Before posing my questions, here’s a very quick summary from another thread that will help set the context for my questions.
From responses to a recent GW post (including a response from fruitnut, which was very helpful), one can grow most common fruit trees (except perhaps citrus) on a wide range of rootstock in a range of container sizes down to about 5 or 7 gallons and expect that the trees will successfully produce fruit (given adequate time).
IIRC, fruitnut likes to use 10-12 gallon containers but has found that smaller sizes will still work; I think had a picture of four nectarines in a 10 gallon pot. He said that a 10 gallon pot usually results in a 4-6 foot tree, the tree size being limited by the pot size.
Here are my questions about growing trees in containers (I’m thinking 7 to 15 gallons, possibly 20 gallons in a few cases if that is helpful info to have):
Soil: In general, when growing in containers, is it better to have very good soil rather than so-so soil? (When growing in-ground rather than in a container, creating a small volume of very good soil amidst so-so soil can lead to roots circling the small volume and the tree becoming root-bound rather than growing outwards. However, since we’re talking about growing in containers, this would seem like a different issue.) My main concern would be if this encouraged lots of vegetative growth at the expense of fruiting.
For a rootstock that normally produces a larger tree (e.g., M111), would being grown in a restricted volume (e.g., a 15 gallon container) encourage a shorter time to fruiting in addition to having a dwarfing effect? If so, any idea on how pronounced this effect would be?
Since a tree in a container might not have as many concerns about, say, tolerance to wet soil, a wider range of rootstocks would likely work fine for such trees (my guess!). If that’s the case, where can I find data on the relationship between rootstock and fruit production? (I’ve heard some rootstocks lead to around twice as much production per tree as some other rootstocks, assuming an equal-sized tree. Another way to look at it would be in terms of average pounds of fruit per square foot for various rootstocks.)
Unless you are growing in bottomless containers you pretty much need some kind of easy draining potting mix or conditions will be too soggy. I suppose if you live where there is no rain during the growing season or you shield the pot from surplus precip you could grow trees in pots with actual soil, but it would be difficult to know when conditions were soggy at the base of the pot.
A pot does turn any rootstock into a dwarfing one- which for apples, at least, creates smaller and earlier bearing trees. All species I’ve grown in pots are dwarfed, of course, but I’m not sure how much it accelerates fruiting for pears or E. plums. J. plums and peaches fruit so young in soil that I don’t think there’s much difference.
No data about rootstock performance in the field would be very relevant to growing in pots as far as I know. I suspect comparative dwarfing from say M9 to 111 would not be proportionate to what occurs in the field and the difference would be highly reduced.
I use a lot of woodchips in my container mixes (its free). I usually toss some compost in there, some perlite, maybe some peat moss. I think trees will grow in about anything. I usually like to keep the soil as light as i can when dealing with 15 gallon or bigger pots (back breakers)> . I think you can use any rootstock you want…no matter what the pot will dwarf the tree. There is only so much top you can have with such a limited bottom (bigger pots/bigger trees). I like 15 gallon…seem to be a good balance. I ordered some 25 gallon pots and they are really big…i haven’t put any trees in them yet. Lots of water in the warmer months…lots. Fertilize often. Might need to lime. Pots are the only surefire way for me to get yearly peaches.
A poorly draining mix will greatly reduce the functioning part of the pot as roots will not grow where it remains too wet. The bigger the pot the harder this is to keep track of.
Don’t use normal garden soil in pots it doesn’t drain well enough. Drainage is way more an issue in pots than in ground.
I think dwarf roots might have the advantage of not getting root bound as quickly as vigorous. This would be due to less root growth. But tree size in a pot is limited by water more than anything. There is only so much water even if you water more than once a day. A standard or dwarf root will pull out about the same amount from a pot so similar tree size.
For apple M9 or 26 is good size for pots. You need quick bearing in pots. For stone fruits most anything will bear early. For sweet cherries I like the dwarfing precocious roots like G5 or Newroot 1.
What do you mean, “except citrus”? Citrus have been grown successfully in containers since the Roman ages. I proabably have 15 to 20 citrus in containers in my yard, as well as in-ground. They do exceptionally well. Just go to Italy to see massive container citrus growing
When I arrived at GW a week or so ago, I saw a thread on growing fruit trees in containers that said that citrus frequently struggle in containers and advising against growing this way unless absolutely necessary. (I had the impression that “citrus = hard to grown in containers” was received wisdom on GW.)
My sense was that citrus could be grown successfully in containers if done correctly and I would hazard a guess that the trouble would-be citrus container growers were having weren’t the containers per se and instead were caused by some other problem. However, since I am focused on deciduous fruit, I put that comment in there to hopefully help steer the conversation in the right direction.
muchtolearn, citrus are a piece of cake to grow in containers outside. I’m not sure where you would have read that on GW, as there is an entire Citrus forum on GW, and I’d say at least 1/2 of the active members are indoor citrus growers (outside of the citrus belt - trees must be brought inside for the winter). I’m not sure where you are (you haven’t added your “About Me” section or your “Zone” field, so be sure to update your profile so we know your name, a bit about you, where you are located in general, your zone, etc.) Growing citrus INDOORS can be a little challenging, but not anything that an advanced beginner container gardener couldn’t manage. This because citrus need to have well draining potting mix, and you can battle certain pests with indoor citrus (mainly scale and spider mites, which can also afflict citrus outdoors as well). If you live in zone 8b or higher, citrus can stay in containers outdoors all year 'round and are easy peasy.
While setting up my account, I did put in my zone info as well as my location. The only thing I didn’t include was my name - I left the real name part blank.
