As part of my continuing education for my landscape architect license, I took a course on invasive plant species. These species are plants that are usually introduced by man, overtake a habitat, and then force out native plants. The course pointed out that $1.4 trillion dollars have been spent globally to eradicate invasive plants.
Invasive plants can be sneaky. They work fine for what they were intended for, and then suddenly jump over the garden wall and take over the landscape, especially if there isn’t already healthy competition among native species already in place. Once the invasive species has dominated a habitat, the removal of the invasive species and the restoration of a degraded habitat can require very costly measures.
Control and Prevention
The course made the following suggestions for control and prevention:
1.) Using site-appropriate plant species, i.e. the right plant for the right location.
2.) Create and maintain invasive-resistant plant communities by minimizing bare ground, and encouraging high-diversity plant communities. For example, if you look at our front North Main entry annual bed, there are few, if any weeds there. Why? Because the different types of annuals, although not native, are filling in every possible growing space. Come winter, it is a different story. We battle against chickweed, because the pansies do not fill in the entire space.
The course also mentioned that those of us in the business of suggesting plants on a project have an obligation to identify the pests, set action thresholds, prevent the establishment of new invasive species, control invasive species, monitor and follow-up.
Plant Threat Levels
The North Carolina Plant Society has a list of plants that are ranked according to their threat level. I will list the ones I have noticed on campus recently and in the past:
Rank 1 Severe Threat: Exotic plant species that have invasive characteristics and spread readily into native plant communities, displacing native vegetation.
Ailanthus julbrissin (Mimosa)
Elaeagnus angustifolia (Russian olive)
Hedra helix (English ivy)
Ligustrum sinense (Chinese privette)
Lonicera fragrantissima (fragrant honeysuckle)
Microstegium vimineum (Japanese stilt grass)
Pyrus calleryana (Bradford pear)
Pueraria Montana (Kudzu)
Wisteria sinensis (Chinese wisteria)
Rank 2 Significant Threat: Exotic plant species that display some invasive characteristics, but do not appear to present as great a threat to native communities in North Carolina as the species in Rank 1.
We have the following on campus:
Nandina domestica (Nandina)
Stellaria media (Common chickweed)
Vinca major (Bigleaf periwinkle)
Vinca minior (Common periwinkle)
Rank 3 Lesser Threat: Exotic plant species that spread into or around disturbed areas, and are presently considered a low threat to native plant communities in North Carolina.
On Springmoor’s campus we have:
Buddleia davidii (Butterfly bush)
Lirope muscari (Liriope)
Lysmachia nummularia (Moneywort)
Watch List A: Exotic plants that naturalize and may become a problem in the future; includes species that are, or could become widespread in North Carolina. At this time, more information is needed.
On our campus:
Hibiscus syriacus (Rose of Sharon)
Ilex cornuta (Burford holly)
Watch List B: Exotic plants species that cause problems in neighboring states but have not yet been reported to cause problems in North Carolina.
Springmoor has none in this category.
As you can see quite a few plants bear attention and cause a lot of damage to our natives. Two acres of my property at home have a few of these unwanted guests. In some cases I have had to resort to herbicides to get a handle on them. I plan to shade them out and out compete them in the future with natives.
August Focal Points at Springmoor
Lagerstoemia sp (Crape Myrtles) continue to bloom and provide color to our campus.
Hibiscus syriacus (Rose of Sharon) is another small tree that blooms this time of year.
Abelia grandiflora Kaleidescope (kaleidoscope abelia) continue to bloom until frost.
Buddelia davidii (Butterfly bush) are six foot tall shrubs with large flowering panicles that add color to any garden at this time of year.
August Things to Do
Remove all spent vegetables by mid-August and plant cool season crops such as collards, carrots, cabbage, cauliflower, broccoli, and brussel sprouts. Be sure to watch for the white cabbage butterfly, apply Sevin Dust to combat the worms, or use bird netting over the crops to prevent the butterfly from laying eggs on your fall crops.
Now is the last time to fertilize your trees, and shrubs with 10 10 10, or 8 8 8.
You do not want to promote new leaf growth much further or it will be damaged by the frost.