While the changes may appear gradual, native plant materials are struggling to adapt to the fluctuations in temperature, water cycles, and other environmental conditions. Landscape Architects Tim West, Clay Schneckloth, Andy Meessmann, and Diane Witt converse on shifts in plant zone hardiness and the evolving plant material landscape.
During this second episode of a three part series on climate change, our experts will address each of the following questions:
- How are plant zone shifts effecting plant material selection?
- What impact is biodiversity having on evolving plant requirements?
- How are designs adapting for environmentally sensitive, culturally important, or historically protected areas?
Tim West: (0:20)
We’re seeing significant effects from climate change on a number of our plant communities in the Midwest. Some of these plants that we’ve relied on year after year for spring blooms, unique forms, branching, or maybe fall color, don’t seem to be performing as well as they were say about 15 to 20 years ago. The hardiness of some of these plants is lacking, if not much worse than they’ve been in the past.
Evolving Plant Hardiness Zones
Diane Witt: (0:47)
I just want to kind of give a brief education of the plant hardiness zones of our area. The US Department of Agriculture (USDA) puts out a Hardiness Zone Map and it was recently updated in 2012. You can see throughout the country that there’s warming occurring, shifting the hardiness zones north to warmer temperatures. There’s also some more sophisticated mapping that’s occurring, it shows those urban areas as a warmer zone than some of the surrounding rural areas on that map. Taking that into consideration, we’re seeing a lot more plant species from Zone 5.
Tim West: (1:21)
Do you think these plant zone shifts are something that just was procrastinated, or do you think it’s really changed in the last few years?
Diane Witt: (1:30)
Yeah, there’s a mixture of the climate change as the planet in general is warming. We’re seeing a natural shift of warmer temperatures and extreme weather occurring. The mapping is getting more sophisticated, so they’re able to pinpoint a little bit more and take more averages. They’ve been doing this for 60 or 70 years, so now they have more data to analyze that a little bit better.
Clay Schneckloth: (1:53)
One of the items that has stood out to me over the years, are the ornamental trees. They’ve always been an item that I’ve enjoyed planting, watching grow, trim, see the different blooms, and seasonal changes that we have with them. The redbuds, Japanese maples, are items that I really enjoy and have noticed over time that they just are struggling around here, trying to get those to thrive and work at all.
Successful Use of Seed Mixes
Andy Meessmann (2:20)
Yeah and something that I’m seeing become more and more complex, is how we use seed mixes, the proper way to install them, and how we write our specs. It’s to the advantage of the client, public or private whoever we’re working with, to typically use more of a seed approach to some of these larger swaths of landscape that we’re working with. The science that’s gone into some of the native seed mixes has really expanded over the last few years and coupling with what Diane was talking about with climate shift and some of these temperature changes that are happening, we really have to examine our seed mixes in more detail.
This is something that’s hard for a lot of people. A lot of times these seed mixes are just kind of taken for granted. What I’ve noticed is a lot of shifts from the rye annual crop. Some of those ryes actually taking over more as a weed in terms of specifying tackifier, hydromulching, hydroseeding within a native mix. It doesn’t work as well in terms of the seed actually taking hold. It’s more appropriate to find a good erosion mat for those native seed mixes. That’ll really allow the plants to pop through that mat, as opposed to including some sort of tackifier, that’s supposed to hold that seed down to the ground. These are new developments that are constantly happening.
What I found that works best for me, if I’m working on a big project that includes a lot of seed area, is just to call the local nursery here and pick their brain. These guys are the experts and we take their knowledge and form it into a design with all the other components that we’re putting onto this site. They have a desire to give you the best information, so you keep specking their product obviously. We’re constantly learning from some of these nurseries and the best approaches to go for seeding and sighting trees.
Mulching & Covering to Combat Increased Rainfall
Tim West: (4:05)
I’ve had good luck with contacting even seed companies and seed distributors. They can provide a lot of that information that you’re talking about Andy.
Another area that I think climate change is affecting the seeding, is the intensity of some of the rainfall is really requiring some sort of mulching or cover over those seed areas so that they don’t wash away. There’s been a pretty bad problem with people wanting to utilize hydromulch with a seed slurry mixed in with it to establish that seed into the ground. It’s not getting enough soil contact and I think that’s kind of the lazy way that people utilize that technology. We’re seeing a lot of seed companies sell that as the way to eliminate erosion and get the seed down and growing all at once. But it’s really important that the seeds are drill seated in first and that the mulch is just used as the cover and not a slurry throughout it.
