Planning for Native Plants Interview With Charlotte Glen on Getting Dirty in Your Garden, Extension Master Gardener Radio Show and Podcast

— Written By Lisa Sanderson and last updated by
North Carolina Cooperative Extension Horticulture Agent-Chatham County

North Carolina Cooperative Extension
Horticulture Agent-Chatham County

Charlotte Glen shares her knowledge for planning for native plants in your landscape including plant considerations, soils and soil testing, water, and sun.

Image of Callicarpa americana  by Forest and Kim Starr – CC-BY

TRANSCRIPT

JOHNSON

This is Getting Dirty in Your Garden, brought to you by North Carolina State Extension Master Gardener Volunteers. I am your host, Harold Johnson, and I’m a Master Gardener in Durham County. We’re in the midst of the summer heat. Why talk about planting anything this time of the year? The answer is planning—preparing for future planting. Now’s a good time to develop your plan for adding native flowers, shrubs and trees to your landscape next spring. Charlotte Glen, Cooperative Extension Horticulture Agent in Chatham County gives gardeners tips on determining what plants will thrive in specific locations in the gardeners’ unique landscape. Trained in soil science, Charlotte will guide you step-by-step in understanding the soils in your landscape. Be prepared to take notes—mental notes, if not paper. Charlotte provides invaluable information for all gardeners. And I’m talking with Charlotte Glen in Chatham County. Let’s talk about something that I think is near and dear to your heart and that’s native plants and gardeners. How do gardeners who want to grow tomatoes, but also want to deal with native plants, maybe in their landscape?

GLEN

How do they get started?

JOHNSON

Yeah! How do they get started? What should they do?

Well, to start off with, I think people need to understand why–to know why do they trying to include natives? There are some common things people are looking for. There are plants that are adapted to our climate, to our local soils, summers, winters, so this perception that natives are going to be tough and durable, which for the most part is true. You do have to be careful with your selection. Just like all plants, some natives are tougher than others. Some are adapted to real specific soil types. You always have to do your research. Get the right plant for your site. Think about your sun. Think about your soil. And don’t just expect any native to thrive with no care. That’s a most common misconception or simplification, more appropriate. People tend to simply it down to the idea that native plants are tough, they’re durable. But you need to do the same type of site preparation that you would do for anything: preparing the soil, finding the plants that are adapted to your site, watering these plants until they get established. A lot of our natives will thrive under our native rainfall, our local normal rainfall regimes, but you have to help them get established.

JOHNSON

I happen to know that you’re very tuned in to soil science. Maybe that’s an emphasis you’ve had in education training. Relate that to the natives–your knowledge of soil science and then your knowledge of the natives.

GLEN

The connections are soil types–are what dictates what grows on that soil–the type of soil that’s there when you start to look around at our native plant communities. What determines why is there an oak-hickory forest “here”, whereas “here” there is a swamp forest that is dominated by wetland trees? And so the two controlling factors are the soil type underneath and the moisture regimes. And the moisture is often related to the soil type, as well as the water table and bodies of water–rivers and streams. So when I look at native plant communities, I am always thinking about, “What is the soil underneath and how does that interact with the plants that are growing there?” You know, if you go just south of here to the Sandhills, totally different plant communities, completely different soils–deep sandy soils. And I find that many of the Sandhills plants that are adapted to these deep sandy soils are actually really difficult to grow in a nursery, in a container with potting soil. They are difficult to transplant, from growing them from seed and then trying to transplant them. They are very specialized, these deep sandy soils. Whereas if you go to the heavier, wetter soils, the wetland type plants, they are actually much easier to grow and are in general more adapted. So I am really fascinated by how the soils and the moisture–the hydrology–impact which plants will grow there and the plant communities.

JOHNSON

Interesting, because I think about a stand of wild blueberries—well, why aren’t there more stands within 300 feet of that stand and does that have something to do with the soil? Or is that selection because that’s where the birds drop the beginning seeds?

GLEN

Some of both, you know, blueberries specifically need acid soil, so people will think “I must have acidic soil–my azaleas grow well, so blueberries will grow well.” And a lot of times that true. But even a lot of plants that are considered acid lovers, like camellias and azaleas, they are only happy when the pH is down to around 5.5–maybe as low as 5. Blueberries really thrive when you even go lower than that–4.0, 4.5. I have measured the pH in some of the big, commercial blueberry fields that was 3.8.

