Cold Climate Online Information
The help and information you need are a click away!
Cold Climate Gardening - Info
- Alaska Cooperative Extension Service | Agriculture & Horticulture
"Agriculture and Horticulture in Alaska is distinct. Growers, farmers and gardeners must contend with unpredictably short growing seasons, yearly infestations of various insects, long daylight hours and even the occasional mid-season frost. While consumers may have a difficult time finding informed advice from the “outside,” local Extension Agriculture and Horticulture Agents and Specialists are highly-trained professionals who experience the same challenges as residents."
- Apple trees for USDA zones 3 and 4 - fruit trees for sale
A list of apple varieties recommended by a British company for USDA Zones 3 and 4. Lots of other information, including a fruit pollination checker and tree height calculator.
- Assessing Frost and Freeze Damage to Apple Trees
"This file contains pictures of frost damaged buds, flowers and fruit for growers and home fruit growers who wish to determine frost damage after a freeze. People want to know if a frost has damaged fruit immediately after the freeze. It is best to wait several hours (until the afternoon) to let frozen tissues thaw. Dead and damaged tissues will turn black or brown. "
- Australia Hardiness Zones
Courtesy of Jelitto Perennial Seeds
Ha! Make that Australia's lack of hardiness zones. No cold climate here. Map provided as part of Jelitto's website.
- Average Freeze-Free Season For NY, Cornell University
A map that can be enlarged
The map above shows the average freeze free period between the last frost in spring and the first frost in fall. Use it to help decide which varieties or cultivars of plants to grow.
- Beaconsfield Garden Club
"The Beaconsfield Garden Club is a group of gardeners from communities near the town of Beaconsfield, on the island of Montreal, Quebec, Canada." On their website they have articles and links that would be helpful for all cold climate gardeners.
- Beautiful Botany - Janet Davis Writing and Photography
"Janet Davis is an award-winning garden writer and photographer based in Toronto. For almost two decades, her words and images have been featured in numerous Canadian and U. S. books, magazines, newspapers and packaging materials, and on the website ICanGarden.com. She is also an avid gardener, with a tame city garden and wild country garden."
- Bluebird Nursery
"Although Bluebird is a wholesaler, they are very useful as an on-line reference. Their collection is vast and includes many unusual and uncommon plants. They are also committed to introducing plants from the most northern range of native populations, seeking the most cold hardy. They have a great relationship with the Denver Botanic Garden who have been instrumental in introducing plants collected from high mountains of South Africa."--Craig Levy
- Canadian and US Hardiness Zones Compared
Zoned In: Why Toronto is Zone 6 and Zone 5
Both countries map their landscape into zones to denote plant hardiness -- where a plant will survive, especially over winter. Yet, Canada and the U.S. use different methods to define them.
- Canadian equivalent to the USDA hardiness zones map
"There is interest by some in Canada's horticulture industry to compare the USDA minimum temperature zones to Canada's plant hardiness index. . . . Some plants are traded between the two countries and there is sometimes a need to make such a comparison. The maps allow users to query points anywhere in Canada and get values. Users can zoom into any area and query maps."
- Canadian Hardiness Zones - About
They use Celsius, we use Fahrenheit. Canadians have their own hardiness zones, too, and this page explains how they were developed.
- Catalogues Listed at Canadian Gardening Magazine
"Catalogues help gardeners endure the long winter months and provide many happy hours contemplating the myriad possibilities for next yearâ€™s garden. If you grow from seed, youâ€™ll get a jump-start on spring and a much wider selection of cultivars than those available as seedlings in garden centres. Locate links to mail order catalogues quickly and easily by searching our alphabetical listing by company name."
- Chicago Botanic Garden--Top-Rated Plants
I know, Chicago isn't in zone 4 or colder, so technically it's out of the provenance of this website. But I'm willing to make exceptions for really good stuff. They evaluate a whole bunch of one kind of plant, like yarrows, or bee balms, and see which cultivars are the best, not just in terms of looks, but disease resistance and winter hardiness as well.
- Cold Damage
"Cold weather can cause all types of problems for plants. Freezing temperatures can damage plants by rupturing plant cells as ice crystals form and rapid changes in temperatures occur. Evergreen plants can suffer damage from blowing winter winds and dry out when water is unavailable from ground that is frozen in the colder regions of the state. Chilling injury can occur to many tropical plants although temperatures do not drop below 32 Â°F." Originally written for South Carolina gardeners, this information is helpful to us Northerners as well.
