Zoysia vs. St. Augustine Grass: Differences and Which to Choose

St. Augustine and Zoysia lawn grass varieties are both great warm-season turfgrasses for a variety of reasons. However, each species carries distinct traits that can be essential when distinguishing one type from the other and even when choosing grass for establishing your lawn. But, what is the difference between zoysia and St. Augustine grass?

What does zoysia look like?

Zoysia grass has fine/coarse-textured leaves that appear rolled in the bud shoot. The leaf color ranges from light to medium green (depending on the species) with a dense and compact growth pattern.

The leaves are stiff due to the high silica content, and the presence of rhizomes and stolons make for a significant distinguishing feature of the plant (which can reach 6 to 12 inches in height).

What does St. Augustine grass look like

St. Augustine grass has broad, flat, dark green leaves that appear densely coarse when touched. The grass forms a compact surface making it ideal for use as turfgrass. On maturity, the grass can reach a height of about 12 inches (with some species exhibiting flower and seed development).

Zoysia vs. St. Augustine Grass – Differences

Here’s what you should consider when differentiating zoysia from St. Augustine grass:

Growth Patterns

Zoysia and St. Augustine grass types exhibit unique growth patterns that can help one to differentiate a variety from the other.

Zoysia grass: Grows at its peak in late spring and summer. The plant prefers warm climatic conditions and slowly spreads out laterally over time. The grass spreads through above and underground stems (Stolons and rhizomes) to create a dense green carpet ideal for lawns, golf courses, etc.

St. Augustine grass: A fast-spreading turfgrass variety that grows well under warm weather. The growth is mainly propagated by stolons, making the species ideal for owners looking to quickly fill bare spots on their lawns or other outdoor spaces.

Water/Fertilizer Requirements

Zoysia and St. Augustine grass varieties have specific water and fertilizer requirements that can be useful when distinguishing one type from the other.

Zoysia grass water and fertilizer requirements include:

  • Water requirements: The grass requires only about 1 inch of water per week, ideally during the morning hours. Zoysia can tolerate short periods of droughts .
  • Fertilizer requirements:  During active growth periods(May to August) apply about 1 pound of nitrogen per 1,000 square feet every month.  If soil pH is below 6.0, add lime to increase pH. If soil test show your soil is deficient in nitrogen(N), phosphorus(P)and potassium(K) add lawn fertilizer with ratio of N:P:K of 3:1:1 or 4:1:1 or 4:1:2.

St. Augustine grass water and fertilizer requirements include:

  • Water requirement: It requires about ¾ inches of water per week to remain healthy. It’s best to water the grass twice a week during the warmer months.
  • Fertilizer requirements:  Apply 1 pound of soluble nitrogen per 1,000 square feet of lawn every two months after grass turns green (after dormancy) to promote foliage and ensure grass remains green.  

Ideal Growing Zones

Zoysia and St. Augustine grass varieties thrive in diverse environments and growing locations. The best growing locations vary from one species to another.

Zoysia grass:  A highly adaptable species that can grow in the following conditions:

  • Zhosia grass grows best in USDA zones of 5 to 11. The warm weather grass  can tolerate cold also withstand heat and dry weather.
  • Zoysia grows best when exposed to 6 to 8 hours of full sun, and soil pH of 6-6.5.
  • Zoysia also thrives when temperatures are (80 to 95°F) during sprng, summer and early fall(60 days before the first frost).  

St. Augustine grass: Prefers the following conditions:

  • St Augustine likes warm climatic regions that range from 8 to 11 on the USDA chart. It is the least cold tolerant of all the warm season grasses.
  • St. Augustine grows best during warmer seasons(spring & summer when temperatures range from 80°F to 100°F).
  • St Augustine like full 90 days of sun before the first fall frost and soil pH of 6-6.5. The 90 days before the first fall frost gives your St. Augustine enough time to grow before the cold weather sets in.

Grass Height

You can distinguish Zoysia from St. Augustine grass by considering the different height averages of individual grass species.

Zoysia grass:  Reach a height of about 6-12 inches if left to grow undisturbed. Some Zoysia grass species grow in dense clumps, which might become more pronounced if the grass is left to grow without regular maintenance.

St. Augustine grass: Reach a height of up 12 inches if left to grow unchecked. The grass also develops small white-red-like flowers and might produce seeds on maturity. St. Augustine grass tends to grow aggressively during its active growth phase (and might demand constant attention compared to other turfgrass species).

Mowing Needs

Zoysia and St. Augustine grass varieties require regular mowing to maintain a sustainable height and keep your space clean and tidy.

Zoysia grass: Spreads more slowly compared to other varieties hence cater to its mowing need by:

1. Mowing once it reaches 1 ½ to 3 inches in height.

2. Maintaining at least  of the average blade height (you can mow to heights less than an inch using specialized equipment).

3. Mowing to about 2-2.5 inches if it grows under partial shade.

4. Mowing after its winter dormancy, preferably from late April to early May.

5. Mowing every 7 to 10-day to make grass thicker and give it a compact appearance.

St Augustine grass: Spreads faster than Zoysia hence you should cater to its mowing needs by:

1. Maintaining mowing height from 2 ½ to 3 inches.

2. Mowing to about 3½ to 4 inches in shady areas.

3. Mowing in early spring after the grass color changes to green.

4. Retaining at least ⅓ of the original leaf foliage height to keep lawn aesthetics and safeguard against scalping your lawn.

