About a year ago we had a long discussion (started by me) about growing fruit in containers. (BTW, although I haven’t posted in a LONG time, I have checked the forum now and then. Also, to repeat the answer to a question I was asked back then, my name is Andrew and I’m in Northern Virginia, just a little way into zone 7a from the z6b / z7a boundary.)
Background to the idea:
Container growing is of interest to people like me who want to be able to take important plants with us if / when we move. It can also be used to control size since a tree will be limited by the amount of volume it can draw water and nutrients from.
Each container growing approach has it strengths and drawbacks. Root pruning using fabric pots has some definite advantages over root development characteristics in plastic pots. Plastic pots also tend to heat up a good bit more than fabric pots. Although this may be an advantage in spring when the weather is cooler, it is a definite disadvantage for those of us who live in areas with hot summers. Water loss to evaporation can lead to some surprises with one’s water bill (if using tap water) over the summer. Although putting the pot in the ground can ameliorate this, it can lead to a couple of other problems in turn. In particular, roots will find their way through holes in a plastic pot, and if fabric is used, the fabric breaks down more quickly in the ground, not to mention that roots will eventually break through that as well.
An Idea
What about taking plastic pots, lining them with several layers of professional grade weed barrier, and then planting the pot in the ground (in an elevated area to ensure drainage)?
This would keep the pot cooler in the heat, make moving easier (plastic pots are easier to move around without bending which I would assume can disturb the root system), reduce water loss, and encourage root pruning (provided some air can move down the sides between the pot and the inner layer of weed barrier).
Several layers of professional grade weed barrier would likely last long enough (including preventing tree roots from completely busting through and then finding their way to and through a hole in the plastic pot) that it would be time to change the potting soil before the tree roots could send significant growth through the holes in the plastic pot (or at least that would be my gut feel).
What does everyone think of this? Have I overlooked any important factors that will likely cause this approach to fail? Or do you think it ought to work reasonably well (or is at least worth trying)?
It’s worth trying. My initial thought is the plant would probably root thru the weed barrier. At least the kind I’ve used which is woven polypropylene.
Most people if planting the pot just let them root into the ground. They’re easier to dig up if the holes are in the lower side rather than the bottom.
Why not use the big root maker or smartpot in ground containers. I think 15 gallon is the largest that rootmaker has. Otherwise you could use something like their fabric.
I use 15 gallon pots that were originally lick tubs for cattle. I drill holes about an inch from the bottom on the sides. This keeps roots from ground coming up from other trees and roots from container getting out. It also provides a small water reservoir in the bottom. Works well in south but could provide root rot problems in the north.
Or, you could just use the in-ground green rootmaker bags once you have finished the first few stages of root pruning. These bags root prune through constriction. Fine roots grow through the holes into the soil outside the bag, but the holes don’t give and as the roots grow in diameter, they are constricted and cause upstream branching. This is probably more effective and less expensive. Once you go into the ground you don’t need a pot at all.
Smartpot containers: I had some idea these degrade relatively quickly (e.g., a year or two) when planted in the ground. The Boxer Brown fabric pots are significantly more affordable but again degrade in a year or two in the ground versus taking a number of years when above ground (or so I thought). My concerns about above ground are water use, reduced stability, and possible overheating (although not nearly to the extent that it happens in black plastic containers).
I don’t mind some fine roots getting through the small holes in a bag or other container (e.g., Rootmaker container) and helping to stabilize the tree and pull in a bit of water. However, I don’t want a lot of roots (or at least larger ones) getting through for two reasons:
Size control: I’d like to keep tree height at 6 to 7 feet or less. In addition to using a dwarfing rootstock, limiting the volume of potting soil / dirt the roots can grow into and draw nutrients from will also act to force a tree to dwarf. This increases choices of what to grow and will also tend to encourage early fruiting (vs. a tree on a rootstock that wants to grow much larger overall, including growing larger before beginning to set fruit).
Ease of moving: Trees should be able to be moved (still in the pot) to another location that could potentially be quite some distance away (e.g., multiple hours of driving), including be moved during summer.
If I’m overestimating the drawbacks of Smartpots, Boxer Brown fabric pots, and / or Rootmaker containers or fabric in regard to these factors, by all means please chime in and let me know.
IL847: That’s a possibility. I’m just thinking that a hard plastic pot will make a tree a good bit easier to move.
If anyone knows from experience (or via the experience of others, provided it’s reliable) what would likely work well for me, please let me know.
When I’ve said that I have concerns about this or that, it DOESN"T MEAN that I don’t think this or that won’t work, it’s just that I can see the possibility of there being an issue. If it turns out that there isn’t an issue there after all - or it’s just minor - please say so.
I am also forced to grow my majority in containers for a few reasons. My conditions here include dry Summers and much rain in Winter. My question for you would be are you providing adequate drainage? I don’t enough about your climate to answer for you.
Well one minor thing I have 20 gallon root pouches and find them extremely easy to move with a dolly. I don’t set them on soil as that will quickly degrade them. On wood or cement my 3 year old bags look great. Now some of the cheaper ones look like they have a 4th year and that’s about it.