- Earth-sheltered Greenhouse
"Triple the length of your growing season with this simple, energy-efficient design."
- Five Cedars greenhouse, gifts and garden center in Theresa NY.
Five Cedars Garden Center and Studio is located in the Thousand Islands Region of New York State. Specializing in regional perennials, hosta and geraniums, we take the time to help gardeners learn about the plants they are buying. In addition to the plants and organic vegetables there are hand crafted bird feeders and houses as well as other original design garden art.
- Flower Bulb Research Program, Dept. of Horticulture, Cornell University
Includes latest research on forcing bulbs and lily perennialization, instructions for creating a bulb labyrinth, and suggestions for great bulb and perennial combinations
- Four Season Farm
This is the website of Barbara Damrosch and Eliot Coleman. They claim that, "for the past eight years, in defiance of our long, cold Maine winters, we have been developing an environmentally sound, resource efficient, and economically viable system for extending fresh vegetable production into 'the other eight months.' We call it the 'winter harvest.' â€¦We currently sell freshly harvested salads and main course vegetables from the 1st of October until the 31st of May." And they sell a manual so you can do likewise.
- Freeze Protection Methods For Crops
This Factsheet provides some information on various freeze prevention methods that are available.
Damage to crops by freezing temperatures causes crop yield losses somewhere in Ontario every year. Such damages range from cold set-back of alfalfa in spring to loss of tomatoes in a home garden in the fall. Some of these losses can be prevented. A number of different methods are available for preventing freeze damage to crops. It is important for growers to be aware of these so that they can evaluate which procedures are feasible and economical for combating freeze damage. This Factsheet provides some information on various freeze prevention methods that are available.
- Freeze/Frost Data U.S. Climate Normals
From the National Climatic Data Center of the U.S. Department of Commerce:
"This product contains station freeze/frost probability tables for each state. Given are the dates of probable first and last occurrence, during the year beginning August 1 and ending July 31 of freeze related temperatures, probable duration where the temperature exceeds certain freeze related values; and the probability of experiencing a given temperature, or less, during the year period August 1 through July 31. For the fall and spring dates of occurrence, and freeze-free period, probabilities are given for three temperatures (36, 32, and 28 Â°f) at three probability levels (10, 50, and 90 percent)."
- Frost Chart for Canada
From the Old Farmer's Almanac: date of first fall frost, date of last spring frost, and length of growing season for many Canadian cities.
- Frost Chart for the United States
From the Farmer's Almanac: Last Spring Frost, First Fall Frost and length of growing season in days for many U.S. cities.
- Frost Dates and Hardiness Zones
This is a collection of links to various listings of last frost dates.
- Fruit That Grows in USDA Zone 3
"The Saskatchewan Fruit Growers' Association (SFGA) is a grower-directed association dedicated to the production and marketing of premium quality Saskatchewan-grown fruit. A voluntary non-profit association, the SFGA is interested in the development of a strong and vibrant fruit industry. To meet industry needs, the SFGA works with researchers, government, processors and consumers. We collaborate with these stakeholders on research, market development, quality standards, and other initiatives. Members receive: the Prairie Fruit Journal, annual membership directory, bulk purchasing discounts, member pricing for industry education and activities, and other benefits." Since Saskatchewan is located in USDA Hardiness Zone 3 and colder, this is a good source of growing fruit in cold climates, even if you don't live in this Canadian province.
- Garden Design: Gordon Hayward and Mary Hayward
Based in Vermont, the Haywards have created a beautiful garden which has been featured in many magazines. This website features images of their garden, information on the books they've written, and Gordon Hayward's ideas for people who want to design their own landscape or garden or work with a professional designer.
- Gardening News from Minnesota Extension Service
• Current, seasonal information from a Zone 4 state •
New cold hardy varieties, seasonal chores, pest & disease information, design advice, and more! Email subscription available.
- Gardens North
In addition to selling seeds, this site has some specialized information on starting seeds. Check out the Germination Corner under the About Us category.
- Griffith Buck Roses
Dr. Griffith Buck bred roses for hardiness and fragrance. This site includes a biography of the man, a listing of all the roses he bred, and sources.
- Growing garlic in Minnesota
Best varieties and planting strategies for growing garlic in a cold climate
This publication provides guidelines for growing garlic in cold climates. The major areas addressed include variety selection, soils, cultural practices, pest management, harvesting, and storage. Most garlic in the U.S. is grown in the mild climate of northern California. Varieties adapted to mild climates and then grown in cold climates often do not perform well and usually develop a very "hot" flavor. Garlic is an adaptable species, however, and over thousands of years, varieties have been selected that grow well in cold climates, often with better garlic flavor than the varieties grown in mild climates.
