As we have discussed over the past few weeks, beautiful gardens don’t happen by accident. You need to analyze and deeply understand your garden over time. Once you have a pretty good handle on what you are working with, you will be ready to begin the process of choosing the right plants. Here are a couple more things to be aware of within your landscape.
Sight Lines
One of the questions I ask clients about their property is “Where will you be looking at your garden from?” Seems like a simple question, but it is often overlooked. This helps orient the plants in the right lines and heights for maximum viewing.
For instance, for an island planting in your backyard, will you be mostly looking at it from your living room or deck? If so then put the taller plants in the back and the shorter perennials along the front. In the case of a foundation planting, then the viewing would be mostly from the street, but you will want to see it from your windows. I would not use really tall plants that block the view from the front porch or windows.
Another aspect of sight lines is screening. Is there a view that you want to hide/screen? Are taller plants needed to provide you with privacy? Both can be achieved with plant material but your need to be thinking about mature plant height. Is there a structure arbor, fountain or garden art that you want to guide people to with a path or by using the clean lines of a flower bed?
Topography and Drainage
Positive drainage away from your house is so important. Basements are ruined with poor drainage around your home. Really work at getting water to flow away from your home before putting any plants in the ground.
Another thing to understand within your landscape is where the water flows. Standing water for a few hours is one thing, but if the water stands for days then plants will be adversely affected. If you have pooling water after a big rainstorm, then you can divert it away more quickly via a ditch or shallow swale. A better idea might be to develop a rain garden?
Butterfly milkweed in the small rain garden at the arboretum
By understanding these aspects of your landscape, you will be rewarded season after season with beautiful, functional, earth-friendly oasis. A garden that works with landscape and not against it. Whether, you just moved to a new home that you are unfamiliar with or want to start over with your current garden, site analysis is the place to start. Good luck!
The more you understand your garden, the easier it will be to choose the right plants for your site. We all have plant preferences but not all of your plant preferences will grow in your garden. Here are a few more aspects to consider as you analyze your landscape.
Soil Type
Here in south central Kansas, our soils are typically alkaline, which is good for growing most prairie plants. Soils can be pH neutral with a value of 7.0, or anything below that is classed as acid, and anything above, alkaline. To determine your pH, a simple soil test can be done by yourself from kits at most garden centers or through the extension service.
Other soil considerations are consistency and texture. At the Arboretum, we deal mostly with clay soils. This soil type compacts easily and drains poorly. You must find plants with root systems that can penetrate through the dense structure of clay, i.e., big bluestem, asters, and indigos. Other soil types are sandy (dries out quickly, low nutrient holding capacity, low organic matter and loose in your hand), Silty (mixture of a sand and clay, easily compacted), Chalky (stoney, exposed subsoil after construction, good drainage) and Loamy (high in organic matter, holds moisture and nutrients).
If you have been working in your garden for any length of time, you have a good idea of what type of soil you have. You can add some compost to your soil if it is really terrible, but typically, you can find plants that will grow in your soil conditions. For example, there are plants that appreciate the consistent drainage of sandy soils especially during the winter months.
If your soil is alkaline, you will struggle growing rhododendrons and azaleas that need acidic soil. Try to gather as much information about your soil and then find plants that grow in it. Finding the right plant for the right place will make you garden smarter not harder.
Think of Garden Aspect
Once you have defined the area you want to landscape, you need to understand aspect. Garden aspect simply means which way your garden is facing. If it north facing, typically shadowed by your house, it needs plants that can grow in shade or partial shade. If it is south facing, then choose plants for all day sun. If it east facing, then choose plants that need six hours of sunlight, but are protected from the hottest sunlight hours. If your garden is west facing then choose plants that can endure the hottest sunlight hours.
South-facing garden with prairie dropseed, blackeyed susan, Amsonia hubrichtii, russian sage and Taylor junipers.
Obviously, trees, structures, and house orientation play a role in garden aspect. The key is to observe your garden at different times throughout the year. This will help you understand completely where the sunlight is coming from and how intense it can be.
One other thing to consider is microclimates within your garden. There may be small areas that behave totally different than other areas ten to fifteen feet away. One example would be a protected area along a fence or under a tree the shields that site from hot west sunlight and drying winds. Or, a low area in your yard that stays consistently moist is another example. These areas might allow you the opportunity to try a few different plants that would not otherwise grow in your garden.
