Which mix should I use for growing tree seedlings from seed? - Transferred from QDMA Forum

[yoderjac]

I've seen that question asked a lot. I understand the general concepts of starting trees in rootmaker cells. You want a well drained mix that leaves lots of space in the cell for root branching to fill. But, how does that translate to all the specific mixes out there?
So far, I've used two mixes, Fafard 3B and Promix BX. I know many of you have used these as well. They seem to work pretty well but until now, I had not seen any hard data on mixes.
As I was poking around today looking at nut grafting techniques, I ran across this presentation related to American Chestnut Restoration: http://www.forestbiotech.org/wp-con...can_chestnut_restoration_research-Maynard.pdf
There is lots of good information in general in the presentation, but I found one section on mixes pretty enlightening. It is the first hard data I've found. They tested 11 different mixes with 5 seed lots and replicated it 3 times. While this testing was focused on chestnuts, I'm fairly confident that it applies to most tree seedlings we grow.
So, who were the winners and losers?

Neither of the mixes I used were in the test. Mixes will change over time, but what generalization can we make about the difference between winners and losers?

When you look at the chart, both winners were the two highest dry weights and the two losers were the two lowest dry weights.
I hope this sheds a little more light on choosing a mix.
Thanks,
Jack

 

[yoderjac]

Good info but neither of those are available in my area. Having it shipped is extremely expensive.

They are probably not available in mine either. The take-away point was to try to figure out what the dry weight is of the mix you are using and make sure it is not on the light end of the scale.
I could not figure out from the presentation exactly what volume they were weighing.

 

[yoderjac]

Does anyone know how much Promix it will take to fill a rootmaker 18? I have 22 trays I am going to need to fill and trying to figure out how much I need.

Thanks
Matt

I bought 2 bags of Pro-Mix FLEX (2.8 cu.yd.) to fill my 18s.....it was hard enough to find anything around here...I really wanted to get some fafard soil, but the Pro-Mix seems OK. Anyways, I have filled 9 trays with one bag and think I have enough for one more still total.....so I would say 10 trays for each bag.
That math seems to jive as well.....
25 cu.in./cell = .0145 cu.yd./cell
10 trays*18 cells/tray*0.0145 cu.yd./cell = 2.60 cu.yd.
The missing 0.2 cu.yd. is likely all over my basement floor! Hahah!
Good luck!

 

[yoderjac]

Does the entire ranking follow through with the weight? I'm sure Miracle Grow would out weigh them all but I'm sure it wouldn't win. My point is, I'm sure its not the weight that is making them win but maybe a coincidence of the top 2 and bottom 2.

Gator,
That is a good point. The really didn't rank them individually. They just identified the two that performed the best and the two they said should be avoided. My guess is that everything in the middle worked pretty well based on my own experience.
I was not trying to suggest that weight is the only factor. Clearly miracle grow would be problematic since it is not well drained. I think the key was they started with good professional mixes and it seems weight was the differentiator between them. Certainly soil would be a poor choice but could easily be heavier than the mixes.
I really wish I had heard the full briefing. I wonder if there is something behind the chart I'm missing. I posted the full link to the presentation in case others had more insight into what was going on. I was just pointing out the obvious correlation between the winners and losers and the chart.
Thanks,
Jack

 

[yoderjac]

Given that each mix is not available in certain areas, could we conclude that whatever mix you use should be well-suited to the ground in which the resulting seedling will be planted?
Taking that logic one step further: If the seedling will not grow well in a shovelful of the actual soil into which you will plant it, should we even plant seeds in a potting mix?
I could probably get away with that around my home in Indiana, but I guarantee it would not translate well to the very sandy soils I'm working with up in Michigan. At the very least, I've always been told to mix local soil with your potting mix, to give your seedlings a little taste of reality. :)

