Know Your ZONE.

Ann-Marie Volz • January 13, 2025

Shopping for the right plant.

The plant hardiness zone included on your plant tag tells you the average lowest temperature your plant can be exposed to and still survive.  Look closely at the tag and you will see a number designation after the word zone, or sometimes just the letter z.  Most plant tags will carry the zone designation, though it is often absent from plants sold strictly as annuals, which are meant to grow for only one season.  

The zone designation is typically derived from the USDA Plant Hardiness Zone Map, first published in 1960.  To create the map, the USDA averages thirty years of temperature data from thousands of weather stations across the country.   When first published, the USDA map was not considered the standard.  Other zonal maps existed using average temperatures from different time brackets gathered from either more or less weather stations, which led to conflicting information for growers, farmers and gardeners.  The current map is a collaborative effort between the USDA's Agricultural Research Service and Oregon State University's PRISM Climate Group.  In 1960, the USDA used data from only 450 stations.  The 2023 revised USDA Hardiness Zone Map utilizes data from 13,412 weather stations.  It's a trusted source.

Looking at the revised map,  many locations saw a change in their zone designation.  There are thirteen zones divided in 10 degree Fahrenheit increments as well as half zones, labeled a and b, further dividing each zone into 5 degree Fahrenheit increments.
I garden in the Twin Tiers of New York and Pennsylvania, which shifted from the 2012 designation of 5b (-10 to-15 degrees F) to 6a (-10 to -5 degrees F).  Translation, our area became warmer in the winter.  Note, the map has nothing to do with summer temperatures.  Do your existing plants need to pack and move to colder climates? No, but they may get some new neighbors.  Your garden may host a few newcomers who previously could not withstand our winters. Does this mean I can have the Crepe Myrtle I've always wanted? No, not yet, not likely.   It isn't a huge shift and having survived nearly fifteen winters here myself, I am going to treat the new hardiness zone with a bit of skepticism.

Whether or not a plant survives any given winter involves several factors, only one of which involves the average lowest temperature.  Is it a new plant or a well established plant? Was it in good health before winter?  Was there adequate moisture available prior to and during the winter months? Was it planted in an ideal spot? Is it in a sheltered area or on an exposed hilltop? While plants do not feel wind chill, they can become desiccated by sustained winter winds, which can be a life threatening condition. And while a zone appropriate plant may survive a quick dip into the lowest extremes of a zone, it does not mean they will survive an extended stay.  It is important to remember that these zones are based on average temperature extremes.  Nature does what nature does, and nature often performs above or below average.

I've experienced a few mild winters here, but the brutal winters stand out in my memory.  I wonder why...  It's hard to forget the winter kill of the hollies you loved, the dogwood you planted, the rose that didn't have enough time to acclimate.  While some of the die back I suffered in the past had more to do with desiccating winter winds than the extreme cold, I think the combination bears some consideration. I'd be very concerned about planting zone 6 plants when I know we may have prolonged temperatures in the single digits and high winds.  I know I sound terribly pessimistic, but I'm equally hopeful that this is good news for all the marginal magnolias, and the dogwoods and hollies and roses that have to struggle through some of our winters.  If we are truly warmer in the winter, maybe, just maybe, I'll go back to designing with Knockout Roses in northeastern Pennsylvania. 

Whether you choose the glass half full or the glass half empty approach, I seem to be choosing both, I still need to stress how important it is to check the zone of every plant you buy online or at a garden center.  In my experience, independent garden centers only stock plants they know will grow in our zone and if you are unsure, I find that there is usually a knowledgeable person on staff to answer your questions.  I used to be one, so I speak with some confidence here.  I have not had that same experience at big box stores.  I have wandered the aisles of retail giants to see what they have and compare prices and found, beneath a huge banner that says Perennials,  hydrangeas, ornamental grasses and flowering perennials whose tags are clearly marked hardy in zones 7 to 9.   

Online plant purchasing is becoming more and more popular. I've been dabbling in it a bit, mostly for varieties I cannot find locally, but more for liner plants that I can grow into landscape plants myself. If you don't see the zone clearly, just search for the plant on other sites before you buy.  In fact, it is always a good idea to read plant reviews and gather information from various sources before buying or ordering any plant.  Plants are living things after all.  Ordering from a lovely catalog is no different.  The enticing pictures and prices may eclipse the small print indicating hardiness zone.  Even I am guilty of over looking the fine print, as I am like most gardeners who do get pretty excited going through gorgeous catalogs.

