Timing is everything with fertilizer

By Heather Kirk-Ballard

LSU AgCenter Horticulturist

Spring is here and the plants are booming. Plants perform best when they are getting the optimum amount of sunlight, appropriate amounts of water and plenty of essential nutrients for good growth and production of flowers and fruit. Optimize plant growth by knowing how and when to fertilize.

Fertilizers provide the nutrients needed by plants to grow, form flowers and healthy foliage, produce more fruit, establish a strong root system and fight diseases and insect pressures. Plants benefit from fertilizer applications most when they are in their peak growth, and spring is one of those times!

The best time to fertilize is when many plants come out of dormancy in the springtime. In spring, deciduous plants leaf out, flowering plant buds begin to burst, stems and branches elongate and new roots are formed. Nutrients will aid in all of this growth, so the rule of thumb is to make an annual application of fertilizer in the early spring.

There are several ways to fertilize plants, including slow-release granular fertilizers, liquid feed applied to soil as a drench, foliar sprays and fertilizer stakes. In addition, using natural fertilizers such as compost can add nutrients to your soil.

Compost is decayed organic material from other plant materials and animal waste from livestock that has a diet mostly made up from plants. Those include chickens, cows and horses. Composts can be found already bagged at many retail garden centers or available in bulk delivery form from local sources.

Compost also can be made from waste such as grass clippings and fallen leaves in your yard, in addition to kitchen scraps such as coffee grounds, eggshells and fruit and vegetable peelings. Worm castings and mushroom composts are two additional composts that add nutrients to your soil.

Plants can have individual needs when it comes to fertilizers. Acid-loving plants such as azaleas, blueberries, camellias, hydrangeas and rhododendrons prefer more of an acidic soil pH to take up optimal nutrients. Flowering plants need more phosphorus to help stimulate stronger bud, fruit and flower development.

Vegetable plants benefit and require more frequent fertilizer applications throughout the season because they are producing and that makes them heavy feeders. Slow-release fertilizers can be incorporated at planting time for extended nutrient release. Side dress with calcium nitrate at the first and third bloom set. Additionally, some growers utilize liquid fertilizers every other week.

Nitrogen is very important for all plants but especially important for lawns and turfgrasses. Woody plants such as shrubs and trees can benefit from an application of three pounds of nitrogen per thousand square feet and perennials benefit from one pound of nitrogen per 1000 square feet in the spring.

Indoor potted plants may be fertilized with a liquid plant food every month for most varieties. Do this once each season in spring, summer and fall, but skip winter for plants that go into dormancy. No matter the plants you are trying to feed, scheduling the correct timing is important.

Applying fertilizer in the wrong season can cause increased tender new growth that can be damaged, especially if applied in cold weather in late fall or in winter. So it is best to stop fertilizing during dormant seasons. Additionally, in zones that can be in danger of a late freeze, it’s best to wait until mid-spring. Everyone could benefit from putting fertilizer application schedules in their calendars.

Here are some general rules to follow when fertilizing:

  • Avoid fertilizing new plants until they are fully established, because it can cause an increase in tender new growth that can make the plant weak and leggy.
  • Always follow the manufacturers recommended rates and application methods.
  • Fertilize outdoor plants in the coolest part of the day, such as early morning or late evening, especially in hot summer weather.
  • Always water in fertilizers well to distribute nutrients throughout the soil profile and to prevent burning.
  • Lastly, avoid excessive fertilizing and perform soil tests annually to see what nutrients your plants need.

With fertilizer prices doubling as they have, waste not!

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A good slow-release fertilizer and use of liquid fertilizer when needed will help produce the most flowers and fruit. Photo by Heather Kirk-Ballard LSU AgCenter

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Mushroom compost can add nutrients to soils and potting media. Photo by Heather Kirk-Ballard, LSU AgCenter

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Slow-release granular fertilizers can be applied in spring for continual feeding. Photo by Heather Kirk-Ballard, LSU AgCenter

4/22/2022 3:17:07 PM
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