Might be one of two things. Yellowing of leaves usually means overwatering which causes chlorosis. Also, it could be very low iron. If its the latter, you need to have the soil tested and if its low in iron, add iron sulfate. Be careful though, as guessing can kill the tree. Iron sulfate also lowers the soil pH and if applied in a dry, granular form, it should be balanced up with a little lime. Ironite is a brand, and is also available in liquid form. When leaves turn yellow and then black, they are obviously dieing. It might be low nitrogen, but that usually will make all the leaves surfaces turn yellow.

Before you do any amendments, make sure it's not pot bound. When you lift it out of the pot, and its filled with roots, you'll need to replant it in a larger pot, or root prune. Any potted herb will greatly appreciate being replanted in new soil. I have seen many potted herbs brought to me to find out why it was ill, only to find that the plant had outgrown its pot and was starving for nutrients.

Here is a link that might be useful: My Garden Travels

Yes, I just realized that I don't recall seeing the poster mention the bay in a pot. Aren't these usually trees? A pot would really cramp its growing. My small fig tree is in a big heavy plastic pot 2'x2'x2' and has had some roots showing up on the surface of the soil after several heavy rains. Its now still dorment in my garage, and has made a small green shoot appearing next to the main trunk of the tree, The fig is only 5 foot tall. If I were to repot it, that would be a major task, not to mention being much more difficult to move it in cold winters here. I woudn't want it to freeze to death outside.

What you describe sounds perfectly normal. Sometimes, just before putting out new growth, it is about that time in your area, bay trees do drop some older leaves. I wouldn't add anything or change what you have been doing. But if you are growing in a pot, follow herblady49's excellent advise. If you do repot, don't up-size too drastically. Bay is fairly sensitive to overwatering so if the new pot is too large the small root ball will not be able to handle all the extra moisture that all that extra soil will hold. I have about 6 bay trees in 16 inch pots but they were in 12 inch pots until last spring. The plants were 7 feet tall and a too big to put my arms around -about 8 years old-and in 12 inch pots for several years at that size. Finally had to repot once the roots split the nursery pots.

ksrogers- yes bay laurel will become a tree-40 feet or more in a favorable climate. My father has 3 huge trees growing outside his Arlington home, right up against the house for protection. They are each about 25 feet tall and 6 feet in diameter. Bay can also be grown as a shrub. However, it is so slow growing it can be grown very successfully in pots for years. Although they would probably benefit from being repotted every 2 or three years.

Here is a link that might be useful: Another recent post about bay.

Not sure if Bay would survive here. I tried growing boysenberries a few years back and chose the cold hardiest ones I could find for Z6. They grew one summer and never returned. Red raspberries (mine are thornless) have big crops, and easily create new canes. About the only tree I would want to try growing in a pot is the fig (brown turkey variety). Its a major task just to move it out of my garage every spring, and then back in for the winter months. I'm not even considering repoting my fig yet. If I did, it would be in the back yard in soil. I would probably build some kind of 'tee pee' to cover it, and its surrounding soil every winter.

ksrogers-try growing the bay and bringing indoors. You likely won't have monster like the fig for at least 8 to 10 years.

Here's another recent post on bay including a picture of a very beautiful bay tree: bay tree

As far as figs, I think I'm going to experiment with figs this year. I'm going to try planting outdoors and covering for winter. It works here (zone 5/6) so says the local nursery I'm going to get them from (link below). I've had really good luck with plants from Millers.

FataMorgana

Here is a link that might be useful: Miller Nurseries - Brown Turkey Fig

Yes, Millers is where I bought my plant from. It will start to bear in the second year. Last summer was its second year of fruits and about half dropped off early as its not big enough to support a lot of figs yet. No flowers show up, and the leaves are highly resistant to any bugs. I spray the foliage with fish based foliar sprays, and have also add a little of the Gardens Alive fruit tree fertilizer (maint formula). I don't use enough Bay to make it worth my effort to grow any. Its added to some sausages, and also the cooking water of corned beef and pastrami coatings, along with ground pepper, mustard seed, and coriander. Basically corned beef IS Pastrami, its just that corned beef doens't have the coating of spices.