride
Deadnettle
Bearberry
Creeping Dogwood
SHRUBS
Winterberry
Dwarf Alberta Spruce
Blue Holly
Limelight Hydrangea
Japanese MapleFLOWERS:
Peonies
Alliums
Hybrid Lenten Rose
Geranium 'Gernic' SUMMER SKIES
Coral Bells
60+ Unique Fruits & Nuts for Cold Climates (Zones 3-5) (practicalselfreliance.com)
The plants listed [in this article] are well suited to grow in zone 3, 4, and 5, providing good yields with minimal effort for a well-planned diverse permaculture homestead.
Canada's Plant Hardiness Site
This site explores the relationship between plants and climate across Canada. One portion of the site is dedicated to plant hardiness zone maps, which have traditionally been used by gardeners to help select which plant species to grow in their area. Another part of the site presents maps and models that summarize the climatic requirements of thousands of plants from across North America. A final aspect of the site gathers data and provides summaries about plants that occur in your area.
Best Climate-Hardy Trees for the North - My Northern Garden
In real estate, the mantra is “Location. Location. Location.” For northern gardeners facing urban conditions and a changing climate, the advice to follow is “Diversity. Diversity. Diversity.” Choosing a variety of trees that can handle salt, weird winters, difficult storm events and new insect predators is the best way to ensure your landscape remains healthy and vibrant.
Green roofs
Green Roof Plant Selection (godfreyroofing.com)
There are many factors to consider during the plant selection process for a green roof system. The type and purpose of the green roof is especially important. The desired visual look and level of maintenance which will be required must be considered. The plants selected should be tolerant to the weather conditions of the specific geographical area.[…]
Extensive green roofs are usually limited to moss, grasses, herbs, and sedums due to the low media depth. Perennials with low growth height are often selected as they have shallow roots. Sedums have fibrous roots that retain water, survive in a drought, and hold it in place during wind or rain. […]
Intensive green roofs permit a larger variety of plants due to their increased media depth. The increased media depths of intensive green roofs allow for deeper root growth and provide more nutrients and water. Depending on the media depth, intensive green roofs can support plants, shrubs, and trees.[…]
Weather conditions are often magnified on a roof top as a roof’s exposure level is high. It is important to consider a plant’s ability to tolerate weather fluctuations, humidity, temperature, rainfall, frost, sun/shade, and drought.
During the plant selection process it is important to consider the desired visual appeal of the green roof. The appearance of a green roof will vary from season to season. […]
Weight loads are important when considering trees and shrubbery for a green roof system. A retaining wall can be implemented in an intensive system to increase the media depth surrounding a tree. Trees are more likely to tip and be susceptible to wind pressure than other vegetation. The size of a tree’s leaves and crown determine how susceptible it is to wind. A tree usually has to be secured into the green roof system through cabling around the root ball in order to provide extra support; this is referred to as anchoring.
Determining factors:
Weather/Climate conditions: Temperature, humidity, and rainfall. Tolerance to drought, frost, temperature fluctuations, sun/shade.
Visual appeal during all seasons.
Maintenance requirements (irrigation, weeding, nutrient supply, perennial vs. replanting).
Extensive Green Roofs | Zinco Canada
Sedum Roof
The economic and attractive way of green roofing
With a plant palette consisting of hardy, drought tolerant sedum species, this is the green roof system with low cost, simple installation, lightweight and low maintenance requirements. Colourful and long lasting, a green roof system with the perfect mix of low cost and durability.
Features:
Compact & Lightweight
Low maintenance
Only 60-80 mm of growing medium required
Flexible planting methods
Easy Installation
(PDF) An evaluation of biotope green roof in Japan -Plant selection, design and maintenance for biodiversity green roofs (researchgate.net)
To achieve the best biodiversity benefits, biotope green roofs are becoming popular in Japan. Biotope green roofs are characterized by using various plant species, usually including native trees and shrubs and forbs known to be food plants for invertebrates, and having a pond and stones to create diverse habitats.
(PDF) CONSIDERATIONS FOR PLANT SELECTION IN GREEN ROOFS (researchgate.net)
It is the vegetation layer that creates the living skin on the rooftop in green roofs, controls the long-term effect of any green roof installation and provides a naturally evolving and changing roofscape. Therefore, plant layer is the most challenging and important element of green roofs. A successful green roof system needs a meticulous plant selection. Considering aesthetic values , different designs are available which incorporate various plant species, but the vegetative layer requires wise consideration in terms of the projected goals and existing conditions. Design goals of the roof define the plant selection process, whether the goals are linked to aesthetic values, performance, education or function. Like any landscape at ground level, vegetative layer that propagate primarily on a green roof may not continue to flourish in the long term as a result of fluctuation in climate and other critical factors. While, aesthetic values and ecological aspects are crucial criteria in roofscape, the selected plants must first be survivable.
