Growing Degree Days: Unlocking The Timing Of Nature

Adopt the pace of nature; her secret is patience.    (R.W. Emerson)

I want to take a minute to talk about a little known and seldom used topic: Growing Degree Days (GDD). A new topic for many, or an old topic just called something else depending on where you live. We all  know at least one piece of folksy garden wisdom such as putting down crabgrass preventative when  the forsythia bloom.  There are tons of little “tips” like this out there. Most of them actually based on science, even if most of us didn’t know it. So GDD is worth taking a minute to talk about.

So What are they?

Basically, they are a measure of heat accumulation to-date for the growing season. It is a tool used in phenology, which is basically the study of plant and animal life cycles. Tracking GDD allow you to predict plant, animal and insect development. These things are biologically timed to enter certain stages at certain times, often based on GDD. So forget about your calendar. Nature has it’s own, and it cares not for our man-made creations.

Growing degrees are calculated when the temperature goes above the base temperature, usually 10 °C. The actual formula is a little more complex because it requires taking into account the high and low temperatures. Then there are formulas for determining cumulative GDD, not just for a single day. The good news is , you don’t need to do math.

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Why Use Them?

If you are a serious gardener, urban homesteader, or even someone just getting started, tracking GDD is something you need to consider. Why? Because as I mentioned earlier, nature keeps it’s own calendar. Some people may go out and do the same things at the same time every year, and get lucky as a result. But why not do things at the proper time, when conditions are optimal and you get the best results? From an integrated pest management and organic gardening standpoint, it’s worth it. Using GDD to time fertilizer and pesticide applications maximizes results. That saves you time, money and reduces chemical usage.

Getting it right the first time is important with plants. As many of us know, depending on what you are growing, you only get one chance to stop an infestation, block a fungus, or correct a nutrient deficiency. Watching your GDD, and knowing what is coming next can really give you an advantage.

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Where Does One Get This Helpful Information?

I told you earlier, you won’t need to do math. You can if you want to, but there is an easier way. For those of us here in the states, it’s simple. Every county has an extension service , every state has its own friendly department of Agriculture who track this data for local farmers. But this data is just as helpful to the gardener as it is for the farmer.

This is the web page for the station nearest me, our local agricultural service has a monitoring station at a local apple farm. Here I use a “base 50” scale. Which calculates GDD using a base temperature of 50 degrees Fahrenheit:

NEWA Cornell at Orbaker’s Apple Farm

I visit this page weekly through mid-season. They have some helpful guides as to what pokes it’s head up when. So I know when to start looking for certain pests. The best defense is when you know exactly what the offense is going to do.

So take advantage of the hard work others are doing. Most of it funded by your tax dollars anyway. You will be the local garden wizard who always seems to know what is going to happen before it actually does. Whether you choose to share your secret is up to you.

Happy growing!

 

 

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Mono Cultural Problems

Monoculture. My Plant Materials professor in college constantly warned of it and the dangers it brings. That same sentiment was echoed in my Integrated Pest Management classes as well. But my Landscape Design and Plant Propagation/Nursery Management professors were at odds with it. So what to believe? Is it good, or is it a thing to be feared?

This depends upon your school of thought. Monoculture is the cultivation of a single crop in a given area. In order to understand it and figure out how it fits in, and whether it is to be feared or not, is all a matter of perspective. So lets start with what it means on a residential level.

Elm-lined streets no longer exist thanks to Dutch Elm Disease

Landscape architects and city planners love monoculture. Elm lined streets were everywhere once upon a time. I can walk the streets of my neighborhood and count no more than 4 or 5 species of trees; Red Oaks, Silver Maples, Norway Maples, Honey Locusts and Plane-trees. The repetition lends a certain look and continuity to neighborhoods. Landscape designers favor it too. Every house on my street has similar shrubs, Arborvitae hedges, mature Rhododendrons…….and all that is fine. Until Dutch Elm disease wipes the shade form the neighborhood streets, Japanese beetles ravage the landscape, tar spot covers the colorful fall maple leaves with unsightly blights. You get the picture.

For you, the established homeowner, it gives you a heads up as to what to guard against. As a new homeowner, it is an opportunity to not have to suffer their fate. Monoculture draws pests. They go where the food is. The most food that will sustain the population. The denser the food/host source, the faster the problem will spread in that geographic area. Disease spreads right down the street with the wind blown rain, insects, wind, blowing leaves, etc. and you cannot stop the spread. It is almost useless to fight against it . As a home owner, you can spend thousands having you lawn treated, and your trees and shrubs sprayed to no avail. Because if the whole area isn’t on the same regimen, the pests or disease gain a foothold. Then the second you are off on your application timing, bang! Cedar apple rust, grubs, powdery mildew and all sorts of lovely and unsightly things come calling.

Recognize these? Everyone in my neighborhood planted them at one time. Why not? They look nice, they dampen road noise and they block your view of that junky whatever-it-is your neighbor has in her backyard. Alas, after a few years of harsh winters and overpopulation, the deer came calling to our neighborhood. With their preferred foods scarce, they ate their way up one block and down the next. They like the tender, new growth on the tips. Our mono cultural buffet attracted a herd of hoofed pests that to this day still come through nightly to see what’s for dinner.

So you homeowners need to be savvy. Plant a good mixture of stuff. Yes, you can use multiples of the same plant material. Before you consider it, see what your neighbors are battling and just choose not to have to fight the same battle if possible. Sometimes it means just switching to a cultivar that is more disease resistant to whatever the big problems are. And above all, a healthy plant is the best defense. So prune when you should, fertilize, make use of beneficial insects, try to use chemicals only as a last resort.

For you avid gardeners out there, take all that with a grain of salt. Gardening is all about monoculture. Modern agriculture gets by on it. Why? Because it simplifies things. For large farms, it limits the diseases and pests one has to deal with. It’s less farm implements required for planting and harvesting, it simplifies the economics and cost analysis and a number of other things. In short, you need it. That is not an excuse for not using Integrated Pest Management principles, or crop rotation, disease resistant strains and other sound practices. Rather, it’s an incentive if one wants continued success.

For you smaller, more realistic gardeners and homesteaders, you have other concerns. First, when possible select plants that are resistant. Be aware of what your neighbors are planting. A community garden group is a great way to do this, but I will expand upon that more in a post coming soon. Also, as an excellent free resource, do not overlook your local extension service. They generally track the bad stuff they are seeing in the area and can be a good form of intelligence against a coming invasion. They also offer practical solutions and their master gardeners are experienced and always willing to help.

Monoculture isn’t as big a problem for the gardener as it is for the commercial farmer, but to a smaller extent it can be a problem. Don’t settle for just one crop, which most of us don’t. I love tomatoes, but I don’t want to defend my entire backyard against horn-worms. So I plant a broad variety of things. And switch stuff up year over year. Including locations. Some things aren’t that mobile and moving to a new spot entirely may disrupt the process enough to break the cycle. Last year I had a problem with powdery mildew, mainly because I planted enough squash and melons to support a small country. This year, I moved their location and have scaled it way back to make the mildew easier to control. The general idea is to make it as difficult as possible for anything to gain a foothold. And remember, a pest, or disease may jump from one type to another. Japanese beetles don’t discriminate, neither does powdery mildew.

So there it is. Monoculture is a different problem based on your particular perspective. So be forewarned, think ahead and avoid it when practical. I would rather you plant nice shrubs, keep a nice lawn, grow huge tasty veggies for you. Not for deer, grubs, anthracnose, mildew, cucumber beetles and so on, and so on…..

Keep growing, keep enjoying.

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