Color theory is both an incredibly simple and an undeniably complex concept. In the most basic sense, it is the art and science of using color.

The three fundamental tenets are the color wheel, color harmony, and color context. Using these tenets you can create a vibrant and well-balanced landscape that influences the mindset of the viewer. Read on for some examples.

The color wheel

Let's begin with the color wheel. You have your primary colors of red, yellow, and blue. Each primary color has many representatives in the landscape whether it’s the electrifying red of a Crocosmia 'Lucifer', the sunny yellow of Hypericum, or the cool blue of Delphinum, blue spruce, or the exotic Meconopsis. Next up you have your secondary colors: green, orange and purple. Obviously there’s no shortage of green in the landscape, from the uniform green of an oak tree, to the variegated green of the Hosta 'Guacamole'. Orange is slightly more difficult to find. Butterfly Weed, Echinacea, and Daylily come to mind. Don't overlook plants that bear bright orange berries, such as Little Goblin® Orange Winterberry Holly. Purple is an easy find, from flowers like Iris, Phlox, and Campanula or foliage of Cotinus, Weigela, Heuchera, and Ninebark. So many options.

Color harmony

Color harmony can be a difficult thing to achieve. In essence it engages the viewer and creates an inner sense of order. Basing your color scheme on complimentary color pairs such as red/green, yellow/purple, or blue/orange creates contrast and stability. Or you might choose analogous colors, meaning colors that are side by side on the color wheel. Typically with an analogous color scheme, one color will dominate, one color will support, and one color will accent. So combining say, a bright DoublePlay® Candy Corn® Spirea (yellow-orange), Hyperion Daylilies (yellow), and 'Frances Williams' Hosta  (yellow-green) creates a wonderful gradient that works well together. Use a primary color to draw the eye to a focal point and two tertiary colors to add dimension.

Another option is using triadic colors, where the colors are spaced equally around the color wheel, for example: 'Ruby Spice' Clethra (pink), Vinca (periwinkle), and Aruncus (cream). Triadic color schemes make each individual item stand out yet still feel balanced.

Color context

Using color to create context in the landscape is relatively simple when you know what each color reflects. Warm colors (colors created using red and yellow) reflect happiness and energy. The color red itself has been show to raise blood pressure and respiration in humans and can have an overwhelming effect if used improperly. Yellow conveys a sense of happiness and permanence. Cool colors typically convey relaxation and calm. Green is a very stable color and can add harmony to most color schemes. Shades of blue can vary greatly from calming to strong and reliable. Purple is associated with creativity and imagination in most of the world, and is also widely recognized as the color of royalty.

During the COVID-19 shutdown this spring, I was sitting on my porch on what was to be a beautiful day. It was early, and therefore quiet, and I heard a sound coming from my boxwood. I leaned in and distinctly heard what sounded like Rice Krispies in milk. Perplexed, I asked Google what was going on, and Google said, "leaf miners are eating the centers of your boxwood’s leaves". They were making quite a racket. They are either noisy eaters, or there were thousands of them. There was probably no time to lose, so I ignored it. 

A few weeks later I saw the damage to the leaves. They were wrinkling up and turning color. I split one leaf open, and inside were tiny orange maggots, from two to six in every leaf I checked. Now that I could see the little orange bastards, it pushed me into action. I asked google how to deal with them without resorting to pesticides. Google said, "you must resort to pesticides". Particularly, a systemic insecticide that would be taken up by the plant's roots and distributed to the leaves. I applied the systemic, but I was afraid I ignored it too long. They were probably stuffed and pupating and turning into adults. 

Two weeks later, my fears were confirmed. What looked like fat orange mosquitoes were flying in swarms around my boxwood, fornicating and laying eggs in the new leaves. The boxwood wouldn’t survive another generation of these Trump-colored vermin. But I was still loathe to use more insecticide. Hoover to the rescue. I took my vacuum cleaner out on the porch, and began vacuuming the mango scum, much to the dismay of my girlfriend who was awakened by the noise, and immediately questioned my sanity (not for the first or last time). To no avail, I explained my rationale about avoiding the use of insecticides that may harm beneficial insects. Verdict... I was a crazy person. I kept vacuuming. They just kept coming. After a while I went inside to take a nap. 

I woke to the sound of a vacuum cleaner. Yes, outside was my girlfriend vacuuming boxwood. We were both obsessed. This went on for nearly two weeks. The neighbors were too polite or too scared to mention our obsession, but I doubt the boxwood would have survived another season without the intervention, and they look well on their way to recovery. I have to admit though, it was a lot of effort for a few lousy boxwood.