Over the past few months, I have been working on some landscape designs. These designs have reminded me how important site analysis is to a successful design. Choosing the right plants for an area begins with a close look at the area being considered for a new garden. In my opinion, gardeners (I include myself in this category) don’t spend enough time observing our gardens throughout the year prior to planting anything. Here are a few important aspects to consider that will help you develop a rewarding planting scheme.
What is the size of your outdoor space?
Site analysis begins with taking a step back to observe the big picture. A small planting bed leading to the front door versus a larger foundation or island planting require different plants. Most plants need space to fully develop. Be realistic when you first start thinking about your garden. Lay out your garden beds with a hose to help define the landscape space. Step back and look at the lines and size of the bed. Is this the look you want for the area?
Another piece of advice I often give is to start small and work on your areas over successive seasons. A new garden can be overwhelming as you work to establish new plants, control weeds and maintain those new plants through the first year. Once the first area is up and growing, you can move to the next area. By starting small, you can build on your successes.
By using a garden hose to layout your garden, you can play with the design and curves before moving any soil. Step back and take a look. Adjust the lines until you are satisfied with the flow and size of the bed. Visualize the area with mature plants.
Control perennial/annual weeds before planting anything
Bindweed
Obviously, the best time to eradicate bindweed is before you plant. I spray the area with Roundup™ several times starting in July and August. Anytime we see green, the area is sprayed. This is the best time to spray because the plant is moving energy from the leaves into the roots for winter storage. The chemical is also moved throughout the extensive root system, killing even those deep roots. Trust me, it is worth waiting to plant until this weed is removed permanently.
Small patches can be hand pulled but you have to stay on it. Every sprig that pops up must be pulled immediately. We have also had limited success with hand painting the leaves with Round-up. Again, every new plant must be found and painted. Essentially, you have to be as ruthless and relentless as this weed is to completely remove it from your garden. I thank my ancestors for bringing this over to America with their wheat seed.
If you are firmly opposed to using any chemicals, you might consider solarization instead, or you may want to read my colleague’s blog post “On Weeding“.
Bermuda grass
This perennial grass is a problem because of its vigorous creeping habit. The plant spreads by seeds and by above and below ground stems that can take over a garden in one season. It is drought tolerant and thrives with neglect.
Like bindweed, bermudagrass is best removed before planting (same as bindweed). If you have it growing next to your gardens, a buffer must be maintained between the perennial display and the lawn area. This buffer can be weeded by hand or sprayed every few weeks with Roundup™ to burn back any new runners toward the garden. Raised beds are another defense against bermudagrass. Don’t blow bermuda grass clippings into your gardens. Again, it is better to wait to establish your new wildflower garden until you have bermudagrass eliminated. I have made the mistake of planting into bermudagrass and I am fighting with it every year.
Keep plants in scale
I don’t always observe or think about proportion and scale until it is too late. Keep in mind that your overall garden size helps determine what plants you can use in your design. Plant scale generally means using plants that are half the bed width. For instance, an area six feet wide needs plants that are no taller than three feet. A tall (8 foot) compass plant would stick out like a sore thumb if used in this area. In a narrow bed leading to your front door, taller plants tend to fall over and get in the way. Shorter plants such as prairie dropseed and black-eyed susans are a better option. Measure up what you have in order to see how everything will fit into place.
Compass Plant is a beautiful wildflower that gets eight feet tall. It is out of scale in a smaller space. Give it room to grow.
This is such an important topic and such a huge problem that we thought it is worth sharing again.
Several years ago, I noticed something disturbing was happening to our prairie reconstruction. Small little trees were popping up throughout the original prairie planting. I could not figure out where they were coming from, but they looked like pear tree saplings. It wasn’t until I saw a large white blooming Callery pear tree in the spring that it all came together.
Callery Pear
Although the flower clusters are beginning to fade, Callery pear’s white blooms are most obvious in the spring. We planted them for their explosion of spring blooms and nice fall color, but this ornamental tree has become highly invasive. It threatens native wildlife habitat and has become a nuisance for private and public landowners.
