The following article is courtesy of tropical plant and soil expert Lynn Griffith.

Calendar-wise, it has been spring for two weeks. March madness is over, and baseball season has begun. However, in parts of the country, they are still shoveling snow and are expecting more. Spring sometimes arrives in fits and starts, with Old Man Winter taking his time getting out of town. So, what is spring like from a plant’s point of view? 

Plants  “know”, in a metabolic sense temperatures are warming and that days are getting longer. Some ornamental plants are photoperiod sensitive, while others are not. This means that some plants respond to how long that days or nights are in addition to temperature. For example, in New England or the Midwest, the onset of spring is unsteady. It may reach the 70s and then snow the next week. If plants only utilized temperature as their signal to start growing, they could easily be faked out. Day length and night length are much more consistent indicators of season than temperature in certain parts of the country. 

With tropical plants, the situation is somewhat different. Parts of the tropics such as South Florida and the Caribbean experience day length variations, while equatorial regions do not. It is sometimes more useful for plants in the tropics to respond to soil moisture and rainfall in order to “know” when to set flower and seed. 

In most of the US, the onset of spring is showtime for plant growth. POLYON® starts releasing at about a 55° soil temperature. Temperature change in field soil tends to be more slow and gradual. Container media temperatures rather closely follow ambient air temperatures, though they are behind by several hours. Once spring growth truly begins, all of that new foliage can place significant demands on potassium and magnesium reserves in the older leaves. Make sure you have adequate levels of those nutrients in your plants, in addition to nitrogen. New leaves absorb foliar nutrients very efficiently. Supplemental foliar nutrition can be very effective in managing and maximizing springtime growth. 

However, insects also sense when spring has arrived. All of that newly flushed foliage is a great attraction. Aphids and thrips get very busy in the springtime, so make sure you are well-stocked with pesticides to control these insects. Infestations are often sudden and severe. Microscopic mites also get busy feeding on new tender foliage, especially when springtime weather is dry. Not all of the miticides control microscopic mites -- be sure you are well-stocked with the proper materials.

I hope spring has arrived by now where you are. If not, hopefully it is just around the corner.

Lynn Griffith
Tropical Plant and Soil Expert
“Get the Soil Right”



Thrips on a lily. Click to enlarge.



Aphid colony. Click to enlarge.



Example of potassium deficiency. Click to enlarge.



Example of magnesium deficiency. Click to enlarge.