These days I have a forty-minute commute to work, and I enjoy the progression of bloom through the season, of everything from landscape ornamentals to woodlots and farm fields. There is always something happening. There are some plants I would like to see less of, though.

In late May the purple, white and pink flowers of Hesperis matronalis, aka Dame's Rocket, bloom in abundance all up and down the roadsides and into fields and woodland edges. I love it, and I don't - it's invasive, having long ago escaped into the wild. It sows itself with abandon, soon forming vast colonies that crowd out and replace native plants. Related to Garlic Mustard, it spreads just as aggressively. If you like the look I would steer you to the tall phloxes, like P. paniculata or P. divaricata because we do not need any more of this plant. Don't get me started on Garlic Mustard, it's not even pretty.

But who says invasive plants *have* to be ugly? Here's another one that is a common sight in Michigan, Hemerocallis fulva, aka Ditch Lily. It's not a true lily, but a daylily, and not a neat clump-forming one, either. No, it spreads by rhizomes and forms large colonies filling the ditches on either side of roads all over the state. I like seeing the cheery orange flowers every summer but again, it's busily crowding out native plants. 'Kwanso' is a double form that is offered in the trade, it is not nearly as aggressive. 

One of the worst offenders is the notorious Lythrum salicaria, aka Purple Loosestrife. In spite of decades of trying to knock it back, by physical removal and the introduction of several species of beetle that eat it, it still occupies acres and acres of wetlands across the entire continent. None of our native animals or insects really need it for either food or shelter and I am personally over the obnoxious color of the flowers, too, because they just remind me of the futility of trying to put the Genie back into the bottle.

There was talk at one time that some of the named varieties were sterile or nearly so, but it turns out that they breed just fine with the wild ones. So even if you find it for sale, don't plant it. If you have it on your property, get rid of it. 

There are loads of invasive plants loose in Michigan, from Autumn Olive to Phragmites, Buckthorn to Spotted Knapweed, Multiflora Rose and Oriental bittersweet, to the honeysuckles - oh, boy, the honeysuckles... To all of them I say, hit the road! 

For more information about these and other invasives, check out these links!

• MSU Extension Field Guide to Invasive Plants - PDF
• Midwest Invasive Plant Network
• Michigan Invasive Species at Michigan.gov

I have been working in the industry a long time, and I have come to look at some plants as... lonely. Lonely maybe isn’t the word, but underappreciated isn't the correct word either. The sparkling Stellas and Endless Summers of the world are not lonely plants. Even plants like Clethra and Fothergilla are not lonely plants.

I do think of all Ilex as lonely but I think of the verticillatas - Michigan Holly - as the loneliest. They seem lonelier than glabras (Inkberry) for some reason. Unlike their loved big brothers who are evergreen with classic holly leaves, the verticillatas are considered old fashioned and without much flair. BUT LET ME TELL YOU! There are some new cultivars and hybrids on the market, and they will make you wish all Ilex were deciduous because, “The berries are where it’s AT!”

The older varieties like  ‘Winter Red’ and ‘Sparkleberry‘ are awesome when the leaves drop and the best berry display is in view. But these older varieties can get a little leggy and out of control if they are not maintained. The older cultivars also have men in their lives that get unruly after a while - go figure!

There are several breeding programs that excite me.

• Berry Poppins®: How about heavy berries, (read COPIOUS) on a 4' tall dwarf plant, perfectly sized for the landscape. The berries are large and an orange-red in color. The leaves also drop a little earlier than other hollies for a longer display. The pollinator is... are you ready? Mr. Poppins®. 

• Berry Heavy® Red: bred for better bearing (copious again) and even longer persistence. The berries are bright red and nicely bunched along the stem. This one will reach 6-8’ in height. The pollinator is again, Mr. Poppins®. (He does get around, along with his friend 'Jim Dandy' who can help out with the pollination duties.) There is also a gold-berried version, Berry Heavy® Gold.

• Little Goblin® Red: this is a 4’ dwarf with extra-large red berries. Her pollinator is Little Goblin® Guy. There is also a orange berried variety in the Goblin series.

We are not always appreciative of new plants. Does that make them lonely? My opinion on these plants is that anything to bring the poor Michigan Holly into the spotlight is good. But I have also been watching these new varieties for a couple of years now and these are good plants and a welcome addition.

P.S. Part two may be on all the cool and awesome new Inkberry cultivars...

