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Learn more about my research Have a question for the ecologist?

Your Comments, Thoughts, Questions, Ideas

grannie's picture
grannie says:

Can family pets get cancer and other illnesses from lawn fertilizer?

posted on Fri, 11/11/2011 - 3:48pm
Maria Kim's picture
Maria Kim says:

In our study, we're learning about people's yard and lawn care choices. So, first I'll talk about what we've learned so far about yard care choices and pet health. About 75% of survey respondents fertilized their lawns in 2010. About 2.5% of those people chose to fertilize only areas where children and pets don't play. In our discussions, some participants stated the reason they don't fertilize their lawns is that they're concerned about their pets' health. So, concerns about pet health do influence people’s lawn fertilization practices but to a much smaller degree than other preferences and concerns.

Our study doesn’t examine the effects of fertilizers on pet health. However, some fertilizer products, both organic and synthetic, do pose health risks to pets. For example, blood and bone meal are organic fertilizers that are both tasty and dangerous to dogs. According to the Pet Poison Helpline, when dogs eat bone meal, it can form a cement like ball in their stomachs which may require surgery to remove ( Also, the Pet Poison Helpline warns that products that contain disulfoton or other types of organophosphates can be toxic to pets. Finally, weed-and-feed products contain both weed-killers and fertilizer; the weed-killers in these products can harm your pet. If you choose to use them, carefully follow their warnings about when to allow your pet to walk on the lawn after application. However, in general, most fertilizers alone are not known to pose significant risks to your pet, provided you follow the instructions carefully.

You can also choose to forgo fertilizer altogether and instead use other lawn care practices to make your lawn healthy. For example, simply leaving your grass clippings on your lawn after you mow provides as many nutrients to your lawn per year as one fertilizer application. Also, letting your grass grow taller (preferably 2 1/2 inches or taller) encourages the grass roots to grow deeper. Deeper roots can reach more water and nutrients, and taller grass helps the soil retain more moisture.

Finally, beyond fertilizers, be aware of other plants and mulch in your yard that can pose significant health risks to your pet. For example, cocoa bean mulch is becoming increasingly popular but is dangerous to dogs. The Pet Poison Helpline ( provides lists of plants and other outdoor materials that are harmful to cats and dogs.

posted on Thu, 12/29/2011 - 12:17pm
Anonymous's picture
Anonymous says:

AS we move beyond 7 billion people in this world (OMG!) we will need more good farmland - not lawns. What do you say about that? My yard is (maybe think in terms of yard versus lawn) 40 by 120 but it's filled with plants and trees, many of which produce edibles such as apples. We have a very small patch of grass and the front and back most are slowly going as I add more plants.

posted on Thu, 11/17/2011 - 10:30am
Maria Kim's picture
Maria Kim says:

About 19% of households who responded to our yard care choices survey said that edible landscapes are a criteria that guide their vegetation choices. And, about 40% of respondents said that they have at least a small vegetable garden. In discussions, some participants talked about choosing to reduce the size of their lawn and plant edible landscapes. However, others have small yards that can't accommodate all the uses they'd like. For example, some participants discussed tensions between wanting a garden and wanting more lawn space for kids and pets to play or to relax and socialize. Others said that just have too much shade.

On a city-wide scale, urban farming is gaining increasing attention--from community gardens to urban agriculture policy. For example, the Minneapolis City Council adopted its first Urban Agriculture Policy Plan in April 2011.

posted on Tue, 11/29/2011 - 6:32pm
skippy's picture
skippy says:

why do you study lawns?skippykh 9 years old

posted on Sat, 11/19/2011 - 3:59pm
Maria Kim's picture
Maria Kim says:

Excellent question!

Lawns and yards are part of our urban ecosystem. (An ecosystem is the community of living creatures, like plants and animals, and non-living things, like rocks, minerals, and water, in an area.) We study lawns to understand why people care for their lawns and yards in different ways and what effects their choices have on our urban ecosystems, neighborhoods, and daily lives.