Another area that I wanted to talk about real quick, before we left this subject, was the microsighting of trees. It’s becoming really important that these trees are planted almost exactly at the design spot. You see a lot of problems with contractors, either switching trees around, there might be a tree at that location, but they may switch it. Have you experienced a lot of trouble with that Clay?
Clay Schneckloth: (5:25)
Yeah, we have. We want to give these trees the best chance that we can to survive. When we’re looking at trees and varieties to work in the specific site, there’s a lot of factors that we key in. We’re working with the nurseries to understand root growth, how they’re being balled and burlapped, all the way to the contractor and how they’re installing it, and then the maintenance of this tree after it’s being installed. So there’s a lot of key factors that we need to have that conversation with starting at the very beginning.
Incorporating Biodiversity Throughout Designs
Tim West: (5:55)
Yeah, definitely. I think that becomes an important element of plant design.
We hear a lot about biodiversity and that’s something that’s easy to say, but sometimes harder to do. What impacts are you guys seeing from changing plant requirements, particularly regarding biodiversity? An easy example is the Dutch elm disease (DED) effect on elm trees in the sixties through the eighties. That resulted in over planting of ash trees and then the onset of emerald ash borer (EAB). Now we’re hearing about the Asian long-horned beetle (ALB) and its effect on maples. What type of strategies are you using for incorporating biodiversity into your plant selection?
Diane Witt: (6:37)
A lot of the communities we’re seeing require that biodiversity now. They’re also aware, they’ve hired arborists on staff or foresters on staff and they’re diversifying their plant lists. With that, we’re seeing a lot of introduction of those Zone 5 trees that may not have worked in our prior Zone 4. With that we’re seeing an increase in invasive species that may have been introduced through that process. Things like golden rain tree, I’m starting to see appear on some of those municipal lists, but it can be also considered an invasive. So we need to watch out for those types of trees that are being introduced.
I would also add that it creates another challenge with some of the existing species that we used to use. Like you mentioned before, Tim, that the pear trees was a very popular tree, euonymus or the burning bush are also species that are now being restricted because of the invasive tendencies that are occurring in warmer regions or surrounding regions. So we may not have seen it quite yet, as prolific invasion like particularly with the pears, but it is a problem that’s increasing in this region. So there’s definitely a change in the plant species that we’re using and caution to be taken as we introduce some additional species into our palette.
Diversity Requirements Through Municipalities
Tim West: (7:54)
One thing you mentioned about the diversity requirements through municipalities, a lot of us follow a 10% rule that you can’t use any more than 10% out of the same genus. That starts to become pretty difficult when you have a restricted plant list that eliminates a number of trees, whether it’s due to pest control or zone control. Do you have any thoughts on that Diane?
I would agree, that’s making it harder to create diversity. There’s some communities that require so much biodiversity that it’s hard to select plants, especially with prior restrictions of non-fruiting trees along a sidewalk. It really limits our palette. So we’re seeing a little bit lessening of that, where they’re allowing more trees that might have fruit. Serviceberrys, they had fruit, and some communities have previously not allowed them, but the fruit isn’t really a litter problem and we’re seeing that used more as a replacement for the pears.
Andy Meessmann: (8:54)
Just the diversity of plant species and one of the challenges we face in terms of diversifying our plants is when they’re installed in the construction sequence and what we’re left with. We spend a lot of time on planting lists, but sometimes we’re required to make some substitutions at the end. If it’s approaching fall and a particular species isn’t left, you always have to have a backup plan for some of those species that you’ve might’ve called out on plans. Which makes it more challenging, coupling that with tree requirements that some jurisdictions require and making sure you’re following all their guidelines and still trying to find that street tree that needs to go in.
Clay Schneckloth: (9:33)
Yeah, I’d agree with that, Andy. You definitely need to check with those jurisdictions. Certain species that you may use, one community might not be allowed in the other or have quantity restrictions. So it’s definitely good to follow up with them.
We also need to take into consideration along with the diversity, we want to make sure we talk with a licensed landscape architect or certified arborist when you’re looking and selecting trees for certain locations. There’s a reason that these people have the education and experience of working with these trees. Getting some guidance from these people is a valuable resource that will help the success of your trees.
