Jean, Sorry it took so long to get back with a description. The leaf starts with a little round circle of yellowish/light green. Then it seems to sprend and turn brown and the leaf starts to dry and curl. That is the best description I can give. I don't know how to post a pic. We have looked for insects but found none. We dug all the dirt out this year in the area where we plant and put in new top soil. The reason was that this happened last year to us also. Thought that we might have a virus in the soil. What do you think?

Edward, are you referring to tulip poplar, Liriodendron tulipifera, or to what some call tulip trees, one of several Magnolia species? The magnolias are often affected by late spring frosts that can abort or impede flowering. Tulip poplars flowers are often not very visible as they tend to appear only at the top of what can get to be very tall trees and are often hidden by foliage as well. If you can share with us the botanical name of the tree in question, we might be better able to help :-))

Do you think increasing the feedings should save this plant? Yes. I am not familiar with that particular product. Does the label indicate that it also supplies micronutrients or just N-P-K? If yes, feed it weekly to get the phosphorus and micro levels back up. If not, some mircos can be gained by adding Epsom salts (sold at all pharmacies and Walmart, Home Depot, Target, etc.) 1 tablespoon to a gallon of water will improve it very quickly. It is a good source of magnesium sulfate and is used by many of us tomato growers routinely. Otherwise yours is a low-dose fert so more frequent apps will be required as i said above. Look for an additional micro fert such as fish oil emulsion and/or kelp products to boost its condition. Many products are available. Hope this helps. Dave PS: Sorry but I can't resist adding this - next year use a bigger container. ;) You'll be amazed at the difference it makes.

So could it be lack of sun? Avocados love sun and water. Or could it be some lack of nutrients or a pest? I've never seen this curling thing on mine, so can't answer, but maybe this will encourage others to chime in. When our citrus leaves curl, it's due to leaf miners. They don't hurt the plant but sure make it ugly.