Zone 7a / Northern Virginia is where I’m at.
I only joined GW a week or so ago, so it was just one post where I read the comment about citrus. Apparently the perspective of the author isn’t shared by most other posters, which I didn’t realize.
BTW, if anyone can give advice on growing grapes in containers, I have a thread on that as well that’s not garnering much response yet.
It’s okay to be anonymous if you want, muchtolearn. Just nice to have a first name sometimes. And, if you go back to your profile and add a little snippet in your “About Me” paragraph, that will up when someone hovers over your name icon (check out a few others on our forum and you’ll see.) So, in your zone, you would have to cart your citrus indoors during the winter, since your temps drop down too low for citrus to manage your winters. So, more work, but doable if you want to give it a try. Again, the key is coming up with a well draining potting mix, proper fertilizing, and managing pests. Check out the Citrus Forum on GW and search for “gritty mix” or “511 mix” for some good potting mix recipes. Most container citrus folks there prefer to use DynaGro Foliage Pro plus Osmocote Plus in combination for fertilizing. Citrus are big N demanders, so you want to make sure you’re using the proper fertilizing for them. Lots of good support for citrus on the GW Citrus forum if you’re so inclined
Point taken on the first name - it’s Andrew. (Normally I want to stay low key as to who I am when posting things on the internet. I’ll add my first name to my profile.)
Thanks for the advice on the potting mix recipes. I appreciate it.
I’ve been using the 5-1-1 mix with great success. Can’t get much easier. The only thing I have to source on the internet is the dolomitic line and perlite. Everything else is local. The mix drains well but still holds enough moisture to make watering a 1-2 times a week thing in soft side containers.
Do you have plans on container choice? Plastic, root maker plastic, or soft side?
Although there are obviously other important factors at work (e.g., watering, growing medium fertility), does anyone have some approximations for the relationship between container size and the size at which trees stop growing?
People on GW were always telling others to run a search for gritty mix and 5-1-1 and rarely giving links. Since I didn’t rejoin when it became part of iVillage, it took me days to find Al’s discussion thread because those 2 mixes are very frequently mentioned. I wound up with lots of search results and much time spent aimlessly wandering through threads. I eventually found it in the Container Growing forum there under the title, “Container Soils - Water Movement and Retention XVII.” Great thread for understanding the importance of potting medium structure and how to construct an appropriate mix.
Sean, I was thinking of using SmartPots. (There are some other similar products out there that are less expensive; however, I’m not sure if they perform as well as SmartPots. If some of them do, I’d be glad to know which ones.)
You mention using “soft side containers.” Is that a SmartPot or something like it?
Those are good ballpark numbers. I’d say expect ~ one lb per gallon of pot. You could probably get more but at expense of fruit size and quality. Fruit will be small even heavily thinned.
I have a second leaf Spice Zee in a 20 gallon Smart Pot, and a have newly potted Cot-n-Candy, Dapple Supreme, Flavor Supreme, Flavor King, and Leah Cot in 20’s also. Next week I’ll be adding a Sweet Treat and Nadia to my collection of permanent cultivars.
Depending on how my temp storage trees preform this season I may actually switch from Smart Pots to Root Pouches. But then that’s all depending on how the 7 gallons react this year. They are supposed to do the same thing, air pruning, but the Root Pouches are less than half the cost.
Look at the Greenhousemegastore website for “root pouches”. They are very affordable and come in a variety of durability types. I have the brown ones in a range of sizes from 1 gallon to 65 gallons.
I use the root pouches and like them. But they dry quickly so for me a 3-1-1 mix is better and I also add 1 part diatomaceous earth as it holds it weight in water and never breaks down. It helps make additional water available to the plant without clogging the structure of the soil. I also add 1 part compost to help prevent root rot. For trees I might skip the compost, for veggies, it works really well. I was just looking at a study on root rot in cucumbers and they used 5 different types of compost in pots. All five decreased the incidence of root rot. It makes the mix a living mix, and that works extremely well. It helps utilize organic fertilizers better too. I’m a huge advocate for living mixes.
Here is the study
It’s quite clear the benefits of compost or compost tea.
Here is a good chart showing the reduction of root rot incidence using 5 different composts. Every one decrease incidence to some degree compared to the control.(table 10 in the study) http://www.hindawi.com/journals/jmy/2013/324570/tab10/
IMHO not only does compost reduce root rot, but many other pathogens. Feeding the soil IMHO is a better approach to gardening than feeding the plant. If you keep the soil healthy it will keep your plant healthy. Especially in container culture where so many factors are artificial.
I was thinking of using compost as an ingredient, along with potting soil - mixing the two together, in other words. Living soils intuitively seems like a good approach.
The Smart Pots are supposed to reduce issues with soil compaction and overwatering. Does anyone know how the root pouches perform with respect to these issues?
On another subject, can anyone advise as to which rootstocks perform well in 20 gallon pots?
From my understanding, MM111 is at the high end of semi-dwarf; maybe semi-standard would be a better descriptor for it. I’ve found that several reputable nurseries in the South use M111 on account of being tougher than the smaller rootstocks, the South being a bit challenging than many other parts of the country. Although it is larger, air pruning of M111 trees in 20 gallon pots seems like it should keep them at a decent size without needing to prune heavily for size control.
Aside from M111, what other apple rootstocks ought to work well in containers?
Just from a size standpoint, I would think rootstocks in the range of 50% of standard on the basis of wanting to avoid staking trees unless really necessary. Just from a size standpoint, some rootstocks that come to mind are M.26, M.7, G.30, G.222, etc.
