Grass turning purple!

Grass turning purple!

Barb N – posted 01 November 2001 14:51

The blades of my St. Augustine have started turning purple in some areas! I’ve never come across this problem before. Does anyone have an idea what’s happening??



seed – posted 02 November 2001 08:06

Barb, where are located? Was this same St. Augustinegrass not doing it last year?

I have seen fall purpling of St. Augustine leaves in South Florida, but it is usually a response to cooling temperatures. Not every leaf will do it.

There are other kinds of stresses, including systemic pesticides, that can do this.


Barb N – posted 03 November 2001 07:58

I’m in Orlando and, no, I’ve never seen this happen before. It’s only in a fairly small area too. I did have a lawn service applying fertilizer/pesticides, etc., but it’s not happening to all of the grass.

I spent megabucks in the spring of this year having my entire yard relandscaped and almost all of my grass has already died. I guess it’s just too shady to grow anything…that’s why I inquired about the artificial turf in another post.

Is there anything I can or should do about the purple grass?

Thanks for your help.

P.S. I have since cancelled the lawn service since the grass just continued to decline.

seed – posted 17 November 2001 09:43

Barb N, I’m still puzzled over the purple grass. I forgot to ask, did you see any bleached white leaves?


Dave – posted 17 November 2001 16:22

I have St. Augustinegrass and many of my grass blades are also turning purple. I have a picture of this to email any who wish to see it. The blades are tipped with purple in some areas of the yard, and are side-by-side with healthy blades. The purple areas of the blade travel down or along the side of the blade, rendering it yellow and finally death ensures. I have diffuse areas of my yard that are 5 to ten feet in diameter that show yellowing grass with purple tipped blades. Who can diagnose this and recommend treatment?Dave, pathogenic57@yahoo.com

seed – posted 21 November 2001 06:52

Dave, thanks for sending me the photo. I’ve posted the purple leaves as a Turf Puzzler:

jspano – posted 03 December 2001 04:20

There two reasons why st. aug will turn purple1 cool weather we did have some cold nightsa while back2 apostolicity (pesticide burns) wrong kind of weed killer improper use of insecticidesI have been in the pest control businessin pasco county (north of tampa) for 15 yearswould look at the photos and would not worry

seed – posted 10 December 2001 09:26

I agree that we are talking about the same phenomenon. There is another thread on this subject in the Gardenweb forums:

Dave – posted 13 January 2002 12:11

It’s been a month since my report of purple tipped St. Augustinegrass.

Since then, I’ve sprayed IMMUNOX brand fungicide and done nothing else except mow it once.

The purple has not advanced. Now it’s frost damage I’m seeing from cold weather (however, one bright spot is the death of crabgrass and tropical signalgrass in my yard).

LGilbert – posted 18 February 2002 12:38

quote:Originally posted by Barb N:I’m in Orlando and, no, I’ve never seen this happen before. It’s only in a fairly small area too. I did have a lawn service applying fertilizer/pesticides, etc., but it’s not happening to all of the grass.

I spent megabucks in the spring of this year having my entire yard relandscaped and almost all of my grass has already died. I guess it’s just too shady to grow anything…that’s why I inquired about the artificial turf in another post.

Is there anything I can or should do about the purple grass?

Thanks for your help.

P.S. I have since cancelled the lawn service since the grass just continued to decline.

I had this same damage in my lawn in Brevard, Cocoa Beach. It was from the pesticides I put on it. 2-4-D is not good on St Augustine. (Sorry this is so late)

seed – posted 18 February 2002 16:14

LGilbert, you say you used 2,4-D but wasn’t it a mixture? Did the mixture also contain mecoprop and dicamba? I have observed experimentally that mecoprop is deadly on St. Augustinegrass, but that 2,4-D has not injured Floratam St. Augustinegrass in my experiments in South Florida.

But I don’t think you can get straight 2,4-D except as an ag product.


Lawnguy – posted 06 March 2002 09:52

This is in regards to the Purple grass topic. I noticed that the dates of the messages are dated in November. I am a “lawncare provider” and I have noticed that around the first cool spell in the fall that these purple St. Augustine blades appear. They will appear anytime during the winter cool spells. I am convinced that treatment of any kind is not needed. Defining fungus symptoms can be very difficult for sure, but purple grass only seems to appear in fall and winter and doesn’t spread as other fungus symtoms do.