5. Mowing every 10 to 14-day.

Sunlight Requirements

Zoysia and St. Augustine grass species have distinct sunlight needs that help distinguish one species from another.

Zoysia grass: Requires at least 4 hours of direct sunlight during its active growing phase. The grass can also withstand 50% sunlight for a period averaging 8 hours of continuous exposure.

St. Augustine grass: Highly tolerant to shade and can thrive under reduced sunlight conditions but requires at least 5-6 hours of full sunlight to maintain its lush green color. Shade tolerant St Augustine strains can also thrive under 4 hours of sunlight per day.

Practices to adopt when growing turfgrass under shade (Zhosia & St. Augustine)

Turfgrass growing under shade is suffering from a lack of sufficient light so it is essential to maintain practices that boost growth. Increase mowing height, use slow nitrogen fertilizer, eliminate sprinklers in shaded areas, avoid foot traffic and apply a pre or post-emergence herbicide for weed control.

Tolerance/Diseases

Zoysia and St. Augustine grass varieties have different tolerance levels to pests and diseases. You can readily distinguish the species by considering their ability to resist diseases and infestations.

Zoysia grass:  Tolerant to chich bugs that attack other types of turfgrass. However, the grass is susceptible to pest like armyworms, billbugs, mole crickets, etc, and fungal attacks.  

Zhosia grass appears bleached with dry patches when affected by diseases like:

  • Root rot
  • Large patch fungus
  • Parasitic nematodes.

St. Augustine grass: A hardy species that can withstand numerous conditions. However, the grass is highly susceptible to attacks from different pests like chich bugs, grub worms, sod webworms, armyworms, etc.

St. Augustine grass will change from green to yellow/brown, have conspicuous dry patches that peel from the soil when affected by:

  • Root rot
  • Brown patch fungi attacks
  • Stolon rot from the Niglospora fungi

Note: Symptoms vary depending on the pest, fungi, or disease currently affecting your grass. Also deal with pest/disease infections as soon as they occur with homemade remedies or  commercial fungicides and insecticides.

Dormancy Periods

Zoysia and St. Augustine grass species are warm weather turfgrass varieties that become dormant as the weather cools or during the cold season. Both types have elaborate dormancy periods that can be useful when determining an ideal choice for your lawn.

Zoysia grass: It becomes dormant when temperatures drop below 55℉. During winter months, your grass stops growing (and might appear dead). The presence of green runners indicates a semi-dormant plant; dry loose crowns may imply that your grass could be dying.

St. Augustine grass:  It becomes dormant during winter when temperatures drop below 55℉. The grass overgrowth turns brown during the dormancy period (though some species may retain their green color).

Dormant grass regains its original color during spring when temperatures are above 80. Dead St. Augustine grass readily gives way to external pressure when you tug at the roots. On the other hand, healthy roots has a firm feel on tugging.

Note: It’s crucial to safeguard dormant grass from foot pressure (when people walk over your lawn surface) as it is highly vulnerable to injury and damage.

Cost Of Maintenance

Zoysia and St. Augustine grass varieties are excellent turfgrass options for your outdoor space. Both cost about $0.30 to $0.80 per square Ft. to purchase quality sods (though prices vary depending on location, delivery, and additional labor costs).  However, each species has a unique maintenance schedule that distinguishes one from the other.

Zoysia grass: It requires constant attention and maintenance to retain its attractive features. The upkeep translates to a time and monetary investment for those looking for an easy-to-maintain turfgrass option for their private/commercial properties.

St. Augustine grass: It has a relatively lower maintenance cost compared to the Zoysia grass variety. However, the grass requires frequent fertilizer applications, and watering requires relatively high maintenance compared to other turfgrass species. St Augustine has a highly aggressive nature meaning you have to invest considerable time mowing the lawn surface during its active growth period.

Which Grass to Choose

Deciding on the best turfgrass option for your lawn can be challenging, especially if you are unsure about what to look for in each species. Weather, temperature, humidity, and soil type are essential factors to consider when determining a suitable grass option for your property.

Choose tall Zoysia grass if:

  • You live within USDA zone of 5 to 11
  • Interested in a slow-spreading grass option
  • Looking for a hardy species resistant to high traffic/physical injury
  • You need grass with low water requirements
  • Looking for  grass that withstands both cold and dry weather

Choose St. Augustine grass if:

  • You live within USDA 8-11
  • Looking for grass with low water requirements
  • Looking for shade-tolerant turfgrass
  • Looking for fast-spreading grass species
  • Live within coastal/saline soils

Will St. Augustine grass invade and overtake Zoysia grass?

St. Augustine grass grows faster than Zoysia grass, which means that the fast-growing species will overtake and inhibit the growth of the other. However, the dense and compact growth of Zoysia grass makes it difficult for invaders to establish roots.

It also depends on the actual of grass you are growing in your lawn as some varieties such as the Palisades zoysia are aggressive growers and can compete with St. Augustine grass for dominance.

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