A Few Notes on Plant Selection

Alrighty kids, today’s lesson is about plant selection. Half of the issues that I see in landscapes, whether they be pruning, disease, or just unhappy plants, are the result of poor plant selection.

There are many factors that you should take into consideration when choosing a plant for you landscape:

Mature size: you see a shrub in the nursery and say “this plant is 3’ tall and 2’ wide and it’s awfully cute and it’ll go perfectly 1 foot away from the corner of my porch!” So you go home and plant it and it looks great! But a few years later (or less) if that shrub is actually say… a Nellie R. Stevens holly- which are sold in cute little sizes- that means your cute little shrub is actually going to try and be a tree and grow to a height of 30’! See the problem? You will be fighting a losing battle trying to keep that thing from taking over the sidewalk and everything else within a hop, skip and jump of where you planted it. (Like the top photo, right.)  A much better option would be something like a Steeds holly, which will politely stay under 5’ tall and about half as wide, with a lovely cone shape.  (The lower photo on the right is a strangler fig growing on top of a ruin. It didn't start on the ground, it started on the top and grew those roots down to the ground, an extreme example of bad plant placement, I know.)

Sun exposure: Have you ever seen a hydrangea looking wimpy in the full sun? What about a rose that’s planted in the shade and never flowers? Plants are biologically programmed to have preferred living conditions. If that hydrangea is planted in afternoon sun; a. it’s going to wilt EVERY day, b. the leaves will literally get sunburned, and c. it will hate you forever. Many plants prefer full sun though, especially heavily flowering and fruiting ones (not necessarily though) which will never produce a good flower show or fruit crop if not given enough daylight. So that means that you should do some research! Reading the tag on the plant may not be enough though. Many plants in your retail garden centers come from the prestigious Monrovia Growers for example, but did you know that Monrovia has nurseries in south Georgia as well as in Oregon? So if a tag on a plant grown in Oregon says full sun that may not mean full sun here in Hotlanta nor will the one from south Georgia that says shade necessarily thrive in the shade in Seattle. So try and find a local resource for your exposure and hardiness research. Oh, and just because a garden center here sells it, doesn’t mean it will survive here. I saw queen palms at Home Cheapo this summer; they’re hardy to zone 9B. We’re zone 7. Big difference.

Pest and Disease considerations: Are you one of the many folks that are moving with the trend to become ‘green’ by staying away from chemicals? But oh, you loooove hybrid tea roses. The problem? Roses get a multitude of pests and diseases: black spot, aphids, thrips…. So what are you going to do? Give in and spray or have crappy looking roses? If you don’t like chemicals buy disease resistant plants that aren’t prone to pests. Again, do your research before you buy.

I've said this before, and I'll say it again:  Like needing the right tool for the job, you need the right plant for the space.

Jessica Watters, GCLP                               Horticulture Technician, Chattahoochee Technical College

Green Roofs: How cool?

     One green concept that has fascinated me for quite a while is the green roof. I am astounded that you don’t hear more about them! A green roof is exactly what it sounds like; it’s a roof that is planted with vegetation.  Please see the photo to the right of a French museum, taken by Simon Garbutt. They’ve actually been around for centuries in Northern Scandanavia and Europe. Checkout the photo of a traditional farm village in Norway, bottom. Did you know, it's estimated that 10% of Germany's roofs are 'green'?

     One of the key benefits of a green roof is temperature reduction of roofing material. As you may know, the majority of buildings in urban areas are roofed with black asphalt and homes are roofed with dark asphalt shingles- they get hot! This combined with asphalt roads and few trees produces a pocket of hot air that surrounds the city, called the Urban Heat Island Effect. This area of hot air has even been known to change weather patterns!

How do green roofs reduce Urban Heat Island Effect, you ask? Well, imagine you’re walking barefooted on a July afternoon in Atlanta. You leave your front door and walk across your lawn; it feels nice on your tootsies. The temperature of your lawn is roughly the same as the ambient air temperature. Now, you decide to cross the asphalt road… “%&*@!” ...and your feet are blistered.  Black asphalt can easily reach temperatures of 175 degrees! It is exactly the same with most roofing materials; while a green roof is the same temperature as the air, perhaps even a couple of degrees cooler because of evapotranspiration, the black asphalt or shingles are significantly (80+ degrees!) hotter. Evapotranspiration (ET) is the process by which plants use water and evaporate it from their leaves- same concept as you sweating, the moisture evaporating cools your skin. Imagine how much of a difference this would make if most of the buildings in a city were to have green roofs… we’re talking an 80 degree difference on quite a bit of surface area here!  The photo to the left is a satelite image of New York City, the top being thermal imaging and the bottom being the vegetation.  Notice where the green is the temperature is cooler?  Point made, thank you.

