As temperatures turn colder each fall, St. Augustine lawns across the South transform from lush and green to tan and brown. The summer dynamo of growth and vigor appears to sputter to a halt, leaving many homeowners concerned. Is this treasured grass in trouble?
The truth is that St. Augustine grass, like all warm season turfgrasses, enters a natural period of winter dormancy in response to frost. This helps it conserve energy and carbohydrate reserves during inhospitable growing conditions. Dormancy is not a cause for alarm, but rather a phase requiring adjusted care.
In this article, I’ll draw on years of experience caring for St. Augustine lawns to explain everything you need to know about dormancy. We’ll look at the triggers that send St. Augustine into hibernation mode, how it changes appearance and growth habit during this time, and what you can do to sustain its health. I’ll also provide tips for bringing your lawn out of dormancy strong in spring.
Don’t let the annual browning scare you. With my guidance, you’ll gain confidence caring for dormant St. Augustine. Let’s delve into the winter sleep patterns of this iconic southern turfgrass.
When Does St. Augustine Grass Go Dormant?
As a landscaper who has cared for St. Augustine lawns for over a decade, the question I’m asked most frequently each fall is when this grass will go dormant. Homeowners want to know the event that signals the transition from active growth to winter rest.
Through years of observation, I’ve pinned down the specific trigger that sends St. Augustine into hibernation mode. Let’s look at what initiates dormancy and what happens afterwards.
First Frost Induces Dormancy
St. Augustine remains lush and green throughout the warm season, actively growing as temperatures allow. But at the first sign of a true frost, lasting long enough to chill the crown and roots, the grass shifts gears dramatically.
Sustained temperatures below 32°F damage the tender tissues that fuel growth during favorable weather. As a survival mechanism, St. Augustine halts all activity, going into dormancy to conserve resources until conditions improve.
So the very first hard autumn frost is the definitive marker telling St. Augustine it’s time to start shutting down for winter. Even milder freezes for brief periods can initiate the transition.
Dormancy Deepens as Cold Increases
The initial light frost is only the beginning of the dormancy process. With each subsequent frost or freeze, St. Augustine’s metabolism keeps slowing as cells harden off for winter.
Exposure to extreme cold, like temperatures in the teens (F) or single digits, completes the transition. The grass descends into a deeper state of minimal function and activity.
At this point, the St. Augustine lawn will remain fully dormant until consecutive warm spring days arrive. The process is gradual but cumulative.
Duration Varies Across St. Augustine’s Range
Timing of the first frost and passage to full dormancy depends on your climate and location within St. Augustine’s range. In South Texas, the grass may stay actively growing into December, while more northern areas see frost in October.
But regardless of timing, the initial frost event starts the countdown to completed dormancy. Once the crown dips below 32°F, hibernation has begun! Be on the lookout for frosty nights.
Knowing the precise trigger of first frost helps homeowners understand dormancy is a natural protective process, not a cause for panic. Your St. Augustine simply needs its winter rest.
How Dormancy Affects St. Augustine Grass?
When St. Augustine grass transitions into winter dormancy, you’ll notice distinct changes to its appearance and growth habits. Understanding these transformations will prevent undue concern over the annual browning.
Let’s examine how dormancy impacts St. Augustine foliage, color, growth rate, and overall vigor. Recognizing the natural effects of dormancy will help guide proper care.
Foliage Stops Growing
The most obvious change is that new leaf blade growth ceases as St. Augustine enters dormancy. Lower light intensity and reduced soil temperature prohibit photosynthesis.
With its food factory shut down, St. Augustine curtails above ground activity. No new shoots or stolons emerge until light and soil conditions improve in spring.
While existing blades remain intact, no fresh foliage appears. Growth stands still throughout dormancy to conserve energy.
Dormant Grass Turns Tan or Brown
Chlorophyll production halts during dormancy, causing St. Augustine’s color to fade. Initially, the grass takes on a washed-out, yellowish appearance.
Prolonged chilling results in fully brown and tan dormant grass. This lack of green color persists from first frost until consistent spring warmth.
It can be alarming to witness your emerald green lawn fade to brown. But this change is completely normal and temporary during dormancy.
Metabolism and Activity Slow Dramatically
All cellular processes grind to a halt once St. Augustine is dormant. There is minimal respiration, nutrient uptake, or movement of compounds within the plant.
The grass basically hits pause on all activity except the bare minimum functions to keep crown and root tissues alive through winter. Growth stops both above and below ground.
This period of inactivity conserves the carbohydrates St. Augustine manufactured during peak growth. Energy is diverted solely to survival.
No Cause for Concern
While dormancy causes dramatic changes, St. Augustine remains alive and well, just resting. Don’t let the altered appearance alarm you.
Trust that your grass will rebound vigorously once ample sunlight, moisture, and warmth return in spring. Go dormant along with your lawn this winter!
Caring For Dormant St. Augustine Grass
Many homeowners ask me if special care is required for St. Augustine lawns during dormancy. While growth halts, some maintenance is beneficial to sustain health into spring. Here are my top tips for managing dormant grass:
Continue Mowing at Raised Heights
Mowing is still necessary during winter dormancy, though less frequently. I advise mowing every 3-4 weeks depending on growth rate.
Raise mowing height by about 1/2 inch compared to summer mowing. This extra blade length insulates the crown and reduces frost damage. Never scalp dormant St. Augustine extremely short.
Use sharp blades and avoid mowing on frosty days when blades are brittle. Clippings should be minimal due to reduced growth during dormancy.
