Potbound Acer

Discussion in 'Maples' started by Letting, Oct 18, 2011.

  1. Letting

    Letting Member

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    My acer was purchased as a gift almost 2 years ago, however as the price was on the variety tag, it was obviously removed! I'm therefore not sure of the variety.
    This was purchased from Wisley RHS and it came with a pot supposedly advised to last 5 years. However roots are now already showing on the surface of the pot. The acer is in magnificent condition. It is however somewhat overbalanced, and is falling over in any gust of wind!

    What do I do - buy a much larger pot, which will encourage even further rapid growth, or try pruning both roots and foliage next spring? Or do I conceded potting defeat, create a large root space in my garden, fill it with ericaceous soil ( my local soil is London clay, which is why I pot garden) and let it go crazy? In a small garden, wanting a focus point on my lawn, this is fabulous. I don't really want it much bigger as it will overpower its setting. Will it die if I leave it potbound? Can I prune it? I am stumped.
     
  2. Ron B

    Ron B Paragon of Plants 10 Years

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    Wash the roots, pull them open, replant in larger pot or in ground with roots spread out. Do not cut back the top.
     
  3. emery

    emery Renowned Contributor Maple Society 10 Years

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    Hi Letting,

    You can keep it in a pot if you want, and keep it whatever size you want. If you put it in the ground it will want to get bigger (depending on variety) and you may need to cut back, which can spoil the "look" of the tree.

    First, I don't think seeing some roots on the top is necessarily a sign of being completely rootbound. Japanese maples are surface rooting, and I often see a little activity up near the top, especially if the watering has been a little spotty. So wait for it to be completely dormant, then tip out of the pot and see what it looks like below.

    If it does need repottiing, you can keep the growth managable by root pruning every few years. This is probably a good time to do that. I don't recommend using a pot that is much bigger than the existing one because it tends to promote drainage problems, or keep part of the soil where the roots aren't too wet.


    -E
     
  4. Ron B

    Ron B Paragon of Plants 10 Years

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    >it tends to promote drainage problems, or keep part of the soil where the roots aren't too wet<

    This is a myth. Commercial growers have potted liners into 5 gallon pots and so on for years.
     
  5. emery

    emery Renowned Contributor Maple Society 10 Years

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    Which explains the fine quality of all those palmatums down at Home Depot, no doubt! ;)

    In any case my experience is different, regardless of your opinion. And I'm certainly not the only one to espouse this view.

    For slightly different reasons JGS Harris in "The Gardener's Guide to Growing Maples" expresses similar sentiments: "It is never a good idea to repot a maple that has been in a small container into a very large container, as iit will make all root growth and no top growth. It is much better to increase the size of the pot gradually."

    In the Fourth Edition of "Japanese Maples," Peter Gregory writes: "It is generally best to increase the pot size gradually, from small to not-so-small, to medium, to larger, and eventually to large, unless planting in a trough or sink with other companion plants."

    So it strikes me that "myth" is perhaps overstated...

    -E
     
  6. mr.shep

    mr.shep Well-Known Member 10 Years

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    Re: O.T. A well intended discussion - my thoughts.

    I will assume the Maple is in a five gallon container.
    It is customary in the nursery trade to bump the
    plant up to the next sized container, either a seven
    gallon, ten gallon, short fifteen gallon or a standard
    sized fifteen gallon, depending on the cultivar. The
    reason for the latter word depending is that when
    dealing with a dwarf or semi-dwarf form, moving
    the plant from a five gallon to a seven gallon or a
    ten gallon container can be acceptable. If the plant
    is a standard size Maple or near there, then it may
    be a whole lot better to go up to the short fifteen or
    the standardized fifteen gallon. If the Maple was a
    Red Emperor, Burgundy Lace, Bloodgood or even
    a dissectum as examples then I'd go from a five
    gallon to either a short fifteen gallon or a standardized
    fifteen gallon. In the nursery we always bumped up
    the fives, no matter what tree it was, straight into a
    standard fifteen gallon container.

    It was purported in another UBC subforum by someone
    I know that moving a very young tree into too large a
    container could lead to trouble with drainage and unusual
    wetness (worst fear of too much wetness is fungal rotting
    organisms for that tree grown as a container plant). With
    my having more experience with the issue than the poster
    had and still has, I respectfully disagreed. [Depending on
    where and how the plant was grown, either indoors or outdoors
    and much depends on our means we use to irrigate (water)
    the plant. As the criterion presented, as a right across the
    board altruism, was that we all chose to supersaturate our
    container trees with hose watering in controlled atmospheric
    conditions, of which the fallacy was that the latter is not the
    case for most of us growing that plant.]

