A few weeks ago I posted on social media that I was going to slow down in the number of articles I posted to my website. This was due to some ongoing health problems and because my schedule has become increasingly busy with talks, book signings and trying to work on Volume 2 of the Gardener’s Guide to Native Plants of the Southern Great Lakes Region.  There just don’t seem to be enough hours in a day to get it ALL done. I was blown away by the level of support I received over my decision – your kindness has been extremely gratifying – even though it’s made my decision to cut back a tad more difficult. 

I asked what it was you’d like to see me continue with, since I could no longer do everything, and one of the suggestions a long-time friend made was that I should write an article about (to paraphrase her) “how I designed my gardens to make them look so nice”. This is an attempt to answer that. 

For starters, I’m extremely lucky to live in Ridgetown, Ontario, a small town in the heart of Canada’s Carolinian Zone. The soil is a rich sandy loam and there’s a good 6’ elevation drop from front to back, meaning I have high and dry, low and moist all in one yard. I also have several large sugar maples (and have planted several other trees) so I have full shade to full sun, and everything in between. And to top it all, my property is a double lot (110’ wide by 220’ deep) with a tiny (25’X27’) war-time bungalow that is located so close to the front of the property that if I ever need to replace my front step, I can’t. It’s actually on city property. So that gives me a HUGE canvas to work with. 

When I bought the property in 2004, other than a few non-native forsythia, a beauty bush, and a lovely saucer magnolia in the back yard, it was basically a bare lawn. I had just started a new job, and I didn’t have a lot of time to garden in the first couple of years, so I started small. I planted a few shrubs in what felt like strategic locations, and a couple of trees. Most of these had to be relocated within the first 2-3 years as I got a better feel for the lay of the land and a vision started to materialize. Don’t worry if you don’t get it right the first time. Plants move – usually pretty easily. 

Needless to say, over the next 15 years, the flower beds grew in number and size as I became more comfortable with the yard. But so far none of this discusses the principles that guided my design. 

For starters, I have no formal training in landscape design. But I am a keen observer of nature, and I have always been fascinated with optical illusions. And my garden designs use both of these interests to the extent that it is possible.  

First off – nature does not produce straight lines. Things flow, in curves and meanders, in nature. This is probably the first rule of design for me. My flower beds are all laid out using a garden hose to mark nice, curved edges (making sure the curves aren’t too tight – I still have to get a lawnmower around the edges).  

But, in my opinion, there IS a place for a few straight edges – especially near buildings. To me these add a bit of contrast, and can help transition the “box” of the building into the garden space.  

And nature doesn’t grow short plants in the front and put the tall ones at the back, either. Instead, she tends to grow plants of similar height together. (This could be as much a factor of tall plants shading out the shorter ones as anything). So my gardens tend to be tall plants, or short plants, or mid-height plants, in their respective beds. But, as with so much in my yard, this is not a hard and fast rule and I do break it often. 

Then there’s the optical illusions. In my yard there are a couple of vantage points that I have chosen as the “viewing locations” for the yard. Because my yard is over 200’ deep, and because it slopes from front to back, I design my beds and pathways to exaggerate this depth. The simplest way is to make the grass pathways between beds get slightly narrower as they go to the back of the lot. This gives a much greater sense of depth and distance than what I actually have.  

To emphasize this, when I built my 10’X20’ garden shed, I put it in the back corner of the yard. But I made the decision to build it with only a 7’ eaves instead of the traditional 8’. This makes the shed look long (and thus large) but the low profile makes it look further away.  

The other thing I incorporate into my design is mystery. From no one location can you see the entire yard. There are “surprise” flower beds, or a hidden gem of a specimen plant, tucked into corners, blocked by beds of tall plants or shrubs, and pathways that meander and take you to secret places.  

If you are timid about designing your space, just spend some time contemplating the area. (I spent 3 years sitting in a hammock-chair observing and contemplating the layout of the “escarpment” I eventually built before I actually started it!) Then just go with your gut. Mother nature will fill the space with colour and insect and bird life, regardless of what the initial layout looks like. And, if you don’t like it – plants can be moved. Easily.  

So far in this series on garden soil, I have looked at soil texture, pH, and organic matter in your soil and their impact on plants. In this, the final article in the series, I will discuss soil moisture and nutrients, and why these things even matter. 

Water 

Some of our native plants need dry, well drained soils. At the extreme end are plants like Prickly Pear Cactus (Opuntia spp). Because these plants have evolved strategies to retain water and have lost their mechanisms for eliminating excess water, too much water will cause the plant to drown because it is not able to get enough air to the roots. In cactus, in particular, too much water will lead to rotting roots because they do not have the ability to fight of moisture loving fungi and bacteria.  

