Greenworks 24V Cordless String Trimmer 21342 Featured String Trimmers

Greenworks 12” 24V Cordless String Trimmer (21342): Product Review

GPR Recommendation

Ease of Use
Cutting Performance
Final Thoughts

With some engineering fixes, this could be an excellent all-round trimmer. As it is, the problems outweigh the positives

Overall Score 3.3

Available on Amazon

Buy It

The Greenworks 12” 24V (Volt) Cordless String Trimmer, model 21342, is yet another battery-powered combination trimmer / edger to hit the market in recent years.

With so many new cordless string trimmers to choose from, it’s hard to know which to buy. Some are marketed as a replacement for gas trimmers (like the Troy-Bilt TB4200 ), others tout their light weight, adjustability and ease of use (like the Greenworks trimmer), while still others focus on battery life.

To help you find the right battery-powered string trimmer to meet your needs, we put together an article on what to look for when choosing a weed whacker / trimmer. You may want to read that first.

Related Article: Best Cordless Battery-Powered String Trimmers

To find out the results of our testing of the Greenworks cordless trimmer, keep reading …

Greenworks 24V Cordless String Trimmer 21342 Opening Shot

String trimmer in use


  • 24V Li-Ion battery
  • 12” cutting path
  • 4-position pivoting head
  • 900 rotating head with edging wheel
  • 065” single line auto-feed head
  • Total weight (with installed 24V, 2.0Ah battery): 5 lbs 14 oz


The string trimmer arrived with no damage.  The packaging was tough and held the unit and the separate pieces securely.  Nothing came out of place while in transit.


The Greenworks 12” 24V Cordless String Trimmer required some assembly.

First, the guard had to be attached by placing it onto the motor, turning it 450 and inserting and tightening two Phillips head screws.  You’ll need your own screwdriver for that.

Next you’ll need to install the auxiliary front handlebar.  It’s an easy process of sliding two plastic pieces over the upper portion of the trimmer shaft.

The manual (which is easy to follow) suggests adjusting the auxiliary front handlebar for optimum balance.  Before doing that however, I recommend installing the 24V Li-Ion battery in the slot located in the rear handle so that you can adjust the balance properly.

Greenworks 24V Cordless String Trimmer 21342 Handle and Battery Pack

The rear handle and battery pack coupled together. Having this weight in place helped me balance the trimmer.

To find the ideal balance point, just move the handle until it feels balanced and tighten the T-handled knob to squeeze the two pieces of plastic together around the upper shaft.

Greenworks 24V Cordless String Trimmer 21342 Handle

The auxiliary front handlebar is fully adjustable from front to back to give the operator a good balance point.

Safety Tip

Remove the battery from the trimmer when performing any work, such as adjusting/changing the trimmer line or any other operation where physical injury could occur if the trimmer had the battery engaged and then was accidentally turned on.

Balancing the String Trimmer

When you have the unit properly balanced, adjust the cutting head so it’s pretty much parallel the ground.  This is an easy task – Greenworks designed a head that pivots through four positions – so you should be able to find a position that works perfectly for you.

Greenworks 24V Cordless String Trimmer 21342 4 Positionn Button

Adjusting the head parallel to the ground was easy using the 4-position head pivot and push button.

Problems With The Cutting Line

During my tests of the Greenworks trimmer, I ran into trouble with the trimming line right off the bat. After trimming for about 45 seconds, the string broke off inside the spool.

I tried to fix the problem by opening the trimming head (after removing the battery pack) and pulling out about a 12” section of cutting line from the spool.  I then put the spool back into the cutting head and reassembled the cutting spool mechanism.  Within 45 seconds the line broke again.  This happened over and over again.

At that point I stopped my testing and contacted Greenworks to see if they could suggest any fixes.  They said that it could be a defective line/spool assembly, and sent me a new one (along with a brand new spool of cutting line).

Greenworks 24V Cordless String Trimmer 21342 Spool and Broken Line

Short sections of cutting line kept breaking off inside spool.

Unfortunately, even with the new pre-wrapped spool installed, I had the same problem again.  There seems to be a problem with the way the spool is wound – the line is so tightly overlapped inside the spool that it’s not able to advance.

