Fielding Questions: Nightcrawler holes, lawn fertilizer timing, carrot seed germination

Fielding Questions columnist Don Kinzler explains what can be done about nightcrawlers, when best to fertilize lawns with Milorganite and methods for growing carrots.

Nightcrawlers have caused extensive damage in this resident's lawn. Fielding Questions columnist Don Kinzler explains what can be done.
Contributed / Bob B.

Q: Nightcrawlers are causing holes and little mounds of soil in the lawn. It’s making the grass difficult to grow and the lawn is very bumpy. I had problems last year also. What can be done? — Bob B.

A: Nightcrawlers and other earthworms have been very active this spring, causing small, visible holes in many area lawns. They create little mounds of worm excrement, called “castings” as they work through the soil. As grass grows, the mounds or holes usually aren’t visible, but mounds can be felt under foot.

When nightcrawler activity is abundant, it can make walking across a lawn feel as though you’re walking across golf balls. Generally, though, nightcrawler activity can assist in aerating a lawn and the castings contain nutrients available to the grass plants.

What can be done when nightcrawler activity becomes a problem? There are no chemical pesticides that are legally labeled for nightcrawler control. Power-raking in the spring and again in mid-August mitigates the mounds.

When watering the lawn, water deeply and less often to encourage nightcrawlers to go deeper. Frequent shallow sprinkling tends to keep nightcrawlers closer to the moist surface.


Growing Together columnist Don Kinzler breaks down why local lawns are ailing and what homeowners can do to restore the yards.

Q: I’m planning to use Milorganite lawn fertilizer and the label says to fertilize for the Northern states around Memorial Day. Must I wait that long? — Connie B.

A: Milorganite is an organic fertilizer and I’ve used it myself on our lawn and flowers. There are even anecdotal reports of it helping to repel deer and rabbits.

The current recommendation for timing of spring lawn fertilizing, based on years of turf research, is after the grass has had a chance to wake up and spend a few weeks actively growing. That’s when grass plants are best able to utilize the nutrition that’s applied.

Fertilizer that’s applied too early, before grass is fully ready to use it, has a greater chance of being washed away, ending up in rivers and streams. That’s why turf research recommends delaying lawn fertilizer applications until the last half of May, preferably closer to Memorial Day.

Will it harm lawns if fertilizer is applied earlier? Probably not, but as long as there’s no advantage to early application, and because there are many good reasons to delay, I prefer waiting.

The reason the Milorganite label recommends Memorial Day is most likely because they’ve found that date to be the most effective use of their product and in line with other research.

Q: I’ve had problems in the past with carrot seed not coming up after planting, and I’ve heard you can lay a board on the ground over the row and that will help. Do you know if that’s true? — Ron M.

A: Getting carrot seed to sprout after planting has been a challenge for many of us. The seed is tiny, is planted very shallowly, and has difficulty emerging through crusted soil.


My mother used to sprinkle damp peat moss over the row to prevent soil crusting and I’ve done the same with decent results. Other gardeners use dried grass clippings that haven’t been treated with herbicide.

When I was discussing the carrot conundrum a number of years ago with Professor of Horticulture Neal Holland, since passed away, he said the old-timers would often lay a board or plank over the carrot row after planting and first sprinkling with water.

He had never tried the method, and I haven’t either, although I will this year. The row must be checked daily and the board removed immediately when sprouting carrots are visible.

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If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at . Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at
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