Lime for St. Augustine Grass (Timing Guide)
Apply lime to St. Augustinegrass only when a soil test recommends it. Aim for the lab’s advised range, often about pH 5.5–6.5, and use its lime rate rather than guessing from grass color or pH alone. Apply when soil is workable, follow the product label, and retest only when the lab advises.
A common question I hear is, “My St. Augustine is yellow; should I put lime down now?” Not without a soil test. Lime raises soil pH, but it is not a general cure for yellow grass, thin growth, or other lawn problems. Used at the wrong rate, it can make some nutrient problems worse.
When St. Augustinegrass needs lime
Lime is a soil amendment that raises pH, a measure of how acidic or alkaline soil is. St. Augustinegrass commonly does well in soil around pH 5.5–6.5, but your local soil-testing lab’s recommendation should guide any treatment. A number outside that range does not, by itself, tell you how much lime to apply.
If your test reports a lime requirement, use that recommendation. It accounts for more than the pH reading: soil type, its ability to resist pH change, and the lime product’s neutralizing value all affect the amount needed.
Yellow grass is not proof that soil needs lime
Yellowing is a symptom, not a diagnosis. Applying lime without a test can raise pH too far and reduce the availability of iron and other micronutrients. That can lead to chlorosis, or yellowing caused by poor chlorophyll formation, and weak turf.
Check soil test results before buying lime. If the test does not recommend it, investigate other causes with a local extension service or qualified lawn professional rather than treating by appearance alone.
Best time to lime a St. Augustine lawn
Lime can be applied when the soil is workable, and it is useful to give it time to react before active growth. There is no universal calendar date that works across regions and soil conditions. Follow the lab’s directions and choose a time when you can spread the product evenly without creating runoff or tracking it across wet ground.
Use soil conditions, not a fixed month
St. Augustinegrass is a warm-season turf, but that does not make a particular month the right time to lime every lawn. Local weather, soil condition, and the test recommendation matter. Applying ahead of active growth gives lime time to begin reacting, but lime works gradually, not overnight.
Avoid spreading on saturated soil or when heavy rain could wash granules into a drain or waterway. If the product label or soil lab gives specific watering directions, follow them. Otherwise, do not assume that heavy watering is needed.
Timing guide
| Situation | What to do |
|---|---|
| Soil test recommends lime; soil is workable | Apply at the test-recommended rate, following the product label. |
| Test recommends lime, but soil is saturated | Wait until the soil is workable and application will not cause runoff. |
| Grass is yellow, but there is no soil test | Test first; do not use lime as a guess. |
| A prior application was made recently | Retest at the lab’s advised interval before applying more. |
| The lawn is due for another routine treatment | Do not lime by calendar habit; use the test result. |
Test the soil and calculate the amount
A useful lawn soil test reports pH and a lime requirement. The lime requirement is the amount the lab recommends to move the soil toward its target. Do not turn pH into a rate on your own: two soils with the same pH can need different amounts because their texture and buffering capacity differ.
Collect a representative sample
Remove surface debris, then collect soil cores from the upper 0–4 inches. Take several cores from spots within one uniform lawn area and combine them as the lab directs. If one section has a distinct problem or is managed differently, sample it separately rather than blending it into the main sample.
Use a clean tool and the lab’s sample container and instructions. A sample taken from only one spot may not represent the whole lawn. Label each sample by area so you can match the results to the right part of the property.
Read the full recommendation
Look for soil pH, lime requirement, and any note about magnesium. The target pH for St. Augustinegrass is about 5.5–6.5, but use the lab’s specific target and directions. If the report is unclear about the product’s neutralizing value or how to convert its rate, ask the lab before spreading.
Measure the lawn area you plan to treat. For example, if a uniform area is 5,000 square feet and the lab gives a rate per 1,000 square feet, multiply that rate by five. This is an area calculation, not a substitute for the lab’s recommended rate or product instructions.
Choose the right lime and prepare safely
Agricultural limestone is the appropriate category for turf. Calcitic lime supplies calcium; dolomitic lime supplies calcium and magnesium. Use calcitic lime unless the test also indicates low magnesium and the lab says dolomitic lime is suitable. The product label’s neutralizing value and particle-size rating affect how well it can meet the recommendation.
Do not use hydrated lime, quicklime, or unlabelled industrial lime on a lawn. These materials can be caustic and may injure people, pets, and grass. Buy a labeled agricultural product and follow its directions.
Before application
Check the test report, label, lawn area, spreader instructions, and any single-application limit. If the product differs from what the lab assumed, ask the lab how to account for its neutralizing value rather than guessing at an adjustment.