    Granted to take a four inch liner plant and move it directly
    into a five gallon container may seem extreme to some
    of us, it has been done in commercial enterprises. Just
    was not recommended sometimes where we grew our
    plants for wholesale and retail sales. Liner tree plants of
    ours went right into one, mostly two and sometimes but
    rarely five gallons, depending on the cultivar, size of the
    liner tree now, amount of root system development,
    ultimate size of the tree later and what kind of tree it is.
    As examples: Dogwood, dwarf Pine and most Palmatum
    type Maple liners went right into two gallons but certain
    Magnolia, Michelia and standard sized Conifer liner plants
    could go but usually didn’t go directly into a five gallon.

    Personally, I feel it is a mistake to wash off the roots
    for any reason, no matter how pot bound the tree may
    be. Perhaps in cooler climates with adequate nutrient
    levels in the soil with adequate microbial activity in the
    soil substrate, it can be acceptable but around here the
    practice of washing off the roots on a growing plant (not
    dormant) to remove soil is major faux pas from a nursery
    or a landscaping perspective. It has been done for trees
    to be sold bare root with success as long as the bare
    root trees had some time to overwinter in a heap, sand
    or humus, prior to planting. Even when we pull the
    overwintered bare root trees out of the heap, we do
    see signs of some of the heap soil being attached to
    the roots and this is what we want to see. To take a
    washed off root system from a growing tree and then
    plant the tree in soil or even pot up in a potting soil
    requires settling time for the tree to adequately
    respond to its new location. The roots are quite
    susceptible to non-beneficial pathogen and perhaps
    in isolated cases some parasitic invertebrate invasion,
    even root burn from nutrients and salts, during this
    transitory period. There is a reason why a bare
    root tree is moved into sand or a humus heap
    almost immediately upon its arrival to overwinter in.
    There is also a reason why a Spring root washed
    and shipped bare root tree is frowned upon. even
    some disclaimers stated in writing for overseas
    Spring shipped bare root trees from reputable nursery
    sources into the U.S. for direct planting, as opposed
    to a Winter shipped root washed bare root tree from
    the same source.

    Surface roots in a container is normal much of the
    time. This is exactly what we want to see for Citrus
    grown in a container - means our root system for the
    tree is doing well. When the roots start to circle
    around the bottom of the container or the surface
    roots circle above the surface of the soil in the can,
    easy to spot either from lifting the tree out of the
    container or by eyeballing the surface, then it is no
    longer a normal condition and is beyond time to
    repot or plant the tree in the ground.

    Jim
     
  7. Gomero

    Gomero Well-Known Member Maple Society 10 Years

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    I have never understood why peole make a difference between planting a small maple in a big pot and planting the same small maple in the ground

    Gomero
     
  8. Houzi

    Houzi Active Member 10 Years

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    This has puzzled me at times also.The only argument I've seen that stands up is that every pot of soil must hold a certain amount of standing water at the bottom(variable with different soils)..therefore there is a chance some roots may venture into this soggy area.This can be prevented by putting the drainage holes in contact with more soil by sinking the pot in the garden or inside another pot of soil,thus lowering the water table in the rooted pot.However it must be possible to oversize the pot enough so the roots would never reach the soggy soil,though I realise it could impractical sometimes.
     
  9. emery

    emery Renowned Contributor Maple Society 10 Years

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    Well I suspect we're giving the OP more than they bargained for! :)

    I go from the premise that potting mix is not always ideal. My personal experience is one of struggling to balance drainage with water retention. I go through this to a greater or lesser extent every year. Pots that I get from nurseries show wide variation and I'm not always that happy with those results either. Now I'm reasonably experienced at this by now, though not in Jim's league of course, so I think it's not that easy for the average amateur to come up with the perfect soil that doesn't, as Houzi says, build up some wet in the bottom.

    Gomero, in terms of water flow, even a big pot sets up a boundary value that doesn't exist in the open earth case. We both know that such boundaries can have surprising effects even at some distance. I haven't studied soil mechanics and my math skills are too rusty to try and figure out the pdeqs that govern flow and saturation in a pot. (Soil mechanics looks like a pretty vast study anyway.) But if you can work out the math, I can set up a numerical simulation... ;)

    -E
     
  10. Gomero

    Gomero Well-Known Member Maple Society 10 Years

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    Emery,

    This subject came up in the forum a couple of years ago and I am pasting what I wrote at that time:


    I never quite understood the logic behind this widely held practice. Of course I understand that when the pot is root bound you either move up in size or root prune. But here the advice is that you should not jump 2 or 3 sizes.

