I have absolutely no sense of direction. Don't believe me? When I leave a building with a group of people who know me, they always watch which direction I turn. Since I'm almost certain to turn in the wrong direction, the people I'm with turn and walk the other way. I'm often amazed how well most people get around.
I can always find my way around my yard, though, where my sense of direction never fails. But then, the yard's not that big, and I work in it all the time. I'll bet you don't have any problems finding your way around your landscape either.
But do you know the compass directions in your landscape? Can you stand anywhere in your yard and point north, south, east and west?
If you can't, you need to dig that old Scout compass out of the drawer and go outside. Or, borrow one, or even buy one. It's worth the investment.
You won't need the compass to find your way around your yard, but you will need it to make sure your plants are getting the right light.
It doesn't take many years of trial and error to discover that you must learn the light preferences for a plant, and then provide that amount of light as closely as possible.
Other factors -- such as soil, drainage and climate -- are important, but nothing else matters if you don't get the light right. It's that critical.
Plants are solar-powered
Please allow me a moment of botany. As a gardener, you need to understand a fundamental principle of plant life.
Plants consume light to provide the energy they need to power and build their bodies. Plants are solar-powered organisms. They use light energy to build sugar out of carbon dioxide and water.
The sugar molecules created by photosynthesis store the energy of the sun in their molecular bonds. This sugar is used, along with tiny amounts of minerals absorbed from the soil, to power the plant's biological processes and build its body.
So, it's not surprising that getting the light right is essential to successful gardening.
How do you put this knowledge into practice?
Say you learn that a plant is best grown in part shade. To make this information work, you need to know 1) what does "part shade" mean? and 2) where in my yard does "part shade" occur?
This is where the compass will come in handy for determining where different light conditions occur in the landscape.
Types of light
Here are some good working definitions of the terms we commonly use to denote light conditions in our landscapes:
- Full sun indicates locations that receive 8 hours or more of direct sun daily.
- Part sun areas receive about 4 to 6 hours of afternoon sun.
- Part shade areas receive about 4 hours of morning sun.
- Shady areas receive about 2 hours of direct sun in the morning or bright dappled light through the day.
To find the proper location in your landscape to provide the right light conditions, you need to know where those light conditions occur in your landscape. And for that, it really helps to know the compass directions.
The path of the sun across the sky follows the compass directions: It rises in the east and sets in the west. Since we live in the northern hemisphere, the tilt of the earth's axis puts the sun in the southern sky as it crosses from east to west.
A changing situation
The movement of the sun interacting with various structures (such as your home), trees, walls and larger shrubs creates light conditions that may vary through the day.
Knowing the compass directions is very important in understanding these changes.
The eastern exposure receives several hours of direct sun in the cooler morning hours and provides part shade.
Because the sun crosses the sky south of directly overhead, the southern exposure gets sun most of the day and is considered full sun.
The western exposure, like the eastern exposure, receives several hours of direct sun. But since the sunlight occurs in the more stressful heat of the afternoon, the western exposure is considered part sun.
Because of the sun's position in the southern sky, shadows are cast to the north. The northern exposure is shade.
A little detective work
Unfortunately, you can't simply go out and evaluate the light conditions in different parts of your landscape just before you head out to the nursery.
Rather, you should spend at least one day walking around all parts of your landscape noting what kind of light each area receives -- how many hours of direct sun, and when they occur.
In most yards, the light patterns change dramatically throughout the day.
To complicate matters, the sun moves differently in the different seasons, and light conditions may change.
So, evaluating the light conditions in a landscape is an ongoing process of observation over time.
Given enough time, light conditions can even change slowly but significantly as young shade trees grow large and mature. Or, they may change suddenly when mature trees are lost to storms.
The point is, properly evaluating the many different light conditions in a landscape is one of the most important things we do to ensure success with what we plant. And knowing the compass directions of your property can help greatly as you do this.
The great thing is -- thankfully -- you don't have to have a good sense of direction to do it.
DAN GILL'S MAILBOX
I have a magnolia tree on the side of my house. Its leaves are black, and there are white bump-like growths on the branches. It also has made the monkey grass growing underneath black. Can you please tell me what to do?
This is magnolia scale, a sucking insect covered with a waxy shell that may be off-white to yellow. Once they settle down to feed, they never move again. This, along with the waxy shell, makes it hard to realize they are insects attacking the tree. As the scale insects feed on the sap, they excrete a sugary liquid called honeydew. The honeydew drops onto the foliage, branches and anything under the tree. A fungal complex called sooty mold grows on the honeydew -- that's the black stuff you see. The sooty mold is unsightly but does not attack or damage anything. It's the scale insects we need to go after. Spray the magnolia with a horticultural oil, such as Year Round Spray Oil or All Seasons Oil. Make two or three applications covering the entire tree. Oils kill by suffocation; this makes them safe to use, but you must coat the scales for it to work. If the tree is too big to spray, you can apply imidacloprid to the roots. This systemic insecticide is absorbed by the roots and moves up into the sap of the tree. When the scale insects feed on the sap, it kills them. Look for Bayer Advanced Tree and Shrub Insect Control and other brands with this active ingredient. You could even do both, and hit the scale from two directions.
Last year my satsumas had many blossoms, but they all fell off before fruit was formed. I don't want that to happen again this year. They are in full bloom now. How can I encourage them to keep the blossoms?
Other than taking good care of the tree, you have no real control over this. The tree will set what it can, when it will. This is really primarily up to the tree. You don't mention the age of your tree, but we give citrus trees a three- to five-year grace period after planting before we expect the flowers to reliably set fruit.
Can you identify this nasty plant in an Uptown New Orleans garden? My wife touched the plant, and her hand hurts enough to maybe go to (her) doctor today. Thanks for your help.
This is stinging nettle, Urtica dioica. The hollow stinging hairs contain a fluid with chemicals that can provoke a painful stinging sensation and allergic reaction. Most stings don't require medical attention, but some individuals may have especially serious allergic reactions and should seek help. Your doctor may recommend an antihistamine. Stinging nettle is, thankfully, not common in New Orleans, but it does occur. Now that you know what it looks like, hunt it out ruthlessly and eradicate it from your landscape. Wear rubber gloves when pulling it up. Or, spray the plant with glyphosate (Roundup, Killzall). The nettle shown in the pictures is blooming. It is especially important for you to find and weed out every plant that is blooming and setting seeds now. You might want to mention this to your neighbors. If it is in your yard, it is likely in theirs.
Dan Gill is extension horticulturist with the LSU Ag Center.
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