This once favorite tree was planted extensively throughout the U.S. The Callery pear – also referred to as Bradford pear – formed a nice pyramid to rounded shape. The vertical limbs made it a nice median and street tree as well, ultimately reaching 30 to 40 feet tall and 20 -30 feet in spread. This Chinese native was a harbinger of spring for decades with its prolific white blooms. An added bonus was its reddish-purple fall color.
Despite all those positives, these trees have become problematic. This non-native, flowering tree was assumed to be sterile, but it is not. It now cross-pollinates with other cultivars of Callery pear to produce hybrid offspring. The fruit is ingested by wildlife and birds that spread the seeds across the countryside and into your yards. It is aggressively displacing native vegetation, causing economic and environmental damage.
Escaped Callery Pears*
The message to property owners is to remove the trees now while you can easily identify them in bloom. We need to keep them from spreading to native areas. It doesn’t hurt my feelings to see them go, because they are a weak-wooded, thorny mess.
Native alternatives to Callery Pear:
Eastern Rudbud (Cercis canadensis)
Serviceberry (Amelanchier arborea or Amelanchier ‘Robin Hill’)
American Plum (Prunus americana)
Chokecherry (Prunus virginiana)
Blackhaw Viburnum (Viburnum prunifolium)
Rusty Blackhaw Viburnum (Viburnum rufidulum)
Blackhaw Viburnum in springBlackhaw Viburnum fruit and fall color
We have cut down the culprit, but still have a bunch more saplings to remove this summer. There was one more larger tree that was cut down near the Visitor Center. We will continue to eradicate these unwanted invaders in our prairies. It will take time but I believe we can get the upper hand. I would encourage you to remove them in your landscape as well and replace them with native trees. Callery pear has no place in the landscape anymore.
As gardeners, we have many choices of plants to introduce into our landscapes. From trees, shrubs, annuals, and perennials (including grasses), the options seem to be endless. Here at the Arboretum, we gravitate toward perennials for a number of reasons.
What is a perennial?
Unlike annuals that germinate, flower, set seed, and die all in one season, perennials are typically cold-hardy plants that will return again and again each spring. If situated in the right place in your landscapes, perennials will thrive, and will bloom either in spring, summer, or fall.
In my mind, the benefits of planting perennials in your home garden are as follows:
It often takes perennials several years to develop a sustaining root system after being transplanted from a pot. These root systems compared to many annuals is much more extensive and much deeper. During periods of drought, these deeper roots feed nutrients and moisture to the plant. The deeper roots of grass are credited with developing the deep layers of top soil found in many states that now support farm crops. These roots also control erosion, sequester carbon, and break up tough compacted soil.
Xeric Garden interpretive signage located on the Dyck Arboretum grounds. Artwork by Lorna Harder.
Diversity of Perennials to Establish in the Landscape
As I said earlier, there are so many different types and varieties of plants you can choose to establish in your display beds. A well-designed landscape with a variety of perennials will enhance the aesthetics and appeal of your property. With perennials that bloom at different seasons during the year and attractive grasses for fall and winter interest, you can create a diverse habitat for wildlife and pollinators, too. Keep in mind, the habitat you create is provides homes for insects and food for birds during the long, cold months of winter.
Prairie Window Project, August 2016. Photo by Brad Guhr.
Do perennials require less maintenance?
The key to success with perennials such as native wildflowers and grasses is putting the right plant in the right place in the right way. Perennials will NOT require less maintenance if you are trying to grow something in your landscape that has no business being there. Learn as much about the plants you want to use before you put them in the ground.
Perennials typically last several seasons. You don’t need to plant every single year like you do with annuals. By planting them once, you save money and time. You will need to clear last year’s growth in February or March and occasionally divide some clumps of perennial grasses as they expand over time. Perennials are a cost-effective and sustainable choice for landscaping.
Panicum virgatum ‘Northwind’ ready for spring.
Perennial plants can be the anchors to a landscape. While trees and shrubs provide the backdrop, perennials provide the elements of habitat that pollinators and other wildlife seek. These permanent pieces of your garden puzzle add beauty year after year. They can be combined to add continuous blooms and interest throughout each growing season. As perennials come in and out of bloom, a diverse collection of wildlife and pollinators will discover your landscape. This is ultimately the real benefit of a perennial garden.
