Green is a secondary color, made from a mix of the primary colors, yellow and blue. Greens made from lots of yellow, and only a dash of blue, we call lime green, or chartreuse. Yellow and green mixed in equal parts I call true green; I cannot spot a yellow, or a blue cast. Greens made from lots of blue and a dollop of yellow-the blue greens. But to a gardener, green is about much more than a mixing formula. Green is the color of life.
I have never seen a landscape or a garden that did not have green as its dominant color. Why would I? Chlorophyll enables plants to live, be nourished, and grow. Any experienced greenhouse grower can tell if a plant lacks for something a block away, by assessing its green. A plant needing water goes greyish; a starving plant, and an overwatered plant will take on a sallow, yellowish appearance. Healthy, robust plants are robustly green.
Judging from the numbers of people I try to help grow healthy yews who cannot spot that yellow/green yews indicate a water or drainage problem, I think green is so pervasive in a landscape, people stop seeing it. If you are not tuned in to green, you are missing a good portion of the pleasure and satisfaction of a landscape. Designing with green in mind-don’t miss this.
My helleborus angustifolia suffers at the hands of our rough Michigan winters. The foliage is ratty and tattered by spring. But their green flowers make my heart pound, and the hair stand up on the back of my neck. Though my yews, so black green in winter weather, warm in the sun and turn juicy green, the hellebores are my first flowers. Fresh green, they are. They are a sure sign of life in my garden.
I like color. This means I like the green as well as the red, pink, orange, brown, blue, orange and yellow. This all green planting I like as well as a great stand of echinacea. Green enchants me as much as any other color. By the way, that stand of echinacea will be all the more striking if it is companion planted with a blue green panic grass. The blue/red, or magenta flowers look so beautiful with blue/green grass. A garden is about much more than the flowers blooming.
White Christmas caladiums light up a shady area. The variegation is not really white; it is a very pale green. Depending on the light at any given moment, they can be a lively visual discussion about the beauty of green. These leaves are very thin. Substance in any natural material refers to its thickness. Thin substanced leaves transmit light well, and glow.
Many shades of green are represented in this pot. Variegated licorice has a decidedly blue cast; pair it with Dallas Blues panic grass-subtle and gorgeous. The trailing Kent Beauty oregano is blue green as well-the nicotiana alata lime is the center of interest in this pot as it stands out, as it is the only yellow green element. Design is very much about deliberate.
Green can be dark and moody. Inky fingers coleus, and black calocasia are black greens. The dark medium green borders on the Inky Fingers are just light enough to describe the dancing form of the coleus. The dash of lime licorice-an exclamation point.
Lime green is so fresh, it speaks to spring. New growth is this color-on yews, the flowers on the maple trees, the willow trees whose branches tell the story of the spring sap rising. Growing green is pale green. Lime green in the summer landscape can provide juicy definition to a shady area. It can provide punch every bit as good as a blooming plant. Lime green is fresh respite-plant it where you need this.
Nero di Toscano, the Tuscan blue kale, is distinctively blue green. I hear people eat this-but I just want to look at it. It gives great companionship to this blue columnar juniper; the delicate blue green variegated licorice and showy oregano are like a frothy slip at the base. This design is much about proper scale for the planter, and contrasting textures, mass and shape, line and direction, rhythm-but it is so very much about the color green.
Were I pressed, I would have to say Nicotiana Alata Lime is my favorite flower. Everything about it delights me-the simple shape, the nodding habit-but most of all that lime green. I never tire of them. My taste in garden and landscape plants has evolved over the years. My intent to design with the greens in mind did not come to me my first day gardening-I was very busy trying to get some decent horticultural practices in place-among a thousand other things. The fact that gardening still energizes and enchants me after all these years-I chalk that up to the greens.
There are times when color is the most important element of a landscape design. This building, circa 1880, had become home to a well known and cutting edge advertising firm-Harris Marketing. Any commercial client in the design business is keen that the landscape reflect as much attention to design as possible. What you see outside is a visual reflection of what goes on inside. In this case, the architecture and materials of the building itself made the color issue a very important design issue.
