But some weeds are pretty! Are they really that bad?
Yes, they really are. The seeds can get out into neighboring forest
lands by wind, animals, cars, and even your feet. Once there, they
can take over meadows, and ruin the habitat for native plants and
animals. Even though some weeds such as Oxeye daisies and yellow
toadflax are pretty (after all, they’re escaped from cultivation),
they’re aggressive bullies, and won’t play nicely with
our natives.
Photo credits: Irene Shonle
These pictures show the potential threat of oxeye daisy
to our native plant community. They were taken in July
of 2004 at the East Portal area - the gateway to the James Peak
Wilderness. The photo on the left shows a diverse meadow full of
native plants supporting a host of wildlife. The second photo was
taken very near the first photo, and shows where oxeye daisy has
gotten a foothold, and choked out all other vegetation - forming
a solid monoculture which does not support any wildlife. This is
what even a "pretty" weed can do to a wild, undisturbed
area. This is why it is so important not to plant these beautiful
bullies.
Beauty can BE the Beast
By Irene Shonle, Director of Colorado State University Cooperative
Extension in Gilpin County.
What would you say if your neighbor told you she was growing a
plant that was beautiful, long-blooming, drought-tolerant, deer-resistant,
and spreads very quickly? You might say, "Sounds too good to
be true." In fact, it is too good to be true. Here in Colorado,
we have a problem with many non-native "invasive ornamental"
plants which do too well in our climate, and have escaped from cultivation
and are wreaking havoc in our natural areas. Many of these are on
our State Noxious Weed List, making them illegal to sell or plant.
As gardeners, it is our responsibility to know these plants, and
avoid planting them.
Botanical barbarians displace native plants
The Brooklyn Botanical Gardens estimates that there are 300 dangerously
invasive weeds present in the continental U.S. and Canada and of
these, half were introduced as ornamentals. They were brought to
this country intentionally and allowed to gain a foothold before
their harmful effects were known.
These botanical barbarians establish themselves in soil disturbed
by construction, travel, recreation, etc. Then wildlife, livestock,
machinery, recreational vehicles, people, wind, and water transport
seeds from existing noxious weed infestations to new sites. If left
unchecked, it may become impossible to control them in the years
ahead. When they grow unchecked, they can displace native plants,
reduce biological diversity and alter ecosystem processes. These
impacts affect bird, insect, fish and mammal populations which depend
upon native plants for food, shelter, and protection from predators.
According to the Colorado Weed Management Association, of the 1,300
native species of plants in Colorado, 130 or 10% have been displaced
by non-native weeds. If we are not all vigilant, this number could
become even higher in the future.
What makes the weeds so invasive?
There are five key traits that allow them to dominate natural plant
communities: they have abundant fruit and seeds, effective dispersal
mechanisms (either by seeds or strong, creeping roots), they are
rapidly and easily established, they grow quickly, and they have
aggressive, competitive behavior. Even if they are well-behaved
in their country of origin, they arrive in this country without
any of the mechanisms that keep plants in check, such as insects,
disease, and competition.
Is it possible to plant invasive ornamentals responsibly?
Not really. As soon as the "responsible" gardener who
knows about the plants invasive characteristics is out of the picture
(moves away, gives away cuttings or transplants, goes on vacation),
the plant has the chance of becoming a problem. Often seeds can
be eaten by birds, carried by cars, dogs, or the wind and then may
be planted in new locations. Gardeners, no matter how diligent,
cannot control for natural processes, most of which rule the world
of plant invasions.
What can I do to help?
Choose native or non-invasive plants for your garden. It is usually
possible to find visually similar plants to use in place of invasives.
Do not plant invasive ornamentals. Remove any invasive ornamentals
in your garden.
Become familiar with invasive species and report their presence
on public lands to the agency.
Ask your greenhouse and/or nursery to stock more natives and fewer
invasive non-natives.
The Colorado Native Plant Society is a wonderful resource for people
wanting to use more natives in their landscaping ( they’re
good for drought, too!). They offer planting suggestions for the
Front Range, information on where to purchase native plants, and
workshops. For more information: www.conps.org.
Our worst ornamental invaders
The worst ornamental invaders across all of Colorado include: purple
loosestrife, ox-eye daisy, Russian olive, tamarisk, Bouncing Bet,
Dame’s/sweet rocket, perennial sweet pea, Dalmatian toadflax,
yellow toadflax/butter and eggs, Mediterranean sage, common tansy,
scentless chamomile, and myrtle spurge.
Of these, the ones we have to worry about in Gilpin County are:
Oxeye daisy (photo above), Dame's/sweet rocket, yellow toadflax,
Dalmation toadflax, common tansy, mystle spurge and scentless chamomile.
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Dame's rocket
Planting alternatives:
Columbines, garden phlox, Russian sage (Perovskia), bee balm
(Monarda fistulosa) Delphinium or larkspur, blue
vervain, silver lupine (Lupinus argenteus) violet
sage (Salvia x superba), Fireweed (Epilobium spp).
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Dalmation toadflax
Planting alternatives:
Annual snapdragons, Coreopsis, yellow columbine ( Aquilegia
chrysantha), Evening Primrose, (Oenothera macrocarpa'),
Golden Banner (Thermopsis spp.), Wallflower (Erysimumasperum).
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Common tansy
Planting alternatives: Golden banner (Thermopsis
spp.), Black eyed susan (Rudbeckia hirta), Golden
aster (Heterotheca villosa)
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Scentless chamomile
Planting alternatives:
Native daisies and asters (Erigeron and Aster
spp), Shasta daisy, (Rudbeckia hirta), and Blanket Flower
(Gaillardia aristata), Purple Mountain Sun Daisy (Osteospermum
barberiae v. compactum 'Purple Mountain'). |
Myrtle spurge
Planting alternatives:
Sedums. hen and chicks, sulphur flower (Eriogonum umbellatum)
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