Tuesday, February 03, 2009

let there be light

My green thumb came only as a result of the mistakes I made while learning to see things from the plant's point of view. - H. Fred Ale

Alright this post is the first of three about the nuts and bolts of sun soil and water. While putting together this material it quickly became clear that to cover these subjects in their entirety would take considerably more space than is available here. Indeed many books have been written about sun, soil and water as individual topics and I have no illusion of being able to do proper justice to every aspect of each of these topics today. What I am going to try to do is to provide an overview that will help you put together plans for your outdoors spaces. Please ask questions as they occur to you and I’ll try to answer them individually. All questions are worthy of consideration. If you don’t want to bring them up publicly send me an email. Just click here.

It’s important to remember that outdoor “rooms” are much more complex than say a living room or even a kitchen. Indoor spaces are static and have basically the same pieces in the same places all the time. They stay at roughly the same temperature all year round and have few if any plants in them that change with the seasons. Outdoor spaces are living ecosystems that change with time and this consideration means that your design will change as well, as you observe your yard throughout the year.

So where to begin? There are three elements that must be given utmost consideration when planning your landscape: sun, soil and water. Let’s start with the first. A quick warning. The following targeted mainly at those living in the mid latitudes in the Northern Hemisphere.

Let’s start with something we all know, the sun rises each morning and sets every evening. Of course it does but depending on the time of the year, the sun rises and sets in a different part of the sky? In general the sun rises in the east and sets in the west. That’s pretty well understood but it doesn’t start or end its daily journey in the same location in the sky.

By the way I am fully aware on board with Heliocentirc model of our universe that has the sun at its center. However to make it easier to understand I’m talking here ni terms of how the sun’s position changes in relationship to those of us living on the surface of the Earth. It’s just easier to visualize.

Ok so the sun ries and sets in different parts of the sky depending on the time of year and the sun does not travel directly overhead. In fact it doesn’t even follow the same path throughout the year. I’m going to post an image here that will help with the rest of the explanation to come.

Take a look at the blue line. It represents the path of the Sun in the Northern Hemisphere on the spring and autumn equinoxes. It rises due east and sets due west. However in the winter the sun rises south of due east and sets south of due west. That’s represented in the image above by the green line. This means the sun is shining for fewer hours during the day. During the winter the sun also travels lower in the sky which means sunlight strikes the Earth’s surface at a decreased angle. The combination of the two is the reason we have winter with the colder temperatures of that season.

The opposite is true in the summer when the sun rises and sets north of the east/west cardinal line. This path is represented by the red line which shows the path of the sun on the summer solstice. Notice that the sun is higher in the sky which means it strikes the Earth at a more direct angle. It’s important to recognize that the sun never travels directly overhead as it travels through the sky. In fact the sun remains in the southern part of the sky at all times. This is why the northern face of a building is always in the shade. It’s also the reason why boy scouts talk about finding their way through the forest by looking for lichens on tree trunks. Lichens of particular species don’t grow in direct sunlight and therefore can only grow on the northern most side of a tree trunk, the part that stays in the shade all day. Let’s look at a few more images that might help.

Notice the great difference of sun angle throughout the year. By the way the actual angle of the sun on your property on any given day at any given time will vary depending on your latitude. You can use a solar angle chart to find the particular angle of the sun at a certain time of the day on a particular day of the year using these charts.

This one is for 40 degree Northern latitude. At 10 AM on June 21st the sun is at 60 degrees in the sky. Here an excellent site for creating your own sun chart. If you don't know your latitude and longitude try this site.

Ok you say but what does all this have to do with gardening? Well first the obvious. When the sun is higher in the sky and up for more hours during the day, it’s warmer outside and plants of all types have more sunlight to work with. A slightly more subtle aspect to consider is how much shade your house and the trees on your property will create. Large structures and trees will shade the portion of your property directly to their north for much or all of the day. This is not the place for most food producing plants. Some like lettuce will need less direct sunlight but many, in fact most will need at least 6 and preferably 8 hours of spring/summer/autumn sun. Remember as we get closer to the summer solstice the sun will be higher in the sky so it will clear more tree tops and roof lines.