A note about annuals
When I think about annuals in the landscape I don’t think about petunias. I choose annuals on their ability to provide nectar for pollinators. Nectar-rich annuals need to be drought tolerant and self-seed, too. See this article about a mostly annual garden.
This time of year we are looking for any hint of spring. Often we can find tips of green from bulbs or swelling buds of the silver maple. On other trees, such as birch, hazelhut, alder and later willows, you can see catkins dangling from their branches. One of the first harbingers of spring here at the Arboretum is the Ozark witchhazel.
Flowers
Ozark witchhazel, with the scientific name Hamamelis vernalis and pronounced ham-ah-MAY-lis ver-NAH-lis, is a native shrub found in Missouri and Arkansas spreading down through Oklahoma and Texas. In January to early March, depending on the winter, tiny yellow to reddish-purple flowers pop open along the stems. The flower petals resemble twisted ribbons. These muted yellow flowers add winter interest to the garden since they open before the leaves emerge. Our shrubs are just now starting to open.
First plant to bloom in the Arboretum this spring
Leaves & Habit
The wavy, oblong leaves expand in the spring to make a nice screen or hedge. Each leaf is a medium green with a whitish waxy coating. These leaves turn a nice yellow in the fall.
These shrubs can get large (up to 10’-12’ tall) over time especially in consistently moist soils. Our specimens are planted in clay, but there is good drainage away from the crowns. For the most part, they are drought tolerant, but appreciate a little extra water during drier periods. Leaf scorch occurs in hot, dry summers without adequate moisture.
For best flowering, plant these shrubs in full sun but they do tolerate some afternoon shade. There are no serious pests at this time.
Typically, it is a multi-stemmed shrub with straight upright habit. As the plant matures, the branches will arch and become broader. If it is really happy, it will develop root suckers. In our experience, these suckers have never been problematic or aggressive. Pruning will restrain colonization and spread. The best time to prune this shrub is in spring after it finishes blooming because next year’s blooms are set on this year’s new growth.
If you have the space, this large shrub can be a nice addition to your garden. The delicate flowers when nothing else is blooming is reason enough to try this plant. The vase-shaped habit with along the attractive oval-shaped leaves that turn a golden yellow in the fall are added bonuses. Why not give one or two a try? I am always amazed each time it blooms.
This winter has been one of the harshest Kansas has had in quite some time. Plants and animals have been tested with extreme cold, frozen soils and snow. It’s incredible to imagine that anything can endure these conditions. Over the past few weeks, I have watched the birds find food where they can. They are relentless in their pursuit of seeds and berries. After all, their lives depend on them.
Selecting plants that attract wildlife – including birds – to your garden is an important horticulture trend. The key to increasing wildlife diversity in your landscape is having as many different habitats and food sources as possible. Fruiting trees and shrubs provide food and shelter during these cold periods for wildlife. Leaving these sheltering spots, birds can find seeds from wildflowers and grasses during the day.
Here are several trees, shrubs and perennials that I have observed birds scavenging for food on over the past few weeks. They provide great winter food for birds.
This large shrub or small tree (20 feet high by 20 feet wide) can be found in eastern Kansas. It has creamy-white flowers in April and May followed by blue-black fruit in September. These fruits persist on the tree into winter, but are devoured quickly with the first snowfall. Buds are a rusty color that open to glossy green leaves and turn a beautiful reddish-purple in the fall. It is a very under used plant that provides excellent winter food for birds.
Blackhaw viburnum is the other native viburnum to Kansas that has abundant small prune-like fruit in the fall. With a mature height of 12 to 15 feet and a spread of 8 to 12 feet it is slightly smaller than Rusty Blackhaw Viburnum. In spring, it is covered with cymes that are 2 to 4 inches in diameter. The dark green leaves provide consistent fall color of red, yellow and orange.
Possumhaw is the only holly native to the Great Plains. It can grow to be 15 feet tall and wide. Branching is often dense and after leaf drop the round red fruit are revealed. The shrub is a heavy producer of fruits that are persistent into the winter months. When snow and sleet cover their regular food, birds flock to possumhaw and clean the branches in a short time. Deciduous holly are dioecious, meaning that there are both male and female plants and both are needed in close proximity to each other in order to have fruit set.