Wear gloves, eye protection, and a dust mask while handling lime. Keep children and pets away during application as directed by the label. Protect pavement, drains, and nearby water by keeping product in the intended lawn area.
Apply lime evenly at the recommended rate
Use a calibrated spreader and the test-prescribed amount. Uneven coverage can leave some areas under-treated and others over-treated. If the recommended total exceeds the product label’s limit for one application, split it into label-compliant applications; do not exceed the label rate to finish faster.
Step-by-step application
- Confirm the area and the total product amount from the lab recommendation and product directions.
- Set the spreader according to the label and calibrate it as the manufacturer directs.
- Apply evenly across the lawn, avoiding piles and overlap that could create heavy bands.
- Keep granules off pavement and out of storm drains. Sweep up any that land on hard surfaces.
- Water lightly only if the product label directs it, and keep a record of product, amount, area, and date.
A practical check is to note how much product you put in the spreader and how much lawn that amount covers. If the product runs out well before or after the measured area is covered, stop and review your rate and spreader setup before continuing.
Field examples: how the timing decision works
These examples show how to apply the decision process; they are not claims about a particular property or substitute for a soil test. The same grass can need different treatment in different soils, so the lab report remains the basis for the choice.
Example: a low pH reading with a lime recommendation
A homeowner’s representative sample reports acidic soil and includes a lime requirement. The soil is workable, and the product label allows the amount to be applied as one treatment. The homeowner follows the lab rate, selects the product type based on the report, and records the date for future reference.
Example: yellow turf but no lime recommendation
A test shows no need for lime, even though parts of the lawn look yellow. Adding lime could push pH too high and limit micronutrient availability. The better next step is to investigate other causes rather than repeat a treatment that the soil test does not support.
Example: magnesium is low
If the soil test indicates low magnesium as well as a lime need, dolomitic lime may be appropriate. The lab’s recommendation should determine the type and rate. Do not choose dolomitic lime solely because it is available or assume it will correct every nutrient issue.
Retest and store the product properly
Lime reacts gradually, so the lawn may not show a quick change. Watch turf condition, but use a follow-up soil test—not grass appearance alone—to decide whether more lime is needed. Retest after the interval specified by the testing lab; do not repeat an application simply because a set number of months has passed.
Keep leftover lime dry in its original labeled container and secure it from children and pets. Clean the spreader after use to limit residue buildup and corrosion. Keep your test report and application record together so the next test can be compared with the previous one.
Frequently asked questions
When should I put lime on St. Augustinegrass?
Apply lime when a representative soil test recommends it and the soil is workable. Applying ahead of active growth gives it time to react, but there is no one calendar date for every lawn. Follow the local testing lab’s timing advice and the product label.
What soil pH does St. Augustinegrass need?
About 5.5–6.5 is a suitable soil-pH range for St. Augustinegrass. Treat that as a general guide, not a reason to calculate a lime rate from pH alone. Use the target and lime requirement provided by your soil-testing lab.
How often should I lime my lawn?
There is no routine annual schedule for lime. Retest at the interval recommended by the soil-testing lab, then apply more only if the new recommendation calls for it. Reapplying by habit can raise pH too far and harm nutrient availability.
Can I lime St. Augustinegrass in summer?
The season alone does not determine whether lime is needed. Apply only when the soil test recommends it, the soil is workable, and the product can be spread without runoff. Ask your local lab whether its guidance sets a timing limit for your region.
Should I use calcitic or dolomitic lime?
Use calcitic lime unless the soil test also indicates low magnesium and the lab recommends dolomitic lime. Calcitic limestone supplies calcium, while dolomitic limestone supplies calcium and magnesium. Choose based on the test, not on grass color or product price alone.
Will lime fix yellow St. Augustinegrass?
Not necessarily. Yellowing can have causes other than acidic soil, and lime does not provide a general cure for poor growth. Test first; if lime is not recommended, adding it may raise pH too high and reduce the availability of iron and other micronutrients.
How deep should I take soil samples?
Collect cores from the upper 0–4 inches after removing surface debris. Take several cores from each uniform management area and keep distinct problem areas separate. Follow your testing lab’s collection and mixing instructions so the sample represents the lawn you intend to treat.
Can I apply the full recommended amount at once?
Only if the product label allows that amount in a single application. If the test recommendation exceeds the label’s single-application limit, split the total into applications that comply with the label. Do not exceed the recommended total or apply extra to speed up the result.
(This article was written by one of our staff writers, Victor Dempsey. Visit our Meet the Team page.)