Though the building was large, and several stories high, there was very little land on which to landscape. The building facade was comprised of brick of an astonishingly bright orange color, and stone. In addition, the right of way space was paved in orange brick. Any successful landscape design would need to address that color in a thoughtful way, and then create visual interest in a very tight space. My first decision was to choose one plant element that would represent that brick color-a Crimson Sentry maple. Since the right of way locusts were planted at regular intervals, and framed in brick, I planted a row of these columnar red/orange/brown leaved maples in the spaces between the locusts-this visually added the right of way trees, and the land in which they were planted, to my landscape design. 
I rarely plant dark foliaged trees, as the color can be hard to work with, and muddy at any distance. This siting places these maples close to the viewers eye, backed up by that bright orange brick; the color of those leaves worked well. Large bottomless planter boxes made from corten steel served a dual purpose. The eventual orange brown of the steel would make my color references stronger. They also permitted me to make a grade change in a small space. They made a 3-D representation of the brick borders around the locust trees. This unexpected element catches the eye. 
I planned to plant hydrangeas in the boxes, and Sum and Substance hostas in the ground. The greenish white flowers of the hydrangeas, and the lime green foliage of the hostas would contrast with those orange brown leaves in a sparkly way. We lined the planter boxes with sheet insulation; once the ground would freeze in the boxes, I wanted it to stay frozen. Too much freezing and thawing might hinder my chances for success with hydrangeas, whose roots would be above grade.
Making this long run in several boxes dramatically reduced the fabrication cost, and made transport much easier. The boxes and hydrangeas would also screen the basement level windows, and window air conditioners from view. Old buildings like this one a very difficult to adapt to modern air conditioning. This fact did not need to be part of the public presentation of the building.
A stripe of PJM rhododendron unexpectedly repeats the maple leaf color. I think it is a good idea to be clear in executing what you are trying to achieve. There would be no opportunity to explain to passersby what I meant. If I need to explain the intent of a design, I need to rethink the design. 
It would take some time for that corten steel to orange up. Corten steel only rusts to a certain point, and then becomes stable. Once the hydrangeas matured, they completely screened the lower floor windows. Though I would not ordinarily block light to the interior of a building, there were security issues that my client decided were more important.
The finished landscape has a beat. A lively rhythm, and attention to the color relationships established by the building and environment attracts attention-any business hopes for this. I would have been happier for more evergreens given our climate, but my client reasoned that few people would be walking by in the winter. The orangy brown boxes would make a statement to people driving by. Any strong geometric statement would attract the kind of attention they were looking for. 
en grisaille: to paint in a limited palette, light in value, and monochromatic-usually grey
I have grown serviceable, if short lived stands of delphinium belladonna and bellamosa, but blue is brief in my garden; pansies, violas, lobelia, and phlox divaricata. My big blue garden season is the winter. The combination of snow, sky, and dark turns everything in the landscape blue. 
Our climate supports many evergreens whose green needles have a distinctively bluish cast. Frazier fir is a blue green color. The stately giant Concolor Fir is a pale blue grey. The color stands out such that I have never known how to place them in a landscape where they seemed beautiful, and not theatrical-except at a great distance from the eye. 
Blue spruce is a very popular evergreen to plant, though I have never done so. I find most properties I deal with are too small to carry that blue color convincingly. When I think blue in a landscape, I think about mountains, hazy with evergreens, very far away. These dwarf Serbian spruce are not quite as blue as the spruce in the background, but they quietly reference the color blue. 
We have the blue of the sky and the water. Michigan is home to the great, the medium, and the small lakes-all of them beautiful. Years ago I never thought about water in a garden; I would not do without the color and the sound of water now. 
I grow lots of plants that are blue green. Rosemary, curly liriope, and variegated licorice-my favorite combination this past summer. Planted in an English lead pot, set on a bluestone terrace-a modest celebration of blue.
I do have clients who like their swimming pools Florida blue. Fine. She had such a thing for that blue, we painted the inserts in her steel boxes blue, to match the frames on her windows. This may not appeal to everyone, but it doesn’t need to. I like seeing people pursue what makes them happy. 
Silver foliaged plants are a good source of blue. This cardoon makes subtle reference to blue-as do lamb’s ears, achillea Moonshine, thyme lanuginosus, silver plectranthus, and so on. Any number of non-hardy succulents make a bigger visual deal of blue-if drop dead blue pleases you. 
Our natural blues are those moody grey blues. This color is easy to work with. White is great. Red is striking. Pink is sweet. Green is a natural. Yellow is friendly and outgoing. Lime green is cool and sophisticated. Orange and blue attract attention. You get the idea.