9 Fertilizing Mistakes That Are Ruining Your Lawn and Garden, According to Experts

Fertilizer is an essential part of gardening. It boosts plant growth, improves yields, adds key nutrients to the soil, and enhances disease resistance. But fertilizing your lawn and garden incorrectly can do more harm than good. Applying the wrong amount of fertilizer or doing so at the wrong time can cause leaf burn, decreased flower production, and other issues. To ensure you fertilize your yard and plants correctly, we spoke to gardening experts who shared the most common pitfalls people make when using fertilizer.

Over-Fertilizing

Too much of a good thing can be harmful to plants, as is the case with fertilizer. "Too much fertilizer can burn plants, disrupt soil microbial life, and lead to excessive leaf growth at the expense of fruit or flowers," says Luke Hammond, expert gardener at Seedtime. "Salts can accumulate in the soil, making it harder for plants to absorb water."

To avoid this issue, always follow the label rates listed on the packaging. If you used a water-soluble fertilizer, Damon Abdi, assistant professor of landscape horticulture at Louisiana State University, recommends heavily watering the soil to dilute and leach excessive fertilizer from the root zone. "If a slow-release fertilizer was used, try to remove some (provided it’s easy to see and hasn’t been out for too long)," he says.

Under-Fertilizing

Under-fertilizing plants can also be an issue. "Too little fertilizer can limit growth, reduce plant aesthetics, and impact fruit quality," says Abdi. "Furthermore, plants that are starved for essential nutrients may be more prone to environmental stresses, pest pressures, and disease issues." To correct deficiencies, consider adding more or a different type of fertilizer.

Incorrect Timing

Applying fertilizer at the wrong time can encourage growth too late or too early in the season. "Be careful about applying fertilizers too late in the year—you would not want to spur new growth right before winter when the plant is vulnerable to cold weather," Abdi says. "Similarly, do not apply fertilizer too early in spring. Early spring fertilizer applications can cause new growth to emerge…only to be wiped away by an untimely late frost."

He recommends applying in mid-spring to help spur new growth after a tough winter or in summer to help refill the nutritional needs of your plants. "If fertilizers were applied at the wrong time of the year, then physically removing granules or leaching existing nutrients from the soil via heavy irrigation may address the issue," Abdi says.

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Fertilizing Midday

Applying fertilizer in the middle of the day when the sun is most intense can cause foliar fertilizers to burn leaves and liquid nutrients to evaporate too quickly, says Hammond. To ensure proper absorption and avoid harming your plants, our experts recommend fertilizing in the early morning or late afternoon when temperatures are cooler.

Using the Wrong Type

There isn't a one-size-fits-all approach when it comes to fertilizer. "Different plants have different nutritional needs," Abdi says. "Selecting fertilizers for your crop or ornamental species can offer a more precise prescription for the plant. For example, there are fertilizers formulated for plants that thrive in acidic conditions like azaleas and gardenias, as well as options specifically for lawns and vegetable gardens.

Applying to Dry Soil

Dry soil makes it difficult for the nutrients in fertilizer to reach your plants. According to Abdi, liquid fertilizers may run off and not move through the soil to the root zone, while granular fertilizers may blow or wash away. "Fertilizers (a salt) may become more concentrated in dry soils when there is limited water to dilute it, which can cause salinity issues," he says. Watering the soil before or after fertilizing can address this concern.

Inconsistent Application

Irregular feeding can cause uneven growth, disrupting the health and aesthetic quality of your landscape. "For a row of plants, inconsistent application practices can cause clear differences in growth," says Abdi. "In lawns, inconsistent applications can cause patches of vibrant, healthy grass and patches of struggling turf areas."

Be as precise as possible when fertilizing your garden to ensure even amounts are applied to each plant. Abdi recommends using a measuring tool, such as a tablespoon. "For lawns, make sure that fertilizer tools and equipment (such as a broadcast lawn spreader for granular fertilizers) are calibrated correctly," he says.

Fertilizing New Grass Too Soon

New grass can be overwhelmed or burned by fertilizer if it is applied before the roots are well established, says Hammond. "If the grass establishment isn’t good, top dress with a thin layer of organic compost and add additional seed," he says. Wait until your lawn has been mowed at least two to three times before the first fertilizer application.

Not Testing Soil First

Fertilizers are labeled with three numbers, representing nitrogen, phosphorous, and potassium. For example, a 10-10-10 fertilizer is 10 percent nitrogen, 10 percent phosphorus, and 10 percent potassium. Conducting a soil test will tell you what nutrients are and are not present in the soil, helping you choose a fertilizer suitable for your plants. "Soil testing can also provide insights into soil texture (the composition of sand, silt, and clay, as well as organic matter), which can influence how water and fertilizers may behave in the garden," says Abdi. "Soil testing and assessments can be performed through your state’s extension service, providing locally based information to guide your gardening practices."