Just curious to know what the use of commercial fertilizers has to do with making basil into pesto? Plants absorb exactly the same ions from the soil, regardless of how they originated. "Chemicals" from normal usage of fertilizer do not accumulate in a plant any more than the same chemicals from organic fertilizer or compost.

Nitrogen, for example, is always absorbed as ammonium or nitrate. The only difference between a chemical fert. and an organic source is that the former provides them directly and the latter requires bacteria to perform an intermediate step of converting protein to ammonium and then nitrate. No difference in the end.

This post was edited by Slimy_Okra on Mon, Jun 2, 14 at 23:44

That's not the only difference when the organic source you're using is your own compost. When plants grow in soil they interact with a complex system, not all of which is understood. When you remove the plant from that soil system and instead use a commercial fertilizer in a container filled with potting mix, the plants are getting a) a range and combination of ions that is far from nutritionally complete (an analogy is substituting commercial vitamin preparations for food) and b) who knows what else, since soil amendments and fertilizers may contain industrial and other waste products, like sewer sludge. I don't like using it on food.

I'd rather put my own soil and compost in the pots but, as I said, I don't know if the downy mildew is living in it.

Fresh garden pesto is a family tradition. I hope container growing works!

Growing in a container - essentially a closed environment - is vastly different from growing plants in the ground. The correct potting medium is essential and that does NOT include one's own garden soil or even much compost. Particle size is too dense/uniform and drainage and aeration are greatly compromised.......and these are critical factors for good container growth.

Get a good quality potting soil (not Miracle Gro!). Potting soil is nutrient-lacking so fertilizing is necessary regardless of the plant grown. Maintaining an organic program is tricky unless you rely on liquid ferts like fish emulsion or a compost tea. And even those may not be able to deliver the nutrient charge the plants need. Organic fertilizers need to be processed by soil organisms for plants to be able to access the nutrients they provide and there are just insufficient populations of these critters in potting soil to make this entirely efficient.

FWIW, downy mildew on basil can occur on container grown plants as well as those in the ground. The pathogen can be airborne and is encouraged by high humidity, warm temperatures and excess moisture. Good air circulation is key. Control these as best you can and avoid water on the foliage.

Thanks garden gal, that's exactly what I wanted to know. I've wondered if downy mildew would affect my potted basil plants. A couple of people told me theirs worked better that way, so I thought I'd try. How can I distinguish a good quality potting soil from others?

BTW, do you happen to know if downy mildew persists in the soil? I can ask my county extension...

Wow, what a learning curve! I've been reading a lot about container growing, including using Al's 5-1-1 mix. I had no idea growing in containers was so specialized!

Maybe i'll be lucky and this will stop the basil from getting downy mildew. We'll see. They don't seem to know a lot about it yet -- my county extension didn't know if it was soil-borne or not, or whether it originated in greenhouses or is in the seed itself.

I just did a quick Google search. I was curious whether commercial greenhouse growers, the people producing those little basil capsules, would follow any clear pattern in their methods. I found an interesting story.

Here is a link that might be useful: Herbs: Organic Greenhouse Production

I grow lots of basil for pesto (Italian large leaf) in containers. I just use regular potting soil from the store, nothing special, although I won't use Miracle Grow potting soil because thats pretty much just peat moss and fertilizer. Brands and actual mixes vary around the country, and what you would get in NY is not what I can get here. Just ask at the nursery for a decent one - not the cheapest.

They like heat, so I have mine on the west side of the house, and they like water, so I have mine right by the garden hose. They also like a lot of nitrogen to grow fast and with large leaves, so you can use anything from alfalfa tea (made by steeping pellets) to bat guano to lawn fertilizer to diluted household ammonia.

I add a monthly shot of regular compost tea

The size of the pot matters re how often you're going to have to water. When they get over 18" tall, pretty much every day.

Just keep snipping off the flowers, every now and again cut them in half, and you can harvest a whole lot of basil.

We rinse it off, use a salad spinner to dry it, then food process it with olive oil and lemon juice, then freeze it in zip-locks. Thaw it out, add the rest, and voila pesto.

David, what do you mean cut them in half? Cut the whole plant in half, height-wise??

Pretty much - its just to keep them at a manageable size and producing new branches and leaves. It also seems to slow down the bolting and flower production.

In case anyone is interested in the follow up, I grew 25 plants, in 14" pots, with a compost based potting soil. I tried some with a reptibark version of one of "Al's mixes" (using semi-crushed up reptibark, perlite, peat moss). I spread the pots out on the sunny deck for good circulation, and watered them only when the
top inch of soil was dry. The good news: no mildew, and a good harvest.

The plants in the reptibark weren't doing well, so I repotted them into potting soil. The mix was draining too fast, no nutrients or water seemed to remain. Granted, reptibark is bigger than the recommended pine bark fines, which I couldn't find, so I can't draw any conclusion about Al's actual mix.

A lot of the leaves started to turn a little pale, so I decided to use a mild solution of Foliage Pro once or twice a week. I'd like to try again next year without it, keeping closer track of leaf color, to see if the potting mix alone provides adequate nutrition.

I didn't think the basil flavor was as wonderful as usual, but I may be imagining it. I'll try a different variety next year.

I take the easy way out. Potting mix and plant foods are all Edna's Best organics. Less on my mind and worth the price for that reason alone.

I grew some huge basil in pots this year. The container experts recommend using fresh potting mix every year because it breaks down and loses its porosity, becoming more dense like soil. I do reuse my potting soil by mixing in some coarse compost. That gets put in the bottom half of the pot. I buy a fresh bag to fill up the pots. That way any diseases carried over are buried deep in the pot. Blights often get on leaves after splashing up from the soil. I mulch the top of the pot with wood chips or grass clippings.

Since you're harvesting a lot of leaves, it seems to me basil would need nitrogen supplements. Mine certainly does better in higher N conditions.

I confess I use MG Potting Mix if it's on sale. It seems to be a good quality product. Sometimes I'll blend with cheaper potting soil and/or compost to stretch it.