CO-Horts Blog

Tuesday, April 21, 2015

Avoiding Abiotic Afflictions …in the spring garden

Posted by: Mary Small, Jefferson County Extension Plant Diagnostic Clinic

Abiotic plant problems are brought on by environmental or cultural conditions. They often mimic disease, but are not caused by any living organism. They plague many gardens and landscapes, even, unfortunately, at the very beginning of the growing season.

Planting seeds is a favorite springtime rite. Once in the soil, they’re watered and watched for what seems like an interminable amount of time. And then….nothing…or spotty germination. More time goes by…hmmm….what’s a gardener to do?

Check the age of the seed.  All seeds don’t remain viable for the same amount of time. For example, corn stays viable for around two years, yet tomato seed is viable for five years. If you are using older seed, you may first want to conduct a “rag doll” test. Take 10 seeds, place down the middle of a paper towel, roll it up and fold the sides under, so seeds don’t drop out. Moisten the paper towel and place in a sealed plastic bag on the kitchen counter. Once the time to germinate has elapsed (found  on the bag of seed), open everything up and see how many seeds have germinated. If 7 out of 10 did, then you have 70% germination. You may want to sow seeds a little thicker to make up for the reduced germination rate.
"Rag doll" test for seed germination
Some seeds produce weak seedlings and may need some help emerging through the soil especially if it crusts over easily.  Carrots are a good  example of this. This year, try planting the seeds as usual, then cover the row with a piece of burlap or a board. This helps prevent soil crusting and allows the tender seedlings to germinate. When it gets close to the expected germination date, lift the covering and start checking the progress. Once most of the seedlings are up, you can remove the covering.
Weak seedlings are the reason radishes are often interplanted with carrots.  The stronger radish seedlings germinate first, making way for the carrots. They’re harvested in about 30 days and create even more room for the developing carrot roots, although thinning may still be needed.
Carrot seedlings planted with burlap
Beans sometimes have germination problems.  If placed in soil that’s too cool, they don’t sprout and  may rot. Even when beans germinate, I often get questions about how to control  “the birds ( squirrels, rabbits or any other critter observed near the garden) that are eating the leaves off the bean plants”. This problem is not caused by animals. It’s called “baldheading” and is caused by mechanical injury to the growing point of the seedling. Crusty soils and damaged seeds are the likely culprits here.
"Baldheading" of beans caused by mechanical injury to seedlings
Sweet corn planted in too cool soil, like beans, does not germinate (or germinate well) and may rot. Supersweet varieties actually need soil temperatures of at least 60 degrees F to germinate.

To check soil temperature, insert a soil thermometer several inches deep into the soil. The soil must be the desired temperature for several days before planting. 

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