When should I fertilize my lawn during spring?

Patience is more than just a virtue when it comes to fertilizing lawns in spring. There is no benefit to fertilizing frozen soil.

MSU Extension's Lawn Care Tip Sheet advises avoiding fertilization until May.
MSU Extension's Lawn Care Tip Sheet advises avoiding fertilization until May.

Just a few weeks ago, temperatures across Michigan were well below zero and 50 degree days were only a dream. Though winter seemed like it would not go away, we finally saw warming temperatures by mid-March. Warmer days bring on spring fever and the desire to see “green,” and not just from Spartan fans. Garden centers and television advertisements are already encouraging us to get out and fertilize our lawns. I believe I saw my first fertilizer commercial the first week of March, while all of Michigan was buried in snow. Even once the snow disappears, we may still have frozen ground or significant frost in the ground, often until early April in southern Michigan and even later towards the north.

So what is a Smart Gardener to do? Be patient, my friends! First, we need to understand that we should never fertilize frozen soil in the home landscape. Fertilizer particles are not going to green up a lawn while the ground is still frozen. These tiny pellets can be washed off the frozen turf into storm drains after a rain storm, damaging lakes, streams and rivers with unnatural plant and algae growth.

Once soil temperatures begin to warm in spring, grass roots break dormancy and begin growth well before the grass blades start to green up. Turf root system development in early spring is critical for grass health. Deeper roots that form in spring help the vigor of the turf during summer’s hot and droughty conditions. Fertilizing in early spring can encourage lush top growth at the expense of root growth. Our desire for a green lawn early in spring is not always best for overall turf health.

A turfgrass fertilization guide from Pennsylvania State University states that high rates of nitrogen on the turf in early spring encourages excessive foliar growth, which uses up carbohydrate reserves meant for root development and disease resistance. Michigan State University Extension’s Lawn Care Tip Sheet advises avoiding fertilization until May. This may be counter to the advertisements we hear on the television promoting combination products that fertilize the lawn early in spring and are also meant to control crabgrass.

Since crabgrass starts to germinate prior to May, these products encourage early use of fertilizer along with the herbicide. To avoid early fertilization and still manage crabgrass, it may be best to purchase a product that is only meant for crabgrass control. Pre-emergent herbicides that control crabgrass must go on before the crabgrass seeds germinate. This is often applied about the time forsythia begins to bloom. Not everyone needs crabgrass control, however. A thick lawn reduces light penetration to the soil surface, shading crabgrass seeds and preventing their germination. Only use a pesticide when it is needed and only where it is needed. Avoid blanket applications of herbicides and treat only the areas needed.

Snow mold on lawnOne other “smart” task for the lawn in early spring is to lightly rake the grass where the snow was piled for much of the winter along your driveway and sidewalk. It is common for snow mold fungi to grow on grass blades under insolated snow piles. The picture of snow mold was taken March 15, 2015 in Saginaw, Michigan. This matted-down grass is a moist environment where the fungus can thrive. Lightly raking these areas provides better air circulation down into the turf, drying out the area and reducing damage from the fungus.

Enjoy this spring and remember that being patient is also a task of the Smart Gardener.

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