Jason – posted 21 March 2002 02:09

Hiya guys, i’ve been a greenkeeper/superintendent on golfcourses for about 11 years now, i now am the turf manager on a turf farm and we grow St Augs. Purpling off of leaves in turf is due to a lack of potasium in the turf, try a light fertilizing of a high K fertilizer, it should fix the problem, best of luck

Larry Williams – posted 23 March 2002 08:27

Dave, There is actually a simple explanation for the purple leaves in your St. Augustinegrass. I see it all the time. If you look closely at the photos you submitted, you will see wounds on all but one of the leaves. The color change is nothing more than the leaf tissue responding to a wound. The leaf on the far left in the photo was bent (you can easily see the bend). It shows up as a tan colored line. Above this point, the leaf has turned purlple. These types of wounds are caused from nothing more than a human foot or lawnmower physically bending the leaf. The second leaf, from the left, has been split and bent. The third leaf shows no sign of a wound at the time the picture was taken but it may be evident on the opposite side of the leaf (not shown in picture). The fourth leaf has a leaf spot (probably caused by one of the leaf spot diseases). Note the purlple border around the spot. Again a response to a wound. The leaf tissue is no longer functioning properly because of the wound and the chlorophyll (green pigment) breaksdown allowing other leaf pigments to be seen such as anthocynanins, which produce a purple color. This is a minor problem. No need to worry. Other causes for purple or reddish leaves include response to cool weather, nutrient deficiencies and herbicide injury. But in most cases, the grass recovers as it begins to grow. The breaks, bends and splits in the leaf blades will occasionally happen. We don’t live in a perfact world. Take this to the county agent that was stumpted by this question and see what he or she says.

Kaleal – posted 22 May 2002 19:50

I see this same type of behaviour in El Toro..I live in Hawaii and the purple will move around..never killing the grass. I can always find purple patches somewhere and I also found it quite strange. In the above post someone stated that leaf damage is evident. Well none of the purple areas in the El Toro have wounds that are discernable to the naked eye.

Kaleal – posted 22 May 2002 20:06

CERCOSPORA LEAF SPOT Causal Fungus: Cercospora fusimaculans Host Range: St. Augustine

Host Susceptibility: Yellow-green (common) selections are more susceptible than blue-green (bitter-blue) selections.

Disease-favorable Conditions: Periods of warm, humid weather favor disease incidence and severity.

Symptoms: Leaf spots may occur on both blade and sheath tissue. Individual lesions are small (1-3 x 0.5-1 mm) and appear dark brown to purple in color. As spots age, the center may develop a tan color. In situations of high disease severity, entire leaves will yellow, wither and die. Large areas of turf will appear to thin or “melt out” as with other leaf spot diseases.

Cultural Control: Nitrogen applications may reduce disease. Irrigate deeply only when needed. Apply water in early morning, when dew is already present. Bitter-blue selections are more resistant.

Chemical Control: Fungicides, such as Daconil, Dithane, Duosan, Fore, or Manzate 200, which are used to control other leaf spots will control this disease as well.

Ducati – posted 05 June 2002 21:54

It looks to be a fungus that can be easley controled. From the pictures it looks like “brown patch” or “dollar spot”

seed – posted 06 June 2002 17:14

The leaf with the arrow at

southern lawns tech – posted 30 June 2002 18:12

I’ve been a lawn tech for southern lawns in montgomery for 6 year.The purple grass your talking about is from a fungus called brown patch.some of your previous answers were partially right.This brown patch usually happens in the fall.when you have warm to hot days,followed with cooler nights dew and over watering canset the perfect situation for this fungus.When these situations come around again cut back on watering,and limit watering to late mornings to early afternoon.The person that used the fungiside ,if done right,should’ve noticed that the discoloration didn’t spread.that unforunatly is all you can hope for.this usually stars fairly small and creeps outward in a basically circular patern.once you see it starting put down the fungiside.thisstops it’s speading although even this isn’t garanteed I’ve never seen it fail.After it’s stopped put out a light rate of slow “release” fertilizer 32-0-15 or similar 50lbs.per 9,000sq.ft.Hope this helps.

