Doug Tallamy answers your questions

Don't try this at home! Above: Tallamy in the field with graduate student Chris Phillips as they collect insects (using a modified leaf blower fitted with a nylon mesh bag) to study the effects of native plants and non-native plants. Photo courtesy the University of Delaware UDaily.

Last week I posted on Doug Tallamy’s book, Bringing Nature Home (and Susan posted here). Many readers had comments on native plant-related issues, so I emailed Tallamy a few questions that seemed most representative of our discussion. Here are my questions (in ital) and his responses:

Many gardeners are very open to planting more natives, but want to keep things mixed up, with exotics, annuals, and "alien" perennials as well. For example, I have canna, musa, palms, and oriental lilies as well as rudbeckia, viburnum, and erythronium in my urban courtyard garden. Is the ultimate goal a 100% native plant garden?

I am not a purist and I don't expect many other people will be either. I think taking the hard line and insisting on all natives will go a long way toward killing the movement. I wrote the book so people could understand the consequences of gardening with aliens. Every time we use an alien plant when we could have used a native, biodiversity is lost. It is up to the individual gardener to decide how to deal with this trade-off. I am learning some things that make the "should I or shouldn't I" decision easier. The most important is that woody plants support much more biodiversity (in general) than herbaceous perennials and annuals. In our ranking or plants that support Lepidoptera (bird food), for example, oaks are number one among woodies, and seve as a host plant for 534 species of moths and butterfles just in the mid-Atlantic region.

The number one herbaceous genus is Solidago, the goldenrods, but they only support 115 species. That is still a lot of biodiversity, but it is nearly five times less than oaks.

Most herbaceous species support less than 20 species. So, being creative with alien herbaceous plants is less harmful than using woody aliens.

The purpose of my book is to explain why your garden has an important ecological function today that it didn't used to have. That does not mean that it cannot simultaneously be an outlet for artistic creativity. Increasing the percentage of natives in your garden is a good goal to start with and should generate feelings of accomplishment rather than guilt.

Fifteen-feet-wide is a lot of space. What can urban gardeners with small gardens do?

Small gardens are a bigger challenge than large ones because of the space constraint. But even tiny properties usually have space for one or more canopy trees. Adding those trees will make a huge difference in the neighborhood, particularly if you can get your neighbors to do the same. Small gardens can make other important contributions. This past summer friends of mine installed a garden in a courtyard behind the Department of Ag building in the center of Dover, Delaware. The entire garden was not more than 10'X10' and was surrounded by cement and buildings. The garden was designed to provide plants for native bees, but three species of milkweeds were included in the mix of flowering plants. Here's the exciting part. In the first year, that tiny garden produced 250 monarch butterflies ( from egg to adult)! In my own yard I have one square foot of pussy toes, the host plant for the American lady butterfly. That foot of my yard produced at least three American ladies this summer. Of, course, the more habitat and food that is created, the better, so if people with tiny gardens can convert their neighbors with tiny gardens, the gardens are no longer as tiny and their effectiveness in supporting life will increase.

What about deer? Leaving aside the fact they eat anything, attracting them with native plantings leads to road hazards and accidents, not just ruined gardens.

I live in an area of the East in which there are more than 80 deer per square mile so I understand the issue well. We created the deer problem by eliminating predators and fragmenting the eastern deciduous forest to the point where it is just about all edge-habitat: perfect for deer. It's true that we could reduce the deer problem by removing all native plants in our neighborhoods, but that approach just creates other serious problems. There is only one real solution to too many deer, and that is to reduce deer populations. Don't groan! We had no trouble shooting all but a handful of the millions of buffalo that once roamed the plains, so we can control deer as well if we decide it is important enough.

Hiring sharpshooters for your neighborhood has been proven to be safe and effective (though costly) time and again. Deer will not voluntarily leave suburbia until we pave it over entirely, and I doubt if anyone sees that as an acceptable solution.

I think most of us agree completely about the tragedy of America's cult of the lawn. But how to convince landscapers, city inspectors, and suburban neighbors who consider everything a weed that's not tightly mowed? Many people who grow native wildflowers in their front yards run every risk of being harassed.

I have started a new book that will deal with this issue in depth, but I can say a few things here about what drives our landscaping paradigm. We often landscape the way we do so that we will be accepted or, even better, admired by our neighbors. We seek acceptance, approval, and, yes, status in everything we do, and for the past 200 years the ability to have a large manicured lawn sparsely planted with specimen trees was a signal that we had free time and lots of money. Today, anything else is interpreted to mean that you don't care about the values imposed on you by your neighbors. But we change what we consider to be desirable or valuable all the time.

