Gardening for You: Mistletoe is a menace
Mistletoe hanging in a doorway may be a fun way to steal a kiss during the holidays but mistletoe hanging from a living tree is another story. Mistletoe can be downright harmful to a tree if it is ignored.
Mistletoe is more than a mere menace. Left to proliferate, growth of infested trees is reduced and weakened; infested areas can become deformed and die.
Mistletoe is an evergreen hemiparasite, not wholly parasitic but as a hemiparasite partially depends on its host to live. Since it has green leaves and stems mistletoe can photosynthesize and make its own carbohydrates.
Thick, oval-shaped leaves are borne on green stems that multiply into a clump. Pale yellow flowers appear in the spring and mature into sticky, mucilaginous, pearly-white flowers in late autumn. Clumps become visible in winter months on limbs of deciduous trees after autumn leaves have fallen.
Even though mistletoe can make its own carbohydrates, it depends on the host plant for its water and mineral nutrients. Mistletoe cannot survive independent of a host plant.
Birds are the primary vector for mistletoe and because birds like to perch high on the tops of taller trees, mistletoe is usually found up high in the canopy. Birds scatter mistletoe by ingesting the seed-containing berries; seeds pass through their system and sticky seeds are excreted. Mistletoe becomes established wherever the birds have landed.
Mistletoe attaches to branches of the host tree and penetrates the bark by sending out structures called haustoria (singular, haustorium). Haustoria are the organs that absorb water and nutrients from the host tree, sometimes mistakenly called roots. While haustoria are the absorbing organs for the mistletoe plant, they are not roots.
The most effective control of mistletoe is to eliminate infested branches; simply cutting off the mistletoe plant will not eradicate the haustorium. It is necessary to remove all infested tissue. Haustoria become embedded in the branches, penetrating deep into the water conductive tissues of the host and travel downward as they absorb water and nutrients from the host. The infested tissue can be far removed from the mistletoe’s leaves and stems.
The only control is to eliminate the mistletoe by cutting back infested branches completely to the juncture of a heathy, secondary branch. Make pruning cuts just above the branch collar, the raised tissue that forms a ring around the larger secondary branch. Removing infested limbs early in establishment helps to prevent spread of mistletoe to other branches. Make every effort to remove the mistletoe before it flowers and sets seed.
After a cut has been made sterilize tools with a 10% beach solution using one part bleach to 10 parts water. The month of January is the ideal time to take care of this menace.
Ellen Peffley taught horticulture at the college level for 28 years, 25 of those at Texas Tech, during which time she developed two onion varieties. She is now the sole proprietor of From the Garden, a market garden farmette. You can email her at firstname.lastname@example.org
This article originally appeared on Lubbock Avalanche-Journal: Gardening for You: Mistletoe is a menace