JM,
No, I don't think that is the case. These professional mixes are not regional. Greenhouses all over the country buy the mixes that best suit their needs and cost profile.
The problem for us consumers is that we just buy a bale or two not by the pallet. The big cost for all of these mixes is transportation. There are so many different kinds of mixes (even within a brand), it does not pay for retailers to carry lots of them. Most places carry a few mixes that sell in the most volume. Since most folks using these mixes as consumers are not growing trees, the mixes available locally tend to be more general purpose.
Everyone will eventually be limited by their dirt, just like with food plots. The idea of starting trees indoors and using root pruning containers is to get the biggest most healthy tree you can under highly controlled conditions so that when that tree is placed in the field, it is highly advantaged over the competition. Growth in the field will, of course, be limited by the resources available in the field which will differ from location to location. Keep in mind that planting root pruned containerized trees is different than planting bare root trees. The root ball is not disturbed. Roots start in the mix but need to get into the native soil quickly. This is especially true for folks like me with clay soil. One of the issues planting containerized trees in clay is that that water infiltrates through the mix much faster than through the native soils. This means you can get ponding if you are not careful and the mix can dry out quickly. That is why I think these root pruned trees only make sense if you can provide supplemental water during the first year of establishment or you live in an area where you climate works for you. I'm still trying to figure out the best planting approach for my area and soils.
I think the argument you are touching on is whether it is better to root prune seedlings and grow them in containers for a couple years before field planting them or whether it is better to direct seed them or go somewhere in between. I think depending on your location, arguments can be made for each.
This thread presumes you've decided to start your seedling from seed indoors under lights. Given that, which mix should you choose?
Keep in mind that the presentation I dug up is old and some of the mixes they listed are no longer sold. I just went back and dug up some old Sungrow sales information since they had a mix listed on both the winner and loser list.
Here are their descriptions:
Metro-Mix 390
Great lightweight mix for a wide range of plant types and
container sizes. Features coir to aid in water holding properties
and reduce shrinkage.
Ingredients:
Canadian Sphagnum peat moss
Coir
Coarse Perlite
Starter Nutrient Charge (with Gypsum)
Dolomitic Limestone and our long-lasting wetting agent
Metro-Mix 560 Coir
This heavyweight mix is outstanding for bedding plants,
potted plants and perennials in mid to large size containers.
Features the benefits of coir.
Ingredients:
Bark**
Coir
Canadian Sphagnum peat moss
Coarse Perlite
Bark ash
Starter Nutrient Charge (with Gypsum) and slow release Nitrogen
Dolomitic Limestone and a wetting agent
They look pretty similar but note that the 560 is listed as a "heavyweight" mix. I think this is the key. Look for a professional mix that is listed as heavyweight. I think these are generally recommended for larger containers, not cells, but with the rootmaker 18s, I think they work great in cells because of the air pruning aspects.
Thanks,
Jack

 

[yoderjac]

I've done a little more and more each year of this. I use only the pro mix for indoor growing. I get too many funky growth patterns indoors when I dabble with thickening up the soil.
If I grow in RM trays outdoors, i do a mix of Pro-mix, bulk nursery soil, then some local soil. So it ends up in 1/3 ' s
Then out of the trays if they are not getting directly planted from them (my goal) I transfer to 1 gallon pots that are 1/2 destination soil, and 1/2 nursery soil, which is mostly left overs from a local peat operating that mixes for nurseries. They take all the left overs from each professional mix and put in a big pile. They load me up with that pretty cheap. It has all the goodies in that mix, For about 1/20th the price they bag it up for and sell.
This has been mostly with Chestnuts. They seem to get really wild if I go to heavy medium in the cells indoors. I have not seen the same with Acorns. They seem to do just fine with the heavier soils. I still use the promix with both however because it's not as messy, and little risk of overwatering. Two little kids helping me, I'll take any advantage I can :D

 

[yoderjac]

I bought 2 bags of Pro-Mix FLEX (2.8 cu.yd.) to fill my 18s.....it was hard enough to find anything around here...I really wanted to get some fafard soil, but the Pro-Mix seems OK. Anyways, I have filled 9 trays with one bag and think I have enough for one more still total.....so I would say 10 trays for each bag.
That math seems to jive as well.....
25 cu.in./cell = .0145 cu.yd./cell
10 trays*18 cells/tray*0.0145 cu.yd./cell = 2.60 cu.yd.
The missing 0.2 cu.yd. is likely all over my basement floor! Hahah!
Good luck!