It was once a sign of status to smoke. Now we know better. Last year it was a sign of status to drive an SUV. Knowledge and peer pressure is changing that status symbol too and soon SUV owners will be ridiculed for heating up our planet. It is becoming more socially admirable to drive a Prius or ride a bike instead.

In the past having native plants in your yard meant you had abandoned all efforts to beat back nature. It was a sign of the absence of landscaping, rather than progressive landscaping. But that will change as more and more people install artfully designed landcapes with smaller lawns, more woody plants, and a higher percentage of natives.

These folks will be the trendsetters. Choosing acres of manicured lawn over high-end native gardens will become the socially unacceptable option in the future. It won't happen overnight. But the timing is right; both the biodiversity crisis and the climate crisis are pointing us away from lawns.

Comments

[tai haku]

Excellent responses from Doug to all the questions - a veyr balanced, common sense approach to some difficult issues. I'm really tempted to get this book even though I'm not in North America - is it very continent specific or is there more of a universal principles thing going on?

[eliz]

I think the principles may be universal but I would guess the species he is talking about are largely indigenous to NA. There is a lot of bug-specific info--that is his specialty, actually, more than plants. That's why I like the book as I know very little about the bugs that surround me.

[Michele Owens]

Obviously, I need to buy Doug Tallamy's book. I have fields of native flowers in the country--I love the goldenrod in the fall. But in the city, I'm increasingly interested in edible landscaping. Why give up space for an Asian rhododendron when you could plant a paw-paw? Does Tallamy recommend any fruit or nut bushes or tress?

[Common Weeder]

I think Tallamy made two especially important points for homeowners. First that we don't need to be purists - and second that woodies are the the most valuable natives. Thanks for having him answer these questions.

[Marte]

Yes, thanks for this valuable posting.

[firefly]

Great post. Interesting take on plant priorities, woodies versus perennials -- I don't think I've heard that anywhere else. It makes me very glad I started the garden beds with native shrubs and small trees.

I can't wait to read the book.

[eliz]

There are quite a number of fruit/nut trees discussed, Michele.

I wish I wasn't so surrounded by alien woodies I can't replace, but at least now I know what to do if something happens. Up until now, most of the talk I've heard on tree replacement is centered on hardiness, disease resistence and so on, not on providing habitat for not just birds, but also bird food.

[Pam/Digging]

Great interview.

[Joan Carroll, Master Gardener UCRiverside, CA]

I grow things that I like in my small garden surrounding my mobilehome in a Sr. park. I have roses, Jerusalem Sage, Michaelmas
daisies, Tacoma Stans, sweet potatoes, Butterfly weed (hatched 8 Monarch's this year), have
succulents, limited amount of cactus in pots, a Zutano Avocado
tree, various citrus trees and a very young mango tree grown from
a seed from a neighbor's tree.
Our KOI pond is surrounded with
tropical plants that may freeze this winter. We can go down to 27F during a hard winter here and up to l25F during a very hot summer. We have plenty of native creosote bushes, cholla, beavertail cactus surrounding the
Park property.
I understand diversity and growing trees to clean the air,
give shade, etc. but there is only so much I can do here. Our lot is
Zero lot garden here.
I'm in the county near Desert Hot
Springs and above Palm Springs.
Grandma Joan

[susan harris]

I appreciate Tallamy's emphasis on wildlife and am totally on board with using my land in a way that's beneficial to them. I just don't buy that growing so-called aliens is inherently harmful, as Tallamy argues it is. Alloting a few square feet to a plant like super-sustainable and always-covered-with-bees sedums is harmful? Compared to what? Unlike most Americans, who contribute bupkis to wildlife or biodiversity, most avid gardeners FILL their gardens with a wide variety of plants from a wide variety of places. And often it's the joy of "getting creative" that motivates us to do all that. And let's not forget what our gardening does to heal the soil, clean the air, soak up stormwater, and make us more committed to nature with every stab of our trowel.

[chuck b.]

This is a big topic that deserves complex, ongoing treatment. I hope you'll keep coming back to it.

I want to throw in a couple things:

Biodiversity can be talked about in least two different ways: species richness and species evenness. This has to do with relative abundance of different species.

