Wolf, I haven't done this but often use old boards for raised beds. Probably the most successful were 1 by 10 cedar from an old fence. Also, odd hard-wood boards from a cabinet shop lasted really well against the soil.

A previous gardener in one small garden I have used railroad ties and I don't like that. Besides the creosote treatment (& whatever else might be on them), the grass grows up between and out from under the ties. Besides rotting, this would be my concern with using large pieces of wood, as you may be thinking of for your garden.

I have seen some folks put short pieces of small logs upright around a bed in their front yards. Depending on their home style, I think that looks quite good, rustic but good. Varying the height, or how deep they are in the ground, makes for an interesting frame. However, (& a BIG however) because of the curves, the problems with the grass and weeds would be really difficult to deal with unless there is a wood chip mulch or something around them.

Just my 2 cents.

Steve's digits

I have a couple of raised beds made out of logs. It does have a very rustic look. My beds do have a curve in them and there were a few gaps, but the soil and roots eventually fill in these holes. When I made the bed, I stacked the logs more outward at the bottom, then leaning inward as I worked up. I also staggered the joint areas so each seam, so to speak, would have a solid log above and below it. I love the fact that lichens grown on these logs, too. The only downside is that the logs get soft over time and start to decompose (mostly because of me watering), so you would need to replace logs after a couple of years. Also, sometimes you have more insects living in the wood, so keep an eye on that. I wouldn't use logs for raised beds right up against a house for that reason. Otherwise, I love the logs in my raised beds and for garden edging around my paths. We even used large firewood pieces for outlining my veggie patch.