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Heat Zones
January 20, 2014

(Winter Robin.)

Winter is back.

A few days with temperatures near 40 degrees F. were a nice break.

More like a tease.

You could almost feel and smell spring.

Two more months of official winter remain.

Still, the days are growing noticeable longer.

Keet (Akita) doesn't mind if there is an inch or so on the ground, but Ziggy the toy poodle is out and in before I can close the door.

He does his business at the base of the steps and zoom, back in.

Yolanda seems to be no worse for wear, though she is fighting a small cold right now.

I paid to have the ice off the roof removed and some heat tape put on.

I simply am not physically able to do certain things anymore.

Caring for Yolanda wears down a body, and what I have left is reserved for her.

(Whoever coined the phrase "growing old isn't for sissies" was right on.)

We thank the good Lord that we can afford a few minor incidents.

The birds continue to gorge like there is no tomorrow.

Same with the over weight squirrels.

The squirrels can glean from the ground, just stay off the feeders that aren't baffled.

Keep an area clean of snow for the fur kids is a challenge sometimes.

Several American robins have over wintered.

While there is still some food in the field and woods, the fermented Bradford pears bring them in a for feed from time to time as well.

It is not uncommon for a handful to over winter, especially if there is a swamp and food sources nearby.

I final saw a White-breasted nuthatch this past Saturday, but no Tufted-titmice visiting right now.

The lovebirds are perched on me right now, and Bobo is still a mess.

A couple of weeks ago, I mentioned Heat Zones.

While most, or all of you are familiar with the USDA's Hardiness zones.

Cold isn't the only factor determining whether our plants will survive and thrive.

Heat zones are something few know about.

You need to be aware of the impact that heat has on our plants as well.

Especially in drought years.

With some help and credit given to the 'American Horticultural Society' (AHS), I will attempt to help you with this issue.


The effects of heat damage are more subtle than those of extreme cold, which will kill a plant instantly.

Heat damage can first appear in many different parts of the plant.

Flower buds may wither, leaves may droop or become more attractive to insects, chlorophyll may disappear so that leaves appear white or brown, or roots may cease growing.

Plant death from heat is slow and lingering.

The plant may survive in a stunted or chlorotic state for several years.

When desiccation reaches a high enough level, the enzymes that control growth are deactivated and the plant dies.

Using the Heat Zone Map:

Use the AHS Plant Heat Zone Map in the same way that you do the Hardiness Map.

Start by finding your town or city on the map.

The 12 zones of the map indicate the average number of days each year that a given region experiences "heat days"-temperatures over 86 degrees (30 degrees Celsius).

That is the point at which plants begin suffering physiological damage from heat.

The zones range from Zone 1 (less than one heat day) to Zone 12 (more than 210 heat days).

(Our Canadian friends will pretty much understand their heat zones by the number of days at 30 c.)

Thousands of garden plants have now been coded for heat tolerance, with more to come in the near future.

You will see the heat zone designations joining hardiness zone designations in garden centers, references books, and catalogs.

On each plant, there will be four numbers.

For example, a tulip may be 3-8, 8-1.

If you live in USDA Zone 7 and AHS Zone 7, you will know that you can leave tulips outdoors in your garden year-round.

An ageratum may be 10-11, 12-1. It can withstand summer heat throughout the United States, but will over winter only in our warmest zones.

An English wallflower may be 5-8, 6-1. It is relatively cold hardy, but can't tolerate extreme summer heat.

Gardeners categorize plants using such tags as "annual" or "perennial," "temperate" or "tropical," but these tags can obscure rather than illuminate our understanding of exactly how plants sense and use the growth-regulating stimuli sent by their environment.

Many of the plants that we consider annuals-such as the petunia, coleus, snapdragon, and vinca are capable of living for years in a frost-free environment.

The Heat Map will differ from the Hardiness Map in assigning codes to "annuals," including vegetables and herbs, and ultimately field crops as well.

Plants vary in their ability to withstand heat, not only from species to species but even among individual plants of the same species.

Unusual seasons-fewer or more hot days than normal-will invariably affect results in your garden.

And even more than with the hardiness zones, we expect gardeners to find that many plants will survive outside their designated heat zone.

This is because so many other factors complicate a plant's reaction to heat.

Most important, the AHS Plant Heat-Zone ratings assume that adequate water is supplied to the roots of the plant at all times.

The accuracy of the zone coding can be substantially distorted by a lack of water, even for a brief period in the life of the plant.

Although some plants are naturally more drought tolerant than others, horticulture by definition means growing plants in a protected, artificial environment where stresses are different than in nature.

No plant can survive becoming completely desiccated.

Heat damage is always linked to an insufficient amount of water being available to the plant.

Herbaceous plants are 80 to 90 percent water, and woody plants are about 50 percent water.

Plant tissues must contain enough water to keep their cells turgid and to sustain the plant's processes of chemical and energy transport.

Watering directly at the roots of a plant-through drip irrigation for instance-conserves water that would be lost to evaporation or runoff during overhead watering.

In addition, plants take in water more efficiently when it is applied to their roots rather than their leaves. Mulching will also help conserve water.

There are other factors that can cause stress to plants and skew the heat-zone rating.

Some of them are more controllable than others.

How the Map was Created:

The data used to create the map were obtained from the archives of the National Climatic Data Center.

From these archives, Meteorological Evaluation Services Co., Inc., in Amityville, New York-which was also involved in the creation of the Hardiness Map-compiled and analyzed National Weather Service (NWS) daily high temperatures recorded between 1974 and 1995.

Within the contiguous 48 states, only NWS stations that recorded maximum daily temperatures for at least 12 years were included.

(Due to the amount of missing data in Alaska and Hawaii, the 12-year requirement was reduced to seven years at several stations.)

Because they were too difficult to map, data from weather stations at or near mountain peaks in sparsely populated areas were not incorporated.

A total of 7,831 weather stations were processed; 4,745 were used in plotting the map.

Are you still confused?

Purchase a copy of the map: Durable full-color posters of the AHS Heat-Zone Map are available for $10.00 each.

To order, call (800) 777-7931 ext. 133, or email

Several things must be considered when purchasing plants.

Water, heat, cold, sun, shade, soil......................

Now you may have an idea on why lupines don't do well in South Carolina or other climates.

In extreme years (2012), through the heat map out.

Even in Michigan we have years where heat and drought are off the charts.

Plants are weak going into winter, and though it may be zone hardy for cold, it may not survive.

Gardeners, whether for pleasure, food or for wildlife must be armed with some basic knowledge.

Well, it is time to fly for now.

Before I go, here is your positive thought for the day.

God Bless.

" The greatest mistake is in believing that we are 'only human'... We are human in expression but divine in creation and limitless in potentiality".

Eric Butterworth, minister and author

Devine Creation Indeed...........

Then the Lord God formed a man from the dust of the ground and breathed into his nostrils the breath
of life, and the man became a living being.

Genesis 2:7

"Treat the earth well:

It was not given to you by your parents,

It was loaned to you by your children.

We do not inherit the Earth from our

Ancestors, we borrow it from our Children."

Ancient Indian Proverb

Your friend indeed,

Ron Patterson

PS. If you enjoy these letters, please forward them to friends, family and co-workers.

Better yet, have them sign up so they can receive their own letters.

Gardening For Wildlife.

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