Home Lawn Care Newsletter Issue #37 – March 16, 2026
Welcome to the latest issue of the Home Lawn Care Newsletter from UMN Turfgrass Science! We provide up-to-date information to address all your lawn care tasks at the times when you need to know.
Current Topics
Turf mathematics: How to know how much fertilizer or grass seed you need
It can be intimidating to shop for lawn care products in the store or online. Even if you know the right product, how do you know how much you need? Knowing how much to purchase affects your pocketbook, and using the right amounts of fertilizer or pesticides ensures a healthy lawn and can reduce potential negative impacts to the environment. In some situations, there may be legal restrictions on the amount of product that can be applied. So understanding how to calculate the correct amount to buy or apply is always important.
Calculating how much fertilizer to apply begins by knowing a target amount of nitrogen for one application or for the year. Except for the lowest-input lawns, splitting nitrogen into two or three applications is usually good practice for overall lawn health. University-recommended amounts of nitrogen are most often expressed as either 0.5 or 1.0 lbs. of nitrogen per 1000 square (sq.) feet (ft.).
All fertilizers are labeled with the percentage by weight of total nitrogen, phosphorus, and potassium in the bag or container. For example, a 22-pound bag of granular fertilizer with an analysis of 24-0-12 has 24% nitrogen, 0% phosphorus and 12% potassium. Within this 22 lb. bag, there are 5.3 lbs. of nitrogen (0.24 lb. nitrogen x 22 lb. fertilizer) and 2.6 lbs. of potassium (0.12 lb. potassium x 22 lb. fertilizer). If the lawn area to be treated is 5,500 square feet and the target rate is 0.5 lbs. nitrogen per 1000 square feet, how many pounds of fertilizer would be needed using the 24-0-12 fertilizer across the lawn area?
Step 1. Determine the amount of fertilizer needed per 1000 sq. ft.:
Desired rate in lbs. of N per 1000 sq. ft. x % of nutrient in fertilizer (in decimal form) = Amount of fertilizer per 1000 sq. ft. That is:
0.5 lbs. of N per 1000 sq. ft. x 0.24 = 2.1 lbs. of 24-0-12 per 1000 sq.ft.
Step 2. Calculate the amount of fertilizer needed to treat the area:
Amount of fertilizer per 1000 sq. ft. x number of 1000 sq. ft. in area = lbs. fertilizer needed to treat total area. The number of 1000 sq. ft. in area is determined by dividing the lawn area (5,500 sq. ft. in this case) by 1000 sq. ft. – that is, 5.5.
2.1 lbs. of 24-0-12 per 1000 sq. ft. x 5.5 = 11.55 (or 11.6) lbs. of 24-0-12 fertilizer to treat the 5,500 sq. ft. lawn.
In this case, about half of the 22 lb. bag of 24-0-12 would be used to apply 0.5 lbs. N per 1000 sq. ft. The unused amount can be kept for the next desired fertilizer application. Many fertilizer products state on the bag how large an area can be treated with the entire bag, but they may or may not show how that area was determined. Checking the math can help you choose the right amount of fertilizer to purchase as well as identify which fertilizer product offers the best value.
Calculating the amount of grass seed to purchase is very similar to calculating the amount of fertilizer needed. Like nitrogen fertilizer, recommended seeding rates are stated in terms of pounds of seed per 1000 sq. ft. For example, if you wanted to overseed the above-mentioned lawn using tall fescue seed at 7 lbs. per 1000 sq. ft., you would repeat Step 2 from above:
7 lbs. tall fescue seed per 1000 sq. ft. x 5.5 = 38.5 lbs. of seed.
- Calculating the pounds of fertilizer to apply | Purdue University
- Purdue turf fertilizer calculator | Purdue University
- Buying turfgrass seed for Minnesota lawns | University of Minnesota
What should you do with older unused pesticides or fertilizers?
The most common way in which a pesticide or fertilizer becomes unusable is when it physically or chemically changes. Examples of this might be when fertilizers solidify or pesticides settle out and they cannot be re-suspended in solution. If the container is leaking or if the product has been compromised, it should not be used. Another way for these types of products to become unusable is if the container label is unreadable or missing.