Some plantings are difficult.  Poor soil, deer, high ph, lack of irrigation, or a combination of some or all of these issues.  The more factors in combination, the more your plant list gets whittled down.  One of the plants you can count on to be available to use when the whittling is done is diervilla, or bush honeysuckle.

Diervilla grow in most soil conditions, all light conditions, and are deer and drought resistant. They all sport somewhat inconspicuous yellow flowers. The Kodiak® series, developed for the landscape, sport various leaf colors for more summer interest and are non invasive.  All of these colors, including amazing fall colors, are more intense the more sunlight the plant gets.

Kodiak® Black sports a blackish-purple leaf which contrasts well with the usually inconspicuous flowers.  Kodiak® Orange and Red are also available with hints of orange and red in the leaves.  The most intense fall color seems to come from Kodiak® Orange. 

These plants get between three and four feet tall and wide.  Their habit can be considered a little messy and leggy if left to grow naturally.  I like to prune them regularly to maintain a smaller size and encourage increased branching, but do it in late fall so as not to miss any of the fall color show. 

Diervilla is a tough plant for tough conditions, but the Kodiak® series gives you an attractive plant even when conditions aren't tough.

Social Distancing for... plants? Yes, you read that right.

Social distancing for plants has two distinct applications.

The first is to keep plants apart that simply don’t get along well. Examples include those affected by Cedar-Apple Rust such as crabs, hawthorn, and quince and their alternate hosts of Juniper (virginana, horizontalis, and scopulorum). The deciduous get orange spots on their leaves and early leaf droppage while junipers get galls. Similar to this is Pear Rust which affects our ornamental Asian Pears , Bradford, Cleveland, et al. This, too, is caused by over-planting and proximity to Juniper species. The results are similar to Cedar-Apple Rust. A more recent fungal problem exist with our boxwoods and pachysandra. While not alternating hosts, plantings of these as complementary may increase risk of Boxwood Blight. Some genera simply need some distance or even not being included in the same landscape altogether.

The second application of plant distancing is proper spacing. This requires planning and knowledge of plant size, growth rates, and growth habit. The first crime in planting I would call the model home or interior-decorator syndrome. The landscape is planted for the here and now. It has to look lush and lived-in – NOW. The result in a few years is usually a crowded, jungle-like landscape. Much of the original plant material will need to be pulled out. The second crime is a planting that looks nice but really does not reflect the true growth habit of what has been incorporated into the landscape. Remember the Colorado Blue Spruce on the corner of the house; thirty years later you cannot see the house. The development of columnar trees and evergreens has solved this problem. Also, the introduction of many dwarf or compact versions of the old standby varieties has expanded the pool of variety and color palette. Only people my age remember the old Vanicek Weigela (a monster) that yielded to W. fl. ‘Red Prince.’ And now, we have Weigela florida: ‘Wine and Roses, Fine Wine, Dark Horse, My Monet, et al.’ How small can they get?

The art and discipline of plant spacing depends on a great knowledge of plant growth rate and maintainable size. If a new landscape is developing nicely in about three to five years, then you did a good job of placement. Larger trees and evergreens can take around three years to really establish. This is evidenced by greatly increased leaf size and improved coloring in evergreens. From this point on you should see an increase in growth rate. Most woody ornamentals are filling in and exhibit much heavier blooms during this same time. Perennials and groundcovers establish showing very little top growth first season – the Iceberg Effect (roots first, then foliage and flowering the next season).

We are at the mercy of tag information which is far from perfect and landscape architectural drawings rendered by an industry with low plant knowledge. If you take your landscape installation seriously and are interested in long-term results, become familiar with nursery varieties as fast as you can and keep up with new introductions.

We’re not talking about something not agreeing with you. We’re asking can plants pass on disease to humans?

Humans have a number of viruses in common with plants and animals. Three such families exist: the Bunyaviruses carried by insects (like mosquitoes, ticks and sandfly) causing the diseases Crimean-Congo Hemorrhagic Fever and Rift Valley Fever and rodents causing Hantavirus infections; the Rhabdovirus better known as rabies causing encephalitis; the Reoviruses which causes gastrointestinal and respiratory disease primarily in infants and young children.

Many of us have experienced dermatitis from poison ivy and other plants. People often misidentify plants and become sickened or even poisoned after ingesting. A fairly common disease throughout the world is Sporotrichosis caused by the fungus Sporothrix. This fungus exists in soils, plant debris, sphagnum moss, hay, and on rose thorns. It usually enters the body through small cuts or punctures from rose thorns ( sometime called the rose-gardener’s disease). It can manifest as small bumps or blisters at entry site, more seriously if breathed in it can cause a type of pneumonia, and if entry wound is near a lymph node it can become disseminated throughout the entire body.

