Meanwhile, loosestrife was colonizing wetlands throughout the
country due to its prodigious seed production and vegetative
vigor. For decades, highly reputable nurseries were selling
lythrum cultivars, declaring them sterile and avowing they would
not contribute to the demise of our native cattails, sedges and
Lythrum is a Noxious Weed in 26 States
In the 1990s, horticultural scientists did research on the many lythrum cultivars being sold and found that they were fertile,
producing viable seed and fertile progeny. Since that time, 26
states have classified Lythrum salicaria as a noxious weed. Many
have included its hybrids in that category and five have
prohibited it altogether. In Pennsylvania, lythrum and all of
its cultivars are classified as noxious weeds.
Loosestrife crowds out native plants that wildlife utilizes for
food, nesting and cover. Many of the cattail plants muskrats
used to build their homes have been replaced by lythrum.
Waterfowl, especially ducks, avoid wetlands where it
predominates. Songbirds do not eat its seed.
Problem in Waterways
Waterways colonized with lythrum have reduced water flow due to
the plant’s dense root system and lush foliage. This process
promotes the deposition of silt, degrading water quality and
necessitating the dredging and cleaning of drainage ditches.
Shorelines clogged with it reduce access to hunters and
Lythrum is found in many traditional perennial borders and has
been a pass-along plant for generations. However, the presence
of vast purple swaths of the plant lining our waterways and
filling our wetlands should be the impetus for responsible
gardeners to dig up the plant and discard it.
The Pennsylvania Department of Agriculture recommends that
lythrum no longer be planted. It is best controlled by digging
it out and hand-pulling seedlings. If you are utilizing an
herbicide, use only those approved for aquatic areas. Before
applying any pesticide to Pennsylvania waters, a permit is
required, issued jointly by the Pennsylvania Fish and Boat
Commission and the Department of Environmental Protection.
Contact the nearest regional office of either agency for more
Some Choices other than Lythrum
Several excellent plants fill the void left behind. If you’re
growing lythrum for its spiky flowers, consider Liatris spicata
or gayfeather, Veronica longifolia ‘Pink Eveline’ or
Veronicastrum virginicum ‘Pink Glow’. The veronicastrum will
need a bit of shade, but the liatris and veronica thrive in full
Plants with similar flower color but different form include
swamp milkweed (Asclepias incarnata), Joe-pye weed (Eupatorium
purpureum) and queen-of-the-prairie (Filipendula rubra). If
you’re looking for a tall, elegant perennial, try Thalictrum
rochebrunianum ‘Lavender Mist’. It tops out at a stately 6-8
feet tall, but its foliage is delicate and airy. It looks
terrific paired with phlox, daylilies, monarda and coneflower
and it blooms for 6-8 weeks in midsummer. All of these plants
will enhance your garden and you won’t have to worry about
harboring a noxious weed.
Grapevine Soil Prep
Flowers you can eat