Imagine my surprise and dismay at coming upon a large patch of butter-and-eggs on the beach berm just north of the Endicott River. This member of the snapdragon family goes by several names besides butter-and-eggs: yellow toadflax, wild snapdragon, ramsted, flaxweed, Jacob's ladder and Linaria vulgaris.
Call it what you will, it outlives its welcome quickly by taking over and refusing to give up. This lovely, but misbehaving, character is normally seen in gardens and escapees lurk around towns and along roads. But there it was, holding its own against the cow parsnip, beach rye, beach pea, fireweed and other native shoreline plants. This was the first report of butter-and-eggs in wild areas away from human habitation in southeast Alaska. The nearest notable infestations are in Haines.
So what is the big problem? As with other invasive plants, it operates with several strategies to out compete and overwhelm its native neighbors. Take seeds, for example. A mature plant can produce 30,000 seeds each year, which are spread by wind and water. The seeds can remain viable in the soil for eight years. Its close relative, Dalmatian toadflax, may produce up to 500,000 seeds annually, and those can lie dormant for 10 years.
Another survival feature of this aggressive perennial is the deep and extensive root system. Tap roots can reach down three feet and lateral roots may be several times as long. Stems develop from special buds on these roots. Vegetative reproduction from the buds can occur as early as 2-3 weeks following germination and is possible from a piece of root as short as half an inch. Each of these buds produces its own root and stem system and becomes independent the next year.
Imagine the resulting complex maze of roots competing with native plants for water and nutrients. Imagine, also, the difficulty in removing all of those roots. In one study, a patch of butter-and-eggs increased by 418 percent in one season, and another one-acre patch spread to 85 acres in five years. If left to their own devices they will form a monoculture.
The lifespan of these plants can be up to five years, but averages 3.8. This bodes well for controlling this species. Two key factors are important for control: don't let them go to seed, and destroy seedlings arising from the seed bank before they can become established. Carefully hand pulling plants when the soil is moist will facilitate removing the most root. Seedlings have small root systems. Disruption of the mother plant stimulates new growth from root buds, so treating them when beginning to flower (usually June), when the root carbohydrate reserves are the lowest, would make it more difficult for the root system to recover.
Monitor in following months, and annually, for new sprouts or late-flowering plants, and treat those. A butter-and -eggs plant has a waxy coating which resists herbicides to some degree and some brands don't work at all. Don't expect permanent, long-term control with herbicide treatment alone. Studies have shown that areas cleared of toadflax have a very high potential for recovery, especially those in good condition. Planting competitive native grasses and forbs can help accelerate the process.
The Anchorage area has massive infestations of butter-and-eggs and efforts are underway to determine if importation of certain insects partial to this species is a viable option for control. A particular weevil observed on plants of this species over the last two years was recently identified as one of these biological control agents. Apparently, this non-native insect came into the state on this non-native plant and has already set up shop. None of the insects being considered would eradicate this invasive plant but would greatly reduce the vigor of the plants and their seed production. It will be interesting to see what happens now.
Ellen Anderson is a Forest Service botanist and can be reached at firstname.lastname@example.org.