Tuesday, January 26, 2010

So you like birds and butterflies? Better make room for Caterpillars!

When I started my project on the use of North American native annuals and biennials in Residential landscapes, I began to list some reasons for using native plants. This list included the particular benefits of annuals and other short-lived species that come with the greater emphasis on reproduction, resulting in more pollen, nectar and seeds. To be successful these are dependent on the pollinators gardens, the butterflies and bees that so many gardens wish to attract to their.

After a little more thinking and reading books like ‘Bringing Nature Home’ by Douglas Tallamy and Sara Stein’s ‘Noah’s Garden’, I began to appreciate that if you want butterflies, there must be a place for caterpillars nearby. Caterpillars are not only the source of butterflies; they are also an important source of food for birds. Insects, particularly herbivores, are a major component in the diet of nestlings.

Douglas Tallamy points out that most species of caterpillars are specialists, in that each has evolved to eat only a narrow range of plants – ones that they have co-evolved with for many thousands of years. Exotic and non-native plants ( ones that have not shared an evolutionary history) are of little use to these specialists. The bottom line is that most native insects need their own native food plants to survive.

Another aspect to nurturing pollinators is for the gardener to develop a tolerance for leaves with a few holes in them, and not to run for the pesticide at the first sign of attack by these native herbivores. In an ecologically balanced environment there are sufficient predators that will keep the caterpillars and other herbivores in check. Take a look at some websites or blogs on organic and habitat gardening approaches, such as the National Wildlife Federation (www.nwf.org/In-Your-Backyard.aspx) or http://www.ecosystemgardening.com/ , to learn more about creating a fully functional habitat garden.

Here's an example of a caterpillar infected with  parasitic wasps.

To learn which native plants support a given species of caterpillar/butterfly, check out the appendices in ‘Bringing Nature Home.’ Also the website for Butterflies and Moths of North America (www.butterfliesandmoths.org/ ) lists many facts about butterflies and moths found in North America, including their host plants for their larvae. (This site is searchable by insect’s species and state; doing the reverse, to find a list of insects feeding on a particular plant is not trivial.) The Wildflower Center’s website lists some plant-insect relationships in with their plant descriptions.

I’ve heard a little bit about putting sacrificial plants in the back of the garden to draw herbivores out of the more ornamental parts of the garden. Has anyone out there had experience with this approach?

As more native habitat is converted to human use, incorporating native plant species into the residential landscape is a step in the right direction toward supporting out native wildlife.

Wednesday, January 20, 2010

Nursery Available Native Annuals & Biennials in New England

Commercial annuals are bred and selected for such things as appearance (bloom and habit), disease resistance, consistent performance and rate of growth. In a conventional annual planting these are desirable traits, since you won’t have to weed out random plants the following year. Ability to survive in an unmanaged habitat is not an important factor for a six pack of impatiens. Many of the more spectacular annuals feature double blooms, which tend to be sterile. These produce no seed to continue the species and therefore have less wildlife value (also less pollen production). Check out ‘Bringing Nature Home’ by Douglas Tallamy for an in deeper discussion of why fully functional native plants are so important.
As I mentioned in the previous entry, to get the true species seed is the best source. However many of us lack the time, inclination or resources to locate and grow our own plants. The lists that follow contain a few plants which I have seen available in retail nurseries that are or are close to North American annual and biennial species. These lists include plants that have been horticulturally improved or breed for use in garden environments. Selection of less hybridized forms (e.g. single, rather than double flower forms) may improve chances of production of viable seed. (Unless noted there is evidence that these plants can produce viable seed and reproduce on their own in the Northeastern US - see the link to USDA Plants Database to get information of the distribution of plants growing wild in the US and Canada.)

Native to Northeast – native to New England
There aren’t many of these out there that I know of, so this is a short list.

Helianthus annuus, Annual Sunflower, had its origins in western North America but was spread across the continent by Native Americans on account of its food value. There are many highly cultivated forms available. (These are sensitive to root disturbance, but are easy from seed.)

Hibiscus moscheutos, Wild Cotton, can grow as a perennial shrub, but is also reported to grow as an annual. This is most commonly available as a cultivar or a hybrid form.

Rudbeckia hirta, Black-eyed Susan, is an annual or biennial (it dies after a season of blooming). Many fancy cultivars are available.

Native Annuals and Biennials from other parts of North American (including Mexico)
This list contains North American native annuals and biennials that have a good possibility of returning by self-seeding and are available as plants in retail nurseries.

Bidens ferulifolia, Apache Beggar Ticks, originally from the Southwest and has been cultivated into a compact freely blooming annual. I’ve seen this returning from seed in the Boston area and gave it a try this past season (2009) – we’ll see.

Cosmos bipinnatus, Garden Cosmos, had it origins in Arizona and throughout Mexico. There are a huge number of cultivars of this plant. I have seen the single-blooming forms returning from cracks in sidewalks around here (Eastern Massachusetts).

