Should I Bag My Grass Clippings If I Have Weeds?

You know that you finally “get” the whole yard work thing when lawn care stops being a chore and starts becoming a hobby/pet project. Chore or not, mowing can definitely sometimes get messy, and getting rid of clippings is a subject of intense debate amongst enthusiasts.

Your reward for an afternoon spent mowing is that fantastic smell of freshly cut grass, the knowledge of a job well done, in addition to a sizable pile of clippings. This pile can also contain the remains and seeds of cut weeds, fungus, or other pests that can plague your lawn.

Many think that bagging your clippings seems like the best choice, especially if your yard has a weed problem. Is this true? Should I bag my grass clippings if I have weeds?

The Quick Answer: Yes, If You Want to Play It Safe.

If you are relatively inexperienced and aren’t confident that you can correctly identify the lawn weeds you have, it is best to play it safe and bag the clippings. Certain weeds like crabgrass are self-spreading, self-seeding, and seasonal. During warmer times of the year, this common weed sees overall increased growth regardless of your actions.

There are many types of weeds (Dandelion, Creeping Charlie, Ragweed, Purlspane, Yellow Dock, etc)  that can plague your lawn, each with its own growth and reproduction cycle.

So if we were pushed to give a “yes or no” answer to the question of whether you should bag your clippings if you have weeds, we’d say “yes”, as it’s definitely the safer option. But it’s not a “you-life-depends-on-it” kind of yes. As you’ll see below, mulching can still be an option providing certain conditions are met.

Factors that Can Influence Whether You Should Bag or Mulch

As we just touched on, the answer is not always black and white, and we can definitely go deeper into the weeds (pun intended) on this subject. The choice between bagging and mulching in the context of a weed infestation depends on a few factors:

1. Have the weeds set seeds? – Weeds have fairly predictable life cycles, and many of them depend on spreading their seeds in order to reproduce. These seeds are not housed all over the weed stem. They are mostly found in the seed head.

   If your lawn is not that large, it is possible to check it and manually remove the seed heads as you find them. Of course, you will not get them all, but getting a decent proportion of them will minimize the risk of the weeds spreading significantly.

   If the weeds are only lightly covering your lawn and it’s not a full-blown takeover, manually removing weeds or their seed heads may be enough to allow you to mulch.

   Also, the seed-spreading parts of most weeds are located where they can maximize surface area contact with the wind: the top of the stem. If you are the type of person who mows the lawn often, you won’t give the weeds a chance to grow a seedhead. So…one of your best ways to protect your lawn against weeds is to mow frequently.

   To summarize: There isn’t that much risk in mulching if the seed heads have not sprouted yet, or you keep the lawn regularly maintained so they are not able to grow.

2. Types of weeds – The term “weed” is very vague, and it describes plants from different families. Entire books have been written on this topic, and it is up to you to decide how extensively you want to research. We will be mentioning the main two categories of weeds that can be spread (given certain circumstances) by mulching. We will also include a weed that you may actually want to have as part of your lawn:

   • Broadleaf lawn weeds – Overall, these weeds stand out because they cannot be easily confused for grass blades. Popular examples include chickweed, clovers, plantains, and dandelions. Chickweed and dandelions are very easy to pick out, as they are flowers. The flowers can easily be manually removed while mulching the stems with the rest of the grass.

     If you do not like them, do not give them a chance to grow by mowing often.

   • Grassy lawn weeds – As their name suggests: they look like grass. Members of this family include orchard grass, foxtail, and crabgrass. While dandelions and chickweed are at least pretty to look at, these grassy weeds will give your lawn a patchy, asymmetric look, ruining that carpet-like appearance that many owners want. They also outcompete the lawn grass when it comes to resources (not good for the health of your grass).

   • Clover – We wanted to give a special mention to clover as it’s technically a lawn weed, but actually has quite a few beneficial characteristics.

     Clovers are found almost everywhere, and they spread like wildfire. Yet, there is almost no detrimental effect to having clovers amongst your grass blades, aside from personal aesthetic preference. If your lawn has many clovers, you can go ahead and mulch.

     Many think that clover makes your lawn prettier, and it has a pleasant, fresh smell. In addition, it is resistant to pests, and it helps aerate the soil.  Clover can also add nitrogen to the ground, making it richer and improving its ability to sustain your lawn.

Lawn Weeds That are Particularly Prone to Spreading

• Crabgrass – If your lawn is infested with crabgrass, in particular, you should definitely bag your clippings. Crabgrass can reproduce through seeds, but minced pieces of its stem can also take root.

  It will grow and spread anyway during warmer seasons, but you risk accelerating the process by mulching.

• Ragweed – A single ragweed plant can produce 60,000 seeds per season. By mulching them and spreading the stems and seeds around, you can easily cause a widespread problem.

• Purslane – This weed can be spread by its stem fragments taking root. It is best to stay away from mulching if your lawn has these plants.

Does Mulching Grass Spread Weeds?… Why You Shouldn’t Be Anti-Mulching

Let’s play devil’s advocate for a bit and look at mulching. Does mulching grass spread weeds?

Not if you pull out all the seed heads. Many weed stems are harmless, and spreading stem pieces across the lawn will not do any damage. Many seeds and spores will spread regardless of your input via wind or carrier animals and insects. 

Also, there are plants such as Quackgrass that reproduce via their underground segments. Mulching won’t help or hurt in any of these cases.

Mulching can be a great solution providing a few conditions are met:

1. The grass is cut on a regular basis to prevent the growth of seed heads. Also, smaller clippings decompose faster.
2. The area in question is smaller, i.e., a backyard. A larger, park-sized area filled with mulched clippings can turn into a mess, especially if it is windy outside (one of the disadvantages of mulching). Hand-plucking weeds and seedheads is also easier over a smaller lawn.
3. Warm, dry-ish weather is needed, as the cold slows down the decomposition of the mulch.
4. If the weeds your lawn has are prone to spreading and can be harmful to the grass (like those we described a little earlier), you should first remove the weeds by using organic or store-bought solutions. For example, many weeds hate vinegar. Afterward, you can start mulching.

Your lawn’s health should be your primary concern, and there’s no doubt that mulching can help in achieving that goal.

There are even cases when mulching acts like a blanket, covering young weeds and denying them sunlight. Even the toughest seeds will not germinate without sunlight.

Conclusion

So let’s circle back to our main question: Should I bag my grass clippings if I have weeds?

This is what we’d ultimately recommend:

If you are a beginner, or your weed problem has gotten out of hand, it is best to play it safe and bag your clippings.

Otherwise, there are a few things you can do to make mulching a relatively safe option:

• If the weed reproduces via a seed head, remove the head and make sure you mow often to prevent re-growth.
• If the weed reproduces via stem fragments or roots, it is best to consider organic or store-bought pesticides. Use these and wait for the weeds to die before you attempt to mulch.

Mulching is a great way to turn waste into fertilizer, keep your lawn healthy, and even trap moisture in the soil. If you take the necessary steps to minimize the risk, you can enjoy these benefits without spreading weeds around your lawn.