Aggressive Native Plants Have Their Place

Aggressive plants are generally not popular. Many a curse has been spoken against them as a gardener has attempted to rein them in. Others folks simply declare them to be a “WEED” and tackle them with weed forks, shovels and chemicals. I’m here to say that aggressive native plants have a role to play in their local environments. Understanding them is key to deciding how they might fit into your space.

Trumpet creeper, Campsis radicans

While it might seem like these plants move in and take over the average garden space, there are specific benefits that they offer which can be considered: soil retention, support for pollinators, and food for songbirds and many other critters.

Soil Retention and Erosion control

Many of the aggressive woody plants can be found streamside. Their purpose is to create an extensive root system, usually by suckering, in order to hold the banks of a stream in place.

Hazel alder (Alnus serrulata)

These plants include hazel alder (Alnus serrulata), elderberry (Sambucus nigra ssp. canadensis), Virginia sweetspire (Itea virginica), yellowroot (Xanthorhiza simplicissima) plus many rushes (Juncus) and other perennials with thick roots. Invite any of these folks into a garden with rich soil and good moisture and you will have plenty to go around.

Many of the aggressive herbaceous plants (annuals, perennials, grasses) are early succession plants. Their purpose is to cover bare soil to hold it in place until woody seedlings can arrive.

Small's ragwort (Packera anonyma)

This is where you'll find many annuals like fleabane (Erigeron annuus) and ragweed (yes, it's native!), and aggressive perennials like asters (Symphyotrichum), yellow ragwort (Packera anonyma), violets (Viola), primrose (Oenothera), some goldenrod (Solidago), and grasses like broomsedge (Andropogon virginicus).

Weedy woody plants that move in later include pines (Pinus), sweetgum (Liquidambar styraciflua), maples (Acer rubrum for example), boxelder (Acer negundo), and black locust (Robinia pseudoacacia). These early colonizers can handle poor soil and, in some cases, such as the locust, even help to improve the soil.

Beautiful and fragrant Robinia pseudoacacia

Support for Pollinators

Doesn't that look like a feast?
Viburnum nudum var. cassinoides

Pollinators need a lot of flowers to get what they need. From the tubular flowers that support hummingbirds (Coral honeysuckle, Lonicera sempervirens, and Trumpet creeper, Campsis radicans) to the nectar-rich flowers that support bees, wasps, beetles and flies, our landscapes are not what they were 300 years ago. So much land has been reshaped to be subdivisions, businesses, roads, paved surfaces, and millions of acres of non-native grass (lawns).

Fleabane (Erigeron annuus)

 The roadsides, on the other hand, are full of the flowers these pollinators need - ragwort and fleabane are both blooming now. Later in the year the rambunctious Canada goldenrod (Solidago canadensis) and the asters (Symphyotrichum) will be there while virgin's bower (Clematis virginiana) scrambles over every shrub and fence. Their numerous and dense flowers provide much food.

Food for Songbirds and others

Numerous flowers often make for numerous fruits/seeds, a trait that is relished by many small creatures such as songbirds. Seed heads on plants like dog fennel (Eupatorium capillifolium), asters, maples, sweetgum, pines, sedges and grasses help determine how many birds can live in a certain area. I've seen birds peck at the dried legume pods on redbud (Cercis canadensis), a prodigious producer of pods in some years.

A spring flowering sedge (Carex)
is making seeds now

Tiny, numerous fruits on plants like black cherry (Prunus serotina) and elderberry might seem excessive to us, but they help support the birds we love long after their flowers supported pollinators.

Fruits that fall to the ground are gathered by small mammals like field mice - which then become food for hawks and owls.

Different plants have fruits/seeds throughout the year, allowing the birds and small mammals to find food as they need it. Nature takes care of the scheduling!

In the last few years people have become more aware of how native plant foliage supports birds by way of the insects that develop on the leaves. Most of the birds you don't see at your feeders are looking for insects to eat. They often find them as caterpillars on plant leaves. The black cherry that so many people criticize as a weed tree supports over 450 different species of Lepidoptera as a host plant. How many insects there are available to birds contributes to how many birds can live in an area.