We all know that plants need water to grow. How much they need (or will tolerate) depends on a variety of factors, not the least of which is the conditions under which they evolved.  

At the other end of the spectrum are aquatic and semi-aquatic plants. Plants like Soft Bulrush (schoenoplectus tabernaemontani) will quickly desiccate and die if left out of the water because they have no mechanism to retain moisture (such as the thick walled cells often found in plants like cacti). But why don’t they drown? In order to get the necessary oxygen down to the roots that are in waterlogged soil, these plants have specialized cells, called aerenchyma, which form tubes to conduct air down below the water level. 

But most of our native plants fall somewhere between the two extremes. In average garden soil, there will be periods that the soil is very wet, such as after the spring thaw and after a period of rain, and times when the soil is quite dry. The moisture retaining capacity of the soil, as we saw in the first two articles in this series, has to do with soil texture and the amount of organic matter present. And if you grow plants that are suited to the soil conditions in your garden, they will easily tolerate these variations in soil moisture. 

We know plants need water, but what role does water actually play in plant growth. For starters, water is essential for photosynthesis. Photosynthesis is the plant’s superpower – being able to convert water (H₂O), carbon dioxide (CO₂) and sunlight into nutrients for the plant, then discarding the excess oxygen (O₂) as a waste product – which is very convenient for oxygen breathers like us. During photosynthesis, water provides the hydrogen (H) atoms required to make glucose (C₆H₁₂O₆) – the simple sugar that serves as the primary source of energy for the plant. 

Water also dissolves nutrients – both organic and inorganic – in the soil, making them available for uptake by the plant’s roots. It is also the medium through which the glucose and soil nutrients are distributed to various parts of the plant. 

Finally, water also plays a role in the plant’s structure and shape by creating a constant pressure, called turgor, on cell walls. When a plant doesn’t have enough water, the cell walls contract, causing the wilting that we see in plants that need watering. If allowed to remain dry for too long, the cells reach a point where they can no longer reabsorb the water and the plant dies. 

Matching your plants to the appropriate soil moisture can be a tricky task. Fortunately, most of our native plants are very forgiving and will tolerate short periods outside of their moisture comfort zone. After all, we have dry years and wet years, as well as those crazy years than bring a pile of rain followed by two months of drought. If plants couldn’t cope with these vagaries, we’d have very few plants. 

Plant Nutrients 

There are 17 nutrients that are essential for plant growth and these can be divided into two categories: macronutrients – those nutrients that are used in large amounts – and micronutrients -those that are used in small amounts by the plant. The macronutrients hydrogen, oxygen, nitrogen and carbon contribute to over 95% of a plant’s entire biomass. Micronutrients are present in plant tissue in quantities measured in parts per million. Carbon, oxygen and nitrogen are all absorbed from the air, while the other nutrients (including H in the form of water) are primarily taken up from the soil through the plant’s roots. 

Each of these nutrients plays an important role in the plant’s growth. We’ll first look at the role of the three principle components of fertilizers – Nitrogen, Phosphorus and Potassium (N, P & K) – followed by a quick look at the other macronutrients. 

NPK 

Nitrogen is used by the plant to create amino acids, the building blocks of protein, and is used by chlorophyll in photosynthesis to convert sunlight into energy for plant growth, among other roles. Insufficient nitrogen can result in leaf yellowing and stunted growth.  

Nitrogen is a water-soluble element that is primarily available to the plants from soil water in the form of nitrite (NO₂-), nitrate (NO₃-), or ammonium (NH₄+) ions. Bacteria in the soil convert nitrogen gas into ammonia, which plants can use. Lightning also converts atmospheric nitrogen into ammonia and nitrate, which enter the soil with rain. When plants and animals die, or when animals excrete waste, the nitrogen in their organic matter returns to the soil. Compost, which is primarily the excrement of soil organisms, is a great source of nitrogen. 

The primary role of Phosphorus in plants is storage and transfer of energy produced by photosynthesis for growth and reproductive processes. It is necessary for seed germination, photosynthesis, protein formation, flower and fruit formation, and is particularly important for good root development. Without adequate phosphorus, plants will be slow to mature, will have poor flowering, will drop flowers and fruits prematurely, and their growth will be stunted.  

