Complete guide to fertilizers and weed control for your lawn

When you want to increase the growth of your lawn, protect it from disease and eliminate weeds, adding fertilizer and weed control seems to be the logical conclusion. But before you run to the store, there are some factors to consider and some very important preparation that is needed, the same as when you are treating a lawn disease or overseeding to increase your lawn density. Applying products without preparation could end up being ineffective – which is costly – or, worse, burn your lawn – which would be even more costly.

Below is a step-by-step guide to help you make a great start to fertilizing and controlling weeds in your lawn, so that you can enjoy a lush green carpet of grass each and every year.

Step 1: Get the Details on Your Situation

Timing is just as important as the kind of fertilizer you will need. For instance, if you are in a cooler climate with longer winters, you may find that the best time to fertilize is around Labor Day in early September with an additional feed before winter sets in. If you are in a warmer climate, with warm-season grasses like Bermudagrass, Zoysia, St. Augustine, sea papsalum, etc., you might choose to fertilize in April, before the lawn fills in with new growth, and again in fall.

The only time to avoid adding fertilizer is when conditions are hot and humid, over 85 degrees, or when temperatures are dropping near freezing.

Also, fertilizing, if done correctly, is only needed one or, at the most, two times a year – half of what some retail companies and products recommend.

Consider as well the health of your lawn. If your lawn is already doing well, adding fertilizer in the spring will only increase top growth but may weaken grasses and make them vulnerable to disease.

Having pinpointed a time to fertilize, next consider the type of grass in your lawn as different products are made for different grasses. Do you have cool-season grasses like Kentucky Bluegrass or ryegrass? Or, do you have warm-season grasses, like Bermudagrass, zoysia or St. Augustine. Or is your lawn a combination?

Also, you will need to know your lawn’s square footage (length x width = square feet) so you can choose the right type and amount of fertilizer for the coverage you need. If your lawn is irregularly shaped, define sections, then figure out the square footage of each section and add the totals together.

Step 2: Don’t Skip Testing Your Soil

The next step is to analyze your soil. Experts recommend skipping past the store kits which can be inaccurate. Instead, take about a dozen samples of soil using a trowel and digging out a scoop of soil 3-4 inches deep, without roots or vegetation, from different areas of the lawn. Mix the samples together, then scoop one cup out into a plastic bag and take it for analysis to either your local county extension office, garden nursery or other soil testing facility.

When you receive the results, the analysis will tell you most importantly what the soil’s ph level is – you want between 6.5 and 7.0. If it’s lower than ideal, then you will need to “sweeten” (aka add lime) to your soil before doing any type of fertilizing. If it’s too high, you will need to add sulphur or a fertilizer that contains sulphur to bring the ph level down.

Also look at whether you need phosphorus (for root development) or potassium (strengthens soil against drought). Soil analysis will include figures on these macro nutrients but not on nitrogen (promotes rapid growth) – one of the most needed nutrients for your lawn. Most lawns – not all – will need nitrogen.

Nitrogen (N), phosphorus (P) and potassium (K), are indicated as N-P-K on fertilizer products and always in that order. When you see on a fertilizer bag or bottle numbers such as 10-5-5 or 32-0-4, it is telling you the percent of N-P-K, so 10-5-5 is a mix of 10% nitrogen, 5% phosphorus and 5% potassium.

Experts say to choose products with P and K only if your soil analysis shows they are low. In addition to not wanting to add something to your lawn that it doesn’t need, the lawn care industry is making a concerted effort to decrease the amount of phosphorus run-off from lawn care which has been shown to enter waterways creating algae blooms and other significant environmental damage.

In general you want to choose a fertilizer with a higher amount of N and lower amounts of P and K.

Step 3: Easy Math = Buying the Right Amount of Fertilizer

To prevent burning your lawn or causing grass to grow too rapidly, you need to have an understanding of how much of each of these macronutrients you need delivered by the fertilizer.

Calculating the right amount of fertilizer takes two simple multiplications and one division equation. The first calculation will tell you how much of each nutrient you have in pounds in one bag, the second how much nitrogen you have in square feet coverage in one bag, and the last calculation tells you how many bags of fertilizer you need.

Calculations are broken out here and in a chart below:

1.   To start, calculate the pounds of each nutrient in each bag by taking the percent (%) of the nutrient x the pounds (lbs) of fertilizer in the bag to equal the pounds (lbs) of that nutrient. So if for example you have a 40lb bag of 10-5-5 fertilizer you would calculate the amount of nutrients in the bag by multiplying:

10% (0.10) x 40lbs = 4lbs nitrogen, and

5% (0.05) x 40lbs = 2lbs of both phosphorus and potassium.

