August is an ideal time for gardeners to give their plants a boost into the later stages of growth.
Many people who are just learning how to garden at home overlook the benefits of fertilizing their plants. Even experienced gardeners don’t always use the best fertilizer for their particular plant type. Those who fall back on cheap fertilizers often end up with disappointing results and don’t get the most out of their gardens.
With this in mind, we’ve put together a quick guide for evaluating your late-season fertilizer needs.
Supporting growth and improving soil quality
Generally, all plants will deplete the soil they’re growing in over time. Even plants that start out in high-quality soil will consume the nutrients in the soil as they grow. Backyard gardeners who are not already feeding their soil will definitely want to consider fertilizing multiple times throughout the growing season: soil in developed areas can be seriously depleted, sometimes taking years to restore.
Flowers and vegetables -- especially fruiting plants, like tomatoes and peppers -- demand even more nutrients from the soil. Vegetables will use up certain types of nutrients as they grow early in the season. Later on, as they begin to produce fruit, plants demand even larger amounts of nutrients.
The beginning of the fruiting phase is the best time to supplement fertilizers into the soil; otherwise, fruit production could be limited, and vegetables might turn out small.
Not only will fertilizers help fuel vegetable growth toward the end of the season, they’ll also boost soil quality for the next planting season. Well-fertilized plants in your garden will finish out the growing season with a nutrient surplus instead of a deficit. This means healthier soil, which means stronger early growth for plants starting out the following spring.
Even if you know you’re planting in good-quality soil at the beginning of the season, late summer is an opportunity to renew your soil by adding nutrients.
Nutrient deficiency in plants
Of course, the best time to fertilize is before plants start showing signs of nutrient deficiency.
Nutrient deficiency in plants can be difficult to identify visually -- especially for beginner gardeners who are unsure of their soil composition.
The only reliable way to detect specific deficiencies is by doing a soil test, but there are some identifiable symptoms to watch for:
Nitrogen deficiency tends to be more common and easier to identify than other problems. Symptoms usually appear in older growth first and move up the plant; leaves will turn light brown and begin to yellow. Leaf stems will turn brittle and reddish in color, and sometimes shorten. Purpling leaves can also indicate a nitrogen problem, even though they’re typically associated with phosphorus deficiency.
Phosphorus deficiency is more difficult to detect: when visual symptoms start to appear, the damage has already been done and is difficult to reverse. Upper leaf surfaces will darken and become shinier. Leaves will become reddish-purple underneath.
Potassium deficiency usually shows up in the form of leaf scorch. Growth will slow, and plants like strawberries will start producing fewer runners. Leaf stems will also be short and brittle.
Recommended fertilizers for late-season crops
The soil consultants at GreenTree recommend the following products for boosting soil later in the growing season:
Rainbow Mix Bloom 1-9-2 by Earth Juice: August and on is the time for fruits and flowers. Use a low-nitrogen blend to keep from inhibiting fruit production. High-phosphorus mixes like the 1-9-2 will scorch kale and other greens, so deliberate application is important. GreenTree offers this product in a 5-pound size and a 20-pound size.
ProGro 5-3-4 by North Country Organics: ProGro is a solid all-purpose mix. It has a well-balanced assortment of nutrients and is designed to support a full range of growth. Good for overall soil productivity and plant growth. Please note that our store only carries this product in a 50-pound size, but we do have similar products available in smaller sizes.
Bat Guano by Down to Earth: Bat guano is an excellent single-ingredient supplement for gardeners interested in a greater degree of control over their fertilizers. Down to Earth offers a high-nitrogen option alongside their high-phosphorus product, depending on the application. Unlike more inert fertilizers blends, bat guano also introduces biological activity to the soil. We carry both the high-nitrogen and the high-phosphorus blends at GreenTree, in 2-pound to 5-pound boxes.
As always, if you have specific questions about your soil, you can speak to one of our consultants by coming into the store, giving us a call, or emailing firstname.lastname@example.org.