In 2004, when we started the Native Arboretum project, all of the woodland at the Marie Butler Leven Preserve was badly infested with invasive alien plants. In 2007, we decided to work towards a long-term goal of completely eliminating invasives from the Preserve, and we focused first on this area. (We now call it the Restored Habitat area.) As you can see, this portion of it was completely covered with English ivy (Hedera helix). (May 2004)

The English ivy had completely suppressed the native groundlayer. It was also covering many of the trees. Such infestations are unfortunately a very common sight in the forests of the DC area. (October 2003)

A clearing in our focus area was infested with Asiatic tear-thumb (Polygonum perfoliatum)—a spiny, annual invasive alien vine that grows so fast it’s sometimes called “mile-a-minute weed.” That shrub on the right is also an invasive alien species: It’s Amur honeysuckle (Lonicera maackii). Most of the shrub layer of the Preserve was composed of alien species when we started working there. (May 2004)

This is what that tear-thumb infestation looked like every August, after about five months of growth. The Amur honeysuckle is completely covered, as is the dead snag farther back. (August 2004)

Looking into the focus area from the main lawn. In the middle of the picture, there is a thick curtain of a woody vine called porcelainberry (Ampelopsis brevipedunculata) on a Norway spruce (Picea abies). Like other invasive alien vines, porcelainberry can overwhelm the trees that it climbs, making them more susceptible to wind-throw. The Norway spruce is also alien, of course, but it’s very well behaved. It’s not invasive. (October 2003)

In partnership with a group of volunteers from HSBC Finance Corporation, we started work in the area in April 2007. We focused first on cutting the English ivy and porcelainberry off the trees, and began clearing the ivy out of the ground layer. (April 2007)

Clearing the ivy was hard work. We pulled out all of the top growth and as much of the root mass as we could readily remove, then covered the exposed soil with burlap to prevent the slope from eroding. The burlap also helped suppress resprouting ivy. (April 2007)

Removing an infestation this large creates major logistical challenges: You have to manage the exposed soil to prevent erosion and drying—and you have to figure out what to do with all the ivy! Our solution was to “stockpile” it for a couple of months outside the work area, where it could dry and lose its leaves. That made it a great deal lighter. In later slides, you’ll see what we did with it afterwards. (April 2007)

The end of our first day of work. The burlap-covered area is all that we managed to clear on that first day, despite the efforts of about a dozen people. The boxes that Matt is carrying out contain “bio-stakes,” biodegradable fasteners made from corn. We use them to anchor the burlap. (April 2007)

Another view of that first day’s work. We dropped some branches on the burlap to help keep it in place. (April 2007)

We learned two important things on that first day. 1: Eliminating the invasives was definitely feasible, but 2: We would need to step up our work schedule considerably in order to do it. So we hired several summer interns—a couple of whom were already seasoned volunteers—and they really went at it. (June 2007)

As the ivy gave way, the burlap extended farther and farther into the forest. We cut holes in the burlap to accommodate native saplings, like that little American holly (Ilex opaca). (June 2007)

The burlap was eventually covered with four to six inches of wood-chip mulch, visible here around the tarp. We got “mulch support” for our project from Fairfax County—by the dumptruck load! The mulch provided further insurance against erosion, further suppression of the ivy, and encouraged fungal growth. (Fungus is a critical component of healthy forest soils.) Here volunteer Kerry Lyon and Sangha board member Margaret Garigan collect a tarp-load of ivy, which they will drag out of the woods. (July 2007)

A month or so after they had started, our interns were clearly achieving a very high level of control. More and more ivy was disappearing, along with a host of other invasive alien species in and around it. (June 2007)

Sometimes, as here, the invasives were left in place on a steep slope, until the areas above and below were cleared and stabilized. Erosion control was a constant concern—we didn’t want to lose a speck of soil if we could help it. (June 2007)

A lunch break. The Preserve may be degraded woodland but it is a very pleasant work environment. (June 2007)