Matt,
One more thing to keep in mind when doing your calculations. You can buy most mixes either loose or compressed in bales. The compression ratio is not quite 2:1.
Thanks,
jack

 

[yoderjac]

I'm going to go check at a couple of the local nurseries and see what I can find. Last year I just had 5 rootmaker trays and I used miracle grow. It worked but since I'm up-scaling big time this year I want to go with a more professional mix.
Matt

I use promix organic that you can get at most hardware stores for like $6 a bag, right or wrong I have no clue but it seems to work fine for me. I think we over think a lot of this stuff. It is a little "dirtier" than some mixes aka rocks/sticks in the mix but like I say works fine for me.

 

[yoderjac]

I'm currently using metromix 360 in the pp's

Dork fish,
Sorry if I confused everyone with my previous post regarding 360. 360 is right in the same class with the other mixes that did well but were not the winners. The mix they suggested to be avoided was 390. I just updated that previous post to provide the information on 390 as I had originally intended.
Thanks,
Jack

 

[yoderjac]

It's really great timing that you've brought this up! I'm in the process of potting up a lot of my plants that were started in October.
I've been using a 2:1 vermiculite to promix in my newer plantings to avoid overwatering. These are in larger containers ~2 gallons. My reason for this is that indoors I've had trouble with not enough drainage. Inside, I've found that drainage and compaction are the #1 problems. I based this off of Dr. Whitcomb's own mix. For my 2 gallons and my DIY pioneer pots I'm watering about once a week, with allowing the mix to dry out almost completely. I haven't had a problem with either of these in this large particle mix. I don't think this will be the case when I move them outside, though. When I move them outdoors, I'm thinking of mixing a coir based mix with some pine fines to give it the better aeration. Inside I was worried about the coir mixes holding too much water, but I think that outside, it'll be a good mix between moisture retention and drainage.

This following parts are me thinking out-loud, I'm walking through how I justify what I'm doing. Feel free, everyone, to point out things here that I overlooked.
As far as mixing in field soil, I'm not sure. I think that almost all of the trees we grow indoors are going to have to catch their feet once they are field planted. I think that no matter what we do with the soil we use, the biggest benefit that they get over bareroots is that they have their own little "biosphere" in tact when they are planted. The relationships between the roots and the bacteria/fungi are already there.
I can, however, see an advantage to matching your final potting mix to that of your field conditions. By this, I don't necessarily mean that you should use the field soil, but rather that it should have the same characteristics of your field soil, specifically with regards to water retention. I'm switching from perlite to pine fines and using coir once I'm outside because I think that they are going to be better in the soil once I plant my tree. In the ground, the coir will dissociate and the pine fines will dissolve. When they are in the pots, I am thinking that it'll work similarly to my current 2:1 mix of perlite to promix, but with more equal water retention, and allowing more time between waterings. I think that if I put my current mix outside, I'd be watering daily.

As pointed out, this is for starting the trees indoors. Does anyone have certain things that they do for pre-field containers? I'd assume that Dr. Whitcombs gritty mixes would work well.

Rally,
I think it is pretty common to add native soils to the mix in larger containers. I too noticed that Dr. Whitcomb uses sand as well in larger containers. I think one of the drivers here is cost. It is one thing to buy these expensive professional mixes to give trees a good start in the small cells where drainage is very important. This may even make sense in 1 gal containers. It quickly becomes cost prohibitive when you gut to 3 gal and up with volumes of trees.
I've actually tried starting with a professional mix and then adding sand and such to approximate some of Dr. Whitcomb's larger container mixes. It definitely changes the water flow through the container.
I did notice somewhat slower growth anecdotally compared to using a straight promix in 1 gal RMs. I don't have enough experience with 3 gal and beyond to have an opinion. Whether or not the slightly increased growth I got from using professional mixes in 1 gal containers is certainly debatable.
By the way, the trees I got from the Wildlife group in the 5" Roottrapper bags were growing in something that was primarily large chunks of pine bark with sphagnum peat moss.
Thanks,
Jack

 

[yoderjac]

This thread got me to start looking locally again for these mixes. I've found a place that doesn't normally sell but sounds like they will sell Promix B3 for $60 a bale and something similar (their words) Baccto Lite that is $9.50 for a 40 quart bag.
Can anyone help me choose?

