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Don’t start gardening yet. Even though you can start gardening outdoors earlier this year in the Carolinas thanks to a change in the USDA’s classification of Plant Hardiness Zones for North Carolina and South Carolina, we’ve got at least one more cold snap this week.
This week on the Carolina Weather Group, Candice Jordan hosts a special conversation with her colleague from the Schiele Museum of Natural History in Gastonia, North Carolina.
Few the detailed and interactive USA Plant Hardiness Zone Map at https://planthardiness.ars.usda.gov/.
This episode was available early on https://patreon.com/carolinawxgroup
See typical dates of the last freeze:
North Carolina: https://www.weather.gov/rah/FrostFreezemaps
South Carolina: https://www.dnr.sc.gov/climate/sco/ClimateData/SC_Frost_Freeze_Dates.pdf
USDA’s Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. Starting in 2024, the Carolinas were adjusted because of warming temperatures and rapidly increasing data sets.
The new version has 13 zones across the United States and its territories. Each zone is broken into half zones, designated as “A” and “B.” For example, zone 7 is divided into 7a and 7b half zones. When compared to the 2012 map, the 2023 version reveals that about half of the country shifted to the next warmer half zone, and the other half of the country remained in the same half zone. That shift to the next warmer half zone means those areas warmed somewhere in the range of 0-5 degrees Fahrenheit; however, some locations experienced warming in the range of 0-5 degrees Fahrenheit without moving to another half zone.
The 2023 map is based on 30-year averages of the lowest annual winter temperatures at specific locations, is divided into 10-degree Fahrenheit zones and further divided into 5-degree Fahrenheit half-zones. Like the 2012 map, the 2023 web version offers a Geographic Information System (GIS)-based interactive format and is specifically designed to be user-friendly. Notably, the 2023 map delivers to users several new, significant features and advances. The 2023 map incorporates data from 13,412 weather stations compared to the 7,983 that were used for the 2012 map.
Approximately 80 million American gardeners and growers represent the most frequent users of the USDA Plant Hardiness Zone Map. However, they’re not the only ones with a need for this hardiness information. For example, the USDA Risk Management Agency refers to the map’s plant hardiness zone designations to set certain crop insurance standards. Additionally, scientists incorporate the plant hardiness zones as a data layer in many research models, such as those modeling the spread of exotic weeds and insects.
Plant hardiness zone designations represent what’s known as the “average annual extreme minimum temperature” at a given location during a particular time period (30 years, in this instance). Put another way, the designations do not reflect the coldest it has ever been or ever will be at a specific location, but simply the average lowest winter temperature for the location over a specified time. Low temperature during the winter is a crucial factor in the survival of plants at specific locations.
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A lot of people they’re listening to this and they’re like okay we’re extending the growing season we’re getting more food like that’s a great thing right like we should be celebrating this but really there are negative impacts that are hey guys it’s Candace Jordan here with the Carolina weather group I’ve got
On my different hat today but we here at my work location The Shield Museum of Natural History we’re out here on the farm it’s a little misty out when we’re recording this but all good and I’ve got my good friend here Nathan Chapman hey Nathan thank you oh thank you for having
Me yeah so I brought him along because we’re gon to talk about a really really important topic here and the reason I picked him to come help me talk about this is because we’re going to talk about the relationship of plants and climate and Nathan here is one of our
Program educ cers and he specifically focuses a lot on our outdoor things so tell us a little bit about your background first so I’ve been an avid Gardener since I could walk basically so always out in the garden exploring eating things that I maybe or maybe shouldn’t eat from time to time out
Nature um I did eventually go to NC State University get a Bachelor of Science in environmental science and plant biology so know way too much about what’s going on inside of a plant no too much um but generally that interest and that passion carried over into agriculture gardening and then just
Wanting to be able to share that so that’s kind of like my background yeah so uh when I when I asked Nathan if he wanted to come talk to me about plants and climate and I was like yo can you talk for at least a few minutes about
This and he was like no problem no problem got this hours could be spent right so for those of you at home I don’t know if you’ve noticed this over the years but you may have noticed that certain plants are blooming a little earlier um you plant them a little
Earlier they’re getting a little later in the year that what you always expect is kind of Shifting and changing a little bit right definitely um tell us a little bit about that so the largest shift has been that our spring frosts have moved back in time so you can grow
Things like summer vegetables earlier and our fall frosts have moved back have moved back also so you can actually grow things later in the year than you normally would so there’s benefits and tradeoffs with both of these but we’ll kind of get into the details of that in
A moment yeah so what are some of the like broad impacts of the climate crisis on agriculture we kind of heard this about climate crisis you know uh with temperatures uh globally that are increasing you know we’re seeing um more natural weather events that borderline you know not so great for the
Environment so tell us a little bit about how that’s kind of impacting agriculture the largest thing is that our normal weather patterns normal temperatures normal rainfall amounts um everything’s kind of becoming more extreme so if we’re going to have a drought during the summer it’s going to
