Radishes, onion slips, some strawberries, and a pepper plant all seem healthy and to like the mix. Lettuce, spinach, peas, and beans are all sprouting as well in the same mix.

The tomato plants, however, are losing their dark green coloration since I planted them 5 days ago. I have purchased and planted a third plant, just in case something bad is happening.

The plants were living outside and 12-15" tall when I purchased them. Additionally, there some gnats and aphids on the plants, but were removed manually - and the plants were robust and vigorous anyway.

What are the most common causes and solutions of fading in the scenario I've described? Were they too big and are shocked? Is it possible that I need to fertilize with this mix? or possibly soil too rich?

It most certainly is possible, it will be required. Lots of discussions and information available on how compost, used as a source of nutrients, doesn't work in containers as it does in-ground. You have minimal to no soil micro-herd (bacteria) to convert the nutrients to a usable form for the plants. The differences you are seeing is based on the different nutrient needs of the particular plants.

It is your choice as to what to use but regular supplemental feeding will always be needed with containers plants since nutrients leach out every time you water. Most find that when using organics, liquid forms are much more effective than granular forms.

You can learn much more about this and the other unique issues of growing in containers over on the Container Gardening forum here.

Dave

Am I accurate in inferring that you think I *should* fertilize now? in other words, you think that it's reasonable that the fading is due to low nutrients that the fertilization would help?

Also, thanks for the heads up on the Container Forum.

Your post compares several different vegetables all with very different water, pest tolerance, and nutrient needs. Comparisons of that type are very mis-leading so you need to focus on the specific needs of the specific variety.

So no I'm not saying fertilize everything just as I wouldn't say water everything all the same. Your beans, radishes, peas, strawberries and peppers require much less N than your tomatoes or lettuce or spinach, The water needs are very different too.

But if the tomato plant is fading in color and

(1)assuming it hasn't been over-watered (fungus gnats indicate that it has) and that

(2) you eliminate the fungus gnats problems ASAP and

(3)treat for the aphids then they may recover fine.

If they don't then yes, they may well need feeding.

In other words, fertilizing isn't your only problem or even your main one right now, just the particular part of your post I addressed in response to your question about your potting mix and container needs in general. OK?

Dave

And the gnat and aphid issues I believe are handled as well.

Thank you for the insight, I didn't mean to ruffle any feathers.

I'll feed the worst looking one and see if it helps.

Thanks again for the tips.

Oh you didn't. Not at all. Sorry if it came across that way. I just didn't want to confuse the issues - or make it even more confusing than I already had.

So my try at clarifying it likely only did what I was trying not to do. Typical for me. Apologies.

Dave

Planting the tomatoes deeply will allow roots to form along the buried stem and will lessen the need for watering.

Perhaps the stress of transplanting may make the leaves yellow for a short while, but they should soon become robust again.

If not give them a shot of an organic fertilizer such as liquid fish emulsion or some similar product.

Have patience while they adjust to their new environment and they should do well.