Learning to Grow: Needy plants know ...
When friends ask what the trick is to a great garden, my simple response is, “It’s all about the soil.”
As gardeners, we wish it was just as easy as “fixing” the soil, which involves shoveling no end of compost, careful watering and of course fertilizer.
I find myself amazed at the variety of fertilizer you might find on the shelf at the store, so it is no wonder people are confused what fertilizer is “best” to use. Unfortunately, there is no one answer, but the information on the bag of fertilizer, as well as information about the plant, can help steer you toward the best choice.
The most scientific way to address this problem is to send off your soil for testing, and the results will provide you with specific instructions as to what type and how much fertilizer to apply. As you become familiar with your soil and plants, you can also select one for yourself. The key is to study the numbers on the bag, commonly referred to as N-P-K (i.e. 20-0-5).
These numbers refer to the percentage of nitrogen, phosphorous, and potassium per pound. Nitrogen promotes leaf and stem growth. Phosphorus is involved with flowering, fruiting and root development.
Potassium encourages root development and hardiness. Extension “Plant Datasheets” will provide valuable information on the nutrient needs of your specific plants.
The N-P-K value provides insight into both the purpose and potency of a fertilizer. Chemical lawn fertilizers have values such as 40-0-5, providing high quantities of nitrogen, no phosphorus, and a bit of potassium.
This aligns with our desire of strong top growth on the lawn and the ease of only needing a 50 pound bag to cover an entire lawn. More delicate perennials might benefit from an application of 1-0-0 cow manure. Just like medicine, strongest is not always the best. Incorrectly applied, fertilizers with high N-P-K can burn plants or cause plants to “over-react,” producing undesired results. Generally, more organic sources of fertilizer have lower values and pose less risk of shock to plants.
Fertilizing is a critical element of gardening, but also a tricky one to master. With the wide array of fertilizers available, combined with varying needs of plants, the whole issue can quickly become confusing. This is where the extension resources can provide guidance on selecting the right fertilizer for your situation.
Plant Datasheets can outline the feeding requirements of plants and may even advise against any additional fertilizer beyond compost. The key is to use the resources and learn the best course instead of grabbing any bag of fertilizer on the shelf.
• Jim Stendler is a University of Illinois Extension master gardener for Kane County. Call the extension office at 630-584-6166 for more information.