The following two communities are equally biodiverse (same number of different species); the first one has higher species richness, and the second has higher species evenness.

1. There are 100 trees. 90 of them are blue oaks, 10 of them are black oaks.

2. There are 100 trees. 50 of them are blue oaks, 50 of them are black oaks.

Which one would you pick to preserve biodiversity? Which one more closely resembles Susan's hypothetical perennial bed?

Many would consider group 2 to be more valuable in terms of biodiversity because the population of black oaks in Group 2 has five times as much genetic diversity as the population in Group 1, while still having ample diversity of blue oak.

This relative abundance of oak biodiversity runs through the ecological interrelationships these trees have with the insects and birds who use them.

The garden planted with an array of aliens increases species richness, but it won't budge evenness.

***

I garden with a lot of California native plants. Out here, in the trade, there are many popular native plant cultivars. (That might not be the case in the east coast scene--I don't know) But cultivars are all asexually reproduced clones. Propagating clones doesn't do much for genetic diversity either. So I would encourage people to, whenever possible, get excited about using native plants grown from seed.

***

I also want to say Tallamy overdoes it with the tree-love. It may be fine to go native tree crazy on the east coast which grew out of huge expanses of woodland forest. But if you garden in Texas or Florida or California or mid-western prairie grassland or any other environment that would have something else going on besides forest, please be aware that planting your native trees might not be the best plan for preserving biodiversity (in your local if that becomes a gardening goal).

It's all very local.

[Gloria]

Great interview! I will be getting Tallamy's book soon.
I understand the woody plants bringing in more diversity in wildlife species. Oaks in particular but most trees and shrubs.Size, number of blooms and leaf surface are going to be greater than what may be provided by a hand full of herbacious plants and some trees will then provide bark to hide under for over wintering insects. Berries and seeds (like acorns or maple wings)feed many mammals as well as birds.
Evergreens provide cover from storms and predators. It is a very complex system.
It is not bad to have the nectar feeding the more generalist bees that can forage most pollen. But what about the leaf cutter bees and the early mason bees or bumble bees that will be moving about during much cooler harsher weather.
Some bees have long tongues to help get at nectar deeper in blooms than short tongued bees are able to access.
Some native bees live as adults for only a few short weeks. There must be blooms available during that space of time or the bees can not provide for young which will have to live off of what the adults were able to collect in such a short life time.

I am reading a book 'A Natural History Of The Chicago Region' by Joel Greenberg 2002 University of Chicago
Every region has books about its soil , climate,flora and fauna. It makes for fascinating reading.

[Bob Vaiden]

Planting native forbs is VERY important...much of the native tree cover still exists (but not everywhere), but the forbs\herbs have been virtually obliterated. Most roadsides are just short of entirely alien. In Illinois, only the most aggressive milkweed and goldenrod species (1 each) are common.

Illinois oak groves are often composed entirely of oaks and european grass...they LOOK like they did 200 years ago...but they're not.

My own yard is an Oak grove\ prairie mix (with no oaks, ironically:)

Even so, although I have a mostly native yard, I have a fair number of European bulbs and flowers... I restrict them to certain areas.

One problem is folks who move next to parks and forests, and plant aggressive nursery material. Many such plants move right into the parks, and there goes another stand of wildflowers. Even some varieties of Butterfly Bush shows signs of being a problem.

[Michelle Derviss]

In the words of Rodney King,
'can't we all just get along in the horticultural world?'

What, are we right wing horticulturists now ?
" All you alien plants go back where you came from and take your nutritional values with you."

sheesh.
aliens indeed.
what's next, horticultural immigration rights ?

[Brent]

I enjoyed reading this interview and agreed with most of the opinions and philosophy, but I have to take exception to this sentence:

"Every time we use an alien plant when we could have used a native, biodiversity is lost"

Most of the potted native plants that I purchase are reproduced from cuttings and are therefore genetically identical. Is it really all that biodiverse to have 10 Salvia clevelandii x pachyphylla "Celestial Blue" planted in my garden?

[Nancy Bee]

Check out this website
http://www.bugs.group.shef.ac.uk/BUGS1/bugs1-index.html

They related insect biodiversity to various aspects of garden structure. Results are on the website and also in a book, published in the UK and hard to find in the US.

The take home message that I remember (a year after reading the book) is that adding dead wood, compost piles, nesting blocks for solitary bees and a water body increased biodiversity.