Jenni Carr-Extension Agent
‘Pampered’ Plants Risk Salt Poisoning
Do you have “pampered” houseplants that you are tending over the winter months? Have you wondered if they need fertilizer and how much? Well here is some information from K-State Research and Extension horticulturist Ward Upham.
When fertilizer dissolves in water, it becomes a soluble salt. That can be a good-bad thing, particularly for houseplants.
“Roots can only absorb liquid meals,” explained Ward Upham. “If they receive more food than the plant needs, the leftovers simply remain in the soil.”
The water in left-over fertilizer soon evaporates, however, leaving salt behind. That’s why overfeeding can lead to a salt buildup that damages or kills plants, Upham warned. Houseplants are most at risk. They spend months or even years enclosed in the same soil and pot.
Salt damage can include wilting, scorched leaves, dropped leaves, reduced growth and dead root tips. Salt also can form a yellow-white crust on top of the soil or on the pot itself.
Upham recommends houseplant owners take these steps to head off such results:
1. Don’t fertilize when outdoor plants are dormant. (Indoor plants respond to seasonal light changes, too.) Apply no more than the recommended amount during the growing season.
2. Water only when the soil’s top 1 to 1.5 inches is dry to the touch. Then apply until water comes out of the pot’s drainage hole.
3. Empty the saucer. Pots should not sit in water.
4. Once or twice a year, leach houseplant soil -- wash out the salts. Apply twice the amount of water you’d need to fill the container. For example, a 6-inch pot can hold about 10 cups. So, you leach its soil by applying 20 cups of water – preferably outdoors or over a sink or bathtub.
“Take time, so water doesn’t overflow the rim,” Upham advised. “If salt’s still crusting the surface, remove it. Or, if doing so will mean removing more than a quarter inch of the underlying soil, consider repotting with new material.”
To Halt Wilt Disease, Destroy Dead Pines ASAP
The central U.S. pines turning color now could be victims of either drought or pine wilt. In either case, they also could be a kind of time bomb for healthy pine trees.
The reason is a long-horned, cylindrical insect called the pine sawyer beetle. It prefers laying its eggs on stressed or dead pines -- including recently cut pine logs. Its newly hatched larvae will overwinter there.
Unfortunately, these sites are also prime spots to find a microscopic worm called the pinewood nematode. Its claim to fame is that it can reproduce so fast during a typical summer that its numbers can literally shut down a pine’s circulation system within weeks. The result: deadly pine wilt.
The only way to stop the disease’s spread is to break the unique tie between beetle and nematode.
The two don’t truly get together until spring. Then a new generation of pine sawyer beetles gears up to fly to find another pine on which to feed. At the last minute, though, up to 100,000 tree-clogging nematodes quickly hitch a ride in each beetles’ windpipe.
The nematodes will enter their new host through the feeding holes the beetles create. The symptoms of that death sentence will usually appear by August through December.
Typically, the needles of an infested tree will wilt. The symptoms can appear across all of a tree or in progressive parts. The tree itself will die within a matter of weeks or a few months. The dead needles will hold on for up to a year.
The way to break this cycle is to get rid of the beetles’ and nematodes’ overwintering sites. Dead pines must be down and gone by May 1 -- at latest. Even a stump can foster pine wilt’s spread. The resulting wood must be chipped, buried or burned, to eliminate any possible haven for the deadly pests.