Tea Leaf Problem
Hi and thanks for contacting Ask an Expert.
I have looked at your pictures and wonder if the plants are getting too much sun even at this time of year. I have also perused many pictures of rust on tea leaves and cannot say definitely if this is a fungus or not.
Tea plants are relatives of camellias which do not like too much sun. If your plants are getting morning sunlight and afternoon shade they should be fine. If not this could be the reason for the burns.
If they are in the shade and have this brown on the leaves I would look at the underside to see if there is any pollen or orange/brown dusty appearance. If so, this is probably a fungus and needs a spray program. First remove the diseased leaves (bag and put in the garbage), you can spray with soluble sulfur (follow the directions on the package) and then in 10-14 days with Neem oil (again, follow the directions). Make sure you spray both the upper and under side of the leaves, soak thoroughly. Both substances have been reviewed and are okay for organic growers.
Now that the weather is starting to warm up the new growth should be starting. Fertilize your Tea Plant just as new foliage growth begins, and again in early summer using a fertilizer that is identified as suitable for "azaleas, camellias, rhododendrons and other shade and acid-loving plants.” Tea Plants are acid-loving plants. And as an acid-loving plant if the soil is too alkaline, the plant will not be able to take up the fertilizer well.
I would check your pH soil levels. If it is 6.0 or above, you would need to add peat moss to the soil and elemental sulfur to bring it down to a more acidic pH level. These are organic amendments and as such do not work overnight, but while they take longer, they also last longer. Linn County Extension (541- 957-3871) has a free service to test your pH soil levels. They may have the same service in Marion County.
Adding peat moss will also help retain water. Mulching around the base of the plant aides in retaining moisture or a ground cover growing at the base will also keep the roots cool and moist.