Mystery of the cosmos solved: Hindsight can be 20-20-20

I’m back, as promised, continuing to try to reconstruct the events that propagated my cosmos “firewood” supply.

By Kim Woodford

WSU Master Gardener

I’m back, as promised, continuing to try to reconstruct the events that propagated my cosmos “firewood” supply — thick, healthy stems with very few flowers.

Cosmos are fairly easy to grow and generally quite hardy, although some gardeners (see, I’m not alone) report that their cosmos do not bloom as expected.

I recall a day (one growing season before I became a Master Gardener) searching through my garden shed, sorting through products of every nature. I saw an old box barely holding its contents intact. It was moldy and covered in cobwebs (oh, come, you’ve seen this type of thing before). When I gingerly picked it up, a grouchy spider stared at me before spidering off.

I viewed the exterior of the box and was unable to decipher all but a few pronouns and the numbers 20-20 and — was that another 20? Carefully, I attempted to unfold an origami-like paper inserted in the dilapidated box. This being unsuccessful, I turned to the clear cellophane sleeve of pretty blue crystals. What harm could come from these innocent unidentified crystals of … fertilizer?

A handy little scoop was in the pouch, facilitating — even encouraging — my miscreant behavior. In a flash, the little scoop was full and emptied into my watering can and applied to my pot of cosmos.

Later, during Master Gardener training, I learned that one of the first rules is never, never, never to use a product in the garden without reading all of the information contained on the product package.

Thinking back to the mystery of the pretty blue crystals, I sheepishly decided to find out what the secret numbers meant. I donned my brand-new Master Gardener ID badge and went to the garden store.

There, I was faced with an overwhelming array of fertilizer options, many with a series of three numbers like 10-10-10, 20-20-20, 10-8-10 or many other combinations of numbers. What do the numbers on a fertilizer bag or box mean? “These are NPK values,” a store clerk advised, looking at my badge, smirking. OK then, what is NPK?

At this point, I sat down on the floor and summoned my MG guru. I was on the verge of a panic attack. Holding my hand, my guru explained the three numbers on fertilizer represent the value of the three macronutrients used by plants.

These macronutrients are nitrogen (N), phosphorus (P) and potassium (K). The higher the number, the more concentrated the nutrient is in the fertilizer. For example, numbers on fertilizer listed as 20-5-5 has four times more nitrogen in it than phosphorus and potassium. A 20-20-20 fertilizer has twice as much concentration of all three nutrients than 10-10-10. Confused yet? These numbers will appear on any fertilizer purchased, whether it is organic or nonorganic.

Why is NPK important to our plants? My guru stops to take a breath and rest then continues pedantically in a falsetto voice: “All plants need NPK to grow. Without enough of any one of these nutrients, a plant will fail. Nitrogen is largely responsible for the growth of leaves on the plant. Phosphorus is largely responsible for root growth and flower and fruit development. Potassium is a nutrient that helps the overall functions of the plant. Knowing the NPK values of a fertilizer can help us select one that is appropriate for the type of plant we are growing. For example, if we are growing leafy vegetables, we may want to apply a fertilizer that has a higher nitrogen number to encourage leafy growth. If we are growing flowers, we may want to apply a fertilizer that has a higher phosphorus number to encourage more blooms.”

Aha! Overfertilization is the reason my cosmos were reluctant to bloom. Although nitrogen is a necessary nutrient for healthy green growth, too much can be a bad thing. If that 20-20-20 that I could barely decipher is NPK, the cosmos were getting too much nitrogen fertilizer.

My cosmos plant did not flower, but produced a lot of healthy-looking leaves and phenomenal stems; it fits. I placed my MG ID badge back on my shirt with pride. Looking over at my guru, I noted her thumbs-up gesture, and guess what? Yes, it was green.

Kim Woodford, WSU Master Gardener Class of 2016, gardens in Westport.

Mystery of the cosmos solved: Hindsight can be 20-20-20