For example, think about the yards and lawns in your neighborhood and in your town. How would you describe them? Are they similar or different? Remember a weekend in the summer. You may have heard a lawn mower or felt some water drops from a lawn sprinkler. You may have seen someone digging up some grass to make room for vegetables or flowers. There might have been kids playing or a neighbor just sitting outside, enjoying the warm weather. People care for and use lawns and yards in different ways.

You may have also walked by a lake or stream and seen algae covering its surface. Chances are rain washed some nutrients from grass clippings or fertilizer left on a sidewalk or driveway into the lake, where they "fed" the algae. You may have also seen rainwater racing off a driveway during a storm, while the grass absorbed it. Lawns can have both environmental costs and benefits.

We study lawns and yards to investigate how and why people make their lawn care choices and the effects these choices have on the urban ecosystem and our daily lives. We also study lawn and yard care choices to help people have the kinds of lawns and yards they want while keeping our urban ecosystem healthy.

posted on Tue, 11/29/2011 - 6:08pm
Anonymous's picture
Anonymous says:

does grass grow every second our does it just grow every once in a while?

posted on Fri, 11/25/2011 - 1:40pm
Maria Kim's picture
Maria Kim says:

Grass does have a growing cycle!

In Minnesota, we have "cool season" grass. (Warmer areas like Texas have "warm season" grass.) Cool season grass starts its growing cycle in early August. Grass shoots (what we often call the blades and stems of grass) and grass roots grow throughout the fall. Growth slows as winter approaches and temperatures cool.

In the spring, when the temperatures warm up, the grass continues its growth cycle. Grass flowers in the spring, but most grass is mowed before the flowers form, so we don't see them.

In the middle of the summer, grass growth slows again, until early August, when the cycle starts over again.

posted on Tue, 11/29/2011 - 6:29pm
Andrew's picture
Andrew says:

As a someone studying lawns in an interdisciplinary way, have you thought much about the domesticating influence of lawns. For example, how do lawns contribute to relationship and gender norms? What are ways you see people challenging such norms in your work?

posted on Thu, 12/01/2011 - 12:21pm
Maria Kim's picture
Maria Kim says:

Our study doesn't examine that question, but it would be interesting to investigate. There are commonly held assumptions that men tend to prefer lawn care and often strive for a meticulously well-maintained lawn while women tend to prefer gardening and other landscaping endeavors. There was a humorous opinion article in the StarTribune that alluded to lawn gender norms and the quest for a perfect lawn -- "Couldn't that grass be greener" by Brian McGrory,

As we analyze our data, I'll keep your question in mind. I'll post an update for you to let you know if our data support or challenge these commonly held assumptions.

posted on Thu, 12/29/2011 - 1:27pm
Anonymous's picture
Anonymous says:

in the winter how dose grass not die

posted on Fri, 12/02/2011 - 1:33pm
Maria Kim's picture
Maria Kim says:

Most lawn grasses are perennials. That means that they can live for several growing seasons. (Some types of grasses are annuals; they have only one growing season and may die in the winter.)

Perennial grasses (and other perennials) survive the winter by becoming dormant. When grass is dormant, it stops growing and the leaves or blades of the grass (the part we can easily see) turn brown. So, the grass looks like it is dead. But, the crown of the grass -- the part of the grass where the roots and the grass leaves meet -- is alive and waiting for the warm weather to return. When the weather warms up, the grass starts growing again. Grass can also become dormant during the hot, dry part of the summer.

posted on Thu, 12/29/2011 - 1:30pm
Adam's picture
Adam says:

Why do people say it is good to pick up leaves, aren't they a good fertilizer?

posted on Thu, 12/08/2011 - 4:17pm
Maria Kim's picture
Maria Kim says:

Leaves can be a good fertilizer, depending on where they fall and how many there are.

It's good to pick up leaves if they are on the driveway, sidewalk, or street. These surfaces -- or any impervious surface -- cannot absorb the nutrients from leaves as they decompose. Instead, the nutrients leaves contain can easily wash into storm drains, most of which empty into nearby lakes, rivers, or streams. So, if you leave leaves on these surfaces, they can "fertilize" lakes, rivers, and streams. This contributes to algae growth -- the greenish substance that covers water bodies in the summer.

