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Root Production Method: RPM, do you know it?

Austin Verde


Joined: Apr 13, 2012
Posts: 13
posted Today 14:43:03
So, basically from what I can surmise: RPM involves raising trees in containers that allow for air pruning of roots. When the roots come into contact with the air, they stop growing/die back and this encourages new root growth.

Check it out here: http://www.fs.fed.us/rm/pubs/rmrs_p024/rmrs_p024_020_021.pdf

It seems like they just use pots that dont have bottoms and are shallower & wider than normal. This nursery: www.fknursery.com raises seedling trees using RPM here in MO.

I guess I'm curious to learn more about the air pruning technique. Does anyone have any knowledge on the subject? There are a lot of products out there that claim to air prune such as at http://www.rootmaker.com. But it seems that at forrest Keeling nursery and in the RPM pdf that the bottoms are just cut off of regular pots.

I'm interested in this because I order hundreds of seedling trees every spring and their bare-root systems are as sad as can be. Over the past few years I've had barely a 60% survival rate and those that do survive grow slowly. I'd love to be able to spend a year nursing these seedlings into having vigorous developed root systems before planting and then not loosing so many trees.

So far all Ive figured out is
step 1: put seedlings in pot without a bottom
step 2: put seedling in bigger pot without a bottom.

There's got to be more to it than this.
osker brown


Joined: Jun 28, 2011
Posts: 146
Location: Southern Appalachia
There is a permaculture nursery in my area (Useful Plants Nursery), that puts some of their larger trees in "RootTrapper" fabric pots (the same ones you linked to). I have an Illinois Everbearing mulberry in one that I haven't planted yet, so I'm not sure how the roots look in them. They also use the smaller airpruning plastic seedling pots from that company. I haven't handled their plants enough to say for certain how well they work, but the guy who runs the nursery has been in the horticulture business for 35 years, and I've seen their nursery.

I have used airpruning fabric pots quite a lot with containerized annuals. I sewed up my own version of Smartpots using landscape fabric, which took a decent amount of time but cost very little. The advantage with that over just bottomless pots is that the lateral roots also get pruned, so once you transplant you have a solid root ball surrounded by loose soil, rather than a root mass on the sides with mostly loose soil in the middle. I've also cut out the bottoms of all my seedling pots for the past 2-3 years and it seems to cut down on transplant shock with veggies.

Also worth mentioning is my potting mix. I don't have exact percentages, but it's about 1/3 biochar 1/3 rotten wood chips 1/3 compost. The biochar holds lots of air pockets, the wood holds lots of water. The mix is quite a bit heavier when wet than the potting mix you buy at the store, but I find that the added aeration from the fabric and bottomless pots compensates.

I'm going to be experimenting with this a lot this year so I'll update as I start playing with more tree/shrub seeds.

peace



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