- Growing Garlic, Harvesting Garlic, Planting Garlic, Garlic Scapes
A British Columbian perspective
Garlic growing is easy in the home garden.
Maintaining top quality requires care and attention. Weeding is important as garlic does not like competition. Watering and not watering, harvesting on time and curing properly are all important for producing bulbs with good keeping qualities.
- Growing Short-Season Sweetpotatoes
How sweet it is!
IF PEOPLE HAD TOLD ME SEVENTEEN YEARS AGO THAT YOU COULD GROW
SWEETPOTATOES IN CANADA, I’D HAVE THOUGHT THEY WERE PULLING MY LEG. At the
time, my gardening mindset placed sweet spuds just this side of pineapples and
bananas—way out of range for Maritime gardeners. After all, didn’t supermarket
sweetpotatoes hail from places like Louisiana and Tennessee?
- Hardiness Zone Maps Around the World
Courtesy the Pacific Bulb Society
Collected by Lee Poulsen: " the best USDA Hardiness Zone maps that I've found so far for various regions around the world . . . . I'm still
in the process of adding explanatory text. . . . Some of the maps are JPEGs and some are PDFs
(which usually contain a lot more detail). All are supposed to use the same (USDA) methodology for determining the zones, but I think some were more accurate at doing this than others. Also, it appears that some had more detailed temperature data than others had (and/or better mapping algorithms). But all in all, it's a first cut at being able to compare similar climate zones (or at least winter-time expected cold temperatures) among any of the various countries and continents that we all live in, or from which the plants we want to grow originate."
- Heritage Perennials
"Heritage PerennialsÂ® is the name of our line of perennials, grown in their distinctive trademarked blue pots. We are Valleybrook Gardens, a family-owned nursery farm, one of North America's largest wholesale producers of herbaceous perennials. We grow millions of plants each season at our two facilities: Abbotsford, British Columbia (near Vancouver) and Niagara-on-the-Lake, Ontario (near Niagara Falls)." But they are more than just growers--their website is full of useful information, including a search utility based on plant criteria, how-to articles, free downloads--tons of information. You can learn a lot here.
- High Altitude Gardening | Planet Natural
Getting Results From A Short Growing Season
The high-altitude gardener’s main concern is the length of the growing season. Attempting to raise a winter squash that requires 90 or 100 days to mature in a zone that provides only 70 to 80 frost-free days (or less) is a recipe for disappointment. Yet with wise planning, preparation and attention the high altitude gardener can grow such squash as well as a myriad of other vegetables, including tomatoes, eggplant, beans and peppers. Choosing the right vegetables to grow for your conditions, starting seeds indoors, protecting plants at the beginning and end of the growing season as well as doing everything possible to encourage quick, healthy growth will reward the high altitude gardener with results to rival his flatland counterparts.
- How to Divide Ornamental Grasses
Tips on dividing ornamental grasses from a cold climate nursery
"ICanGarden.com began in 1995 by Master Gardener, Donna Dawson, with a view to providing information to gardeners. Since its origin, ICanGarden has grown to include information on over 400 garden clubs, almost 300 public gardens, over 3500 articles from over 150 garden writers, gardening events from around the world, over 800 links, over 750 suppliers and thousands of forum and member items." Two writers I recognized were Des Kennedy and Susan Wittig Albert.
- Interactive USDA Plant Hardiness Zone Map for the Continental United States - Plantmaps.com
Click on a hardiness zone icon. It will show you all the areas on the U.S. map that have that zone. Type in a zip code. It will zoom to that location and tell you what zone it is. Near the bottom is a drop down list of native plants. Choose a plant (such as shagbark hickory) and it will show you the native range of that plant. You can get all this information elsewhere, but it is fun to see the overlap between a certain hardiness zone and a plant's native range.
- Introduction to Short Season Gardening in Idaho
Published by the University of Idaho Extension
This publication begins a series specifically designed to provide effective, comprehensive ideas for gardeners living within the harshest climates: those rated USDA hardiness Zone 4 or colder, situated at an elevation above 4,500 feet, or with a frost free period of fewer than 110 days.
- Japan Hardiness Zones
Courtesy of Jelitto Seeds. In Japanese.
