Large-scale growing of container basil: potting soil vs 5-1-1 mix
In another post I'd asked for advice on potting mixtures for basil, which I use in large quantities for pesto. I'm growing it in containers because the downy mildew disease that has recently begun to afflict basil has hit my garden. Maybe this can help others now that basil is becoming difficult to grow in garden beds.
I read that basil doesn't like a lot of fertility and does like good drainage. I planted most of the seedlings in a high quality potting soil (McEnroe Organic), which contains compost, sand and other ingredients. I planted others in a variation of the 5-1-1 mix I learned about on this forum. I couldn't find pine bark fines, so I substituted Repti Bark, which has a bigger chunk size, up to 3/8" - 1/2". I've been watering when the soil 1" from the top feels dry, using a weak solution of Foliage Pro.
It seems basil doesn't need extreme drainage, because the plants in the 5-1-1 mix aren't growing nearly as robustly as those in the potting soil.
The season is still young, so I'll see what happens in the long run. So far the potting mix plants are thriving, and bushing out from the tip pruning. I'm going to cut back on the Foliage Pro to see how well the potting mix alone supports them. The 5-1-1 mix plants aren't really growing at all, and the leaf color is starting to pale.
I'm not suggesting in any way that the 5-1-1 mix isn't good. It's possible that the Repti Bark's size threw off the mechanics of the mixture, Or it could be that it simply doesn't hold enough moisture for basil.