Could be the excessive rains. Our local farmers mkt has had to cancel the tomato tasting contest because the rains have put a damper on a lot of veg. production as well as diluted the flavor of those tomato fruits that set.

Used railroad ties I wouldn't recommend. They are highly treated with stuff you don't want leaching into your soil.
Wouldn't use tires either for a lot of the same reasons.
Besides, tires are dark and in the sun absorb a lot of heat
not to mention the opening is just not wide enough.

It's end of season and big sales on planters of all sizes. Take advantage of garden retailers sales and get yourself some huge planters with proper drainage holes and unpainted. The painted ones I wouldn't trust not to have toxic paints and coatings. Go for the biggest clay planters unpainted so the whole pot breathes and evaporates excess water. Get a couple of those planter rolling stands
so it will make tipping the pot at harvest a lot easier.
Be sure to steel or aluminum mesh the drainage hole to keep out the varmints.

In my raised bed kitchen garden I no longer have to plant potatoes. It seems I never actually dig up all the tubers when I harvest so volunteer 'taters pup up in just about every bed. They seem to sprout at odd times too, not really tied to the seasons.

You might consider using a big cardboard box. I did that with a computer box one year. Planted some in each corner at the bottom and then just kept piling manure and leaves in as they grew. Worked pretty good and then I composted the box at the end of the season. I splayed the flaps out and put weight on them so the box wouldn't fly away. Opened the flaps on top and secured them upright to make it taller.

sounds like a great idea,chrisb_sc_z7. I may try that next year myself if the jet stream straightens out and quits that looping collection of GOM moisture. We got way too much rain and clouds around here this gardening summer.

I know just the carton. It's triple walled to transport audio equipment. Too heavy to lift filled with anything else so in the ground it goes next spring.