     Another benefit of green roofs is storm water retention. During heavy downpours storm water is a major problem in most urban areas. Storm drains cannot handle a huge amount of water all at once and it causes flooding and puddling. Not to mention all the pollution that storm water washes into the sewers and directly into streams and lakes. A green roof with 4” of substrate (the stuff the plants grow in- regular soil is too heavy) will retain as much as 60% of rainwater. That’s awesome: a green roof will eliminate over half the runoff than what would’ve come off a conventional roof!

     Also a huge advantage is the return on investment that buildings with green roofs get: they lower cooling costs by as much as 30% annually, heating by 10%, and they have double, even triple the lifespan of a shingled roof! Plus, they look really neat!

     The biggest downfall of a green roof is the initial cost of installation. But the fact that energy costs are reduced so significantly and that the roof won’t have to be replaced near as often cancels that out in my opinion! One other drawback is that it is difficult to retro-fit a building to have a green roof, the weight of the substrate and plants is significantly higher than a conventional roof and most buildings are not designed to carry that load. BUT it can be done! The Atlanta and Chicago Citys Halls have installed a green roof on parts of their buildings! See Chicago City Hall, Below.

With all these benefits, why aren’t I hearing more about green roofs? I want to see them everywhere! They’re so much prettier than a nasty old black tar roof, too!

      

Jessica Logan Watters, GCLP               Horticulture Technician, Chattahoochee Technical College

Water Woes

     Georgia has had some crazy water issues for the past several years. First it was extreme drought and we couldn’t water at all. Then it was monsoon season and we didn't need to water, now it hasn't rained in weeks! But, here are some tidbits about you should know and utilize about watering your landscape.

    More is not always better. When the state/counties lifted the drought restrictions from level 4 (no watering –ever) you were told you could water 3 days a week, which days depending on your address. So everyone said “Must… water…!” Andy they got out their hoses and sprinkler or set their automated systems to run all 3 of those days. This is way more wasteful than you think. Just getting your grass wet does not make it happy. Water has to penetrate through the grass and down to the soil- preferably down a couple inches into the soil. If you consistently water where only ¼” of the soil gets wet, that’s where your plants’ roots will live. This means that they’ll dry out super-fast and need water that much quicker. Roots should go to a depth of 3-6” where the soil doesn’t dry out as fast. To avoid this: water infrequently (once a week) and deeply. That means you can either calculate percolation rates for your soil and precipitation rates for your sprinklers (I can tell you how to do that if you like) … or you can find a couple spots, don’t pick the lowest areas, and dig around to see how far down the soil is wet. It takes longer than you think to thouroughly soak the soil, a lot longer. If you notice that you’ve got water running down a hill or down the gutter in the street that means your watering too fast… water is hitting the soil faster than it can absorb it. This means that you should take a time out on that area after watering until you see the water start to run off , water another area, go back to the first area when the soil has had some time to soak it up, and water some more. The steeper the slope or harder the soil the less time you can water before you’re just wasting it by sending it down the gutters.

     Technically, you don’t have to water. Unless we’re in an über-extreme drought (worse than a couple of years ago) your turf will make it just fine. It may go dormant (brown, looks dead but it’s not) but as soon as it rains it’ll green right back up. You may have plants other than your turf that will need supplemental water in this situation though, like hydrangeas. These plants should be planted in their proper location- maybe they’d like more shade than they’re getting, and can be watered by themselves instead of watering the entire property to wet one small area. By the way: hand-watering with a hose is the least efficient way to water! So set up an old-school impact rotor on a stake connected to your hose. What’s an impact rotor, you ask? Think about the dance ‘the sprinkler’. Do the sprinkler! I know you’re doing it. Anyways, they are the most efficient sprinkler that can be connected to a hose. (See photo above)

     Use more efficient irrigation techniques. Drip irrigation is by far the most efficient, least wasteful way to water ever. (Sadly, you can’t do it on your lawn, only beds). Whether you install an automated system with the fancy drip hose and emitters or you go to Home Cheapo and buy the black soaker hoses, these options are way better than overhead watering. Why? Because when you water over head there is always wasted water. It gets blown away in the wind, it gets applied too fast and runs off, it’s got to soak through the mulch, blah blah. Soaker hoses and drip hoses lay underneath the mulch where the water is slowly applied directly to the soil where your plants’ roots live.

If you’ve got an automated system and don’t have a rain sensor, (shuts off the whole system when it rains!) shame on you. Get one. ASAP. It’s my water, too, that you’re wasting. Watering in the rain… sheesh.

In conclusion: water smarter- less frequently, more efficiently, and more thoroughly.  Just because the watering restrictions say you CAN water 3 days a week doesn't mean you should.


Jessica Watters, Horticulture Technician, Chattahoochee Technical College