Dave – posted 12 July 2002 19:06

RE: Puple blades in St. Augustine -The purple blades did not occur in a specific area of the turf. Rather, the purple blades were nearly evenly distributed throughout the lawn, and perhaps there were 15 – 30 discolored blades per square meter. There were no circles of discoloration as was suggested in the previous post nor discreet areas of blade discoloration. It’s now mid-July, and the purple blades have not reappeared.

The purple areas on the blades, and the quantity of purple blades in the turf did not increaseafter my application of a fungicide, followed a week later with mowing. I suggest no relationshipt between the fungicide/mowing and the cessation of the purple.

landrew small@hotmail.com – posted 28 December 2002 05:16

It seems that you aree the victim of what could be various symtems and only two or three causes.It can be a P and also a trace element shortage.

The other thing can be a fertiliser burn, brought on by the weaking by the fungal attact. This is typical in a high Fe or similar application.

My advise is to cut short and remove the cuttings and then irrgate to leach the possible overfertilizing and then treat for fungal infectionGood luck

horti-care inc. – posted 01 February 2003 14:02

if this thread is still alive…..the purple grass “phenom” is usually due to the cool weather. i am a lawn spraying tech in polk county, fl and this is a common sight in most lawns.

Will-PCB – posted 11 February 2003 07:25

Yeah, it looks funny, but it sure doesnt seem harmful.

merrillmck – posted 22 February 2004 14:52

In Orlando, this week I noticed the same purple in new sod being sold at Home Depot. It is in the healthiest parts of my yard. It is the my best neighbors yards. I would do nothing or do the less drastic remedies on this thread.

Dchall_San_Antonio – posted 04 March 2004 01:24

If it happens in the winter, I would forget about it. If it happens in the summer, then I’d get concerned. It seems to happen to the taller St Augustines in the winter. Of course mowing clips off the purple part so you never see it.

dstrahm – posted 18 March 2004 19:07

I’ve found that the purpling of the leaves to be associated with cold, near or at freezing, damage. I noticed after a short, windy cold snap that the areas most affected were directly exposed to the wind. The areas that had little or no purple were protected from the cold. Walking on the grass while it was still near freezing appeared to increase the amount of purple.

Dchall_San_Antonio – posted 19 March 2004 08:52

That might explain why the tallest grass seems to be the purplest. Interesting.

Mine is greening up now, so the purple is disappearing.

cohiba – posted 20 March 2004 09:52

I think we have two things going on here.

1. Notice the straight line in the leaves. that is from the mower not cutting and just tearing. The jagged tearing is another sign that the mower blades need to be sharpened or replaced.

2. The purpling occurs mostly in the cooler temps? We notice this alot in bentgrass in the north in the winter months. It has been determined that this is a physiological sign that the plant cannot take up the potassium it needs from the soil. This response will go away as soil temperatures warm up. we try to counter this responce by appling 2# material per 1000sq.ft. of 0-0-50 potash usually in late fall, prior to the colder soil temps.

Just my thoughts……

svcrawf72 – posted 31 March 2004 11:50

It is April , ok 1 day before April here in Jacksonville Fl. I walked out to my yard and saw Purple grass! I quickly ran to this site and read about this. I went to the local Agraculture office and was told that it was new growth that has been affected by cold weather. I said “the low is around 50-60 at night and a few night I remembered it dropped to high 40s. I was told 50 deg on new groth will hurt St Aug grass causing it to turn Purple! Mow it and it will regrow

jlievano – posted 23 December 2004 11:13

I had the same experience with brown patches and areas turning purple. I brought a sample to the broward county extension service and they said it was a fungus called brown patch; which I believed somone already posted the same answer.The extension service in your area will analyze anything for free and prescribe the right remedy for it.

sclifford – posted 11 February 2005 07:00

This is the result of either, exposure to cold temperatures or to chlorine. Chlorine damage is caused by emptying a pool out, but the line between green and pruple is usually not so well defined. There is no reason to worry, it is not a pathogen and the turf will grow out and return to normal. Think of it as “fall color” for the south!

dk – posted 19 September 2009 19:19

I have a organic lawn, and I spray weeds (crabgrass clumps) with straight vinegar and a little soap to kill them. The crabgrass and any augustine I hit accidentally will turn purple almost immediately. So, maybe your weed killer, or some temporary acidity is causing the purple. Just a thought.

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