I’ve planted a substantial number of trees in the last two years with purchased seedlings they are cheap. The RM system is more of a hobby to fool with for me more than anything. Last year I picked up 5 RM18 trays and I just picked up 90 RM 1 gallon pots to dabble with. Jack you have said you have better success after transplanting twice to 3 gallon then direct planting after that what is the reason you think your success is higher after the 3 gallon??? Root system large/deep enough to withstand some drought???
After the initial planting and tubing or caging (depending on the type of tree) my trees in the field get zero care. No supplemental water or anything. If a tree can't grow and produce without care, it is not a good wildlife tree for me. I'm trying to put together a permaculture that will continue on its own long after I'm able to provide maintenance. I'm also designing a permaculture to feed deer which requires a volume of trees greater than I could maintain if I wanted to.
I think I said this in another post, but a tree's ability to extract nutrients and water is directly related to the number of fine terminal root tips. With trees grown in a root pruning container system, you get a root ball with a huge number of these terminal root tips. It can extract a lot of water and nutrients from whatever it can reach. The key is "whatever it can reach". When planted, the root system is only as large as the container. It doesn't take a formal drought for the top layer of soil to dry out in the summer. That is why the trees I've planted in the field from 18's have near zero survival rate for me. I've planted hundreds directly from 18s. We get pretty good rain here, but we do have some dry periods, enough that trees planted from 18s will die from lack of water. Most of the trees I plant from 1 gal containers survive. I think that during dry periods that first year, they are limited on the amount of water they can reach. I think this significantly retards their development and some don't survive. Depending on the tree and the micro-environment (amount of shade, general soil moisture, competition for moisture...) some trees planted from 1 gals will thrive.
In my environment, virtually all trees I've planted from filled 3 gal RB2s have thrived. I think it simply because they are less water limited that first year which means the root system grows more along with increased top growth resulting in it being able to reach further more quickly for water.
Now there is something else you should know about my specific condition that may or may not apply to others. I have heavy clay soil and I use promix as the medium. One major benefit of rootmaker trees vs bare root trees is that you don't get they year of sleep, creep, and then leap. The begin growing almost immediately because the rootball is undisturbed. The RB2 containers unwrap. When you amend soil planting a bare root seedling or plant a rootmaker tree grown in promix in heave clay your create a pond due to the difference in infiltration. During wet periods, water infiltrates promix much faster than clay so you get a pond at the rootball. During dry periods, the reverse is true. Clay retains water much better than promix and you get a drying out of the roots. That makes planting technique in heavy clay important.
Here is the method that I developed that works well for me. I start by picking a location where ground water is not likely to drain into the hole. I then use an auger on my tractor to dig a deep hole; much deeper than the RB2 but almost the exact diameter. I use a hand rake to make sure the sides of the hole did not glaze with the auger. I then backfill the hole with crush stone and then add a little native clay soil on top of the stone. I then put the rootball in the hole. I often have to stand on the root ball to get it to squeeze into the hole. The fit is that tight. I leave the promix about 1" above ground level and then take native clay soil and mound it around and just over the promix. This creates a small mound discouraging ground water from draining into the hole.
So, what happens here? We get plenty of rain in the spring. Water does infiltrate the promix but it continues in infiltrate and forms the pond well below the root ball. Trees are fine with roots growing into a water source. They will adapt as needed. Thus all the tree growing along streams and ponds are fine. They don't want the rootball sitting in water for a significant period. Because these trees begin growing immediately, before our summer comes along and we get dry periods, the lateral roots have grown into the native clay that holds moisture much better than the promix. Thus, these 3 gal trees have sufficient access to water during the summer.
Other locations may be different. Like most things habitat, different places may need to adapt things or use different techniques.
So, that is a detailed description of why I think 3 gal trees perform better than 1 gal trees for me. If you are providing supplemental water and nutrients as needed or have different soil or weather conditions than we do here, things my be different for you.
Thanks,
Jack