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man spreads fertilizer on lawn

Fertilizing in the Summer

Sarasota County is one of many counties in Southwest Florida that have established restrictions on the application of fertilizers containing nitrogen and/or phosphorous. Sarasota County’s fertilizer blackout prohibits applying such products to turf grass and landscape plants from June 1 through Sept. 30. However; there are no such restrictions on applications of potassium, magnesium, and micronutrients, such as iron and manganese.

bagPotassium (K) is an essential macronutrient. Fertilizer bags typically show the percentage of potassium in a product as the third number displayed on the front of the bag (e.g., the “8” in 16-4-8, such as the image shown here). The first number shows the nitrogen (N) percentage, and the second number the percentage of phosphorous (P). Potassium acts as a “vitamin” for turf grass and landscape plants, and also increases plant and root strength and cold hardiness.

Magnesium (Mg), also a macronutrient, is essential for the production of chlorophyll, necessary for photosynthesis, and also plays a part in the movement of carbohydrates from leaves to other parts of the plant.

Micronutrients are elements that are only needed by plants in small quantities but which still play important roles in plant functions. Iron (Fe) is involved in the production of chlorophyll, and is required for certain protein functions. Manganese (Mn) plays a role in photosynthesis and the formation of chlorophyll.

Turf grass often displays a yellow color during the mid-summer rainy seasons due to the heavy rains flushing nitrogen away from plant roots. If your lawn is looking sad and yellow, a little iron can often give a temporary green-up. Iron is not a replacement for nitrogen, but it can work well during our summer rainy season. Applications of chelated (iron-added) micronutrients will also do the trick.

Palms require specialized fertilization because potassium deficiency is often an issue during the summer. Applications of 0-0-16-5Mg+micronutrients fertilizer will help to reverse the problem. Always remember that palms require only one-third as much magnesium as potassium, to prevent a human-caused deficiency due to an imbalance of these nutrients. Potassium and magnesium, both being easily dissolved by water, should always be applied in slow-release form. Once the summer blackout is over, applications of 8-2-12-4Mg+micronutrients should be applied on a regular basis.

For further information, please see the following website:

2 Comments on “Fertilizing in the Summer

  1. Quite a few of my palms are yellow and looking at an agricultural YouTube video I was told that I should purchase 8-2-12 fertilizer. Is this something that I am able to purchase through the county extensions?

    • Hi, Cindy. We don’t sell products here, nor give direct referrals. We would suggest that you contact our Plant Clinic (861-9807 or and speak to one of our Master Garden volunteers who staff these help desks. They can provide you with advice on what type of fertilizer would best meet your needs, when to apply it (noting the various fertilizer-use restrictions for the county and municipalities), and likely offer you general information on purchasing. Hope that helps!