Necessarily, green roof vegetation must be less nutrient-reliant and tougher than plant species currently found in ground level landscape. In this case Crassulacean acid metabolism (CAM) plants are suggested. In Overall, the best plants for green roofs environment are cold, heat, drought, wind, sun, disease and insect tolerant and preferably native plant species. Drought resistant , durable and low maintenance plant species are recommended for extensive green roofs; however, almost infinite plant selection is used for intensive green roofs.
Plants should be chosen based on sunlight, cold tolerance, and watering need.
One of the most critical determinants of a green roof's performance is the type of vegetation planted on its surface. This study examines the factors influencing the choice of plant for green roofing, such as sunlight requirements, water requirements, and cold tolerance, in order to identify the preferred green roof plants for use in cold and dry climates such as Mashhad, Iran, and to provide a roadmap to assist decision making in this regard.For this purpose, initially, fifty different plant species were evaluated from four perspectives: (i) applicability in extensive green roofs, (ii) photosynthesis rate, (iii) availability, (iv) low cost. Then, green roofs with selected vegetation were used in a field test, and the amount of carbon uptake of each of them was measured over one year.
This study found that the best plants for the climate experienced in the field test are Sedum acre, Frankenia thymifolia, and Vinca major, which enjoy good tolerance and performance characteristics and offer the best energy demand and carbon emission. Green roofs with these three plants could reduce a typical building's annual energy consumption by 8.5%, 8.0%, and 7.1%, respectively.
The type of plants cultivated on the roof surface, the soil characteristics and moisture content, and the leaf area index (LAI) are some of the most important factors that influence a green roof's efficiency. The present study investigates the type of plants suitable for green roofs with the factors affecting their performance taken into account to identify the best options for a typical green roof under specific climatic and structural conditions.
The type of plants cultivated on the roof surface, the soil characteristics and moisture content, and the leaf area index (LAI) are some of the most important factors that influence a green roof's efficiency. The present study investigates the type of plants suitable for green roofs with the factors affecting their performance taken into account to identify the best options for a typical green roof under specific climatic and structural conditions.
The plants grown on the rooftop positively impact the indoor and local outdoor air quality and can also reduce indoor cooling loads by blocking direct sunlight on the roof surface. A green roof reduces the thermal fluctuations on the exterior surface of the roof. It increases the roof's heat capacity and heat resistance, which keeps the indoor space cooler in summer and warmer in winter. This results in reduced CO2 emissions, as well as reduced energy loss.
In a study by Cascone et al. (2019), 30 plant-substrate configurations, which included six vegetative species and five types of substrates, were evaluated to identify which one optimized the energy performance of extensive green roofs in Mediterranean areas. The researchers of this study conclude that the Salvia plant has the best performance in summer; however, for the whole year, Sedum and Sempervivum were the best options and had the best results in terms of the height, LAI, leaf reflectivity, and minimum stomatal resistance.
A list of 50 ground cover plants that can be used in extensive green roofs was created. Then the options were narrowed down by removing the plants that are not suitable for the cold and dry climate of the case study area in terms of sunlight requirement, cold tolerance, or water requirement. Ultimately, three plants, namely Sedum acre, Frankenia thymifolia, and Vinca major, were selected as the most suitable options.
Green walls
selection-of-plants-for-vertical-gardening-and-green-roof-farming.pdf (advancedscholarsjournals.org)
The choice of plant species for vertical gardens is strictly dependent on climate conditions and exposure of the wall. The plants should be light, their root system must be spreading and not of the pile form. It is also important to choose evergreen plants, so that a vertical garden will fulfill its role throughout the whole year. Life expectancy is an important factor while calculating the cost of green wall exploitation. It is recommended to choose mosses, ornamental grasses, perennials, shrubs which live a few to dozens of years with a high tolerance to environmental pollution.
The use of different plant species including herbs, grasses, perennials and trees help to make the roof-scape a natural environment. Other factors that should be considered when selecting plants include: the rate of plant growth, nutrient needs, and sensitivity to pollution. The type of plant species and their location on the roofs also depend on the geographical location, the rate of air pollution, rooftop height, shade, growing medium depth and composition, accessibility of roof, run-off water management purposes, irrigation method, thermal insulation purposes, installation techniques and maintenance. A lot of plant species can be used for Vertical Gardens and Green Roof Farming purposes
Plants selection in green roofs/vertical garden has many criteria which are interrelated. Climate and micro-climate and environmental factors have a significant role in the selection of plant species. Especially, average low and high temperatures, extreme cold and hot temperatures, irradiance level, wind speed, and the distribution and amount of rainfall throughout the year will specify what species can survive in a specific region. Drought resistance is important as a high rate of irradiance and low soil moisture characteristics are integrated to shallow growing medium systems. Succulents like sedums, are usually selected in green roofs due to their capability to survive harsh conditions. More accurate maintenance and deeper growing medium allow to use plants that they show less resistance against drought.