Perhaps I misunderstood what you were trying to do. I regularly start trees from seed in the winter under lights, keep them for 1 or 2 growing seasons (depending on the type of tree) and then transport them about an hour and a half to my farm where I plant them in a permanent location.
I start with Express tray 18s to prune the tap root for indoor propagation. Our last threat of frost has passed about mid april. I transplant to 1 gal Rootbuilder II containers. If I’m trying to maximize growth in 1 season like with a chestnut tree, I’ll transplant again to a 3 gal RB2 in late spring or early summer. By fall, I take them to the farm. My chestnuts last year were a little over 6’ tall and about 3/4" in caliper. For slow growing trees like pawpaw, I leave them in the 1 gal RB2s for the entrie first growing season and then take them into a cold room to overwinter them where they won’t freeze. The next spring I transplant them to 3 gal RB2s and will take them to the farm this fall or winter to plant them.
As long as you can provide supplemental water during establishment, you can transplant these Rootmaker trees in the dead of summer. These RB2 containers unwrap, the the rootball is completely undisturbed at planting time and the trees begin to grow immediatly.
I’d be concerned about circling roots on trees in plastic pots unless they were lined with root trapping material. Keep in mind that there are several methods to root prune, air pruning, root trapping, and root constriction.
forestandfarm: As you have pointed out (indirectly), I should have explained a bit more about where I’m coming from.
Mainly this would be for a small number of fruit-bearing trees, bushes (e.g., blueberries), and vines (e.g., grapes, kiwifruit) purchased from a mixture of online and local sources. (BTW, I already have some; they are in a mix of fabric and plastic pots.) Some would be bareroot, while others would be in pots ranging from 1 to 15 gallons in size.
The target for the plants would be to end up in containers of 5 to 20 gallons in size and not get any bigger than what those sizes can accommodate.
I want the roots to be protected from overheating in summer and excessive cold during winter cold snaps. The plants should all be fairly easy to move. Water use should not be excessive to avoid large water bills during dry periods in the summer.
It sounds like a pot-in-pot method with the inner pot being a root pruning container of some type (air pruning, root trapping, root constriction) would be a good way to go.
I suspect I am trying to overthink the details and come up with some perfect solution when all I need is a good solution.
I also grow fruit in containers and I’m also always looking for ways to do it better. I am always amazed at how quickly the pots can dry out even in my climate controled greenhouse. For me plums are the worst. A few years I have had them abort fruit when they got dry. Peaches and nectarines have shriveled some but are quick to recover once I water them. All the drip systems I have tried have flaws so far like an uneven pattern of wetness or clogs. I am wondering if some sort of a wicking set up could be done? Has anyone ever heard of or tried that before?
FWIW I once knew a nurseryman who grew shade trees(not fruit) using pot in pot idea and He told me it didn’t work well for him. The roots eventually broke through the second pot also. That was years ago and perhaps He was missing some details.
I think I got it now. I’d check out the above ground roottrapper bags. I’ve only used the small ones. The inside material is a roottrapping fabric. The outside is white PVC. The white PVC helps with water retention and heat reduction. The 5" bags that I’ve tried are designed to fit inside cement blocks. This also helps moderate heat and water. They do have root trapping pot liners but I have not tried them.
Since you plan to keep these in containers permanently, I think your considerations are different then mine.
Hello ya’ll, I grafted some apples onto m -27 rootstock and I plan to make some thin concrete pots to grow some in. A little heavy but permanent and movable with a dolly, hopefully. Anyone know the recommended size for m-27 optimal growth?
ALL of the plastic pots I’ve ever buried (heeled in), had the roots punch right through the pot and grow out into the soil anyway. Then I had to dig up the tree as I would have had to do anyway, plus cut away the plastic pot.
I’ve seen Alan post photos of his nursery on here and he has pots buried. I’m not sure if he ever had this happen or not.
For me, it happened every single time with apples and plums. These were fairly heavy discarded pots from (mostly ornamental) trees from a local nursery. I guess most were around 10 gallon or larger…2 seasons in ground in most cases.
Wulfman, I’ve had a lot of fun in the past making planters out of hypertufa. So, I wanted to make sure you are aware that the alkalinity needs to be leached out of those pots before you put them to use. Otherwise, the pots can wind up killing your trees.
I’ve used the green rootmaker in ground bags to grow cuttings and seedlings of elderberry, apple, oaks, etc… They are GREAT. I’ve also used the patio roottrapper bags for tomatos on the patio. GREAT!
I guess my question is… would you prefer the plants to be in ground or out of ground? If you plan for out of ground (year round), or you need them to be able to moved around regularly, just go with the 15 or 30 gallon root trapper containers.
If you want them in the ground, and just want to be able to move them if YOU move, go with the root trapper in ground bags (the green mesh ones). They work well. You’ll tear some roots when you dig them up but you’ve still got a big old nucleus of roots to help them set up in their new home.