Another common and opportunistic pathogen is Pseudomonas aeruginosa. It’s what causes soft rot in plants, fruits, and vegetables. It is especially dangerous for people with immunity deficiencies causing pneumonia, urinary tract infections, and oral infections. And, similar to the staph that causes MRSA it is antibiotic resistant. Much of what has been mentioned results in disease caused by the myotoxins produced by the bacterium.

More recently in France people have been showing symptoms of fever, aches, and pruritus (a systemic itching usually caused by a disease) after eating peppers with mild mottle virus (PMMoV). Viable virus has been found in salsas, powdered spices, and in the samples of hundreds of people. Viable tobacco mosaic virus has been found in the mucus and thoracic fluids of smokers.

In India tospoviruses causing tomato spotted wilt and groundnut bud necrosis are passed on by insects, thrips, and humans. Live virus is found in ripe tomatoes only to be eaten and passed on through ground and water. Begovirus which causes the tomato yellow leaf curl virus affects tomato production worldwide and, in turn, affects the insects that carry it by shortening their lifespan and their ability to reproduce.

So as you can see, plant diseases have many paths to make humans sick - but none of the pathogens has, of yet, crossed the line of entering the human cell. Plant diseases for now have no direct route as a human pathogen.

If you’re anything like me, this Michigan shelter-in-place quarantine has been quite the eye-opening experience. While I happen to be very introverted by nature, the lack of human connection during this time has me going a bit stir crazy. At random points in the day I find myself talking to the various plants sprinkled around my apartment. The conversations are a little one-sided, but they got me thinking: does talking to your plants benefit them or you? 

Scientific evidence on this particular subject is somewhat sparse. Although this is not a new theory (Many believe the first mention of this particular ideology is “Nanna oder über das Seelenleben der Pflanzen” by Gustav Fechner) few actual studies have been conducted. In Fechner’s 1848 book, he puts forward the idea that plants have a soul of sorts. Although his premise was founded mostly on his own feelings and observations, it has become the basis for the few studies that exist today. A 2008 study from the National Institute of Agricultural Biotechnology, Rural Development Administration “identified a set of sound-responsive genes in plants” (1). The study suggests that both genes are responsive to sounds above 125Hz. The typical adult male has a vocal frequency between 85Hz and 180Hz, while the typical adult female has a vocal frequency between 165Hz and 255Hz. Sorry guys, women are just better when it comes to plants! A separate study published in the Journal of Experimental Botany found a link between sound vibrations and several outcomes including: “increase the yields of several crops and strengthen plant immunity against pathogens. These vibrations can also prime the plants so as to make them more tolerant to impending drought.” (2).

While there may not a ton of hard scientific data related to the effect of speech on plants, there is quite a bit of anecdotal evidence! On a 2004 Episode of Mythbusters, seven separate greenhouses were set up with varying levels of noise. Stereos playing loops of speech were set up in the greenhouses; Two of negative speech, two of positive speech, a fifth with classical music and a sixth with intense death metal music. A seventh greenhouse, used as a control sample, had no stereo. The control group grew the least out of the seven after 2 months.

Possibly one of the saddest commercials I’ve seen in recent years (with the exception of the ASPCA ads. The song gets me every time.) is a viral video (3) produced by IKEA last year. It was intended to show the effect of unkind words on children. In the experiment, two plants were isolated in identical, controlled environments and received either positive or negative comments through a speaker. After 30 days, the plant that received negative comments was visibly less healthy. Now obviously this wasn’t a strictly scientific experiment, it was an awareness campaign. It’s entirely possible that there were, lets just say ...outside factors... contributing to that poor plants’ demise. I sincerely hope not, because intentionally killing a plant seems a bit over the top for an ad campaign but this is the world we live in.

Here’s my takeaway: until someone initiates a large scale scientific experiment, we can’t conclude that talking to your plants absolutely will or will not help them grow. Really though, what could it hurt? The worst thing that could happen is people could conclude you’ve gone a bit mad. The Mad Hatter said it best “You’re entirely bonkers! but I’ll tell you a secret: all the best people are.” 

As the cooling weather encourages me to change over from iced tea in the afternoon to hot tea in the morning and the blazing summer sun relaxes into a lower place in the sky, our landscape is changing too. Don't think that just because summer is over the yard must be dull and boring. In Michigan we are blessed with four seasons, each of them delightfully distinct.

