If you can find and mow a large number of dead leaves, the leaf mold makes the best soil. You can mix it with regular soil, and/or manure, or composted (even partially) kitchen scraps or yard waste. Basically, anything goes. Something that helps is the introduction of a few earthworms in each box. They will go forth and multiply and create good soil for you out of unfinished organic matter, plus aeration and fertilization. I have earthworms in all my pots, and replenish them and their food every spring. One inch of organic matter per year is all they need to keep the soil fluffy and healthy. For year round veggies, lettuce (choose a variety that does not bolt easily), herbs and chard are good choices. Lettuce and chard will eventually bolt and will need reseeding, but not before they gave you a lot of leaves.

Q. Why can't compost be used indoors? A. Because. There IS actually a very good and well documented reason why compost is not recommended as a major additive to container potting soil, either for indoor plants or outdoor plants. And that is how it affects good drainage, a quality that is pretty much paramount for any sort of container growing. Compost continues to breakdown even as a component of potting soil. The longer it goes, the more frequently wetted and the warmer the container is kept, the faster the material breaks down. And when that happens, the individual particles become tinier and more uniform in size, the pore spaces (the empty cavities between particles) shrink and the whole mix compresses. Compression and lack of pore space has a big negative impact on drainage and soggy soil and rotten roots tend to be a result. That's why most high quality purchased potting soils contain minimal - if any - concentrations of compost. It just doesn't hold up. If you are growing in containers short term, like very seasonal crops, compost can work as an additive (not the base) to potting soil. But for long term success - growing anything longer than 6 months - you want a durable, barky, textural potting medium that is not going to collapse and impact good drainage. The Container Gardening forum has a detailed discussion on this very subject that is the longest running (march '05) thread on GW. More than 2500 posts have entered into the discussion and the knowledge base is pretty high - in fact, the original author is considered an expert on container soils and container gardening in general Here is a link that might be useful: Container Soils - Water Movement and Retention

You science guys are making me feel like the laziest gardener ever born. It sounds like the problem ( from only what is written) is just the PH of the soil. Evidence includes not only the story but the type of plants. Clematis prefer a more alkaline sail.. thus it is the plant not affected. Roses prefer a more acid sail, thus my home, Portland Oregon is known as The Rose City. It's the one suffering the most. Nepeta is more forgiving but it does very well here in ore acidic soil. Over the years gardening here with our acidic clay-ish soil, I welcome the rare opportunity of NEW cement on a garden border. I have the chance to grow more alkaline loving plants next to the concrete and watch them thrive for some time because it seems like the concrete leaches out for a couple years..or it just takes that long for mother nature to change the soil back to acidic... not sure which but it happens. I would leave the clem there, get the rose out as soon as possible.. their tough and should be able to rebound, and either dump the nepeta or move it to an out of the way spot as a science experiment. Nepeta is cheap and comes up from seed easily so not having it on display would be my priority. One plant I love and only does okay in our acid soil is dianthis, which is what I chose for a similar situation when I had the end of my driveway replaced. Best dianthis I've had and it was exceptional for several years, when it slowly started to just look normal again. Work smarter not harder and have some fun with this moment in time, it's not going to last forever. The new plants should adjust to your normal soil since it will change so slowly assuming of course you don't pick some weird, rare thing we never hear about that only grows in alkaline soil. You do have many beautiful choices. Trip to the garden store is always a good day. :) How about this search ? Here is a link that might be useful: plants that like alkaline soil

Not sure about cheaper, but my homemade 511 mix is fairly inexpensive to make, and it works very well. Bags of pine bark mulch/soil conditioner, is about $2 a bag, peat moss is pretty cheap, and a large bag of course perlite is a bit pricy, but lasts a long time. Lime is cheap. Not sure how much mine costs exactly, but estimating, I can fill a 15 gallon container for $6 or less..........plus the mix is reusable, so the cost lowers significantly over time.