So I tried winding a new line on an empty spool. This did fix the problem of the line breaking inside the spool, but I ran into another problem – the line wouldn’t auto-feed.

The Greenworks 12” 24V 2.0Ah Cordless String Trimmer model 21342 is specifically designed to automatically advance the cutting line when it gets short.

However, I found that not only did the trimming line not advance automatically (even after I followed the trouble shooting instructions), it constantly jammed inside the spool.

At this point I gave up trying to use it as a string trimmer. Instead, I manually pulled out a full length of cutting line and tested the unit as an edger.

Greenworks 24V Cordless String Trimmer 21342 Spool Tangled String

String constantly jammed in spool.

An Excellent Edger

The Greenwork trimmer is also designed for use as an edger by rotating the cutting head 90 degrees and rolling it on the plastic wheel that’s attached to the cutting guard housing.

To my surprise, the Greenworks string trimmer is an excellent edger. The set-up to turn it from a string trimmer to an edger is simple and elegant. All you have to do is press a button on top of the drive motor and the spring-mounted head automatically turns 90 degrees toward the edging position. You may have to push the cutting head a few degrees to make it lock into that position, but once there it is locked securely.

Greenworks 24V Cordless String Trimmer 21342 Rotating Head Button

Turning the string trimmer head to convert it to an edger is as easy as pushing a button.

The edger is designed to be pulled toward you (not pushed away from you). I used the outside edge of the wheel as a guide and just rolled it along the edge I wanted to cut. It worked perfectly and cut a beautiful clean line.

Greenworks 24V Cordless String Trimmer 21342 as Edger

The trimmer is an excellent edger.

Unfortunately, given the problems with the cutting line advancement, I wasn’t able to edge for long. However, for the 10 feet I did edge, the process was easy, smooth and did an excellent job.

Another problem that cropped up was that the lower shaft would slide into the upper shaft when pressure was applied (such as when using it as an edger).  Basically, the clamp to adjust shaft length was just too loose.  Fortunately the design incorporated a Phillips adjustment screw so I was able to tighten the screw, making the clamp tighter.

Safety First

There was a fair amount of flying debris when edging.  Always wear long pants, sturdy shoes or boots and approved safety glasses.  We recommend the John Deere/Wiley X safety glasses.


The unit comes with a charger and a 24V 2.0Ah Li-ion battery.  The battery arrives completely discharged and will take about 50 minutes to charge to full capacity.  Be sure to charge it fully before using it for the first time.

In my limited tests (because the string kept breaking), the trimmer ran for about 30 minutes on a full charge.

If you plan on doing work that’ll take longer than 30 minutes, you’ll probably want a backup battery. They can be purchased separately.

>> See our FAQs About Li-Ion Batteries

Greenworks 24V Cordless String Trimmer 21342 Battery Package

The battery charged in about 50 minutes. The run time was approx. 30 minutes.


Greenworks offers a 4-year warranty (with proof of purchase) against defects in materials, parts or workmanship for the string trimmer/edger.

Batteries carry a 2-year warranty against defects in workmanship and materials.  Be sure to follow the instructions for charging your batteries or the warranty will be void.


I wish the Greenworks string trimmer had performed better.  I like the weight, balance, handling, and maneuverability. It trimmed well (when it trimmed) and it was a phenomenal edger.  Unfortunately, it had some major problems with the line and spool assembly. I would also have liked to have seen the upper and lower handle tensioning latch set tighter at the factory so that the shafts wouldn’t slip inside one another without having to make the adjustment myself. With some engineering fixes, this could be an excellent all-round trimmer. As it is, the problems outweigh the positives.

Where to Buy

The Greenworks 12” 24V Cordless String Trimmer, Model 21342 (which includes a 2.0Ah battery and charger) is available on Amazon for $85.47.

Extra 24V 2.0Ah batteries are also available from Amazon for $67.72 each.

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Disclaimer – GPReview would like to thank Greenworks for giving us a free sample to review. There was no expectation that it would be a positive review and we received no compensation for writing it. All opinions expressed here are those of the author based on personal experience using the product.

Please note that the Amazon links (and only the Amazon links) above are affiliate links. Should you choose to purchase products through these links, GPReview will make a small commission (at no extra cost to you) that helps to support this website and our gardening product reviews. Thank you!

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