-- Fred Breglia, Executive Director
An invasive plant can be defined as one that has the ability to thrive and spread aggressively outside its natural range, whereas a weed is any plant that grows where it’s not wanted. It is easy to differentiate one from the other. An invasive plant grows so aggressively that it literally takes over, disrupting the entire ecosystem in an area. A weed can be aggressive and invasive in a landscape yet be controlled more easily. An invasive plant can be a weed, but not all weeds are invasive plants.
All invasive plants are non-native and introduced either by accident or for their horticulture attributes. Invasive plants produce large numbers of new plants each season, tolerate many soil types and weather conditions, and grow so rapidly they displace slower growing plants. They spread efficiently and rampantly as they are free of the natural checks and balances that control them in their native range.
According to the Cornell Cooperative Extension Invasive Species Program, the top 10 invasive species in New York State are:
- Buckthorn (Rhamnus cathartica)
- Garlic Mustard (Alliaria petiolata)
- Giant Hogweed (Heracleum mantegazzianum)
- Honeysuckle (Lonicera tatarica)
- Japanese Knotweed (Fallopia japonica)
- Japanese Stilt Grass (Microstegium vimineum)
- Kudzu (Pueraria montana var. lobata)
- Mile-a Minute-Weed (Persicaria perfoliata)
- Multiflora Rose (Rosa multiflora)
- Wild Parsnip (Pastinaca sativa)
The top invasives at Landis are the buckthorn and honeysuckle, although Japanese knotweed and garlic mustard have also been found. Luckily the rest on the list have not made much of an impact here, but we always keep a watchful eye and report our findings to the Sentinel Plant Network (SPN). The SPN’s mission is to contribute to plant conservation by engaging public garden professionals, volunteers, and visitors in the detection and identification of high-consequence pests and pathogens. Go to www.publicgardens.org/content/sentinel-plant-network for more information.
Management strategies to control the invasives at Landis are mainly cutting down and digging out. Cutting the plant as close to the ground as possible can be a successful means of control when done at the correct time, yet cutting back at the wrong time can actually strengthen the plant. The best time to cut is just after its major flush of growth in spring, because the plant uses most of its stored energy from winter to send out new growth. After being cut to the ground, it will have little energy left to produce more stems and leaves. If it does sprout, it should be cut back again before it has time to photosynthesize and grow strong. Usually two cuttings will kill even the most persistent plants. As a last resort, other measures of control involve the use of toxic herbicides. This approach should be considered carefully, since many invasive plants have developed resistance to common sprays or will need several applications. This method may also kill or severely sicken desirable plants as well as the animals that need them. At Landis our first priority has always been to think of the entire ecosystem, including the wildlife and our visitors.