This page contains extracts from knowledgable sources.
THE BIG THREE: The Nitrogen, Phosphorus, and Pot Ash that we see listed on the front of our fertilizer bags deserves quite a bit of discussion. We must understand that our daylilies are not typical perennials. With most of our flowering plants a “balanced” diet is recommended lest we get too much leaf and little bloom. Thus 10-10-10 or 6-6-6 fertilizing programs are recommended. This is not the case with Daylilies. Daylilies are in the family of plants known as monocots. They’re in the same plant family as ornamental grasses or corn! Monocots prefer to feed at a rate of 3-1-2, or when in active growth 4-1-2. Thus, 18-6-12 should be an ideal mix for us.
Compounding the typical lack of nitrogen problem my laboratory tests always seem to reveal is the fact that the middle number in our fertilizer (phosphorus) is not easily soluble, while most of our nitrogen is quickly leeched away. The bottom line is that if we do feed our plants year after year in the same beds we may end up with much too much phosphorus to the point where it is toxic. Before this happens, and if your soil test come back that you have adequate levels of Phosphorus try feeding with small amounts of Calcium Nitrate (which will also help raise a low PH) or Ammonium Sulfate (which will help lower PH) and Potassium Nitrate throughout the season. This will provide the nitrogen our plants like along with other valuable elements. If you make a mistake, make it by putting out too little, not too much of these products. They can be very powerful and can cause severe burning.
Early in the growing season in addition to the basic fertilizer regimen it’s important to add what I’ll call the major minors; Iron, Magnesium and Calcium. Iron can come from an organic source such as Milorganite or an Iron supplement. I get much of my magnesium from Epsom Salts (which is Magnesium Sulfate at a rate of 100 pounds per acre) and additional Calcium from the earlier mentioned Calcium Nitrate. Several professional horticulturists have told me it’s important to get these “major Minors” out early in the growing season as they are required in order for the plants to be able to take up the big three (Nitrogen, Phosphorus, Pot Ash). When I lived on Long Island this active growth period started just after the dormants broke dormancy. Following bloom season with the first cool weather in the early fall was the time for a second very serious feeding period. It’s important not to use a time release fertilizer at this time as we want our rapid growth to end before the onset of very cold weather. This second feeding period can result in twice the plant the following year as compared to unfed plants. In Florida or the deep south we can’t feed too much in the summer due to the excessive heat, so most of the feeding takes place from November through March.