Courtesy of Jelitto Seeds. In Japanese.
- Louisiana Iris Growing Tips for the North
Culture information provided below is the result of trial and error and best guess practices derived from assimilating the mass of instructions geared toward Southern growing, and applying years of practical Northern gardening experience.
- Maine Agricultural and Forest Experiment Station--Electronic Publications
In addition to the Woody Landscape Plant Cold-Hardiness Ratings listed separately below, you might be interested in some of their other publications, such as Why Not Tame the Wild Blueberry? (#415) or New England Killing Frost Records by Zone (#731). If you are a commercial grower, also check out the link to the non-electronic publications.
- McKay's Nursery Blog
We're located in frigid Waterloo, Wisconsin. We have a special place in our heart for anyone gardening in cold climates.
Located in frigid Waterloo, Wisconsin, McKay's Nursery is a font of cold climate gardening wisdom. You're sure to find gardening information that truly understands the kind of environment you grow in.
- National Frost Dates by City and State
These are quite general and only of use if you are just starting out in a cold climate and haven't a clue. Seasoned veterans will perhaps get a voyeuristic thrill from seeing what other gardeners cope with.
- Network for Environment and Weather Applications
The value of weather data is greater when it can be shared. NEWA makes it possible for farmers to share resources for weather data collection, analysis, distribution, and archiving
NEWA connects you with data from electronic weather stations in the Northeast through the Internet. Farmers, consultants, food processors, NYS IPM, airports, and Cornell research farms provide the weather stations. The NEWA website provides weather information for more precise IPM and crop production practices. Weather information and pest forecast models enhance decision-making in IPM, especially for plant diseases and insects. NEWA...
provides weather data from >100 locations.
summarizes and displays weather data – find it under Weather Data on the main menu.
displays pest forecast model results – find them under Pest Forecasts on the main menu.
links to pertinent information.
displays weather radar images.
displays and links to National Weather Service forecasts.
- New Hampshire Hostas and Companion Plants
At New Hampshire Hostas, we're committed to providing a broad selection of quality hosta. New cultivars are always being added to our selection.
Our website offers growing tips and other resources. Choose hostas by attribute (fragrance, color, etc.) See 700+ hostas in one place! Our greenhouses to the public Thursdays through Saturdays 9 AM to 5 PM. We're also available for garden tours for Garden Clubs.
- Northern Gardening
Happy was the day I discovered this website! Master Gardener Terry L. Yockey packs it with information to help the cold climate gardener, and provides links to other cold climate gardeners' websites as well.
- Northern Gardening, Suite 101
Mary Henry writes thoughtful articles with the cold climate gardener in mind. I especially appreciated the cold climate emphasis of her bulb article. Unfortunately she is no longer the moderator of this section of Suite 101, so the content is old but still relevant.
- Northern New England, Suite 101
Articles written by Diana Morgan address topics of concern to New England gardeners and others with similar climates. This topic is no longer active, but the old articles still have lots of good information.
- Northern Pond
An Ottawa-based assemblage of garden (theirs and others) photos and garden advice, with particular emphasis on urban and water gardens.
- Northern Shade Gardening
"My garden is located in Edmonton, Alberta, Canada, which is in gardening zone 3, where winter temperatures can drop to -40°C (-40°F). It is usually covered in snow for about 5 months of the year, so the growing season is short. Northern Shade Gardening contains information about the types of hardy perennials, shrubs, bulbs and trees that perform well in these cold climate conditions."
- Northscaping For Northern Gardeners
Northscaping used to be a resource and community website for
landscapers and gardeners living in northern North America (hardiness zones
1-5). It's mission was to empower homeowners living in the challenges of a
northern climate to transform their yards and gardens to make them more
beautiful and functional. The company has changed direction, but still has much important information online. It's not easy to find, but follow this link for a list of articles. I am sad to see it go, while I understand the practical realities for the change. I wrote a highly complimentary review back in 2006. Read more . . .
- Northscaping Landscape And Garden Plant Search
The Landscape Plant Search provided by Northscaping is an easy-to-use interactive database of over 2,000 trees, shrubs, vines and groundcovers specially suited for use in northern landscapes (hardiness zones 1-5). Close to seven years were spent compiling and programming the Landscape Plant Search, which really is their crowning achievement. Ten thousand photos were taken and cataloged. Two thousand plants, each with a hand-written description, were programmed into a database with 68 different parameters.
- Ornamental grasses for cold climates: introduction
This is an excerpt adapted from Ornamental Grasses for Cold Climates.
