Your set-up is nice and you definitely are serious about what you are doing. 20 gallon containers for tomatoes? Wow! The plants should grow HUGE. The only thing that concerns me a little is that the ProMix is a peat based product. It will hold alot of water. Don't get me wrong, ProMix is a good product, and I use it myself from time to time. Since you seem to be trying to get the most out of what you are doing, may I suggest that you take a look at what might be a better growing medium. You can still use some of your ProMix in it. It's a pine bark based mix, and alot of us refer to it as the 5:1:1 mix. 5 parts pine bark fines, 1 part peat (or you can use your ProMix), and 1 part perlite. I actually use 2 parts peat in my mix. Since you haven't planted yet it's not too late to change direction a little if you want. I suggest reading the link below. I'm not trying to throw a wrench in your spokes, just trying to suggest a way to get the most out of your efforts. If you're too far into it this year, maybe next year. Maybe with a minor investment in a few bags of Pine Bark Mulch and a little perlite, you could do an experiment and just try a container or two.

This post was edited by edweather on Thu, May 9, 13 at 16:19

Since you have already completed your mix, it will work. The Pro-Mix BX will hold water longer then you think so make sure you don't over water. If you want to add anything to it, use perlite, it's cheap. I use Pro Mix BX for my tomatoes and they love it. Use Osmocote or Dynamite in the red bottle and add some gypsum for calcium. I believe the Dynamite mentioned will last 9 months, this way you don't have to fertilize all the time. You can spend a lot of money with fertilizers so be careful. Leave the pH alone with your mix, it's already where it should be.

If you want to use organics, use Tomato-toneî 3-4-6 then you don't need to add calcium because it's already in there.

IMHO, the link above is an ideology modified from a bonsai grower. A lot of people like it because it's better than the average mix from the larger stores. I couldn't agree more. I use a lot of different mixes and none of them are a 1:1:1 or 5:1:1 ratio. Just because I don't use those ratios or anything close, doesn't mean they wont work. My point is, there are a lot of different mixes out there, some better and some not. Choose a mix that will work for your watering habits and your zone. If you're not sure about your watering techniques, you will have a learning curve. In time, it will make sense.

Good luck.

Your decision to use Geopots should help to mitigate any ProMix water retention issues. Still, I'd keep a dowel or bamboo skewer in the mix so that I had a good idea of how damp it's staying toward the middle of the pots. The recommendation for a controlled release fertilizer like Dynamite or Osmocote is a good one. I think many or most of the Dynamite formulations have micronutrients, but the standard Osmocote products that you'll find at the big box stores usually don't. While it's more expensive and harder to find, Osmocote Plus is the most complete CRF that I've seen and might be worth the investment. The typical recommendation from experienced growers here in the Container forum is to add one tablespoon of Osmocote Plus per gallon of potting media and then to apply a weak dose of a water soluble fertilizer (Miracle-Gro or, better yet, Dyna-Gro Foliage Pro) at each watering.

As for your other questions...

1. Does the mix look and feel evenly moist? If so, it should be fine.
2. As Ed noted, 20 gallons is plenty of room for a single tomato plant, so leaving 6" at the top should be fine.
3. Just to be on the safe side, I'd probably wait to plant until Tuesday to plant.
4. Answered above.
5. An annual groundcover in between should be fine. In fact, if they're vigorous growers and their foliage shades your pots a bit, even better.

Thanks to all for the advice thus far.

However, it seems that in the process of gathering intel for a good growing medium, as a newbie I significantly misunderstood what was suggested to me in the weeks leading up to now.

My goal was to keep things simple. I have very little time to do gardening work and I take advantage of every spare minute I have to that end.

When I was asking around for a growing medium a couple of weeks ago, I was hoping I could find one that I wouldn't have to mix in ratios and one that was already rich in nutrients so all I would have to do is worry about watering. That was when I learned about Pro Mix BX.

I even went the extra mile to find a local retailer of Pro Mix BX and fortunately within a few days I found one within 10 min of my house and bought 4 compressed bales at $28 a pop.

After subsequently receiving my GeoPots in the mail, I thought I had everything I needed to start my containers. However, it seems that all I really had (based on the above responses) was two pieces of the puzzle. What it boils down to is that basically I have one growing mix ingredient and even that ingredient requires something to be added to it if it is to be used alone.

Lets just say for argument's sake that I have no time to go back and re-fill those containers (which is actually a true statement) with a 5-1-1 mix or something like it. Am I destined to have a disappointing crop this year?

I thought my biggest problem was going to be keeping the Pro Mix in the GeoPots moist considering they are fabric pots. Based on the responses above, it seems like I am going to have the opposite problem.

I am not in a happy place right now.

Could this end up being my biggest gardening mistake ever?

Don't worry, you made the right choice. I have never heard of anyone who didn't like Pro Mix, except for the cost of course. You don't have to grow in a 5:1:1 mix with the recommended mediums, there are plenty of other ratios and mediums that will fit the bill. No matter what medium you decide to go with, there will always be a learning curve when using a new mix and or fertilizer.

There's only one thing I can recommend to help you, try using two different fertilizers at the same time. A perfect example would be Dynamite (red one), and Tomato-toneî 3-4-6. You will not have to worry about frequent fertilizing and salt build up in your mix. I can assure you that your tomatoes will grow very well and taste great.

Ron

Thank you for the vote of confidence.

Regarding the Dynamite, are you recommending the "Complete Plant Food for Flowers and Vegetables" or the "Natural and Organic Mater Magic Plant Food"? They both come in red containers.

And how soon should I apply them? Can these be applied to other veggies like peppers, eggplant, squash, cukes, lettuce, parsley, dill, basil, and carrots?

About the ProMix BX, is is completely devoid of any nutrients? If I don't fertilize, the veggies in my GeoPots won't grow? I was under the impression that it contained beneficial bacteria.

njitgrad, No worries. If those pots get a decent amount of sun you will get very large plants and tons of tomatoes.

This post was edited by edweather on Thu, May 9, 13 at 18:43

Unless I'm missing something, ProMix has mycorrhizal fungi but no fertilizer, so you'll definitely need to fertilize. If you use a granual fertilizer like Dynamite, Osmocote, Tomato-Tone, etc., then I'd suggest thoroughly mixing it into the soil before planting. The big difference between the two Dynamite products that you mentioned is that one is synthetic and the other organic. Were I choosing between the two, I'd choose either the synthetic or a blend of both (as opposed to relying solely on the organic).

njitgrad ,

Flowers and Vegetables is the one I was referring to. Apply both fertilizers ASAP.