JOHNSON

Wow!

GLEN

So blueberries are super acid lovers, far beyond any of our other commonly cultivated fruits or vegetables or even ornamental plants. So acidity–if you see a lot of wild blueberries–that is a sure sign that you are dealing with an acidic soil.

JOHNSON

Now here is a chance for you to put a plug in for testing your soil?

GLEN

Absolutely! Depending on what you want to grow, there is different target soil pH’s. pH is very important because it controls the availability of different nutrients, as well as some things like aluminum that could be really toxic to plant roots. When you get those really low pH’s, aluminum in the soil is more available, and can burn roots. So that’s your first step before you ever plant anything in the ground–have your soil tested, collect samples. Get some boxes and forms from your local extension office. Those are sent to the Department of Agriculture’s agronomic lab, which is in Raleigh. Your results will be posted online within a few weeks, typically. There is no direct charge if you submit those samples between April and November. During the peak season, December to March, it is $4 per sample. But it is going to tell you what your pH is. It is really the most accurate way to get your pH reading. It will tell you if you need lime for what you are planning to grow and how much. It will tell you your nutrient levels for phosphorus and potassium. It will give you a recommendation for applying fertilizer. You can use an organic fertilizer or a synthetic fertilizer, so it is not necessarily going to say you have to use a synthetic. It’s a recommendation you can use for various types of nutrient sources.

JOHNSON

So, once you know what you’ve got, then you know how to change it to what you want or you celebrate that you have got what you want in soil type.

GLEN

Right! So once you know what you’ve got, then you can work within those parameters, grow what is adapted to that, or if you want to grow something that’s not, you are going to have to do a lot of work to make changes to that soil or do some work, at least.

JOHNSON

Just because something is native to North Carolina, doesn’t mean that it’s going to do well in your yard, because as you’ve said, “Soil differs. Fifty miles can go from super deep, sandy soil to the best clay in the world–make bricks out of it!” So test that soil. Adapt very specifically.

GLEN

Right. Testing your soil, that’s going to give you the pH and nutrient content. Also, just get out there and dig a hole. There is no better way to learn about your soil than to dig in it. Dig in it, feel the soil. If it’s clay, it’s moldable. You know you are dealing with issues related to clay—like poor drainage. If you have got the sand that just sifts through your fingers, you are going to have to deal with drought. Hopefully you will have some happy medium–a loam soil that’s got a combination of clay and silt or sand that is pretty rare. Yes, we have–in fact, North Carolina has–some of the most variable soils in the country. I remember several years ago we hosted an agricultural agents’ conference for the whole country. I was on the bus with some agents from Oklahoma or Kansas, and we were riding along to visit a farm and some of them asked, “So, what’s your soil type here?” I was like, “There are several hundred types here and it can change from across one ten acre field. You can deal with several soil types. In a single backyard, you can be dealing with more than one soil type.” They were pretty amazed by that because out in the Midwest, you have big, huge areas–just vast expanses of all the same soil type–while we have just tremendous change, just from a few hundred feet. And that’s why North Carolina was one of the first states to start a soil testing program. We have one of the largest soil testing programs in the country. There was something I wanted to follow up on. The comment you made about the seed where the bird dropped it. That is something worth thinking about in relation to native plants. You see native plants growing where they’re adapted. And the seeds might get spread all around. We have to think about this in the context of our garden. We can try planting all types of things and they may be native to North Carolina. Or hopefully, you will focus in a little more–and native to the Piedmont. But that doesn’t mean they are going to grow in your backyard. Even though these plants we see growing in the wild–they are only growing where the conditions are right for them. So for every wild blueberry you see–or a really good example is dogwood trees–for every wild dogwood you see, a hundred seedlings may have come up and died for the one that survived. In our backyard, we don’t want that. We don’t want to have to plant a hundred to get one to survive. We want everything to survive. So, we have to do a little more work. Even though these plants are seen growing in the wild, it doesn’t mean every seed that has ever dropped out there comes up and makes a plant.

JOHNSON

Boy, you have given a whole new meaning about understanding in your yard, from area to area, what you want to plant. Well, is it conducive to dogwoods or will they just die, if you try to plant them in that area? In your own yard, it can vary. I picture lots of folks go down when the dogwoods go on sale at the big boxes, come home and just plant them, “Well, that’s a native tree, that’s going to do great!” Well it doesn’t. They go back to the big box store, “Well, your plants don’t grow! Why didn’t they grow?”