Gator,
I found that a few Southern States stores in our carry promix-bx compressed bale for $37. http://www.southernstates.com/catalog/vsearch.aspx?searchterm=pro-mix
I figure out which stores carry it regularly by calling some of the stores that the web site says have it. Then when I happen to be going through that part of VA for something else, I call ahead to make sure it is in stock and pick up a bale. That means no shipping.
Keep in mind those compressed bales equal almost twice the volume of buying mix loose in bags.
I'd like to try one of the even heavier weight mixes but can't find anything reasonably priced nearby. I'm considering mixing bark with promix to make it chunkier after seeing what the Wildlife group is using.
Thanks,
Jack

 

[yoderjac]

Any and all trees container trees I've gotten (everything from apples and hazels to dogwoods) were all in a pinebark mix with a bit of peat. I think that many times, sand is added for weight. From the price standpoint, at least if you're producing a ton of trees in large containers, it would be very expensive to not mix your own. I think that for some of the nurseries, this chunky mix might prevent overwatering, thus making it easier for "untrained" people to water the plants.

Yes, I'm kind of in the middle. I don't do enough to make mixing my own completely practical. As I said in my post to Gator, I'm thinking of simply mixing chunkier bark into Promix Bx. I'm thinking that would make the Promix go further will improving results by improving drainage even more.
Thanks,
Jack

 

[yoderjac]

Is there a homemade recipe? Not only am ongoing to have 22 Rootmaker trays I am going to have about 30 Dunstans going into 3 gallon root trapper bags that I intend on babying a second year.
Matt

Sure. Dr. Whitcomb shares his recipe in this article: http://www.rootmaker.com/docs/GrowingTreeSeedlings.pdf
Thanks,
Jack

 

[yoderjac]

Are you buying the promix in the 3.8 cu ft bales? That seems high even for southern states I have been finding it for 25.50 a bale. Are there any nursery supplies around this guy is Amish and buys in bulk said he had enough in stock to last til mid summer. This is also where the universoty gets it's promix for starting plants in their greenhouse.

It really depends on where you are at. Around the metro area where I live, a 3.8 compressed bale of Promix Bx goes for $50 to $70. Down near my farm at Southern States, I'm getting it for $37. I'm sure it is more or less expensive in other areas.

 

[yoderjac]

Dr. Whitcomb says... I use a mix of 30-70 peat and perlite...
Does that mean 30% peat and 70% perlite? Seems like a lot of perlite to me...

Yes it does.
It did to me as well, especially when I actually mixed it. I switched it to roughly 2:1 perlite:promix, which seems to work well.

TACF recommends this mix for chestnuts...
1 part peat
1 part vermiculite
1 part perlite
lime to pH 6

Matt,
Thanks for the post. I just took some "Miracle Grow" from Lowe's and mixed in perlite and vermiculite to make it drain better.
I think I will try their formula (1/3, 1/3, & 1/3) on at least one tray of Chinese chestnuts and one tray of Dunstans.
What type of meter do I need to buy to test the pH of the growing medium?
If you could explain that testing process, it would help out this rookie.
Thanks for your post.
wbpdeer

Near my barns is a narrow strip of never-tilled land that lies adjacent to a railbed that was laid down in the 1850's.....and lies between that bed and the state highway. As such, that strip was never farmed. A number of Michigan's native wildflowers and plants continue to exist there.
OK, that's a preamble to my message. There is a group of native plant collectors/protectors who gather specimens there. They approached me some years back about shovelling up a quantity of the sand/topsoil from my farm across the road in order to have a component of the local soil biology...bacteria, fungi, etc.....when they did their propagation mixes.
Because those folks are educated folks.....retired MSU professors/doctors/high school science teachers, etc. .....I follow their lead when I attempt to make potting mixes. I use the mixes offered by a local 'grower supply' retailer (whose main customers, I suspect, are the expanding group of folks who grow, well, you know what they are growing). So I get a mix they recommend and then I add some of my local soil....maybe 25% or so.
I can't claim super results. Nor bad results. I think of it as insurance.