Ilex decidua ‘Council Fire’
Eastern red cedar (Juniperus virginiana)
Eastern red cedar is the only conifer native to Kansas. This is my top recommendation to homeowners looking for an evergreen tree, since there are so many diseases affecting pine trees these days. There are still some nice pines available, but they are not native. This juniper has dark green foliage and can reach over 20 feet tall with a dense conical habit. The dense branches provide excellent cover for birds during the winter. The female trees are often loaded with frosty 1/8 to 1/4 inch diameter cones that provide excellent bird food in the winter.
Eastern red cedar does have one drawback. Bagworms can decimate a tree. Bagworms have been very problematic over the last several years here at the Arboretum, but regular spraying with Bt (a biological insecticide) has been effective for us, especially when the larvae are smaller than ¼ inch. Begin checking for bagworms about the first week of June.
‘Canaertii’ is a female variety with dark green foliage that sets copious blue-green cones and matures to 20-30 feet. This tree has attractive branching architecture. A formal cultivar of Eastern red cedar is ‘Taylor’ which grows to 20 feet tall but only gets three to four foot wide. It too produces cones that birds enjoy.
Bad Bird Feeders – Ornamental Pear Trees
You can’t fault the birds for finding the fruit of pear trees and eating them. The problem is that a tree that was suppose to be sterile now produces so much fruit that it is on the verge of becoming a noxious plant. Do not plant another ornamental pear tree. They are becoming so prolific that they are pushing out desirable native plants.
Perennials as bird feeders
Coneflowers: These cones feed a host of birds including blue jays, cardinals, and goldfinches.
Birds use their beaks to carefully extract these seeds.
Sunflowers: Our native sunflowers are great sources of food for birds during the winter. Keep in mind that most native sunflowers can be very aggressive in the landscape. I have seen many different kinds of birds this winter working seedheads of Maximillian sunflowers outside my office window.
Rudbeckia: Even though the seeds are smaller than that of other perennials, blackeyed susans attract many different types of birds, including American goldfinch, black-capped chickadee, Northern cardinal, and white-breasted nuthatch.
Native grasses: Big bluestem, Little bluestem, switchgrass, and indiangrass are great food sources for juncos, finches, and many of our native sparrows.
Blaze Little Bluestem seeds. Photo by Emily Weaver.
With every new year comes a renewed sense of optimism about a whole host of things like fitness and health, relationships with loved ones and friends, your occupation, and maybe your garden. In the book The Earth is Enough by Harry Middleton, there is a paragraph that resonated with me, as a horticulturist and a lover of plants, about the struggles of gardening, but also the hope we have in plants. Here it is:
Emerson (one of the old men) believed in plants, though he never completely trusted them. After all, nothing could turn on a man with such cold, merciless indifference as a plant. A curious blight, a virulent plague, a sudden storm, an unyielding march of insects could sour a man’s agricultural fortunes with woeful abruptness, lance his emotions, eviscerate his always desperate accounts.
Harry Middleton
Gardeners need to be eternal optimists. We garden hoping to get something from our efforts, be it a vegetable to eat, beauty to enjoy or shade to rest in. Sometimes that happens but sometimes we fail. As we approach spring (yes, it is coming) and we start thinking about our own native plant gardens, I know that there will be holes to fill in our landscapes because of struggling or underperforming plants. We try to make perfect plant choices for our landscapes, but we are not always successful. Plants have so much to offer to us and the environment around us. Just because there are a few plants that succumb to our harsh climate or pests doesn’t mean we stop planting and believing in plants.