Phosphorus in its mineral form is not readily available to plants – it requires bacteria to convert it to a plant available form. Ideally, soil pH should be in the range of 6-7.5 – soils more acidic or alkaline than this will result in P becoming bound to other elements in the soil and not available for plant use. Chicken and horse manure, bone meal, fish emulsion and rock phosphate (used in the manufacture of organic fertilizers) are all good sources of phosphorus for plants. 

Potassium plays a vital role in photosynthesis and regulates water usage by the plant. It has also been shown to improve disease resistance in plants, improve the size of seeds, and enhance fruit quality. Insufficient K can result in leaf yellowing between the veins of leaves and curled or scorched leaves. Potassium is very mobile in the plant, and plants move it to the younger, needy tissue when it becomes limiting. As a result, potassium deficiency first shows up as a mottled chlorosis of the older leaves and eventually the leaf edges become brown. 

Potassium is mined as Potash (cool fact: the world’s largest potash mines are in Saskatchewan) and wood ash. Manures, compost and other organic materials are also potassium sources, even though the concentration of potassium in them is pretty low, but these materials are typically applied generously enough to contribute a sufficient amount of K. 

The Other Macronutrients 

Sometimes called “secondary nutrients”, the elements of carbon (C), hydrogen (H), and oxygen (O) are absorbed from air and water, while Magnesium (Mg), calcium (Ca) and sulphur (S) are taken up from the soil. 

Carbon, in addition to its role in the formation of glucose for the plant, is an essential building material that gives strength to cells. Adding organic matter, such as manure or decomposing plant parts (rich in carbon– or the browns in compost), to the soil surrounding growing plants is an effective way to provide C for the plants. 

Hydrogen, made available from water during photosynthesis, in addition to being used to form glucose molecules, plays a key role in plant respiration, and recent research suggests that hydrogen also plays a role in mitigating plant stress as well as promoting root growth. 

Oxygen is used by plants in cellular respiration – to break down food molecules and release energy for growth. In addition, the amount of oxygen available to a plant’s root cells affects its growth rate, water and nutrient uptake, as well fruit yield and quality. 

Magnesium plays a critical role in the production of chlorophyll and is a key driver in photosynthesis. It is also involved in the transportation of carbohydrates from leaves to actively growing tissues of plant roots, shoots and reproductive organs. A deficiency of Mg can reduce root or shoot growth, and potentially seed weight, and can appear as yellow bands between the leaf veins. Although Mg is normally sufficient in most garden soils, if necessary, supplemental Mg can be added through compost, Epsom salts (magnesium sulfate), or dolomitic lime.  

Calcium is an important structural component of cell walls. It is necessary for cell growth and division, and influences water movement in cells. In some plants, calcium is required for the uptake of nitrogen. Calcium is found naturally in most limestone-based soils but can be supplemented with crushed eggshells, ground oyster shell or dolomite lime. Calcium can also help to neutralize acidic soils. If Mg levels are sufficient in the soil, adding extra calcium could lead to soil toxicity and cause further problems. If in doubt get a soil test done. 

Sulphur also plays a key role in photosynthesis and the formation of chlorophyll, and in the production of plant proteins. It is also a great tool to help acidify soils for those acid loving plants like blueberries. Sulphur deficiency can resemble N deficiency – leaves can become light green or pale yellow due to the lack of chlorophyll production. Manure, compost, and decomposing plant matter are all sources of sulfur for the garden. 

To learn more about nutrients (and nutrient deficiencies), check out the following websites, or simply google the subject. 

https://nsnewfarmer.ca/wp-content/uploads/sites/5/2018/02/Nutrient-Deficiency-Guide.pdf

https://extension.arizona.edu/sites/default/files/2024-08/az1106.pdf

Summary 

Most soil conditions across the world can provide plants adapted to that climate and soil with sufficient nutrition for a complete life cycle, without the addition of nutrients as fertilizer. In fact, here in the southern Great Lakes region, we are blessed, for the most part, with great nutrient rich soils. When growing native plants, adding additional fertilizers or compost will often simply result in tall, lanky plants that fall over in the garden. And, speaking from experience, it can take several years for the excess nutrients to be used up. So unless you are trying to grow plants in an industrial wasteland, it is highly unlikely that you will need to add extra nutrients to a native plant garden. The deep roots of many of our native species are able to tap the depths of the soil and find all that they need. 

But it is also important to do your homework on the moisture needs of the plants you are growing, and plant those with high moisture needs together and those that like it drier separately. In this way you will greatly increase your success in the garden, and provide habitat and food for many insects and for those that rely on them. 

Happy Native Plant Gardening.