Question
Hello, I have just got back from South Africa and have purchased some seeds. Such as; Dahlia, Zinnia, California Poppy, Nutans, Protea Obtusifolia, leucospermums, Ptotea repens and Leucadendrons. They say to plant seeds in Autumn to spring, and sow in seedbox or welldrained seedbed. Cover with fine sand to depth of seed(1cm.) I am trying to get more info on the plants and when in ATL, Georgia is best to start? also is the soil here good for them, since we have high iron content in our soil. Also; second question: I have been growing Basil. Some have died nd turned black! Are they getting a diseas? What can I do to learn more about plant and herb diseas? Thank you for your time.

James  

Answer
James,
I am away from my office so I don't have access to my reference books regarding the seeds you purchased and your soil.  But as far as starting them, in your area you can sow them now or in Jan/Feb.  They are -for the most part- plants that germinate well in cool temperatures.  I would sow them in seed-starting mix in flats or six-packs, however, not in the ground.  Ground soils dry more quickly, but seed starting mix is vermiculite and peatmoss, and this holds the moisture over a long period of time.  (The only exception is the California poppy - sow that right on the surface of the soil where you want it to grow, and water it when it starts to dry.  Once the plants have germinated you can water less frequently... Calif poppies do not like to be kept wet.)  Once the other seeds have gotten a second or third set of leaves, you can transplant them to the garden or into pots.  

Basil can get a leaf fungus if the foliage is frequently hit with water - this causes the leaves to turn black.  Being a Mediteranian plant, it likes hot sun, periodic but not frequent watering.  If you think that the plant is getting sprinkled frequently (by watering or rain!) that is the cause.  The only other thing that can cause the leaves to suddenly turn black is over-fertilization,  Too much fertilizer can burn the leaves.  

There is a good book you might like to have for reference:
American Horticultural Society Pests and Diseases: The Complete Guide to Preventing, Identifying and Treating Plant Problems

it is by Pippa Greenwood.

If you have specific questions about the seeds you purchased, ask  me after the 10th of November when I am back in my office!
all the best,
C.L. Fornari