So, what should be done with a pesticide or fertilizer that is unusable? Above all, do not pour the unusable chemicals down the drain or throw them in the trash! Household amounts can properly be disposed of for free at waste disposal collection sites within each county (use link below). The Minnesota Department of Agriculture has a website for instructions by county for what to do with the chemicals, including how to transport them to drop-off locations. If you have still-usable pesticides or fertilizers that you no longer need, check with a neighbor or friend to see whether they can be used as intended.
The best way to reduce the amount of unusable chemicals in your home is to buy only what you need. The next best thing you can do is store them properly. In general, chemical containers should be stored in an enclosed bin out of direct light in an area that can be kept above freezing temperatures. It’s also helpful to use a permanent marker to note directly on the containers when you purchased the products. Properly stored chemicals can remain usable for several years, but follow the label instructions to ensure longevity of the products.
- Waste pesticide collection schedule | Minnesota Department of Agriculture
- Is this pesticide on my shelf still good? | Purdue University Extension
Is vole damage worth worrying about?
As snow and ice melt, you might notice tunnels in the lawn or torn-up turf that wasn’t there in the fall. Prolonged snow cover protects voles from predators like hawks and owls as they feed on grass shoots and other plant materials. Generally, the longer snow persists, the more damage voles and their tunneling can cause. Despite this being a relatively mild winter, vole damage has been fairly widespread in lawns throughout Minnesota.
So, if your lawn looks like the above photo, what can or should you do? As the soil continues to thaw and the lawn begins to grow, you can lightly rake up any excess debris that has piled up. This debris can mat down or shade out the turf in these areas and slow the lawn’s greening up or, in extreme cases, kill healthy turf that is smothered. You likely won’t know for several weeks if the lawn in and around the affected areas will come back. In the meantime, you can spread grass seed or just keep an eye on these spots. If the lawn does not come back, you might have to consider managing weeds that emerge in these thinner areas in late spring and early summer. Regardless, focusing on best management practices like proper mowing and fertilization will help your lawn recover later this spring and early summer.
- How to manage vole damage on lawns, trees and shrubs | UMN Extension
- OSU Extension research using drones takes flight to detect vole activity | Oregon State University
Research Update
Do you know how big your lawn is? As we mentioned in the turf math section above, knowing your lawn area and the desired amount of product or seed is crucial for knowing how much to purchase.
Read Jon Trappe's blog post to learn how to calculate your lawn area using your phone or computer screen.
Volunteer Opportunity
Become a Lawn Leader!
If you're a Master Gardener in the seven-county metro area and might be interested in becoming a Lawn Leader, you can learn more about it in the link below. This can be a great way to deepen your lawn care knowledge and help your neighbors manage their lawns better.
Find out more about becoming a Lawn Leader.
Upcoming Outreach Events
Lawn Care Q & A
Members of the UMN Turfgrass Science lab will be at the events below to answer questions on smart irrigation and lawn care as part of our collaboration with the Metropolitan Council.
Saturday, 3/28/2026
8:30 a.m.–2:30 p.m.
Anoka County Home Landscaping-Garden Show
Saturday, 4/18/2026
1:00–4:00 p.m.
Eagan Earth Day Celebration
Saturday, 4/18/2026
9:30 a.m.–2:30 p.m.
Rosemount Community Expo 2026
Rounds Fore Research
If you or someone you know plays golf, there is a great opportunity to play some unique golf courses while supporting turfgrass research. Rounds Fore Research is an auction-style fundraiser for golf rounds at several public and private golf clubs around the region. These golf rounds are donated by the golf courses and hosted by the Minnesota Golf Course Superintendents Association to help raise funds for turfgrass research. Online bidding starts April 5, 2026.
Have a question?
Check out these resources for additional lawn care information from the University of Minnesota.
Look for research updates, lawn care tips, info about field days, and more at UMN Turfgrass Science.
We provide research updates, lawn care tips, info about field days, and more at @UMNTurf on X and UMN Turfgrass Science on LinkedIn.