GLEN

Right! You have to think about “Are you in a location that gets sun all day? If you get shade part of the day, is it the morning or afternoon?” There is a big difference between morning sun and afternoon sun. Afternoon sun is really harsh. You need to choose plants that need full sun to go in those afternoon sun areas. Where your morning sun is very gentle, your shade plants will usually do fine there. Really dark shade, under hardwood trees, it’s going to be really difficult to grow many things there because sunlight is what drives plant growth. If you cut out sunlight, you greatly reduce growth. You also have all the competition with the tree roots under there.

JOHNSON

That makes me think that if I move to a newly constructed home where they generally have taken down all the trees, or the trees not exactly on my lot, but there may be trees neighboring the lot, then I had best mark the sun’s path of sun and shadow for a year so I understand if I plant in this area, summer it is going to be blazing hot, overhead sun, but in the winter that was nice low sun in the sky.

GLEN

Yes, being aware of the sun, and how the angle of the sun and intensity changes throughout the year is really important. It is always good advice when you start a new garden, especially moving in to a new home–it is hard to do–but just wait that first year, and observe. Observe what is already there, how it’s doing. You never know when you move in what is going to come up in a different season–bulbs and things like that–just seeing the way the path of the sun and the areas that receive sun and shade change throughout the year.

JOHNSON

When they build homes, they sometimes do the homeowner a favor and they have topsoil trucked in. What might they be getting?

GLEN

Well you never know. There is not a legal definition for “topsoil”. There is no standard. It is literally the soil that was on top when “whatever scooped it up”, scooped it up! You could be getting a good soil that has a decent amount of organic matter content in it. More likely than not, you are getting something that is, in our area, pretty much clay. The pH could be really low. It could have a lot of weed seeds in it. It could have weed root pieces in it. There could be insects. There could be disease spores. You don’t know what you are bringing in when you bring in topsoil. I would much rather see people bring in some type of compost–any type of compost–it doesn’t matter what it started out as. Bring that in and mix it into the existing soil and improve what you have. Yes, of course, in compost, especially, if you are dealing with aged horse manure, or things like that, you could bring in some weed seed as well.

JOHNSON

I could only imagine that if a field today is barren of trees, it could have been populated for four or five hundred years by a grove of trees and then they were cut down so there could be a farm there–quite a different soil than an exposed field where erosion has taken away any organic matter and you are just left with clay.

GLEN

That is absolutely right. When you remove the trees, you take out that continually renewing source of organic matter–the leaves that fall from the trees every fall. If you think about going into the woods, you have that layer of both fresh leaves and the leaves that are breaking down. And that’s what constantly renewing and improving the soil. So if you take the trees off, you remove that source. Also in the process of taking the trees off, you greatly compact the soil. So if you look at a yard from an area that has been cleared and you built a house–it was basically a construction site for a year–and compare it to a forest–an undisturbed forest, you have reduced the water infiltration rate by 95% and that compaction is going to be really damaging for plant growth, because plant roots need air. If you pack the soil down, you pack those little tiny soil particles close together; there is not room for air. Roots need air even though you don’t think about it and when air is not available they can suffocate. That is a lot of reason plants tend to grow poorly, especially in newly established yards. The soil is very compact; it is really tough for the roots to grow. You don’t get good root growth. You don’t get good top growth. It is directly proportional.

JOHNSON

What about the idea that you want to plant and you probably have a lot of clay. You dig a hole and, I guess, put water in it and see how long it takes to drain, if it ever drains.