By the beginning of July 2007, something like the character of native forest had begun to emerge. The entire area in this picture was infested at the start of the project—and is now completely cleared. (July 2007)

A view into the restored area from the east, at about the same time as the previous picture. The area where the burlap is still exposed has quite a few native saplings. Most of the area had almost none. (July 2007)

A view of the area from near the top of the trail. All of the branches on the mulch layer were placed there by our interns, partly for erosion control, and partly to create habitat for creatures that dwell on the forest floor. (July 2007)

Harry Glasgow, a member of the Fairfax County Park Authority Board of Directors and the Chair of the County’s Tree Commission, visits the site. The pine stakes on the slope are helping to hold our erosion check logs in place. (July 2007)

Volunteers congregate for the first planting of the Restored Habitat area. Here, Chris Bright, the Sangha’s President, explains basic planting procedures. (November 2007)

The objectives of the first planting were to begin reestablishing the native groundcover and to enrich the understory. Healthy forests usually have a “bank” of saplings in their understory; some will never become big trees but others will shoot up into the canopy when a big tree dies and more light becomes available. (November 2007)

This first planting was fairly loose. We didn’t want to pack too many plants into the understory, at least at this point, because the ground layer will need a lot of attention for several years and we must have ready access to it. (Resprouting ivy will have to be weeded out, native herbs reestablished, and any erosion checked.) (November 2007)

A view of the densest part of the first planting on completion. This was the area infested with tear-thumb, shown previously. It is planted more densely because it’s a clearing—it had no tree canopy. The Preserve is heavily browsed by deer so many of the tree seedlings are protected with little wire cages. (November 2007)

In support of our project, the Fairfax County Park Authority funded some professional invasives-control in areas of the Preserve of our choosing. These are field technicians from a company called, appropriately enough, “Invasive Plant Control.” These guys really knew what they were doing. (January 2008)

The IPC crew worked with little chain saws and herbicide, which they applied directly to freshly cut stumps. At our request, IPC suppressed the invasives in an area adjoining our Restored Habitat. This will make it much easier for us to expand the restored area. If the use of herbicide makes you feel a little uneasy, we sympathize! But in this case, there’s no reason to worry. This application posed virtually no risk to either native plants, animals, or people; the herbicide was applied in this area on a one-time-only basis, and only to freshly cut wood. (We do not use herbicide ourselves—we’re not even authorized to apply it.) (January 2008)

All that invasives removal produced huge piles of “slash,” which we dragged out of the woods and deposited nearby. This was far too much debris just to leave, so we had to collect it in dumpsters that the Park Authority brought in for us. Here, a group of volunteers loads a tarp with slash. (November 2007)

A loaded tarp is hauled over to the parking lot. (November 2007)

The slash is deposited in a dumpster. (November 2007)

The dumpster is finally full! The man in the green jacket is Alan Ford, our Park Authority IMA (Invasives Management Area) leader for the Preserve. In addition to his weeding abilities, Alan is an extremely proficient dumpster-packer. It was amazing how much material he managed to jam into that thing. (November 2007)

The Habitat Restoration project has become a year-round affair. In the winter of 2007-08, we pushed southwards, towards the area treated by the IPC crew. (March 2008)

A view of the winter work area from the south. This photo was taken from the area treated by the IPC crew. (March 2008)

As a further precaution against erosion, we installed this barrier along the lawn edge of the Restored Habitat area. The logs come from white mulberry (Morus alba) and black locust (Robinia pseudoacacia) cut from another portion of the Preserve. The dark material is mulch, dropped on the upslope side of the logs. White mulberry is an invasive alien species that we are removing from the Preserve. Black locust is also somewhat invasive; it is native to North America, but probably not to the mid-Atlantic region. We do not plan to eliminate it from the Preserve but we do need to reduce its density somewhat. The green “cages” in the background protect our witch-hazel planting from the deer. (March 2008)