When to feed Rhodis

1) A friend in NYC has two established Rhodis and has heard that they should not be fed until after they flower. The only reason I can think of for this would be that nitrogen will encourage foliage at the expense of flowers. But I have also heard that nitrogen encourages all growth, including flowers. I'm planning to use the normal Peter's Rhodondendron/Azalea blue crystaline food. I believe it's 24-12-12. Any thoughts on whether I can feed now?
2) Also, I'm planning to fertilize all beds, including the above one with a commerical sand and manure (chicken and other, I believe) product. Will I be providing too much nutrition if I feed and compost? In the Rhodi bed I am not digging it in because of other senitive roots (Lilly of the Valley) underfoot.
3) Are the lillies vulnerable to the high nitro or acidity of the Rhodi food and fertilizer? I'm not uure what's been done here in the past.
Thanks,
Michael
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snipped-for-privacy@rcn.com wrote:

I would wait until the chance of frost is gone. That is May 15 where I live in Zone 6. Plants that have been given a soil mixture rich in organic matter probably will not need feeding for several years. Do not stimulate fast growth because it produces long weak stems and few flowers. But if a plant seems weak or sickly, use cottonseed meal or a special rhododendron-azalea-camellia-holly fertilizer such as Peters or Hollytone dusted on the soil in early spring. Supplemental feeding later is not normally needed, but phosphorus and potassium may be applied any time.
Fertilizing after mid summer in a northern climate promotes tender growth in the fall which doesn't harden off before the first frosts of winter. This gets killed by the frost. This growth may have the buds for next years flowers on it which would also get killed by the frost.

Rhododendron have shallow roots. Never cultivate around a rhody. This sounds like way to much nitrogen fertilizer for the rhodies. It will make them leggy and prevent buds from setting. Here is a better option:
I have found the following foolproof formula for chlorotic leaves or a rhododendron that isn't looking healthy:
Purchase a bag of Epsom Salts crystals (magnesium sulfate) (available here in bulk at farm-and-feed outlets), about $4.00 for a 5 lb. bag - and a bottle of FULLY Chelated Iron & Zinc (this is a very concentrated liquid - the chelation means it is in a form that can be readily absorbed by the plant), about $7.00 for 1 quart; In a one gallon watering can, put in 2 Tbsp. of E.S. crystals and 2 Tbsp. of Iron and Zinc liquid - fill with warm water and stir to dissolve; Sprinkle this over the rhododendron - by that I mean drench the leaves with the solution and pour the remainder around the drip line of the root ball.
In 1-2 weeks, the leaves should be nice and green. You could repeat the process at this time if the leaves aren't fully green.
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