When planning a landscape I love to focus on a few plants for each season so there is something to look at every month of the year. In the spring, trees are flowering and bulbs are popping up. Summer brings on bolder, more vibrant colors from blooming perennials, contrasted by thick, dark green leaves. From late summer into autumn there is an interesting transition period where some of the summer perennials are still showing off, whilst the cooler weather plants begin to display their offerings, like bright fruit and glowing fall foliage. Finally, the days become shorter and our warming sun cannot keep up with Old Man Winter. Branches turn bare, perennials retreat underground, and evergreens take prominence.

Use forethought when designing the landscape. Plant diversely and consider what each of our splendid seasons has to offer and how your plant choices will display during each. Hiding in plain sight during warmer months are the showstoppers of colder months. Leafy bushes shape the structural backdrop, whilst other plants offer contrasting foliage to your summer flowering showcase. In the fall, these ignored plants begin to get some attention. You may hardly notice a crabapple after it’s week of spring flowers, but then in the fall it begins to display shiny red apples. A juniper can get lost in the scene until it’s steel blue needle tips poke through the windblown leaves and snow.

When those first chilly end-of-summer mornings surprise you, look around and you’ll notice the Great Lakes native Joe Pye Weed (Eutrochium purpureum) standing tall. Another striking perennial is Helenium, with it’s daisy-like flowers in deep oranges and reds, blooming late summer into early fall. 

Ninebark is a fantastic three-season shrub that offers spring and summer foliage interest, late summer flowers, and has cool weather hangtime with colorful seed capsules and handsome, peeling bark. Consider Diabolo® for it’s stunning dark foliage, or Summer Wine® for a more compact version.

When snow has covered the ground, don’t fret! There are plenty of plants in our landscape to keep the winter doldrums away. The red chokeberry, for example, is a great choice for those lower damp corners that you don’t know what to do with. Aronia arbutifolia  ‘Brilliantissima’ should make your shortlist as it offers something in every season. White flowers, red fall color, glossy red berries, with dark woody twigs for the snow to settle on. Remember the clumping grasses you planted in the spring? What about the hydrangea you added soil amendments to? Standing clumps of dormant brown grasses and sturdy dried flower heads can present an engaging contrast to the white winter snow that sits atop of them.

Another aspect of our Michigan winters is the colorful population of birds. Wherever there are berries and seeds you will also find birds. Picture a tufted titmouse in a crabapple, hopping from branch to branch. For persistent fruit, Malus ‘Adams’ is still a popular choice. For a darker, almost red flower check out ‘Prairiefire’ and Royal Raindrops­®.

Color in the garden is important, but don’t forget texture. Seven-Son Flower (Heptacodium miconioides) is a plant that I recently noticed while meeting with a customer on their jobsite. It’s a small tree (or large shrub) with white flowers in late summer or early fall immediately followed by showy, red-pink calyces, and a peeling brown bark that reveals lighter tan beneath for winter interest. This is one of those plants that few people know about and they can be hard to find. We get a few in now and then and can also special order for you, so please inquire.

In my time off from Christensen’s I love going to different zoos and gardens to shoot photos. I’ve been into photography for about 35 years and now my oldest daughter is into it as well. I’m a self-taught photographer and became more interested in photography when a Lowland Silverback Gorilla threw a clump of grass at me that came within inches of my head. I wish I had been able to capture that shot!

 I shoot with a Canon EOS 800D and a Tamron 18-400mm zoom lens, and this kit gives me a lot of flexibility for shooting both landscapes and wildlife.

My favorite place to go is the Detroit Zoo. Within the past two years the zoo has opened two new exhibits that feature plant material from Christensen’s Plant Center. The new exhibits are the Holtzman Wildlife Foundation Red Panda Forest and the Devereaux Tiger Forest.

Christensen’s has supplied massive amounts of plant material over the past two years for the new exhibits. The red panda exhibit has a suspended bridge over two display areas that are fully landscaped. The pathway to the end of the tiger exhibit is spectacular, it goes on forever it seems, featuring trees, shrubs, perennials and ornamental grasses. The tiger area has tripled in size from the old display area and the tigers really seem to enjoy their new habitat.

In addition, over the past five years we have supplied plants for the river otter and giraffe exhibits, and many of the display berms and gardens throughout the entire zoo. Next time you are visiting the Detroit Zoo, look at the plant displays as well as the animal habitats, you might get some great inspiration for your landscaping designs. We know where you can get the plants!