 

[yoderjac]

I just got a bale from southern states in midlothian for $15.99. I was expecting the $37 price I saw online.

That is a great price. I actually paid $30.50 rather than that online price and that is not close to the $15.99 for Promix BX. Next time I'm near the Midlothian area, I'll need to make a point at stopping by there.
Thanks for the heads up,
Jack

 

[yoderjac]

I'm heading to a couple of nurseries today to see what I can find.

Very interesting topic and good info from all those who posted. I've been using good ole Miracle-Grow potting mix for past two seasons primarily b/c it's easily accessible and reasonably cheap. I've found it is an adequate potting mix for the Quercus species I've grown that can tolerate moist conditions.
This season, I'm growing DCO's and white oak hybrids in my pioneer pots and bags. I've began adding pine bark mulch to the MG at 1:4 ratio to improve drainage and prevent waterlogged growing conditions. Maybe even more importantly, I've learned to be much more judicious with my watering habits which seems to be the biggest factor in maintaining appropriate growing conditions.
I bought a $22 bag of Happy Frog potting mix which contains myc from a local nursery to experiment with a different medium. It's an impressive looking mix but I'm skeptical of the value of the added myco that isn't Quercus specific....

Struck out at two different local nurseries. One of them thought I was crazy for wanting to buy Promix and he still looked confused after I told him what I was trying to do. I may be making a trip to Dallas area.
Matt

 

[yoderjac]

Is $42.99 a decent deal for a 3.8cu compressed bale of Pro Mix BX? I found some a True Value Hardware store of all places but I will have to drive 30 minutes to get it.

It really depends on your location. In the DC metro area it runs $50+ for a bale. About 2 hours away in the Richmond area, Gator found some for $15.99.

 

[yoderjac]

I always have the best luck getting anything I need from the people who do it best. The indoor growing shops, for "medical" herbs;)
I was amazed at how many of these shops are local when I did a Google search for indoor growers/growing. Those guys have everything, and know their stuff :)

I second that. I've gone to 3 around my house. 2 of the 3 I would absolutely recommend, and I actually recommended that my mom go there to get things for her orchids. One the guy is great, and pretty knowledgable about growing anything/everything in containers. If I ever have a question, I go to him and he does his best to help me even if I'm not purchasing anything. One has a guy who was super nice and helpful, but openly admits that he doesn't know much about growing things other than MJ outdoors, and tomatoes. The third one, the guy was just a sleazy salesman and seemed to not actually think that I was growing oak trees. Both of the first two that I mentioned offered to order something/anything for me, and I wouldn't have to pay for shipping because they get shipments from their suppliers weekly. I didn't get anything, but if you can't find what you need, they might be able to direct you in the right direction or even have it sent to them.

Nice the ones around this area carry a LOT of different types/sizes of air pruning containers. Not having to pay shipping on small amounts of these pots is very helpful as well.

 

[yoderjac]

I found Promix BX from True Value Hardware store for $46 and some change and they will ship it free to the store. The only problem is that the nearest store is 30 min drive for me. So it will end up costing me well over $50 after you figure in gas. I guess it all just comes down to how bad do I want it. LOL This is the best deal that I've been able to find in my area. Oddly enough we do have a local hydroponics grower and I thought for sure he would carry Promix or could order it. His response was that there was not enough demand to justify paying to have it shipped up here.
Matt

You know there are a lot of other mixes that will work just as well. My purpose in starting this thread was to try to help identify the characteristics of a mix that make it good for our purpose so that folks could buy whatever was least expensive in their area that had the characteristics.
I went to my local Lowes the other day and bought a couple bags of mini pine bark nuggets. They were only a few dollars per bag. I won't be using this in cells because the chunks are a bit too large for that, but I will soon be transplanting trees into 1 and 3 gal rootbuilder containers. My plan is to "cut" the promix with these. I don't have the facilities to fully mix my own, but when you look at some of the recipes for larger container mix, having 1/3 in pine bark is not uncommon. If anything, this should improve my drainage while lowering my cost.
Thanks,
Jack