Why is fertilizing in the fall important?
As the weather starts to cool and the sweltering heat of summer is coming to an end, your garden will finally begin to breathe again. What better way to bring life back into your garden than fertilizer? The summer heat requires you to water more, which over time leaches nutrients from the soil, especially in the sandy soils of the Gulf Coast. So, in the fall you need to replenish those nutrients with fertilizer and amendments. Mid-September to early October is the ideal time for fall fertilizing in zones 8 – 9 of the western Florida Panhandle, as plants are just beginning to slow down and go into winter dormancy.
What is NPK?
What do the three numbers on the fertilizer bag mean?
When you pick up a bag of fertilizer you will see three numbers. You may be wondering what those numbers mean and how they affect your plants, so let’s break that down a bit.
N: Nitrogen. This is the first number on the fertilizer bag. Nitrogen is required by plants for healthy, lush foliage. Nitrogen also plays a role in the plant’s ability to capture sunlight and turn it into energy. Without proper nitrogen levels in the soil plants grow slower and can become stunted.
P: Phosphorous. This is the second number on the fertilizer bag. Phosphorus has many roles in plant growth and health, but the key factors we notice the most are root health and flower production. Fertilizers with a higher middle number (phosphorus) will stimulate bud and flower production in the spring and summer. Proper levels of phosphorus also help plants fight off diseases and bug infestations because the plant overall is healthier and can withstand “infection”.
K: Potassium. The last number on the fertilizer bag. Potassium, like phosphorus, plays a key role in the root development of plants. Healthy roots allow plants to take in water and nutrients more efficiently. Potassium also helps “winterize” plants as they prepare for cool temperatures and dormancy. A lack of potassium can lead to poor roots, which can in turn lead to plants being more susceptible to root rot and other pathogens.
N-P-K are the main (macro) nutrients in fertilizer that plants require in larger concentrations, but they are not the only ones. Fertilizers also contain many micro (supplemental) nutrients. Micronutrients play many complex factors in plant health.
There are so many different fertilizers! How do I know which one is right for my garden?
You may be overwhelmed by the options of fertilizer available. Here at Wildwood Garden Shoppe & Nursery, we are eager to share our knowledge to enhance your garden.
Let’s discuss the different types of fertilizers, how they are used and some of their pros and cons, so that you can make a more educated decision on which fertilizer will work best for you and your plants!
There are two main categories of fertilizer that everyone has the most questions about; Inorganic vs. Organic.
Inorganic Fertilizers
Inorganic fertilizers are generally synthetic, manufactured products derived from inorganic chemicals and earth minerals. These fertilizers can be either slow release or water soluble (quick release).
Slow-release or Controlled-release fertilizers are the small colored pellets you find in bags of fertilizer. The colored coating will break down over time when you water, slowly releasing nutrients into the soil.
Pros of Slow Release Fertilizer
- Fertilizer is released over time, requiring less frequent applications
- Less likely to burn grass
- Encourages uniform growth
Cons of Slow Release Fertilizer
- Nutrients are not immediately available to the plant; green-up will be slower
- Higher risk of burning shrubs and tender perennials if used incorrectly
- Affected by soil temperatures. Cool temperatures inhibit their effectiveness and are best used in the spring.
Water soluble fertilizers are those that can be dissolved in water and in some cases, used each time you water. Most synthetic water-soluble fertilizers are in crystalized form; however, some are already in liquid form. These types of fertilizer are most commonly used for houseplants, tropicals, and annual beds.
Pros of Water Soluble Fertilizer
- Fertilizer is immediately available to plants for quick greening
- Easy to use
- More uniform application than granular
Cons of Water Soluble Fertilizer
- Requires more applications than slow release
- Have a shorter shelf life than granular
- May be more expensive than granular
There is a higher risk of “burning” or damaging plants if inorganic fertilizers are used improperly. Over-fertilizing beyond the recommended rate or fertilizing too close to the plant’s trunk can cause damage. It is always important to carefully read the fertilizers instructions, or ask one of our horticulture professionals if you have questions about recommended rates. Water soluble fertilizers can also have similar effects if used in too heavy of a concentration.
Organic Fertilizer
Organic fertilizers are derived from naturally occurring minerals and materials. Examples of these ingredients can be manures, guano, blood meal, fish emulsion, shells, phosphate rocks, and organic potash. Organic fertilizers not only feed your plants but also your soil by replenishing nutrients and improving soil structure. Microbes in the soil work to break down the organic materials into a form the plants can use.
Similar to inorganic fertilizers, organic products can be in granular or liquid form.
Pros of Organic Fertilizers
- Less likely to burn or damage plants
- Lower salt index than inorganic fertilizers
- Improves soil structure
Cons of Organic Fertilizers
- Nutrient levels tend to be lower than inorganic
- Some products may not contain the primary nutrients (N-P-K)
- Quality can vary significantly depending on the brand used
Fertilizer Supplements & Stimulants
Fertilizer supplements are additional minerals used along with regular fertilizers. Examples of these supplements can be micro-nutrients like iron or gypsum.
Fertilizer stimulants are like vitamins for your plants. Like supplements, they work with regular fertilizers to increase fertilizer and chemical effectiveness. Stimulants also increase root mass which allows the plant to better take in nutrients and retain moisture.
Fix It Quick – Fertilizer Tips
Iron Deficiency in Gardenias
Gardenias are heavy fertilizer feeders, especially in our sandy soil. It is recommended to fertilize Gardenias at least twice a year (spring and fall) with an acid-rich fertilizer. If you start to notice yellowing of leaves and darkening of veins on your gardenias this is usually a sign of an iron deficiency. Fertilizer supplements like granulated iron or chelated iron will often fix this problem and green your leaves back up!
Potassium Deficiency in Palms
According to the University of Florida IFAS Extension, potassium deficiency is one of most common in palms. Potassium leaches from sandy soil very quickly, especially after heavy rains and tropical storms.
Symptoms of potassium deficiency vary by palm species. In general, yellow spotting of the palm frond, leaf tip browning (necrosis), and black spotting are the most common symptoms.
As a good rule of thumb, it is best to use a Palm Fertilizer up to 3x per year (Spring, Summer, Fall) to help prevent nutrient deficiencies in your palms. However, if potassium deficiency becomes a problem you’ll want to amend the soil with Sulfate of Potash.
Be sure to watch Sydnee’s information video on the fertilizers we offer at the Garden Shoppe and how each one will work for your specific plants!
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