Plant Virginia creeper for the birds
and enjoy the fall color too.

As you can see, many plants support birds two ways - by way of their fruits and also by the insects that feed on their leaves. Five-leaved Virginia creeper (Parthenocissus quinquefolia), often mistaken for poison ivy, has flowers for pollinators, tasty berries for birds and supports caterpillars of the sphinx moth (several species).

You can minimize plant aggressiveness using traditional gardening techniques. For aggressive seeders, deadhead some of the flowers before they go to seed. Mulch the areas around them to reduce the number of seeds that sprout. Pull up seedlings early when they are easier to dislodge.

For plants that sucker, site the plant appropriately either by only planting it where it can be allowed to sucker or by doing what you can to avoid root disturbance (some plants sucker more aggressively when their roots are disturbed by digging around them).

So if aggressive plants invade your space, think about what they can do for you before you tackle them. They might be just the ticket ....

Heggie's Rock - Natural Pools of Wonder

Several months ago I wrote about some of the plants found at a small rock outcrop area. Earlier this month I had a chance to visit a very large granite outcrop in Georgia and explore some of the special plants there - in the company of a knowledgeable trip leader and fellow members of the Georgia Botanical Society.

Heggie’s Rock is a 130 acre outcrop in Columbia County, about 20 miles from Augusta, GA. The Nature Conservancy has created a Preserve that encompasses about 101 acres of that outcrop. Heggie’s Rock was designated a National Natural Landmark in 1980, one of only 10 such designations in Georgia.

The foreground shows the red leaves of Diamorpha smallii;
what a beautiful and totally natural scene.

According to the TNC website:  “The preserve is near Little Kiokee Creek which joins the Savannah River about eight miles downstream from the preserve. While the preserve includes a perimeter forest of oaks, pines and hickories, it is the granite outcrop, Heggie’s Rock, which dominates. It is here you see exposed granite, lichen and moss covered rock, soil islands and the beautiful vernal pools, or dish gardens, which support rare and unusual plants, and capture the imagination.”

With so many flowers and leaves in the picture it was hard to
get good focus, but here you can see the tiny white flowers
that top those bright red leaves (Diamorpha smallii).

Heggie’s Rock is named for Archibald Heggie, a Scot who acquired the property around 1808 through his wife, Martha Ramsey, whose grandfather built a grist mill on nearby Little Kiokee Creek. In 1983 The Nature Conservancy purchased it from Robert Pollard, a lumber company executive who had bought the land in 1981 to protect it from quarrying. It had been owned by two quarry companies since the 1950’s but thankfully never quarried.

As I said in my earlier post, special environments like these contain populations of very special plants, some of which don't grow in any other environment. It was early in the year when I wrote that other post, so now I can share some pictures of those same plants in

Tradescantia hirsuticaulis

bloom.

This is hairy spiderwort (Tradescantia hirsuticaulis), a much better behaved relative of the usual garden thug, the smooth spiderwort (Tradescantia ohiensis). But then maybe growing on a rock would be limiting factor!

Diamorpha smallii

Elf orpine (Diamorpha smallii) is a showy plant but it is an annual plant - it grows anew from seed every year. 

Piedmont sandwort (Minuartia uniflora) with Diamorpha

Another annual plant is Piedmont sandwort (Minuartia uniflora). We found it mixed in with still other annual plants such as bluets (Houstonia sp.), dwarf dandelion (Krigia virginica), and, as shown here, with the Diamorpha. With the thin soil pockets on outcrops, it's not hard to imagine that shallow-rooted annual plants might be very well suited indeed.

The vistas were incredible. It's hard to represent what it looked like - how incredibly talented Mother Nature is when it comes to her own designs.

Here a variety of mosses, lichens, and grasses swirl and mingle with the red Diamorpha

Moss, lichens and Diamorpha with a natural stream

You might think a granite outcrop presents a harsh environment for plants. We were given a list of plants found on the preserve that was over 20 pages long! There are two pages of lichens alone. Of course only a few of those plants live ON the rock, but there was obviously plenty of places for more deep-rooted ones.