Other determinant factors in plant selection process are the project purpose and the favourite roof appearance. If a more natural environment is the aim of the project, local species may be chosen. Irrigation is, however, typically important not only to use native plants on the roof, but for long term survival of individual plants and the plant community as a whole (Durhman, Rowe, & Rugh, 2006), leading to the need for further maintenance. Another factor that influences the plant selection process is the canopy structure of plant species. Plants should be selected that have mostly horizontal leaf distribution and/or an extensive foliage development, in order to reduce the transmission of solar radiation. It should be noted that the main role of canopy in green roofs is shading (Barrio, 1998). With a suitable green roof structure and sufficient depth of growing medium (with higher water supply, nutrients and root penetration volume) growing a variety of plant species in complex mixtures is possible.
Greenwalls — also known as vertical planting systems, vertical gardens, plant walls or vegetated walls have been successfully implemented in several projects around the world over the past 17 years. European projects and Canadian projects have taken the lead in implementing these planting systems. Most greenwalls are simply planting system used for both interiors and exteriors of buildings. The basic greenwall system is created by providing a planting substrate into a vertical planting system (http://www.newenglandgrows.org/pdfs/ho_Anderson14H andoutFRI.pdf).
Checklist: How to Choose the Right Plants for Your Greenwall (growup.green)
Designing a green wall should be a fun and creative process for both you and your client and having this checklist will ensure you get the right plants for a beautiful green wall. Remember that each living green wall is individually designed for a specific project, and all walls are different, so let your creativity flow with this checklist in mind.
The most common plants used in living greenwalls:
Ferns - They are one of the garden plants that are preferred for their adaptability and humidity resistance. Ferns are easy to grow and they cover the area quickly.
Purple waffle plant, red ivy - This plant is an elegantly trailing evergreen perennial in warm to tropical climates. The purple and silver foliage make it a great accent plant on a green wall. It is fast-growing and has tiny white flowers bloom that in spring and summer. It can handle a range of soil pH levels and thrives in warm, wet but well-drained conditions.
Succulents - Some great succulents are crassulas, sempervivum (a hardy succulent great for tough climates), sedum and echeveria. Echeveria tend to have rosette growth formation which makes the green wall even more beautiful.
Selecting Plants for Green Walls | Landscape Business (landscape-business.com)
The plant palette for green walls is much wider than for most green roofs. The term “green walls” encompasses all forms of vegetated wall surfaces — green façades, living walls and retaining living walls. Living walls can be indoors or out, and made of soil, fabric or synthetics. They are nearly always irrigated, so drought tolerance is not particularly a constraint. In choosing plants for a green wall project, these parameters need to be outlined to give shape to the plant list. For indoor walls, tropical plants need to be used. Even with auxiliary lighting, the light levels indoors almost always necessitate plants that do not expect winter, which generally means tropical species.
Outdoor walls can grow a wide range of plants, and the direction a wall faces is critical in determining the plant list. For example, a north-facing wall will sometimes never receive a single ray of direct sun.
In selecting plants for green walls, I strongly recommend that designers look at existing walls and how they are faring, and how much maintenance is done to keep them that way. Keeping a line on availability for green wall plant replacements is also important. When plants die on a wall, the owners generally want replacement asap, since walls are showcases in most places. Not all plants are available everywhere all the time — plan for this. And, as always with green walls, it’s all about the water; keep the water flowing, and have backup water sources just in case.
How to Keep Exterior Green Walls Alive in the Winter (livingarchitecturemonitor.com)
Due in part to their beauty and dazzling array of benefits, there is a growing demand for planting exterior green walls in cold climate areas of the northern US and across Canada. But freezing cold temperatures can take a toll on plants in these systems[…]
Living wall plants are much more exposed to the elements than plants growing in the ground or on flat green roofs. Typically, smaller more compact species are pre-grown as plugs or in small pots to transplant into small pockets or modules. Hydroponic living walls are even more exposed to extremes of weather conditions. Soil is removed from the plants roots and they are planted bare rooted between layers of fabric.
Choosing the right plant for the right location is an essential role of the designer and/or green wall specialist. Local knowledge of climatic conditions and hardy plants indigenous to the region is an asset. Poor plant performance can also be attributed to lack of moisture at critical times during the growing season, and especially during the winter months. Living wall plants used in colder climates often have shallow fibrous root systems that thrive in thin soils. Consider a plant layout which features a diversity of tough hardy evergreen groundcovers and ferns, deciduous shrubs with attractive foliage and winter branching as well as flowering perennials and seasonal interest. For green facades, hardy climbers include Clematis, Climbing Hydrangea, Honeysuckle, Virginia Creeper and Wisteria.