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DAMPING OFF DISEASE THREAT TO SEEDS STARTED INDOORS
I've planted lots of seeds during the past two months. Many of them are growing beautifully and provide a daily dose of gardening satisfaction as I check their progress under the basement shop lights.
Unfortunately, I've had a number of containers where seeds either didn't germinate at all or started to grow and then shriveled up and died.
What went wrong?
The most likely cause for both conditions is a fungal disease known as "damping-off disease." According to Chad Behrendt, University of Minnesota plant pathologist, damping off is a term used to describe rotting of seeds before they germinate, rotting of the young plant before it emerges but after it germinates, or rotting of the roots or lower stem on young seedlings which causes the plant to fall over.
In other words, damping off is a catchall term that refers to the death of seedlings caused by one or more fungi. Literally, the dampening (damping) of the soil causes the plant to be infected and die (off).
Damping-off fungi can strike seeds and seedlings planted indoors or outdoors, and can be present in plant containers and on tools, according to Lorrie Stromme, Hennepin County Master Gardener. Damping-off fungi, such as Pythium, Phytophthora, Rhizoctonia, and Fusarium, attack seeds and seedlings growing above and below the soil line. Pre-emergence damping-off rots the seed before it germinates or before a seedling breaks through the soil. Post-emergence damping-off attacks seedlings just after they emerge above ground, pinching off the stem tissue at or just below the soil line. Damping-off fungi favor cool, wet conditions.
The best prevention methods are the use of a sterile soil or soil-less mixtures in sterilized containers, keeping seedlings from getting too cold, and not allowing soil to stay overly wet. Containers and tools can be sterilized in a bleach solution (1 part bleach to 9 parts water) for 30 minutes. Allow the soil to dry between waterings, and maintain good drainage.
If you've had seeds fail to germinate, or die shortly after germination, I suggest you simply fight back the tears and plant some more seeds. I've become a happier gardener since I quit expecting that 20 seeds planted will become 20 healthy seedlings. If, however, you always score 20 for 20, let me know your secret!
Toll from 1998 storms devastating to trees I came across some eye-opening statistics recently that reveal the extent of damage to trees from last year's spring and summer storms. Based on surveys of communities in 20 counties, the Minnesota DNR has documented that more than 117,000 public and private trees were lost to storms, and nearly 50,000 more were severely damaged.
In Minneapolis alone, 7,000 public and private trees were lost and 70,000 cubic yards of wood chips were processed from 128,000 cubic yards of debris collected after the storms - enough mulch to cover 154 acres four inches deep!
With only 55% of communities reporting, clean-up costs have exceeded $11 million. These are out-of-pocket expenditures for cleanup and hauling debris and don't include costs for replanting, lost value to a community's character, or additional heating and cooling costs associated with lost canopies and windbreaks.
Follow-up storm analysis by the University of Minnesota on 600 damaged trees pinpointed several specific weaknesses in trees and site conditions that contributed to tree damage.
The most common damage category (57%) was complete uprooting or breaking at the ground line. The second most common category (27%) was canopy damage - broken branches, ripped branches, split-out leaders.
The two most common preexisting conditions for trees suffering any type of damage were presence of decay (13.3%) and stem girdling roots associated with deep planting conditions (10.1%). For all trees that failed totally, 17.8% were planted too deep.
Of all trees suffering "total failure," the species than failed more than any other was Colorado spruce, followed by green ash and littleleaf linden. More than four out of five Colorado spruce that suffered any damage had no preexisting conditions for failure.
One explanation for the high incidence of uprooting that occurred among Colorado spruce, little leaf linden and Norway maple is the high degree of wind resistance of these species due to their dense foliage and relatively shallow roots.
There are no magic formulas for protecting trees from the kinds of storms we experienced in 1998. The best we can do is to select healthy trees in the first place, make sure they're planted correctly, and then prune them so branches form strong unions with larger limbs, and limbs form strong unions with the main stem.
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PUTTING DOWN ROOTS:
A Delightful Blend of
Gardening Wisdom, Wit
and Whimsy
$10 + $2 for shipping
by Cliff Johnson |
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