However, it can be beneficial to leave some leaves on your lawn or other areas where soil and plants can absorb their nutrients as they decompose.

For lawns, the amount of leaf cover is important. The general recommendation is that you should still be able to see the blades of grass among the leaves. More leaves than that may cause some of your grass to die and make your lawn more susceptible to disease.

In other yard areas, you can use leaves as mulch to cover bare soil or around other plantings. Leaves can help prevent weeds from growing and can help soil maintain moisture. They also provide nutrients to the soil as they decompose.

posted on Thu, 12/29/2011 - 11:54am
Anonymous's picture
Anonymous says:

is real grass better than sod? what aree the differences?

posted on Wed, 12/28/2011 - 5:20pm
Maria Kim's picture
Maria Kim says:

Planting grass sod and planting grass from seed have different advantages and disadvantages.

Planting sod is basically transplanting a plot of grass that has been raised somewhere else. The advantage of this is that you have mature grass right away. This can be particularly beneficial on slopes to prevent erosion. In contrast, planting grass from seed requires much more initial care.

You can also plant sod any time during the growing season. In contrast, the best time to plant seed in Minnesota is in late summer or early fall.

However, with sod, your choice of grass type is limited. Most sod grasses here are Kentucky Bluegrass mixes. If you want a low input or low mow grass, it probably won't be available in sod.

Also, although sod establishes itself more quickly, the roots of the grass won't be as deep and hearty (at least initially) as grass roots planted with seed.

Finally, sod is generally more expensive than seed.

posted on Wed, 01/18/2012 - 4:26pm
Anonymous's picture
Anonymous says:

Can I use MN grasses like kentucky bluegrass, rye, and fescue in North Carolina? Seems most yards have zoysia grass which isn't as nice.

posted on Sat, 12/31/2011 - 7:04pm
Maria Kim's picture
Maria Kim says:

Minnesota grasses are "cool season" grasses, which means that they actively grow in the spring and fall and are dormant in hot or dry weather. In contrast, "warm season" grasses actively grow in hot weather.

North Carolina is in the transition zone between warm season and cool season grasses, so MN grasses might work. If you live in the western part of the state, there's a good chance cool season grasses will grow well, but warm season grasses are better for the eastern and southern part of the state. You should also consider the "micro-climate" of your yard. A short article from North Carolina State University describes these factors and should help you decide whether your yard can support cool season grasses:

posted on Wed, 01/18/2012 - 4:43pm
pete's picture
pete says:

I've considered getting rid of all of my grass and replacing it with clover because it's soft and never gets too tall. What would be the downside of doing that?

posted on Sun, 01/01/2012 - 5:16pm
Maria Kim's picture
Maria Kim says:

Clover has many benefits. It fixes nitrogen (so it provides nutrients to your soil and grass), it requires no care, it stays green, and it attracts pollinators. Many people even like the smell of freshly mowed clover.

Until around the 1950s, clover was an accepted lawn resident. (It lost this status as pesticides to kill dandelions became more common...and killed the clover along with them.) Now many people see clover as a weed.

So, although there are no major downsides to clover from a turf biology standpoint (and in fact there are benefits), your neighbors may not like it. In our discussions, there were a few strong proponents of clover. Others sought to rid their lawn of it and described frustration that their neighbors' clover was spreading into their yard.

