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When should I fertilize this spring?

We always ask ourselves each year, “when should I dethatch and put down fertilizer?”. There is no perfect answer to this question. A good rule of thumb is when you start to see green shoots of growth emerge from the yellow thatchy look that winter has left behind is the perfect time. Another good indicator is when daytime temps are consistently in the high 50’s and low 60’s. If you plan on dethatching make sure you do this before you apply fertilizer with crab grass preventer. If you apply it before you dethatch you run the risk of breaking the barrier that the crab grass preventer creates to prevent crab grass.

Dethatching is something most people ponder in the spring. If your lawn is spongy when you walk on it that may be an indication you have too much thatch. At least a half an inch of thatch is good. (picture from Garden Myths) More than a half inch is helpful to remove. You can accomplish this process either professionally or by raking. Using a power rake works as well but do not be too aggressive. Over aggressive dethatching can do more harm than good. It needs to be done when the turf is not too wet and once active growth has started. The dethatch process does stress the lawn so best to do it when it is cool in the spring and not during the heat of the summer. A good dethatch will help air, water, and nutrients to get into the soil so the grass can take advantage of all the stuff it needs to be healthy.

The spring requires a two-pronged approach to fertilizing. The first prong is to find a fertilizer that is somewhere between a 15 and 21 for a nitrogen number. If you can find a fertilizer that has some slow release to it that is even better. Since spring means plants naturally grow vigorously you do not need a whole bunch of nitrogen to help develop your lawn unless it is unhealthy to begin with. Heavy nitrogen will cause to much shoot growth. This is not optimal for cool season grasses in Minnesota because it takes away from the completion of root growth needed for summer heat and drought tolerance.

The second prong of spring fertilizing is crab grass prevention. There are a couple of chemicals out there that will do the trick and are common to most fertilizers. Both prodiamine and dimension are the active ingredients that help to halt crab grass from germinating. It kills the process midway through the seed developing into a plant.

Once you have dethatched and fertilized make sure you mow your lawn regularly. Try not to mow more than quarter to half an inch off at a time. Always mulch the clippings back into the lawn rather than bag them. If you still are leaving clippings on top of lawn after mowing then you waited too long to mow. Make sure you rake these up. Normal clippings help to add nitrogen to the lawn as they breakdown. They also aid in creating good thatch that is required for a lush thick lawn. This will stave off weeds and other unwanted greenery from popping up in your lawn later in the summer.

Proper care and patience will result in a very lush green lawn. Making sure your thatch layer is not too thick and proper fertilizing and weed control will start your lawn off right in the spring. Following this up with regular mowing and mulching of the clippings will keep your lawn looking nice all summer long. We hope you have a great spring and enjoy the new vibrant season that is upon us.

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