Preventing Disease in Trees
Diane Witt: (10:10)
One of the issues we’re seeing with the severe weather conditions or the fluctuation in weather that we’re having, that brings on a lot of disease to trees. Having the right location can help offset that a little bit. If you have the right tree for the right spot, it might not be as severely impacted by those changes. So it’s important to understand the species and what site they’re adapted to.
Tim West: (10:35)
So if a lot of these plant ecosystems are changing and landscape materials are changing, how do you adapt those changes into your future designs to protect either traditionally environmentally sensitive areas or culturally important areas or historically protected areas? How do you go backwards in time, while using a new plant palette or material palette?
Creating Environmentally Sensitive Designs in Culturally Important Areas
Diane Witt: (11:04)
As the climate gets wetter and we have more precipitation, we see plants leafing out earlier and flowering sooner. That’s impacting a lot of our environmentally sensitive areas and our conservation practices. It’s impacting our native plant material.
The bur oak is the state tree and Iowa’s very proud of our oaks, but with oak wilt on the rise and impacted by the shifting climate, we’re seeing a shift in those plant materials, those plant species. It’s not happening overnight, but it is happening. It’s something that our conservation projects that we work on are aware of that and monitoring that and trying to increase that diversity as much as we can to see what works and what doesn’t.
Clay Schneckloth: (10:49)
I want to talk a little bit on the cultural important landscapes. We’re talking mostly on plant material, but a lot of times when we’re working with landscapes, we incorporate some limestone features, marble, or stone of other products. One of the items that has been brought to our attention, that we’ve worked on in the past, is protecting limestone maybe a wall or column that’s been registered with the state historical society.
When you’re dealing with culturally important landscapes, it’s not just the plant material, it’s also the structures that are incorporated within that landscape. When you start talking about a stone material, a lot of times there’s some buildup of algae or other products on this limestone, and we’re trying to do a restoration project on this, but we definitely want to try and protect it as much as we can. We definitely want to halt the process of deterioration and stabilize the condition of the product. Repairs on these items are basically, we’re going to consider it with minimal disturbance when we start doing restoration to these limestone features. Trying to keep them culturally protected as much as we can.
There’s a few different products out there that we’ve used. EaCo Chem is a chemical that has been used by many different restoration contractors. That is an eco-friendly type product that will not harm the environment, but still be able to clean and protect these limestone features. We came across another product that they’ve used dry ice to help clean these features. So there’s some new products that are out there and there’s some pros and cons of each, and we can definitely walk through some of those items with you.
Tim West: (13:30)
We’ve had a lot of projects that have had some sort of aspect protected through the state historical designation. You have to be really careful with modifying those.
We did some work out at Camp Dodge. We’ve done some planning down in Knoxville, where we had some historic elements and structures that really can’t be touched and they need to be restored. So the use of new materials has to be blended in carefully, but there’s always a lot of benefits from using more hardy materials or recycled materials. We’d encourage you to look for opportunities to incorporate those in your design.
Selecting Adaptable Plant Species
Diane Witt: (14:09)
As the climate shifts the plant material is going to shift. Iowa, around the end of the prehistoric era, went from more of a woodland state to a prairie state. Now Minnesota is looking at this same transition where they’re anticipating a loss in their forested areas. We’re seeing this transition and it is moving at a faster rate than we’ve seen historically. But I think the best way to address this is by choosing adaptable plant species, trying some of the newer species, seeing what works, again diversifying. I think the communities are on the right track with trying to increase biodiversity in their tree species. It is difficult, but I think it’s a necessary step we have to take to try to preserve tree canopy within our communities and urban areas.
Andy Meessmann: (14:54)
What we’re seeing change in the environment, I think that landscape architects have a unique perspective of living in the environments that we design. We’re constantly learning from these environments since we’re walking through them and we understand them better than most people. We really see these changes first hand when we explore urban spaces, natural settings, plant survivability, material constructability, and it’s longevity. I think we just continuously learn as landscape architects and we bring this to every single project that we work on. It’s not necessarily doing the CA (construction administration) work for our own projects, but we just see it unfold in the spaces that we enjoy, and we put that to practice on every project and each project gets better because of that.