Be longer and drier if we’re going to have a flood in the winter it’s going to be much more rainfall and our temperatures can swing much more dramatically even more than they normally would in North Carolina so um you know December is pretty it’s getting fairly common to have 70° days which um
Even from my childhood is rare like non-existent up till just a few years ago so mainly extreme temperatures and these weather extremes impact agriculture through drought which we’ve kind of already kind of discussed like plants have to have water to be able to grow um heat waves and also these
Extreme weather events can impact livestock so uh cattle for example like in our large pastures um they can only survive certain temperatures so if it gets very very hot and very humid it is very detrimental to their health and can result in their death and that is becoming unfortunately more and more
Common and that goes for all of our livestock pests disease all the stress of this heat this cold these fluctuating temperatures leads plants to be more stressed so more prone to diseases more prone to Pest and even for kind of like on the human side of things like
Agricultural workers who have to go out and work it is also very hazardous and dangerous to their health like either from extreme temperature or from wet bulb events where our bodies basically just cannot cool ourselves it’s too hot and too humid yeah we talk a lot um as
Meteorologists we talk about the heat index you know and so that’s taken to account what the temperature is and also what it feels like you know your body can kind of perceive humidity and so when it’s nice and dry outside you know you can feel the heat but when you have
A layer of humidity on top of that it’s like the air you can wear you know it’s just sweltering outside um now one thing I want to touch on because I know you said this you said that the plants get stressed and you they’re more prone to
Diseases and such is that kind of similar to humans I know when humans get stressed we get tired you know we’re mentally spent like you know a lot of kind of side effects can happen when you’re overstressed chronically so is that similar to plants exact exactly the
Same so pretty much all organisms um that are alive so animal plants mushrooms even germs even um if they encounter stressful situations or areas that are not beneficial or good for them they can have a really hard time of just maintaining themselves kind of like we kind of like people if we’re really
Stressed it’s really hard to maintain ourselves and it’s also we’re lot much more susceptible diseases and things of that nature so plants the exact same way great so I know there’s this thing it’s from USDA it’s called like the hardiness zone map what is is that like what does
It tell us you know why do we care about this map right so the USDA hardiness zone map is basically a map of the entire United States and territories and it basically is a guide to what you can grow here in Gastonia Charlotte area where Zone 8A so it basically says it
Gets too cold on average over the winter time for you to grow Pine apples bananas kind of like tropical fruits right and it’s also an indicator of what plants you cannot grow due to summer temperatures so you can kind of extrapolate like we can’t grow cranberries here anymore we used to be
Able to just a few years ago but we can’t any more just due to the high heat levels during the summer months other plants um rhubarb cauliflower and broccoli are even having a harder time in this climate due to those kind of like shifting temperatures not being
Able to grow something or being able to grow something now um kind of on both spectrums that’s not only a local thing like this is like a worldwide economy now with food yes so are we seeing differences even now starting yes so um in general um this is this will kind of
Help it might be a tangent but tents um so most of our food plants that we can think of like when you think of a food like potatoes rice Tomatoes anything like that most plants stop growing at temperatures above 86 degre they go from you know growing happy
We’re going to make lots of food to we’re just surviving so they basically sit in the ground conserve resources make all kind of um basically proteins that help protect themselves in drought and they’re not focused on growth so that is like 86% of the food crops that we eat so if it gets
Above 86% 86 degrees fah outside in the summertime most plants you see stop growing and they’re just sitting waiting for it to cool off um there are a few plants that can handle higher temperatures and this is restricted to Corn sorghum and Millet the one that we
Mainly care about here in our area is corn and it can handle temperatures up to 95 degrees but above 95 degrees it even stops growing so it just sits there so when it’s a 100 degree day the plants outside just stop stop um and above that you’ve only got things like pineapple
Agave and certain cactus that can handle the crazy extreme temperat yeah so um trying to get back to the question um basically all of our growing areas are going to have to either start like adopting plants from further south or if you’re Southern H feem kind of things
Closer to the Equator adopting those plant species to grow farther north and then our cold weather plants that we love and depend on like wheat all of our cabbage things cabbages and things like that all of those crops are going to gradually start growing and moving northward so like our Grain Belt that’s
In the midwest can slowly maybe even with this in this Century if we’re not addressing the problem could move up into Canada potentially so devastating impacts that it’s just going to take a lot of cooperation on human and countries scale of like working together
So we can you know have food and um kind of accommodate our needs so this hardiness map I mean it’s it’s literally showing kind of these different zones how often is it updated because it would be really neat to see you know even like you’re saying even in your lifetime
You’ve noticed that like cranberries aren’t a thing around here anymore you know like how often does that map get updated and can we see the trends over time so I don’t believe that there’s a set update time I believe it’s as needed um I believe there was an update in ‘