This is an excerpt adapted from Ornamental Grasses for Cold Climates. The book used to be sold through the Minnesota Extension Service. Now it seems it is sold through the Arboretum, but I couldn't find it on their website. In the sidebar of this excerpt you can see the table of contents for the rest of the book, and it looks like it has a lot of valuable information.
- Overwintering Your Perennial Containers
"I’ve gambled and left pots out all winter and some made it and some did not. So what do I need to do to make sure my potted perennials come back next year? I do recommend (particularly in colder zones) to consider the following"
- Plant Elements of Design
From the Sustainable Urban Landscape Information Series developed by the University of Minnesota Extension Service, this is a searchable database of plants hardy in zone 4. You can either look up a plant and find its characteristics, or you can search for a plant that blooms in summer and grows 4 feet tall, for example, and get a list of plants that fit the criteria. Handy, huh?
- Plant Hardiness Zones for Australia
This just goes to prove that Australia doesn't have a cold climate.
- Plant Hardiness Zones of Canada 2000
Agriculture Canadaâ€™s map of plant hardiness zones. If you live in Canada, itâ€™s your guide to the best plants for your region.
- Plants Database Reference. Compare reviews & ratings.
"The PLANTS Database provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories. It includes names, plant symbols, checklists, distributional data, species abstracts, characteristics, images, crop information, interactive identification keys, automated tools, references and onward web links. This information primarily promotes land conservation in the United States and its territories, but academic, educational, and general use is encouraged." You can filter by number of frost-free days or by winter hardiness, so this can be a good resource for cold climate gardeners.
- Pleasant Valley Conservancy
Pleasant Valley Conservancy is a site of The Prairie Enthusiasts (TPE), an organization active in the upper Midwest.
Pleasant Valley Conservancy State Natural Area No. 551 is a 140 acre Preserve in western Dane County, Wisconsin. It consists of extensive restored oak savannas, dry, mesic, and wet prairies, wetlands, and oak woods. If you are interested in restoring a natural area that shares a similar climate, this website will be of interest to you.
- Pollinator Partnership
Invite pollinators to your neighborhood by planting a pollinator friendly habitat in your garden, farm, school, park or just about anywhere! Our ecoregional planting guides are tailored to specific areas of the U.S.
You can find out which ecoregion you live in by entering your zip code
These guides were funded by the National Fish and Wildlife Foundation, the C.S. Fund, the Plant Conservation Alliance, the U.S. Forest Service, and the Bureau of Land Management with oversight by the Pollinator Partnership, in support of the North American Pollinator Protection Campaign.
- Renegade Gardener
Don Engebretson proclaims himself the "lone voice of horticultural reason for USDA Zones 2 through 4." He's opinionated (check out the ten tenets of renegade gardening), funny (read his bio), and informative (study up on his garden myths). I would like to think that this website is another voice of reason for the cold climate gardener, but his site is a definite must- read. My only complaint is that he still doesn't have a syndication feed.
- Rose Gallery - Far North Gardening Forum - GardenWeb
Pictures of really hardy roses growing in real gardens
If you think you can't grow roses in your cold climate, think again! Browse through this forum thread to see photos--with names--of roses that are thriving in the far north.
- Roses for the North : Garden : University of Minnesota Extension
Performance of shrub and old garden roses at the Minnesota landscape
An excerpt from an informative book(let) published by the Minnesota Exension Service. Minnesota is almost entirely USDA Hardiness Zones 3 and 4, so this is valuable information for all cold climate gardeners.
- Roses That Challenge The North - Rose Magazine
Learn which roses are hardy enough for your climate.
Owner and operator of Birch Creek Nursery, just outside of Prince George in north central British Columbia, Canada, Barbara raises roses and puts them through the rigors of testing. She propagates some varieties, brings others in from half a dozen different wholesale growers in Canada and the United States, and also collects hard-to-find hardy specimens through specialty rose growers to test and perhaps use as breeding stock.
- Snowfall - Average Total In Inches
Data provided by the National Climatic Data Center
If you are curious how your local snowfall compares to the rest of the U.S., this page should satisfy your curiosity. If you are considering a move to a different part of the country, this will give you an idea of what you are in for.
- Syracuse Rose Society
Syracuse Rose Society meets the second Thursday of every month (except December and February) at the Reformed Church on Teall Avenue two blocks south of James St. The well-lighted parking lot is entered from Melrose Avenue. The public is always welcome, and meetings begin at 7:30 p.m. (Founders’ Day Dinner in January begins an hour early.) There is also good information about rose culture in upstate NY on the website.
