Perilla Frutescens ~ Perilla Mint ~ Shiso

If you’ve been following my blog you know that I recently had a devastating loss of nearly my entire flock of sheep and goat, all due to a toxic plant called Perilla Frutescens. You can read about my story here, but this post is going to be an informational PSA. There will be some graphic images at the end. If you have any experience with Perilla please comment on this post or email me at squarepegfarmfl@gmail.com

Perilla Mint- also called Shiso, Beefsteak Plant and by other regional names- is a non native invasive that is grown as a culinary herb or by permaculture gardeners. As a member of the mint family it has the characteristic square stem, extensive underground root system and minty smell. The smell is more earthy and less sharp than a peppermint or spearmint, but still distinctly minty. The leaves are more broad than most mints and it can be confused for a member of the basil family (if you aren’t sure, smell it– it smells like mint, not basil!) Perilla comes in green or purple. The variety that is on my property is green, but you can see pictures the purple variety here.

Most information I’ve found about Perilla says that livestock will not eat it unless they are desperate.. Do not let this make you complacent about the dangers of this plant!!

If your animals have not been exposed to perilla before and are introduced to it either due to a move to a new pasture or to the plant spreading to your property then they may not know to avoid it. In fact, they may actually seek out its minty flavor. My flock actively hunted for it, ignoring the plentiful grass and other forage in favor of perilla.

If you have always had perilla in your pasture you may think that you are safe because your animals have ignored it in the past. Unfortunately that is not true. If we have a particularly hot or dry summer your regular pasture forage may get crispy and unappetizing. Perilla doesn’t require much water so it will remain lush and green, inviting your animals to give it try. Because Perilla kills so quickly and there is no treatment, you may not have any warning or get a second chance. 

Identification

• minty smell
• square, bumpy stem
• small purple flowers (and later seeds) on a stalk
• leaves: broad, ovate, with serrated edges

Toxicity

• deadly to all ruminants (cattle, goats, sheep) and horses
• all parts of the plant are toxic, both living and dried
• death can occur within 24 hours of exposure so you may never notice symptoms– I didn’t. if you do notice symptoms you may see heavy panting or difficulty breathing
• death is due to respiratory distress. lungs may swell and fill with fluid (pulminary edema)
• necropsy findings include hemorrhaging (bleeding) throughout the respiratory system (mouth/throat/lungs) and heart. Photos below are of one of my 3 month old lambs  during a field necropsy performed by veterinarians from the University of Florida
• necropsy may also reveal undigested pieces of the plant in the rumen/stomach contents and/or a minty smell

large hemorrhage in throat

hermorrhages in lungs

hemorrhages on outer surface of heart

Where to Find It

I know for sure that perilla can be found in pastures throughout the southeast US from Tennessee to Florida. If you have seen it growing wild in other areas please let me know!

When looking around your property pay special attention to fence lines and shady areas. You can practically map the spread of perilla in one of my pastures by looking at the shade cast by the trees running down the fenceline.

Also keep an eye on any newly disturbed areas. A neighbor of mine just discovered several plants growing in an area where she recently lost a tree. Remember that even if you haven’t seen it in the past, any changes to the land could provide an opening for it.

Update: after posting this people have let me know that they have found perilla  growing wild in the following states: FL, AR, NC, KY, CA

Keep in mind that these are observations of individuals who are not professional botanists and Perilla can be confused with other wild mints. However if you live in one of these states and find a plant in your pasture that might be perilla, its certainly worth a closer look!

Next Steps

If you find Perilla on your property what do you do next?

1. If you have livestock in the affected field you may want to move them to a non-affected area while you deal with the perilla. If this isn’t possible, make sure that they have plenty of other options for food- supplementing with additional hay or grain if necessary.
2. If you have small areas of mint, you can remove by hand making sure that you get the roots. If it has already gone to seed make sure to check the area frequently to remove any new plants. Perilla makes a lot of seeds and new seedlings grow rapidly!
3. If you have a large areas of perilla (like we do) you may need to spray with a broadleaf pesticide. Our agricultural exenstion agent recommended 2-4D. So far we have had moderate succses spraying with 2-4D. Unfortunately it is difficult in Florida to time your spraying to avoid rain and it only works if it doesn’t get washed off. Once you kill off the current crop of perilla you will need to check back often for new growth, either from seeds or from small plants that the spraying missed. Depending on how bad your situation is it may take several sprayings to get rid of it all. Make sure to check back the following spring for any new growth and re-treat.

Dead perilla all down the fenceline after spraying

Prevention

I’m still researching this and would appreciate any advice or links to additional resources. From what I’ve learned you can keep it from taking over by mowing before it goes to seed, however it grows so quickly that I wouldn’t risk keeping animals on a pasture that has had perilla mowed down since while this might prevent it from spreading it won’t kill what is already there. I’m also hesitant to recommend keeping it mowed short because it opens your pasture up to creeping indigo, which will only survive in short grass. In order to prevent CI from coming in where the perilla used to be, I’m planning to plant a fast growing cover crop anywhere we clear.

 

If you have any experience with Perilla please comment on this post or email me at squarepegfarmfl@gmail.com. I’d really like to find out more about how common perilla is, whether it has affected your livestock or not so please let me know if you identify it in your pastures! 

 

Additional Resources

• Tennessee Meat Goats
• Video from Alabama Extension
• Florida Extension Office (note that the map referenced here is incomplete)
• Perdue University
• Tennessee Extension