It was fun to find some of the plants we are very familiar with, somehow making it work in pockets of favorable growing conditions here and there. As we finished up our loop trail back to the entrance, we spied this blooming plum (Prunus sp.).

All in all it was a great trip to help us learn about and appreciate one of the many different natural environments in Georgia.


If you’d like to visit Heggie’s Rock, The Nature Conservancy does offer scheduled tours. Please click here to see the scheduled trips.

Violets Are Blue Too

Yes, violets are blue but they are also purple and white and even yellow. Scorned by many as a weed, the common lawn violet (Viola sororia) has brightened many a small child’s day with its colorful flowers that are so easy to pick. Approximately 24 different species of Viola are native to Georgia with a great many more natural hybrids and color forms. These little plants flourish in all environments from sun to full shade and from dry prairie to wetlands.

The long spur violet, Viola rostrata

Much of the scorn for violets comes from their ability to reproduce in high numbers. If you have planted pansies (bred from Viola tricolor, a non-native violet), you may be familiar with the seed capsules that form. For the weedier forms, that is not the whole reproductive story. Species like V. sororia, the common violet, also have cleistogamous flowers. Those flowers are located at the base of the plant, they do not have petals and they never open so they are self-pollinated (and they reproduce exact copies of the parent). 

Violets are host plants for several butterflies, primarily for species in the Greater Fritillary group, but they are also used by some species in the Lesser Fritillary group (which also feed on passionflower).  I found an interesting tidbit in an article on the North American Butterfly Association page. The article says that eggs on not laid on the plant itself, but rather on nearby debris like dead leaves. In addition, the caterpillar feeds at night and hides in the debris during the day rather than stay on the host plant. Another good reason not to clean up dead leaves!

Viola tripartita

I have come across more violets than I would have imagined in my plant wanderings – until I took the time to identify them and count them up. I found 3 different species on a trip to The Pocket of Pigeon Mountain one spring: Viola canadensis (Canadian white violet), Viola rostrata (long spur violet, found in both blue and white forms), and Viola tripartita (a yellow violet whose name is meant to describe the variation in leaves).

Canadian violet, Viola canadensis

Common violet, Viola sororia

Around the neighborhood I have seen both common lawn violets: Viola sororia and Viola bicolor (an annual species known as field pansy and a welcome early spring flower).  

I have also found in my wooded areas a deep purple Viola rostrata and the silvery-leaved Viola hirsutula (Southern woodland violet).  

Viola bicolor on left; Viola hirsutula on right (click to enlarge)

Viola x primulifolia

A white violet that I found in just one area of my yard appears to be known as a natural hybrid: Viola x primulifolia. I have less of it this year perhaps due to crowding by some of the plants I have added to the area. The seeds probably came in with something else.

 

The woodland Viola hastata

The large flowered Viola pedata

On plant rescues in my area we often find the yellow Viola hastata (halberd-leaf violet) in the woods. It’s a cheery sight in the shade. Sometimes we have found Viola pedata (birdfoot violet) in sunny areas with poor soil. 

In my opinion it is one of the most beautiful ones – large flowers are complimented by very attractive foliage. It thrives on poor soil and some gardeners have killed it with too much love (rich soil).

Recently I was on a field trip near Augusta and had a chance to discover a Coastal Plain violet, Viola lanceolata (lance leaved bog violet), in the moist conditions of a Carolina bay. It was happily growing and blooming in both standing water conditions and drier areas nearby.

Quite a variation in color forms exist among the violets, especially the blue ones. I have seen white forms of several of the species noted for being blue; V. bicolor has a large variation on a regular basis probably due to good cross-pollination.

"Confederate" violet variation of V. sororia

The one variation that seems to get the most attention is a blotched form of the common violet, V. sororia.  Sometimes listed as Viola sororia priceana (a name which does not follow binomial convention) or Viola sororia f. priceana or it is known by the common name “Confederate violet”. It is basically just a color variation that can be fairly widespread once it appears (probably thanks to those cleistogamous flowers).

Ok so that is ten different ones for me – I’ve certainly got quite a few more to find. Next time you see one of the many, many violets, I hope you will think kindly of it and smile.