A regular lawn fertilization schedule is your BEST defense against weeds, fungus, and insect damage! We recommend a lawn fertilization application AT LEAST in spring and fall. However, if your lawn is badly damaged, you may benefit from the additional fertilization recommendations listed between the spring and fall dates. The following dates are guidelines for when to make your lawn fertilization applications. Keep in mind that the weather is really what we need to go by. It can dictate an earlier or later application time.
San Antonio Lawn Fertilization Schedule
- Mid April – Mid May For Spring Lawn Fertilization: Grass must be actively growing to absorb fertilizer properly. After the second mowing of the season, apply a simple 19-5-9 formula for an early green-up. Rainbow Gardens 19-5-9 premium lawn fertilizer is specially formulated for our region. (4-6 weeks earlier for organic lawn fertilizer (Mid Feb – Mid March)
- Mid May – Early August For Summer Lawn Fertilization (if needed): Apply slow-release 3-1-2 or 3-0-2 fertilizers or a liquid lawn fertilizer like Medina’s Hasta-Gro lawn food.
- June-September For a Chelated Iron lawn Fertilization Application (if needed): This is not always necessary, but if turf grass looks yellow (iron chlorosis) and weak you could apply a granular or liquid iron supplement. Every second or third month during the warm season should be enough. Hi-Yield Iron Plus granules and Dr. Iron are two excellent choices. Stay away from Ironite……it doesn’t have much effect in our alkaline (high PH) soils.
- October-November For Fall Lawn Fertilization: Apply winterizing formulas for winter hardiness. Ratios vary, but make sure they are “winter” or “fall” formulas designed for southern grasses. Rainbow Garden’s 18-6-12 winterizer formula is a great choice These formulas will make lawns winter-hardy and provide for early spring green up. 4-6 weeks earlier for fall organic lawn fertilizer.
*Try your best when applying fertilizers (synthetic or organic) to keep it on the turf as much as you can. Avoid over-spreading onto sidewalks, driveways and streets, as this leads to run off. Fertilizers with iron can stain concrete. Nitrogen and phosphorous are great for the lawn but not for our water supply.
Recommended lawn fertilization formulas for warm season southern grasses in South Central Texas
- 19-5-9 + minors ……………..(Rainbow Gardens Premium Lawn/Tree & Shrub Food )
- 18-0-6 + Trace ……………….(Fertilome Greenmaker)
- 24-0-10 …………………………(Fertilome + Chelated Iron Premium Lawn Food)
- 18-6-12 + minors ……………(Rainbow Gardens Premium Fall Winterizer Lawn/Tree & Shrub Food)
- 6-1-2 …………………………….(Nature’s Creation organic – Manure Free)
- 6-2-4 …………………………….(Texas Tee organic)
- 3-2-3 …………………………….(Medina Growin’ Green organic)
FAQ’s about lawn fertilization:
What do the numbers on the fertilizer bag mean?
They are the ratio of nitrogen (N) to phosphorous (P) to potassium (K). Nitrogen is responsible for making turf green, phosphorous (slower-acting) promotes root development, and potassium works to feed turf and keep it strong during drought or other stressful conditions.
What’s the big difference between synthetic and organic fertilizers?
- Both organic and synthetic fertilizers contain active NPK ingredients. It’s the source from where those ingredients come from that is different.
- Synthetic fertilizers get their NPK from chemicals. Organic fertilizers get their NPK from naturally derived elements, like manure, biosolids, and the like.
- It’s important to remember that timing for applying organic fertilizer is earlier than applying synthetic since it takes longer to break down and become available for plant uptake.
Should I choose a synthetic or organic fertilizer?
This is a decision you will ultimately need to make, but here are a few differences.
- Synthetic fertilizers offer quick turn around and fast green-up as their chemical ingredients are more readily available to be used right away in the fertilization process. Synthetic fertilizers are usually less costly.
- Organic fertilizers take a little longer to work as their ingredients must be naturally broken down and processed in order to be used. However, most organic fertilizers actually increase the health of your soil by improving its ability to digest and absorb the fertilizer ingredients.
Soil Testing
If you continue to have issues with your lawn, even after sticking to a lawn fertilization schedule, it might be time to have your soil tested. The turf on top can’t do much if the soil below is horrible. Follow the Texas A&M Agrilife Extension advice in this link to properly obtain and send in soil samples.
~The Happy Gardener, Lisa Mulroy
Do you suggest fertilizing newly planted grass? I have placed an order of Bermuda Celebration and not sure what fertilizer to use for this type of grass and when to fertilize?