In particular, I believe in plants that are native to Kansas, because they:
beautify the landscape – with careful design, your garden can have flowers year round
nurture pollinators and other wildlife
provide food and shelter for birds, hummingbirds, butterflies, and other pollinators
save water
thrive in our local climate if properly matched to a site
are adapted to our natural cycles, responding to cool, wet winters with lush growth and slowing down during the hot, dry summers
prefer our soils or can grow in just about any soil type
do well in our native soils and do not require soil amendments or fertilizers
reduce pesticide use
typically have fewer pest problems than non-natives because they have co-evolved with native insects (unless there is a new introduced predator or pest)
minimize your carbon footprint
reduce maintenance over time in a well-designed garden
can easily be started with smaller sized plants, saving on installation costs
cool the environment
play an active role in the water cycle, adding cooling moisture to the atmosphere
harmonize with diverse garden styles
create a sense of place within our prairie state
Gray-headed coneflower with Bearer of the Ammonite by Paul Friesen. Photo Courtesy of Jen LeFevre
Just Keep Planting
Some plants are going to let us down. Or maybe we let them down by trying them in an ill-suited location in the first place. Whatever the case may be, keep believing in plants. They are good for you and the environment. Try to find joy in the beauty around you even though it is not always perfect or ideal.
Each and every year, we struggle with plants here at the Arboretum just like you do. But we are rewarded by our imperfect efforts time and time again. The journey of tending a garden is not an easy, straight line. It is a winding road of highs and lows. Keep believing in plants anyway.
The start of the new year is a great time to make changes in your life and dedicate yourself to the things you value most. In 2024, I have a few simple resolutions that involve health, travel, and nature. Some of these adjustments in my life will improve my overall health and enjoyment of the world around me. Here are a few thoughts I have as we start a new year.
LOOK UP
Over Christmas break, I read the book The Earth Is Enough: Growing Up in a World of Flyfishing, Trout & Old Men by Harry Middleton. I chose this book because it was about fly fishing, a hobby I have taken up in the past few years. However, this book didn’t dwell on fly fishing, but more on the experiences of being outside in the environment. The reader was able to connect with the sights, sounds, and feelings of being outdoors.
Too often lately, I have hurried through my times in nature and the beauty around me has been missed or taken for granted. The outdoors is a complex, diverse and beautiful place with many lessons to teach us. As you walk, be intentional about connecting with your surroundings. I am convinced I/you will be healthier and happier by just pausing for a few moments in our busy lives to look around. Being outdoors can be very healing.
Take a respite from our materialistic culture
This book made me think about the culture in which we live. We are driven to always want more stuff, which always leaves us hollow and wanting more. In The Earth is Enough, I appreciate the observations the characters made of their natural surroundings as they pondered all that truly matters in life. The eye of the trout looking at you as you release it back in the dark pool. Waiting on the return of the migrating geese marking the passage of time. These are simple but important interactions that help refocus our thoughts. These connections with nature, as well as the relationships we have with loved ones, can bring us joy and happiness.
Find your Why
Without a compelling reason or motivation to make the changes we want, resolutions fail. Why do I need to lose a few pounds? Why do I need to stop and smell the roses, so to speak? What do I need to focus on at work to be more productive? Sure, it isn’t easy to stay focused, but when I keep going back to my why, I find my motivation again. Each of our whys will be different, but what they have in common is that they help us continue moving forward with purpose.
These are just a few thoughts I have had over the past few weeks. I know these resolutions are nothing earth shattering, but they are important to me right now. A little more time outdoors away from television or my phone is not a bad thing. Self-care has never been more important.
Take care of yourself, of others and the natural world around us. Here is to a happier and healthier 2024.
Plant tags can be confusing. They give general information about the plant, but I often wonder, is this realistic for our area? Will this plant really grow to four feet tall? Or will it be beat down by our Kansas heat and wind? Can it withstand our temperature extremes? One critically important piece of information on the plant tag is the U.S. Department of Agriculture (USDA) Plant Hardiness Zone Map (PHZM).
Echinacea purpurea ‘Pow Pow White’ is hardy to zone 3 (-40 to -35 degrees F). So it will grow well in zones 3-8, which is most of the United States.
Purpose and Use
The USDA Plant Hardiness Zone Map was developed to show the average low winter temperature. Plants are rated according to the USDA hardiness zones, which is the minimum winter temperature they can survive. On the map, there are 13 zones with a 10-degree F difference between the zones. Each zone is further delineated with 5-degree F differences dividing the zone further into a and b (6a and 6b for example). Hesston is in zone 6b (-5 to 0 degrees F).
