High Nitrogen, Quick Release of Fertilizers Keep Plants Green during Cold Weather

Q. Our lawn was beautiful during the summer but started turning brown when it got cold here in Mesquite. This is a fescue lawn and we were told it would stay green all winter long.

A. There are several different kinds of fescue, but the fescue used for lawns is technically called “turfgrass type tall fescue”. Tall fescue lawns stay green through the winter in our Mojave Desert climate if they receive an application of nitrogen fertilizer in late Fall and night temperatures don’t drop below about 15° F.

This is a conventional high nitrogen fertilizer called ammonium sulfate. It is used to feed plants only nitrogen for promoting growth of stems and leaves.Where the nitrogen comes from but conventional fertilizers may contain other ingredients in very small quantities. Some followers of organic principles might call these other ingredients, "contaminants" in the fertilizer. Any fast release slow nitrogen fertilizer will keep plants green longer into late fall and early winter then not applying any nitrogen.

            If the lawn is without nitrogen, and nighttime temperatures drop below freezing, fescue lawns will go dormant and turn brown. Apply a high nitrogen fertilizer or compost to the lawn late in the fall before freezing temperatures.

A high nitrogen fertilizer but derived from dried blood. It is also high in nitrogen and releases it fairly quickly but not as fast as ammonium sulfate. This blood meal is not certified organic by the USDA but many would consider it as "organic" nitrogen.

            You can use any fertilizer if the first number is the highest number on the bag. Examples can be 21-0-0, ammonium sulfate, applied 2–3 weeks before freezing weather hits. In our Las Vegas climate, applications would be around Thanksgiving, or possibly even later if nighttime temperatures don’t drop below freezing.

            Nitrogen, the first number on the fertilizer bag, is responsible for a plant’s dark green color and encouraging new leaf and stem growth. It can also keep plants from going dormant during the winter.

            There is a nefarious side to late applications of nitrogen. Nitrogen applications made in late Summer or early Fall can compromise our winter-tender plants such as many types of citrus. Applications of high nitrogen fertilizer to these plants late in the growing season can cause them to be more susceptible to freezing temperatures. Never apply high nitrogen fertilizers during Fall to plants that might freeze during winter the winter.