So pay close attention to the tags, labels, and fine print! The right zone is the first step, not the only step, in choosing the right plant for your location.  Read the tag before you purchase, and do some research. Ignore the perennial sign and any other banner or promotion that smacks you in the face and focus on the zone! Better yet, drive to the nearest local garden center and buy a plant that was selected by a knowledgeable member of their staff to grow and thrive in your garden. 

Happy planting!

Ornamental Grasses

By Ann-Marie Volz • January 14, 2025
Are ornamental grasses really low maintenance?

Landscape Fabric

By Ann-Marie Volz • February 12, 2022
Landscape fabric is a real pet peeve of mine. I have ripped out so many hundreds, maybe thousands, of feet of landscape fabric in my time that I would, if I had the money, take out full page adds in every major publication to tell people to STOP using it in gardens. However, it does have its' uses, as you will see in a moment. First of all, landscape fabric is often sold as a method of weed control. So, let's discuss weeds for just a moment. Weeds that grow in your garden arrived there by one or all of the following ways. They grew from a weed seed that was blown into your garden by the wind or transported there by an animal (i.e. bird droppings) or insect. Or, they grew underground from a nearby location. Some weeds (which is any unwanted plant) can grow very long distances underground! Members of the mint family travel quite well this way. Finally, weeds also grow overground. Ground ivy, a bane to lawn lovers and gardeners alike, is this kind of traveler. Now back to fabric. Fabric will not stop any weeds from growing in your garden. As for the weed seeds, they will sprout in mulch or even stone and the fabric you've painstakingly put down may slow their progress. But most weeds have roots so fine that they can and will weave through the fabric. If you get them before, or just as that process starts, well then, you can say the fabric worked. And by get them , I mean WEED. So, now you are busy pulling weeds so that they do not root into your fabric. How is that different from weeding so that weeds do not root into your soil? I wonder! If you don't get that weed in time, then the roots will grow and when you try to pull out that weed, you will tear your fabric and, very likely, leave enough root matter behind for the weed to grow right back, and better, now that you've made a nice hole in the fabric. As for weeds that grow underground, now there is a real danger to gardens and landscapes. Why? Because those underground runners are looking for a place to surface and grow. I have lifted fabric in established gardens to find massive networks of such roots and runners. Sadly, they often surface at the crown or your plants, that is, where you have cut a hole in the fabric to plant your flower, or shrub or tree. And, chances are , you will not notice it down there until it is far too enmeshed with your prized plant to ever get it out. This is a terrible thing and I've seen it happen over and over again. Those underground roots and runners will also find a place to surface at the edge of your garden, where the fabric stops. And they will surface and grow there with reckless abandon. At that point, the unsuspecting gardener will start pulling, and discover with dismay, that everything they are pulling is attached to long roots and runners. And now, oh what a mess, the fabric is completely pulled up! Fabric may more successfully slow down the progress of weeds that spread by growing overground. And, it may be easy to pull these culprits out of the garden as they struggle to take hold through the fabric. But of course, that amounts to diligent weeding, and I'm pretty sure most people buy and use fabric because they think they will not have to weed. Still, I am a professional gardener and I do buy landscape fabric. Why? For two reason and two reason only. Number one, fabric, even if you have to use cheap fabric, should be applied under stone and gravel. Notice that I have it employed in the picture above. It provides a barrier that prevents your stone and gravel from sinking into the soil below over time. Weeds sprout in stone and gravel eventually, but can be treated with a dash of boric acid, or some other natural herbicide. After the weed dies, it can be removed without making a huge hole in the fabric. Number two, high quality, non-woven fabric can be used by itself as a pathway in vegetable gardens. It will get slippery, so care must be taken to keep it clean. Non woven fabric has the look and feel of thick felt. And it is the only fabric I will use in my two exceptions for using fabric. Here are two more reasons to avoid fabric in gardens and landscapes, which have nothing to do with weeds. Gardens are a process. The soil around your plants should be cultivated from time to time, and amended with organic matter. If you use natural mulch, it is supposed to break down and be reapplied every so often. You can't do any of that when fabric is present. And the truth is, all fabric will eventually get ripped out and thrown into a landfill, and I think it is high time we all become more conscious of how much we send to the landfill! There are those who use fabric seasonally in vegetable gardens. I used to do this myself. But I have been converted to using straw or hay or cover crops. Any or all of which look better, work better, save money, and return organic matter to the soil. So, in conclusion, if you are going to have to weed anyway, why spend your time and money on fabric? But if you are doing anything with stone or gravel, make that anything last longer and cleaner with a layer of fabric beneath. Your comments are welcome! Gardeners learn from gardeners.

The PH Scale

By Ann-Marie Volz • March 8, 2019
Baffled by PH? This post will help you understand the basics.
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