We hate to say it, but winter is coming, Jon Snow. While we’re sad to see the summer go, it’s important to consider the benefits of a fall fertilizer to help green up your lawn come spring time. In the fall, cool season grasses spend time recovering from the stresses of summer, such as drought, heat, and disease. Knowing when to fertilize and how much to use is essential to helping your lawn recover, survive the winter, and flourish in the spring.
Fertilizers usually contain nitrogen, potassium, and phosphorous, three key nutrients that help with growth, cold hardiness, appearance, and disease resistance. When the lawn is fertilized in the fall, turf grass is more likely to resist winter injury and disease.
Potassium vs. Nitrogen vs. Phosphorous
Potassium helps grasses regulate plant metabolism (including the uptake of nitrogen). It helps maintain turgor pressure, which is water pressure inside plant cells maintained by osmosis. Plant cells rely on turgor pressure to keep stems rigid and leaves expanded.
Nitrogen has one major job: Keeping your grass green. Nitrogen is found in healthy chlorophyll molecules, which give plants their green color and creates food through photosynthesis.
Phosphorous stimulates grass growth through optimizing energy processes and helping the plant read genetic codes. Many soils contain enough phosphate for grass to grow – in fact, Minnesota Statute 18C.60.2 restricts adding fertilizer containing phosphorous on your lawn because it’s so damaging to the environment:
“A person may not apply a fertilizer containing the plant nutrient phosphorus to turf statewide, except under conditions listed in paragraph (b).
(b) Paragraph (a) does not apply when:
- a tissue, soil, or other test by a laboratory or method approved by the commissioner and performed within the last three years indicates that the level of available phosphorus in the soil is insufficient to support healthy turf growth;
- the property owner or an agent of the property owner is first establishing turf via seed or sod procedures, and only during the first growing season; or
- the fertilizer containing the plant food phosphorus is used on a golf course under the direction of a person licensed, certified, or approved by an organization with an ongoing training program approved by the commissioner.(c) Applications of phosphorous fertilizer authorized under paragraph (b) must not exceed rates recommended by the University of Minnesota and approved by the commissioner.”
Here are some tips for fertilizing your lawn in the fall:
- Do not apply fertilize to frozen soil or on a lawn where there is snow or ice
- Slow-release nitrogen fertilizers may be more expensive, but they are designed to release a steady stream of active ingredients and help with uniform grass growth. They are also less likely to burn the lawn and other plants
- 1.5 to 2.0 lbs. of slow-release nitrogen fertilizer is recommended for each 1000 square feet
- There is no need to purchase a fertilizer with phosphorous (unless you meet one of the conditions of the state statute above), as that nutrient affects algae growth and harms local ponds when it runs into the storm sewer system.
- Too much nitrogen can damage your lawn. One late summer fertilizer application and a light fall application are shown to produce better lawn results than three or four major feedings over the growing season
- Fertilizers come in bags with 3 numbers, such as “1-0-3.” 1 indicates the percentage of nitrogen, 0 the percentage of phosphate, and 3 the percentage of potassium. In accordance with Minnesota laws, you should look for fertilizers without phosphorous.
- Be wary of what products promise – do you research before going to the store!
By following these tips and doing some preliminary research for what your lawn needs this fall, you’ll ensure a healthy and happy lawn next summer.