Kansas hardiness zones range from 5b (-15 to -10 degrees F) in the extreme northwest corner to 7a (0 – 5 degrees F) in the south and southeast. The USDA PHZM has been recently updated to show gardeners what plants are most likely to survive in their area. Type in your zip code to find your zone and use it as you choose plants for your landscape. CLICK HERE FOR THE 2023 USDA PHZM
Plant Provenance
This hardiness zone map highlights another important factor to consider regarding native plants – provenance. Plant provenance refers to the source of the plant material that was collected for propagation. The reason this matters is that some species have very broad natural ranges that cover several very different ecoregions, hardiness zones. The populations of such species have developed adaptations to their environment at a genetic level even though they are outwardly identical. Seed collected from a northern provenance is adapted to a shorter growing season, colder winter temperatures and often cooler nighttime temperatures compared to a southern provenance seed. All this to say, try to purchase native seed from sources closest to your ecoregion as possible.
This coleus is an annual unless it stays warm all year such as zone 10. Obviously, it must be kept away from freezing temperatures.
Plant lovers tend to push the boundaries when it comes to hardiness. I have been told and shown plants growing in Kansas that are supposed to be hardy to zone 8. It’s possible, but they are the exception, not the rule. Often they are growing in a microclimate, which is a localized area that differs from the average climate with different growing conditions. This could be on the side of a building, red brick wall, a fence or an evergreen tree blocking the sun or wind. This could also be in a valley or on top of a hill.
The USDA Plant Hardiness Zone Map is a valuable tool that helps gardeners and growers choose hardy plants that are most likely to thrive at a location.
Here are a few other helpful pointers from the USDA:
If your hardiness zone has changed in this edition of the USDA PHZM, it does not mean you should start removing plants from your garden or change what you are growing. What has thrived in your yard will most likely continue to thrive.
Remember this is the average coldest night—not the lowest it could go. Gardeners should keep that in mind when selecting plants, especially if they choose to “push” their hardiness zone by growing plants not rated for their zone.
Microclimates, which are fine-scale climate variations, can be small heat islands—such as those caused by blacktop and concrete—or cool spots (frost pockets) caused by small hills and valleys. No hardiness zone map can take the place of the detailed knowledge that gardeners learn about their own gardens through hands-on experience.
Many species of perennial plants gradually acquire cold hardiness in the fall when they experience shorter days and cooler temperatures. This hardiness is normally lost gradually in late winter as temperatures warm and days become longer. A bout of extremely cold weather early in the fall might injure plants even though the temperatures may not reach the average lowest temperature for your zone. Similarly, exceptionally warm weather in midwinter followed by a sharp change to seasonably cold weather may cause injury to plants as well. Such factors could not be taken into account in the USDA PHZM.
All PHZMs should serve as general guides. They are based on the average lowest temperatures, not the lowest ever. Growing plants at the extreme range of the coldest zone where they are adapted means that they could experience a year with a rare, extreme cold snap. Even if it lasts just a day or two, plants that have thrived happily for several years could be lost. Gardeners need to keep that in mind and understand that past weather records cannot provide a guaranteed forecast for future variation in weather.
Other Factors Affecting Plant Survival
Many other environmental factors, in addition to hardiness zones, contribute to the success or failure of plants. Wind, soil type, soil moisture, humidity, pollution, snow, and winter sunshine can greatly affect the survival of plants. The way plants are placed in the landscape, how they are planted, and their size and health might also influence their survival.
Light: To thrive, plants need to be planted where they will receive the proper amount of light. For example, plants that require partial shade that are at the limits of hardiness in your area might be injured by too much sun during the winter because it might cause rapid changes in the plant’s internal temperature.
Soil moisture: Plants have different requirements for soil moisture, and this might vary seasonally. Plants that might otherwise be hardy in your zone might be injured if soil moisture is too dry in late autumn and they enter dormancy while suffering moisture stress.
Temperature: Plants grow best within a range of optimal temperatures, both cold and hot. That range may be wide for some varieties and species but narrow for others.
Duration of exposure to cold: Many plants that can survive a short period of exposure to cold may not tolerate longer periods of cold weather.
Humidity: High relative humidity limits cold damage by reducing moisture loss from leaves, branches, and buds. Cold injury can be more severe if the humidity is low, especially for evergreens.
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