You now know the bag has 4lbs N, 2lbs P and 2lbs K.

1.   Now that you know the pounds per nutrient you can calculate the square footage the nitrogen will cover as the recommended amount of nitrogen is 1 pound per 1000 square feet. So using the example we calculated above, 4lbs of nitrogen would then cover 4,000 sq ft of lawn (4lbs x 1,000 sq ft = 4,000 sq ft).
2.   Now you can figure out how many bags you need by dividing the square footage of your lawn by the square footage of nitrogen in 1 bag. So if you have a 16,000 square foot lawn, you will need 4 bags of this fertilizer (16,000 sq ft ÷ 4,000 sq ft of fertilizer = 4) bags to cover your lawn.

You can use this chart to make the needed calculations in one place:

Step 4: Types of Fertilizer and Weed Control 

Now that you know how much of each nutrient your lawn needs and what that will equate to in number of bags, the last step is to determine what type of fertilizer and spreader you need.

Fertilizers come in slow-release and fast-release pellets or as a liquid. Experts generally prefer slow-release to fast-release as the slow-release allows a strong root system to form. Fast-release, on the other hand, may make your lawn thicken up too quickly, creating too much thatch that chokes out and weakens grasses. Liquid fertilizers are the least favorite with experts because they tend to require multiple applications to reach the desired effect.

Some homeowners are choosing an organic fertilizer, which while good for your lawn is not concentrated, so you will need a lot of compost or dry manure to achieve results, which can be rather pricey. Organic fertilizers contain low numbers of N-P-K, usually under 10, however they stimulate microbes in the soil making the lawn healthier, so they can be used in hotter months when chemical fertilizers would harm your lawn.

There are also weed & feed fertilizers which will help with those weeds listed on the label as well as fertilize. The problem is that you will be putting herbicide all over your lawn and as these products also have high nitrogen, it can also burn your lawn. The experts recommend buying a spot weed killer, preferably in liquid form, that you can spray just in the areas where you see weeds.

Step 5: Applying and Watering Your Fertilizer

To apply or spread the fertilizer, always follow label recommendations. You may find it easiest to divide your lawn in sections as you apply, so you are sure each section is getting the right amount of fertilizer.

In terms of equipment, experts say you will save in the long run by choosing the highest quality spreader possible to achieve even distribution of the fertilizer. Most homeowners use a broadcast / rotary spreader – which spins out the pellets as you push it and usually requires some sweeping up of overthrown pellets. Be aware that cheaper versions may cause pellets to congregate under the wheels.

There are also drop spreaders which will keep fertilizer from getting tossed on driveways, sidewalks and garden beds. These require that you make two passes over the lawn at an angle in opposite directions in order to avoid creating stripes of new grass between stripes of older grass.

Retailers also offer handheld spreaders for smaller spaces.

Fertilizer application usually takes three steps:

1.   WATER WELL
   In applying fertilizer, the main concern is that your lawn is well-watered. Some experts say to water your lawn a few days before you spread fertilizer to push root growth and prepare the soil. Others recommend that you consider aerating the soil as well to open it up for the fertilizer. All fertilizer requires that you water immediately after application to clean the fertilizer off the grass, which prevents burning, and to push the fertilizer closer to the soil so it will form roots.

1.   SPREAD EVENLY
   Spread the fertilizer in the evening time or on a cloudy day, or right before a good rain is expected, so that grass is dry but not under a hot sun. Fill your spreader on a driveway or walkway before moving into the lawn, so spills do not land in the grass. Go at a slow pace, spreading at an angle, so that the fertilizer distributes evenly across the lawn.

1.   CLEANUP WELL
   Clean up is just as important as preparation, so don’t forget to hose off your spreader afterwards to clear any chemicals and sweep up any stray fertilizer. Also, switch shoes so as to not track chemicals into your home. Package information will tell you when your lawn is safe for people and pets to use again, usually within a few days, so that the new grass has had a chance to germinate.

Once you’ve finished, you should see a big difference in your lawn’s growth within a week or two. During new growth, don’t short cut your lawn when mowing, but cut at 2-3 inches so grasses have a chance to strengthen and thicken.

Remember, you can always call on your lawn care expert if you want professional fertilizing as part of your lawn maintenance.

Simply Green Weed Control and Fertilization

Remember, Simply Green Lawn Care experts will carefully evaluate your lawn and determine the best program for your property based on the type of grass, types of weeds, time of year and the underlying issues within your lawn. 

Simply Green specialists will service your yard every four to eight weeks, depending on the time of year, to ensure proper maintenance, superior weed control and effective fertilization. Simply Green Lawn Care Plus only uses high-quality products that are safe for your family and the environment.