Hi Katherine,
very sorry for the delay in my reply. You can safely use Hasta Grow For Lawns by Medina. Just follow the directions on the label to give your lawn a good jump start.
Just got some Dr. Iron. Thank you for the recommendations.
I want to purchase a yellow ribbon magnolia tree that will mature at 15′-20′. Do you have them, and can I plant one now or wait until the spring season?
We do not currently have any yellow magnolias in stock, but as far as planting any tree, fall is the absolute best time to plant trees, shrubs, woody perennials in Texas.
What is the best fertilizer for St. Augustine grass? When should I apply it?
Thank you,
For fall fertilizing, our Rainbow Gardens 18-6-12 is a great fertilizer that has been specially formulated for lawns in our region. Apply early to mid October. In spring, opt for our Rainbow Gardens 19-5-9 formula. More info on application times and why fertilizer is important for our lawns is found on this blog you commented on.https://www.rainbowgardens.biz/news-events/san-antonio-lawn-fertilization-guide/
what about applying weed and feed now, in January. we have 4 days of rain coming and would like to spread it this weekend.
Hi Mike,
We never suggest weed and feed products. Reason being, fertilizing and weed prevention gets applied at different times in San Antonio. Organic fertilizer can get put down mid to end of February. Synthetic fertilizer gets put down mid April.
Weed pre-emergent can start to get put down end of February into March (depending on the weather), or after the second good spring rain.
Is it to late to use a organic fertilizer for fall this year or should I use a synthetic?
The optimal time to put down organic lawn fertilizer is the beginning of September. I am attaching this link about organic fertilizer so you can see why there is a difference in application timing between organic and synthetic fertilizer. October is prime time for applying synthetic fertilizer like 18-6-12.
New leaves on numerous woody shrubs are turning yellow. Is this an Iron problem?
It could be, but sometimes the new growth comes out a little yellow and just need a little time to progress and green up. What is your watering schedule and your soil drainage like? Are these newly planted shrubs or established shrubs. What type of shrubs and what kind of light are they getting?
Hello! We put down 32000 pounds of topsoil on our lawn in the Spring and the St. Augustine looks great overall but there are a couple of areas that are looking a little drought stressed and one small area where crabgrass is working it’s way in. What do you recommend to help keep it all under control? With the drought, is it too early to fertilize? Thanks!
Organic lawn fertilizer like Texas Tee, Fertilome, or Medina, can be put down mid September, or you will need to wait until mid October through mid November to apply a synthetic fertilizer like Rainbow Gardens Winterizer 18-6-12. Fall fertilization can greatly help drought stressed lawns recover through winter and also gives winter protection and allows for quicker ‘green-up’ come springtime. Applying a broad pre-emergent, like Crew, mid September, as well, can offer protection against future weeds, but current needs will need to be either puller or mowed and bagged.
Thank you Happy Gardener 🙂
Absolutely!
And nutsedge in St Augustine! What’s the solution?
Ugh. Nutsedge! It requires at least two doses of product and very specific timing. Here is a link to a quick answer from Neil Sperry, but it is most likely cutting it too close for effectiveness. (But….with the extended heat, could be a possibility?)
My lawn is being taken over by clover or something that look a lot like that. What can I do
Hi Verla,
Right now you will need to pull or mow the weeds. You may be able to spot treat some areas in your lawn with a post emergent wee killer but make sure you read the labels and only choose one designated for your specific type of turf. Applying yearly pre-emergent will help in preventing new weeds from sprouting. However, you must apply these at the right time of year. I am attaching our lawn care maintenance calendar and a blog about weeds for extra info. Lawn Care Calendar, Weed Blog
My Zorro Zoysia lawn is developing rust fungus. Any advice on diy treatment?
Hi Natalie,
Main advice will have to do with lawn maintenance practices, and then I’ll offer some products for severe cases, or if you’ve tried everything already. Just keep in mind that you will most likely have to do multiple applications, and for the most part, you can control the rust with better practices in the lawn. Make sure your lawn is getting enough sunlight. If you have trees that have filled in or overgrown, it might be time for a trim to let in some more light. If you haven’t fertilized yet, now is the time through mid May (if you live in San Antonio). low nitrogen levels can be a culprit for rust developing. When you mow, bag clippings of disease grass and throw them away rather than leaving them on the lawn, and mow often taking only 1/3 of the blades of grass at each cutting. When you water, water deeply and but infrequently. Products that may be helpful are Bonide’s Captain Jack Copper Fungicide (organic), and Banner Max (synthetic). Always read the labels for safe and correct application and to know if you will need any follow up treatments and when. Best of luck to you!