Gaillardia pulchella, Annual Blanket Flower, is another Southwestern native. In the nursery trade there are many cultivars of G. pulchella and its hybrid, G. x grandiflora (G. pulchella + C. aristata, the perennial blanket flower). I got some seed for the straight species from the Wildflower Center in Austin, TX for 2010.

Gaura lindheimeri, Lindheimer’s Beeblossum, is a short-lived perennial in the Northeast US. This plant may be too freely reseeding for many gardeners. It is a Texas-Louisiana native. Several cultivars are available in shades of pink to white.

Melampodium paludosum (actually M. divaricatum), Medallion Flower, is originally from Mexico. There are several cultivars in production. I tried this last year and was not too impressed. A report from the Missouri Botanical Garden indicates that this plant will self-seed in their climate.

Salvia farinacea, Mealycup Sage, is a perennial in its native range around Texas, but treated as a bedding annual in the north. I have had this return from seed in my garden. There are several cultivars sold ranging from near-white to deep blue.

I could include the zinnias from the Southwest US and Mexico, but many of these have undergone extensive breeding. I might consider the ‘Old Mexico’ cultivar of Mexican Zinnia (Z. haagaeana), as it is sometimes listed as an ‘Heirloom’ variety.

I would like to hear for any of you if you know of other natives in the nursery trade, as well as what is available in other regions of the country.

Monday, January 18, 2010

NOW'S the Time to Buy Seed for Native Plants

While there are a few native annuals and biennials that you can buy at a nursery, to get true natives you will most likely need to start from seed. For native plants adapted to, or tolerant of, your climate direct sowing in place, in the fall, can work; although the success rate may be low.  If you’re starting the seed indoors under lights, some special treatments may be necessary to get the seeds to germinate.

Many of the seeds you purchase off-the-rack are for annuals from warm climates, generally referred to as 'tender annuals.' When sown after the danger of frost is past these seeds will germinate when the soil warms up. Unlike seeds for tender annuals, seeds for plants native to colder climates have a mechanism that inhibits germination until they have experienced a period of cold. This can be simulated indoors using a process called stratification. Generally speaking this involves mixing the seeds with some sterile, moist (not wet) material and storing in a sealed plastic bag, in a refrigerator (33-38°F) for a given number of days (anywhere from 10-90) depending on the specific plant you are working with. For this reason, NOW is the time to make some decisions and get those native seeds so that you can have them ready for germination.

Locating seed for native plants takes some work, but use of the internet has sped up this task incredibly. Searching on the plant’s botanical name, in quotes, and ‘seed’ will narrow the field. The New England Wildflower Society has a seed sale that will start up again in Jan. 2011, which offers many native plant species, some of which are biennials. I have found many annuals and biennial seeds from Prairie Moon Nursery, based in Minnesota (http://www.prairiemoon.com/), as well as other native seed suppliers.  Most suppliers provide the germination information required in their catalogs or along with the seed.  One comprehensive source for germination information for all types of plants can be found in Tom Clothier’s Seed Germination Database, http://tomclothier.hort.net/ .

Collecting seed nearby from the wild an effective way of getting seeds for plants adapted to you local conditions. But you need to have permission from the landowners or land managers before taking anything that does not belong to you. Guidelines on seed collection for native plants have been published by the New England Wildflower Society and can be found at their website, http://www.newfs.org/ . Remember, you do not want to remove seeds from plant populations that are not robust.

For those of us who are not inclined to start from seed, in my next entry I will list a few native (or nearly so) annuals that I have found at nurseries in the Boston area.

Monday, January 11, 2010

Introduction to the use of North American native annuals and biennials

While there is a growing interest in native trees, shrubs and herbaceous perennials there are very few native annuals promoted for landscape use in native landscape designs. This focus is due in large part this is because the longer-lived species can be counted on year after year to uphold the integrity of the design. When included in a design, conventional annuals are often used as temporary accent pieces, just to add interest or fill a gap in the permanent landscape. In general, many of the annuals used in designed landscapes and home gardening are of exotic origin and have been further improved horticulturally for maximum visual affect. These plants and methods are not bad or evil; they are just a few steps away from what would be considered natural to a given area. While beautiful, these plants lack local character, certainly on a regional, if not continental scale. To the extent that they are different from the local flora, they may have lost some of their ecological value as food and shelter for wildlife in the area. In contrast, native annuals may function more as perennials. Those that are adapted to the local environment are able to reseed and return year after year. For some people, this may be a problem since the plants will move around, disrupting the design. Others would consider this as a natural phenomenon and appreciate how plants are able to find their proper niche. The ideal native annual could be considered as a plant that develops quickly with more flowers, a longer flowering cycle than perennials, and that reseeds but is not invasive. This blog will discuss many species of North American native annual and biennial plants and explore how they might be used in a residential landscape.