GLEN

That’s a good way to gauge your plant selection. You always want to have a good idea of how wet your soil–the capacity to stay wet. Moisture is a big limiting factor for plant growth. Some plants need to stay wet a lot—most of the time our wetland plants. Other plants will die very quickly if they are somewhere where water stands for even for a day. So a real simple way to gauge is dig a hole. Wait for some time, maybe 4 or 5 days after a rain. You don’t want to do this in the middle of a drought or after we have had historic rainfall. You want to get a really accurate idea. Dig a hole–10inches deep–a foot deep. Fill it with water and see how long it takes to drain. If that water is gone within an hour, you know you have very well-drained soil and you are going to have to go with very drought tolerant plant. If the water is there by the end of the day but gone by the next morning, that’s pretty good. If the water is still there two or three days later, you are either going to have to either build raised beds–build up to give your plants an area of well-drained soil, or choose plants that tolerate very wet sites–things like River Birch, some of our native wetland irises, like Virginia iris and swamp milkweed. There are a lot of plants out there. That is the good thing with ornamentals, especially if you are looking at natives. We have a lot of spectacular wetland native plants. Yes, any time you spend in researching your site before planting is going to be the best expense of your time you can make. It is going to help you make the best decision about the plants to help you save money in the long run because you are more likely to have success with the plants that you select that fit those conditions. Sometimes, especially in the spring, everybody gets excited and you go to a garden center and everything is beautiful, and you want to take it home and put it in your yard, stop and take a breath and think, “What do I need? What space do I have? Where does this specific plant like to grow? Does it need sun, does it need shade? Is it tolerant of drought or moisture?”  And deer is another consideration, too. Make some notes about what you see that is so beautiful in the garden center. Do a little bit of research and then go back and choose the right one!

JOHNSON

You are probably going to have an explosion of growth in the eastern part of Chatham County–lots of new homes will be going up. Is the Cooperative Extension Service, someone like you, available to give some guidance individually? Or would you do it to a group of people? How might you help folks?

GLEN

We have various ways. We aren’t generally able to do individual site visits to yards. We just don’t have the capacity to do that. But we do have classes. I am teaching right now, an extension gardener course–a series of nine classes. That is something we will continue to offer each year. It covers pretty much everything: soils, plant selection, good plants for the area, fruits and vegetables. So that is great for somebody who wants to get a good grounding in all types of gardening. Then, throughout the year we will offer individual classes that may be focused on one topic. Workshops and different conferences are always something that we are working on and offer a couple of times a year–maybe something–a bigger event, maybe on a Saturday. A great way to stay in touch with what is coming up is to visit our website. Our website is Chatham.ces.ncsu.edu. Another good resource, particularly if people are interested in natives, is North Carolina State’s “Going Native” site, which gives you tips for how to design with native plants, how to make the most impact, especially for wildlife because that’s the real focus. That’s the real heart of native plants–the value we can get by supporting our diversity, supporting all the different species of animals. Mostly it pretty much starts by supporting the insects that the birds eat and that the other animals eat, and as you move up the food chain, plants are at the very base. Next tend to be insects. Then you move into your birds and mammals and reptiles. You want to include native plants in our landscapes to support this whole food chain and to support all of our native species. The “Going Native” website talks about that. It has a plant database which you can search. You can search if you are looking for Piedmont natives. You are always going to get the most wildlife value if you choose plants native to your region. You can search for trees, you can search for shrubs. You can designate if you are looking for a plant to attract a certain type of wildlife like songbirds or hummingbirds, time of that year that it blooms–all kinds of parameters. You can even create your own plant collection. You can save your searches into a personalized database of the plants that will work for your yard.

JOHNSON

I’ll bet your very active bee-keepers association would say plant things that also bloom in the Fall, so that the bees have something to tide them over for the winter.

GLEN

Exactly! Fall is an important time. Of course, all times of the year when bees are active from spring; spring can be a really important time too, when bees first start to become active and there’s not a lot blooming at that time. But through the summer we tend to have a lot of resources available when a lot of things are in bloom. Then fall also becomes a critical time. One thing I always try to encourage people to do for bees, particularly in the spring, is to leave some of those spring weeds: Henbit and Chickweed, things that become vilified, but they are really important nectar sources for bees that are coming out early in the spring. When temperatures get up above 50, honeybees will come out (50-55 degrees). A lot of our native bees are active at lower temperatures, so it is really important for our native bees; a lot of them are adapted to feed on native plants. We mentioned the wild blueberries earlier. We have a species of native bee called the Southeastern Blueberry Bee that that is what they feed on. Their whole lifecycle is timed to having the adult active when the blueberries bloom. Then they have a short adult stage. They lay eggs that will be the next generation. And it just starts over again. So, this little Southeastern Blueberry Bee has to have blueberries to survive!

JOHNSON

Golly! It’s informative for me! And I say, super informative, educationally, for anyone who tunes in for this interview! You have been listening to “Getting Dirty in Your Garden” brought to you by North Carolina State Extension Master Gardeners. You may find this and future episodes on our website: gettingdirtyinyourgarden.org. Until next time, why not go out and get dirty in your garden?

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