89 one in 2012 and those largely stayed the same from 89 to 2012 from 2012 to 2024 12 years most over half of the US has shifted 5 to 10 degrees like the cold average cold winter temperature has shifted 5 to 10 degrees warmer in 10 years and this region would normally get
Down to like five degrees but now our average is only getting down to 10 and if that holds will be similar to like Central to Mid Central to lower Georgia within a few decades which is kind of concerning well I mean even you know we were working on an event in
February and jokingly we were like man I hope it’s one of those like 70 degree February days but like when you think about it you know decades ago you really wouldn’t sit there and be like oh you know there’s a good chance maybe we can get that 70 degree February day um you
Know you’re seeing these climate change you know happening and it’s not only impacting human health I feel like that’s all we hear a lot of yes rightfully so I feel like to get humans involved in helping to repair the climate you have to make it human Centric but plants are definitely involved too
Um back with more Carol have you ever seen what an indoor environmental assessment looks like in a commercial building or business during a full assessment we collect data throughout the building and compare the measurements room to room we can also collect samples that go to a lab such as
The small cassette shown here which will be analyzed for types and amounts of mold in the air we follow up with a physical inspection looking for moisture sources and using moisture meters to determine if any of your building materials are wet gog.com or 336 37353 extend the conversation in just a
Moment but first to our question question when can you start gardening safely in the Carolinas well as we’ve been talking about that day it’s getting a little bit earlier and earlier each year but let’s look at this data from the North Carolina climate office most of the Carolinas is in green so that
Really puts us at about tax day somewhere between April 8th April 15th maybe as late as April 22nd that date obviously gets later into May almost June in some places as you make your way to the higher elevations of the western North Carolina mountains and earlier as
You make your way to the coast where it’ll be a little bit warmer a little bit earlier and so you might be able to start planting some of those heartier plants by the end of March this is a look at the latest date in which we can
Anticipate seeing a 32 Dee freeze in North Carolina what about South Carolina I don’t have a map but I have a chart so just to kind of look at some of these numbers here real briefly for you again we’re zeroing in right now on the 32° threshold of most likely having that
Last hard freeze aen March 22nd Anderson March 19th and so this is those dates where you can expect the temperature will hit 32 degrees for the last time that winter as we head into the growing season Charleston that date is more like February 13th so you can certainly start
A little bit earlier there along the coast Chester in the greater Charlotte Area you have to wait more to March 21st maybe even to the end of March our friend chief meteorologist Brad panovich WCNC Shar Charlotte he really emphasizes wait until tax day wait until we get
Into April in Colombia that date again could be as early as February 26th but as we’ve seen just in the past week or so we still have the possibility of some really cold at or below freezing Mornings in portions of the Carolinas even during the month of March so you
Have to watch that very carefully Laurens 32 degrees last date about March 27th give or take Newberry that date is more like March 20th Orangeburg March 2nd so there’s a widespread of course because the climate and the weather is so different across the Carolinas we have both of these resources linked for
You right now in the description of this show wherever you are watch or listening let’s get back out now to the shield Museum are some like strategies that maybe Farmers or garders can do to kind of approach this headon so the largest thing is kind of anticipate so if you’re accustomed to
You know a cold snap anticipate a stronger or harder cold snap maybe later or earlier it’s very hard to predict weather patterns um but kind of having in infrastructure in place to kind of like protect against that so one example would be like if you anticipate a drought during the summer
Like have some way of some ready access to water so either ponds if you’re if you’re like larger scale or even rain bar rain barrel if you’re like a smaller home Gardener um or like mulching your plants very heavy to conserve as much water that does fall so the water stays
Where it needs to be right and that’s largely kind of like some things that we can like on the home scale that we can kind of think about other strategies to be would be just to be kind of aware of where our food comes from um kind of
Like not saying go out and change everything that you do because we’re finite creatures in a basically infinite World um but kind of pick and choose things that you’d like to improve on um diet wise or whatever and kind of you know pick the best option if you are
Able to do so what’s the most surprising plant change that you’ve noticed or you know since the newest update like you know what’s something that’s just really shocking to you in the Carolina area so peaches is peach trees are a fairly good indicator it’s like one of our first
Fruit trees to bloom currently we have some blooming out on the farm and it’s slowly been incrementing back like maybe just on average maybe a day or two days but now it’s we’re moved up to maybe even like almost a full month earlier than we would normally anticipate jles
Are another really good indicator jles or buttercups n things of that nature so are there plants that you know you’re saying like the peach trees and stuff um are there plants that kind of alert you to like or signal you that hey something’s kind of a Miss with the
Climate I mean definitely so so I mean just looking at any tree pretty much um they’re slowly waking up earlier and earlier every year even plants that we don’t expect to even like Leaf out until late April or even into May are now leafing out in mid like mid April so