The norm seems to be changing, and clover may shed its status as a weed and become a welcome lawn resident once again.

posted on Wed, 01/18/2012 - 5:07pm
cole hammum's picture
cole hammum says:

what is the best grass in MN to survive in the winter.

posted on Sat, 01/14/2012 - 4:35pm
Maria Kim's picture
Maria Kim says:

Cool season grasses are the best types of grasses to survive the Minnesota winter. These include Kentucky Bluegrass, fine fescues, and perennial rye grasses. Kentucky Bluegrass varieties are the most common grass type in Minnesota. Fine fescue varieties are becoming more popular, however, because they require less maintenance (e.g., water, fertilizing, mowing) during the growing season.

posted on Wed, 01/18/2012 - 5:17pm
Anonymous's picture
Anonymous says:

we live next to a creek - should we treat our lawn differently than someone who does not live next to a creek?

posted on Tue, 01/17/2012 - 2:23pm
Maria Kim's picture
Maria Kim says:

A common saying here in Minnesota is that we all have lakefront property. Many of the storm drains empty directly into lakes, rivers, and streams, without being treated first. So, whatever is on your sidewalk or street could be washed into our water bodies. This a concern with fertilizer, grass clippings, and even soil particles that may land on the sidewalk or street -- the nutrients they contain can travel to lakes, rivers, and streams via storm drains, where they can "fertilize" algae. So, we all share in the responsibility of managing our lawns and yards well.

However, living right next to a creek does present a more immediate problem; fertilizer, grass clippings, and soil particles have a much shorter and more certain path to the creek. You could leave a buffer strip -- an area of unfertilized lawn -- closest to the creek. You can also pay close attention to where grass clippings go and check to make sure you don't have eroding soil that may wash into the creek. The University of Minnesota Extension has a helpful website that discusses shoreline management: This provides information about how to care for your yard close to water bodies.

posted on Fri, 02/10/2012 - 2:14pm
Anonymous's picture
Anonymous says:

Is there a grass being developed for our climate....that doesn't grow more than four inches? that we wouldnt't have to mow and the neighbors wouldnt complain

posted on Fri, 01/27/2012 - 12:14pm
karina's picture
karina says:

What made you want to be a ecologist?

posted on Fri, 01/27/2012 - 12:19pm
Maria Kim's picture
Maria Kim says:

The world is an amazing place, and I wanted to learn more about it. Some of my favorite memories are wading through the creek at the end of my street and discovering different animals and plants along the way. I also remember seeing the ecological quality of these places decline over time. I wanted to learn more about ecology to learn how to protect ecosystems AND our quality of life at the same time. So, I also want to understand how we make decisions that affect ecosystems and how we can develop and implement policies that promote ecosystem quality in the context of our daily lives and range of values and goals.

posted on Fri, 02/10/2012 - 2:42pm
Anonymous's picture
Anonymous says:

is it better to keep your lawn longer or shorter? In other words can you mow to often? is it better to bag your lawn or let clippings remain on top? Is it bad not to water your lawn?

posted on Sun, 01/29/2012 - 2:10pm
Maria Kim's picture
Maria Kim says:

It's best to keep your lawn 2 1/2 inches or taller. Keeping your grass longer helps the grass roots grow stronger, and it helps maintain soil moisture and outcompete weeds. Longer grass means healthier grass.

Grass clippings contain nutrients that grass needs to grow. So, leaving your grass clippings on your lawn enables your grass to use these nutrients. In fact, leaving grass clippings on your lawn provides enough nutrients to replace one fertilizer application annually.

Lawns can naturally enter a state called dormancy, during which they're not actively growing. This happens in the winter and in the summer when the weather is very hot or dry. Grass naturally starts growing again when the adverse weather conditions subside. However, very hot and dry conditions over an extended period of time can damage or kill your grass. For cool season grass (grass that grows in Minnesota and other cooler climates), you may need to water your lawn if temperatures exceed 90 degrees F for several days. (Warm season grasses can handle these temperatures better.)

As a general rule of thumb, the most water your lawn can USE (and it doesn't NEED this much), is 1 inch per week, including rainfall. You can put out a rain gauge to measure how much water your lawn gets. Or, while you water, you can put an empty tuna can in your yard (which is about 1 inch deep) and stop watering when it's full.

posted on Fri, 02/10/2012 - 2:29pm
Anonymous's picture
Anonymous says:

how often should a lawn be fertilized?

What type of fertilizer is best?

posted on Tue, 04/03/2012 - 3:29pm