- The Alaska garden
Paul Apfelbeck and family
Flowers and veggies which grow up here next to the Arctic Circle, 65 degrees north and at the edge of the treeline. Plus garden tips for those of us who are really in the cold climate zone.
- The Curious Gardener Explores Gardening north of 60°
Gardening in the Yukon videos
The Curious Gardener (Arlin McFarlane) is very curious about all things gardening and in this web-based series she helps deconstruct gardening secrets from local northern experts.
- The North Country Gardener
• writings and musings about cold climate gardening •
The North Country Gardener is my way of sharing with you, my fellow gardeners, some of the pleasures and fun, as well as frustrations and plain old know-how, of my Vermont gardening life.
- Tree Identification Guide
An online tree identification manual. It includes a tutorial if you are new at identifying trees.
- University of Minnesota Extension Service
Another good source of information on cold climate gardening. Their online publications catalog is better organized than previously, but it is still probably better to use the search engine provided if you have a specific topic in mind. Some of their more popular titles have free excerpts available for download, so it's worth taking the time to see what they've got. Ornamental Grasses for Cold Climates and Roses for the North are two of their most popular titles.
- Urban Horticulture Institute, Cornell University Department of Horticulture
If you live in an urban area, you will find useful information here.
The Institute's mission is to improve quality of life by enhancing the functions of plants within urban ecosystems. Our program integrates plant stress physiology, horticultural science, plant ecology and soil science, and applies them to four broad areas.
- US Drought Monitor
"The Drought Monitor summary map identifies general drought areas, labelling droughts by intensity, with D1 being the least intense and D4 being the most intense. D0, drought watch areas, are either drying out and possibly heading for drought, or are recovering from drought but not yet back to normal, suffering long-term impacts such as low reservoir levels. Drought intensity categories are based on five key indicators and numerous supplementary indicators."
- USDA Plant Hardiness Zone Map - National Arboretum
Here is the official USDA Hardiness Zone Map that is referenced by gardening books and mail order catalogs.
- Weedpatch Gazette Archives
"This website is the successor to a newsletter called The Weedpatch Gazette, which was published and distributed in the Midwest for ten years, but ceased because the Internet offers such a great opportunity to share information so much more quickly with so many more people.The information contained in TWG was of exceptional quality, and I am excited to offer you here a searchable database of the hundreds of articles that appeared in the print version."
- Western Europe: Hardiness Zones
There's a little bit of zone 5 in the Alps, but otherwise it's not a really cold area. Finland is not on this map, however. I need to find a better one.
- Wild Blueberries
If you have acid soil and a cold climate, you might want to consider growing wild blueberries. They are smaller, but hardier, than cultivated blueberries, and many people think they have a better flavor. Here is one source of information on growing these plants.
- Wisconsin Hardy Plant Society
"Wisconsin Hardy Plant Society is a membership of garden enthusiasts who learn, teach and work to grow healthy, long-lasting gardens. WHPS was founded more than a decade ago by a group of individuals who wanted to promote the love and appreciation of hardy herbaceous plants to every level of gardening expertise." They have some of their newsletter articles online if you happen to not live in Wisconsin.
- Woody Landscape Plant Cold-Hardiness Ratings
Technical Bulletin #156 from the Maine Agricultural and Forest Experiment Station, is one of the first sources of cold climate information I found. UMaine maintains the Lyle E. Littlefield Ornamentals Trial Garden in Orono. According to the Introduction, "the site is in USDA hardiness zone 4a having suffered winter temperatures as low as -30 degrees F. three times in the last 6 years." (This was published in 1994.) The plants are grown without winter protection except for mulch and are rated numerically to indicate their winter survival: 1= no damage whatsoever and 5=died. However, as Reeser C. Manley pointed out to me in an email dated 3/7/2001, ". . . in some cases only one to a few plants were tested. This is fine if they survive, but tells you nothing if they die since winter survival is a function of so many variables, freezing tolerance being only one." True enough, but it's a good place to start if you don't have a clue as to what trees and shrubs will survive in your climate, and the woody plants are the most expensive. Best of all, the booklet is free for the downloading.
- Woody Plants Database - Cornell
Enables you to find woody plants based on search criteria such as size, light requirements, etc.
- Worldwide USDA Zone Map Links
Many links to zone maps for specific states and for countries in other continents.