Apply Potassium for Cold Tolerance
Potassium strengthens St. Augustine’s cell walls and increases its cold hardiness. I recommend applying a potassium-rich fertilizer 6-8 weeks before expected first frost.
Potassium aids the grass’s transition into dormancy and supports crown and root health throughout winter. Continue potassium applications if temperatures remain mild.
Water Only When Required
Avoid overwatering dormant St. Augustine, but don’t allow severe drought stress either. Monitor soil moisture weekly and water only if the top few inches become very dry.
Dormant grass has minimal evapotranspiration rates and requires little supplemental water in cool weather. But crown dehydration can occur during prolonged dry periods.
Reduce Nitrogen Fertilization
Discontinue nitrogen fertilization after St. Augustine enters full dormancy, typically after consecutive freezing nights. Nitrogen drives foliar growth, which is counterproductive during dormancy.
Excess nitrogen also risks leaching or runoff with winter rains since the grass cannot absorb it. Resume light nitrogen rates after spring greenup.
With a little attentive care, your dormant St. Augustine will stay healthy and prepared for vigorous re-emergence. Don’t neglect it completely just because growth has halted.
When Does Dormant St. Augustine Grass Green Up Again?
After months of tan, brown dormancy all winter, I know homeowners long for their St. Augustine lawns to reawaken with fresh green growth. The big question is, when will dormancy break and active spring growth resume?
Based on years of observations, I can confidently pinpoint the signals that dormancy is ending and greenup will soon begin. Let’s look at the transition timeline.
Soil Temperature Is Key
While air temperatures may rise in late winter, soil temperature is the primary driver determining when dormant St. Augustine will green up.
Consistent soil temps above 55°F at a 4″ depth indicate biological activity is increasing. This rising temperature triggers the grass to break dormancy.
Until soils reach and remain above this threshold for air and soil to align, greenup will not commence even if air temps seem warm. Be patient!
Light Frosts Stimulate Growth
Brief, light frosts act as a transition between cold winter temps and warmer spring weather. These fleeting frosts help stimulate crown activity.
Following a light frost, you may notice crown tissue beginning to green at the soil surface. This indicates winter dormancy is transitioning to spring growth.
Sustained Warmth Returns
Daytime high temperatures consistently above 70°F tell the crowns to accelerate greenup. Combine this warming trend with soil temps exceeding 55°F, and dormancy will quickly break.
I see the first spring greenup flush 7-10 days after these threshold temperatures are met. Then St. Augustine begins another season of lush growth.
Watch For Late Cold Snaps
Be cautious of occasional cold snaps after initial spring greenup. Radical temperature drops can damage freshly growing tissue.
Browning may occur with cold spells, but established St. Augustine recovers quickly. Complete greenup takes 4-6 weeks.
In summary, look for warming soil temperatures, light frosts, and sustained air warmth to signal the end of dormancy. Then get ready for vibrant spring growth!
FAQ
Does frost cause St. Augustine grass to go dormant?
Yes, the onset of frost triggers dormancy in St. Augustine grass. Once temperatures dip below 32°F for an extended period, St. Augustine will cease growth as its tissues become damaged by freezing.
The first light autumn frost causes initial drought stress. But repeated frosts or freezes are what typically send St. Augustine into full dormancy. The depth of dormancy deepens as cold intensifies.
It’s the sustained frigid air and ground temperatures that prompt the grass to halt photosynthesis and enter survival mode. So while a brief overnight frost may cause some initial signs of decline, repeated frosts stop all activity.
What does dormant St. Augustine grass look like?
Dormant St. Augustine undergoes a dramatic transformation in appearance. The vibrant green color fades to a washed-out yellowish-tan hue once growth stops.
Prolonged chilling eventually causes the dormant grass to appear brown. Leaf tissue shrinks and blades lie flat over the ground. The lawn takes on a drab, straw-like color.
No new shoots or stolons emerge from dormant St. Augustine. Leaf tissue remains intact but in a browned state, with no new growth. The grass appears static, showing no signs of life or vitality.
But this bleak dormant appearance is only temporary until warmer spring weather arrives!
Is St. Augustine grass dead when dormant?
It’s understandable to mistake dormant St. Augustine for dead grass. However, quality St. Augustine is very much alive through dormancy, just in a paused state.
While growth halts, key crown and root tissues remain viable but inactive during dormancy. No new blades form, but established ones persist intact.
The grass conserves energy by shutting down non-essential functions. This pause allows it to survive harsh winter conditions that would kill more fragile grasses.
So long as the crown stays healthy, St. Augustine will revive and resume growth when ideal conditions return. Trust in its resilience and rest along with your dormant lawn!
Conclusion
As we’ve explored, St. Augustine grass depends on a period of winter dormancy to survive freezing conditions. This protective pause in growth is a natural adaptation, not a cause for concern. With proper care focused on low maintenance, dormant St. Augustine sustains itself until warm temperatures return.
While discolored and static in appearance, dormant turf remains very much alive. Have confidence in St. Augustine’s ability to rebound vigorously after spring greenup. Avoid overwatering, fertilizing, or excessive traffic during dormancy. But do continue mowing at raised heights to tidy appearance.
Most importantly, know the signals like soil temperature and frost patterns that indicate dormancy is ending and growth will resume. Then get ready to revive your lawn care regimen as green color and lush density return.
Dormancy is a time for both St. Augustine and its caretakers to rest. Implement my guidance to ensure your lawn remains healthy through winter. Soon you’ll be rewarded with the green carpet you expect from this iconic warm season grass. Just be patient – spring will arrive!