Things like black walnut and pan are normally very late leafing out but they’re slowly working their way back to make the most of all the warm fair weather and maybe grow bumper extra crops but they’re just trying to do their thing trying to make it through so
One question I have you know we have these kind of extended growing seasons does that have any impact on the soil health because now the soil especially like with farmers and gardeners you know the soil is being used longer does that impact the soil health so it’s largely
Management strategy so if you have a good um kind of like soil Health practice it can be a an can be an improvement so you have more time to grow plants that can feed the soil you can get more crop rotations out you can actually get more food out of your
Systems but if you have a kind of like soil destructive kind of like productive it can increase and EXA exacerbate kind of like the damage so the damage that would only take that would take several years to show up can could show up in maybe one to two
Years so it’s really comes down to management it’s a double-edged s right right because you know to a lot of people they’re listening to this and they’re like okay we’re extending the growing season we’re getting more food like that’s a great thing right like we should be celebrating this but really
There are negative impacts that are happening right definitely and we may have longer growing seasons in general but the instability of life when that first fall Frost is going to hit and have a significant impact like if you’re trying to squeeze out another tomato crop or another cucumber crop it can
Completely devastate it just due to the instability so it’s very unpredictable right now so another question I have you know you’re looking at your fruits and vegetables and you know the ones you get in the store I feel like they’re always a little bit different than what you
Grow you know on the home turf there um are there any changes that you’re noticing with like for example like tomato side or water content in them do kind of like over the years right so generally like produce from the supermarket is under heavily controlled like production measures like lettuce is normally grown
In green houses under very set parameters um so haven’t really noticed too many shifts in that department um generally your grocer store products have been bred to be have really good shelf life hold their water and color very well maybe not hold the best flavor um but your home crops are definitely
Going to have some kind of like struggles like more pest pressure earlier pest pressure when you’re not necessarily expecting it um diseases and all types of detriments just related to the shift yeah so not even talking about just plants but yeah the pests that go along with the plants are coming out
Earlier and they’re staying later yes has that been an issue yes so one notable kind of like problem um insect is the squash fine bore so it’s kind of like a little grub that comes from a day flight day flying moth so it has steadily been emerging earlier and
Earlier and its favorite food is squash zucchini and pumpkins so we used to be able to get a nice full crop of squash and zucchini before it would show up so you plant the seeds no pesticides or anything needed to get a good good harvest but now it’s showing up earlier
And earlier and it’s kind of eating into that first summer like soft summer squash and zucchini crop and it’s also been a very a very large detriment to like pumpkin crop as well so so I know like we’re like gungho for spring you know it’s like definitely spring but
Like looking ahead to fall have we noticed that pumpkins are are we getting them earlier and earlier so we’re trying to so pumpkins fortunately for pumpkins you can can kind of you have a little bit of wiggle room so and this longer growing season enables that even more so
Normally you’d plant pumpkins May through June like late May till the first of July is the ideal time so it’s not really impacting the early pumpkins as much maybe increasing it maybe like a week or so at Max currently um but it is lengthening the length of the pumpkin
Season it might be marginal only like one to two weeks but it is kind of all right so I’m GNA put you on the spot here okay all right give me your favorite plant F oh no he gets to educate lots of people each day and I know he’s got like a
Wealth of knowledge up here so we’re gonna impart a little bit to you guys today so what’s your favorite plant fact so my current favorite plant fact is has to go back to plants and when they shut down at what at certain temperatures so all different types of plants have
Special adaptions to different climates where they come from and most of our food crops really come from Europe which is a cool climate and most of those plants are C3 plants so yeah way too complicated but basically they like cool wet and not too
Hot um which is we are not no so we’re slowly losing the ability to grow these types of plants over time um still able to do it have to plant them earlier and earlier every year um um but my favorite kind of like fact related to it is Cam
Plants so this is your pineapple Agave cacti things that grow in the middle of the desert they photosynthesize so they get their energy from the Sun during the day they have all their stamata which is our plant mouths that let plants breathe get air breathe out water um they have
All those shut so they just catch energy during the day and then at night they grow and breathe so they basically collect energy during the day and then go through live and do all their things at night where most plants are breathing living growing all at the same
Time all right thank you n here today we’ve learned a lot about plants and climate and the relationship between it all um and how it’s all interconnected within humans and plants the pests the food industry your local backyard gardens basically you can’t just rely on what you’ve always done because even
Like the weather it’s changing yes definitely all right that’s all we have for our Carolina weather group for today so I am Candace Jordan here at the shield museum with Nathan Chapman thank you have a great night
1 Comment
Thank you both for the video.