For those of you with snow still on the ground you can use it’s melting patterns to figure out which areas of your property stay in full shade at this particular time of the year.

This is my front yard. Yes it does occasionally snow in North Carolina. You can see that the angles of our roof line shade a very distinct portion of my yard. Everything still covered in snow received no direct sunlight on this particular day. Everything outside of this area got at least a little sun. As the year goes on the line between sun and shade will move as the sun’s path moves but this is a pretty good indication that the front few feet of my yard adjacent to the house itself gets very little sun. In contrast the rest of my front yard is likely to get plenty of sun as it is still winter and already it’s getting lots of sunlight. This is why we plant corn in the font yard- it’s not just to annoy the neighbors but because that’s our sunniest spot! But front yard corn is for another post.

A great exercise is to take a picture from a particular spot on a regular basis throughout the year. If you have a tripod for your camera you can even mark three spots on the ground and place the tripod in exactly the same spot but just standing in a certain location and taking a picture will get you close. Once a month will prove useful. Once a week would be even better. I saw a slide show once of a picture taken from the same spot every day for an entire year. When the presentation was sped up it was fascinating to what the shadows recede and then grow and then recede again.

By the way this is probably as good a place as any to mention for those of you taking the Garden Planning and Design Class that picture taking is encouraged not just once you’ve established your beautiful garden and built your fabulous chicken shack but now, before any projects have gotten under way. These images will serve as motivation to continue work on all the wonderful plans you’re starting to make but also as a way to show how far you’re come once you’re completed some of your projects. Remember it’s impossible to go back in time and take the “before” picture so break out your cameras and take them now. Upload them under the ‘File’ Heading in the left hand column of the Yahoo Group Site.

Another thing to remember is that this time of year deciduous tress have no leaves. They will have them this spring when you plant your garden! Be sure to anticipate the shade large trees will provide. Such trees are wonderful for allowing winter sun to shine through their leafless branches and into you windows during the winter while blocking summer sun form heating up your home. *But* those same trees through which the sun is shining pleasantly into your backyard might shade a backyard garden if you don’t site it properly. Yes the sun will be higher in the sky and might perhaps clear the top of the tree for most of the day but be sure you’re out of the shadow of such trees or you’ll be moving your garden next year. I speak from experience.

Inevitably there will be parts of your property that are in shade during the growing season. There are useful ways to deal with this inevitability. Depending on what part of the country you call home, summer shade might be very welcome in June, July and August. Here in NC people need shady spaces to enjoy the summer comfortably. Our hammock lives in such a space. My chicken shack is sited in such a place as to take advantage of the shade of a gigantic oak tree and keep my birds cool. Growing mushrooms is a project of ours that can only be done in the shade. Potatoes and some greens like lettuce can be grown in shadier spots in the Southeast. I make use of one particular shady spot by composting stuff there. I could compost (and probably a little faster) in a sunnier spot but I still get great results even if it takes a little longer. Equipment like 5 gallon buckets and various pots and hoses and such last longer in the shade where they’re not subject to the effects of the sun’s rays. My potting table is also located in the shade so I don’t have to stand in the summer sun while repotting plants or mixing soil.

The goal is to take advantage of sunny spots for growing certain plants and shady spots for the different advantages they offer. The key to successfully working with the sun is to understand how it moves through the sky throughout the year and how those movements play out on your particular property. Start observing now and don’t be surprised if years later you’re still refining your understanding of how the sun moves across your property.

Check out this video and the way information it offers about this particular space and its sun.


exactmike said...

Can you provide the source for your sun path chart? Yours looks better than the one I found below:

One source for solar path charts:

and if you need to find your latitude and longitude, try this:

nulinegvgv said...


i got it from oksolar.


I think your link is excellent.

mezzaluna said...

just to be the astronomy pedant that i am... maybe everyone reading this is north american or european, but for anyone inside the tropics, the sun will be directly overhead at some times. and of course for those in the southern hemisphere south/north is reversed in your descriptions, although the sun still rises in the east and sets in the west :)

nulinegvgv said...


Quite right. I've gone back and added a warning. This post was targeted mainly at those living in the mid latitudes in the Northern Hemisphere. Results elsewhere may vary.