    If drainage is the reason, water logging may occur in any pot if the mix does not drain well enough for the local conditions. A few seconds after you start watering a container, all pores are filled with water, displacing the air from the pores. Drainage occurs through the holes at the bottom of the container. After you stop watering, drainage continues and the wet profile slowly moves downward while air moves inside the pores at the top. After drainage has stopped, the lower part of the mix remains saturated with water. The height of this saturation layer is not determined by the number and size of the drainage holes. Saturation is determined by the pore sizes of the mix, which is determined by particle size or texture. A pot filled with a coarse mix (with large pores) will have a smaller saturation zone than a pot filled with a fine (smaller pores) mix. Now, suppose we fill different-sized containers with the same hypothetical growing mix and irrigate all of them. After drainage, all pots will have a saturation zone which is practically of the same height in all containers because it is a function of the size of the pores in the growing mix. However you should note that the saturation zone would be a small fraction of the height of a large container and a significant fraction for the smaller pots. Thus in smaller pots the saturation zone represents a higher percentage of total volume that in larger pots. This also means that a broad shallow pot will retain more water than a tall narrow pot of the same volume.

    A first conclusion would be that to have the smallest relative volume for the saturation zone, it is best to choose large, tall, narrow containers.

    However there is the additional, very important, consideration of what happens to the water that remains in the saturation zone. This water is either absorbed by the roots, lost by evaporation or sits there and, eventually creates anaerobic conditions at the bottom of the pot.

    This means, second conclusion, that to get rid of the water in the saturation zone the roots need to get there which means a small, short, wide container. Just the opposite above!!!

    Right choice is probably given by local climate, watering schedules, etc.


    Gomero
     
  11. maf

    maf Generous Contributor Maple Society 10 Years

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    My quick two cents worth, to add to the interesting comments so far:

    Larger (ie wider) containers have a larger saturation zone, which therefore takes longer to dry out, and means the mix is more likely to break down and lose structure as it is saturated for a longer period of time.

    Part of the way a potting mix functions is that when it dries out fresh air and oxygen is drawn in which is needed for good root health. If the saturation zone is too large, the mix takes too long to dry, or possibly will never dry enough, to draw an adequate amount of air in for good root health.

    A practical way to reduce the effective volume of the saturation zone in any size container is to place large pieces of broken crocks at the bottom of the container for the lower inch or two. The potting mix goes straight on top of the crocks, do not put a layer of stones, gravel, sand or anything between the two as this will cause a perched water table. With this method the saturation zone still starts at the very bottom of the container, and is the same height as before, but the crocks have substantially reduced the effective volume.
     
  12. Houzi

    Houzi Active Member 10 Years

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    Emery was right...though he answered the question ages ago it has sparked a lot of discussion.
    I've often thought it odd that every gardening book or programme I've seen for as long as I can remember always recommends putting crocks in the bottom of pots,yet it always seems to be pooh poohed on this forum.Ok they often say it's to 'aid drainage',though not strictly true,it is as Maf says one of the ways to reduce the perched water.
    Another difference between in ground & potted plants (which I've seldom seen mentioned) is the fact that an in ground tree will have a large relatively dry area under it's canopy,receiving most of it's water from the drip line and beyond.Whereas we soak the whole rootball of a potted plant right up to the trunk.I guess this doesn't help waterlogging either.
     
  13. whis4ey

    whis4ey Well-Known Member 10 Years

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    No wonder my brain becomes fuddled at times :)
     
  14. JT1

    JT1 Contributor 10 Years

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    Hi Letting,
    The signs of a root bound tree are usually water draining sluggishly, dieback of finer twigs, and early autumn colors. You mention the tree is doing great. So my biggest concern is that the tree is blowing over, which could damage your beautiful specimen. So we are back to the question of repotting or planting. You can have success doing either one and it's really up to you. Here is my advice on how I have done either option successfully:

    Repotting- I have best success repotting in the spring as the buds are swelling and it should be done before the buds break open and tender new leafs emerge. I do not like to repot late in the season (fall is a good time to plant, as the ground is warm and the nights are cool, but pots are more exposed to temperature swings). Let your maple rest for now if you choose to keep its home in a pot. No one likes to be disturbed before going to bed.

    -Soil mixture for good drainage- Japanese maples grow best in containers when the soil is light (not heavy like clay) with mixed sand. The goal is to have a soil mixture that is a balance of organic matter and good drainage. I prefer to use composted peat and pine bark fines as organic matter. The composted peat I buy has up to 20% fine sand mixed in it and I believe fine sand helps keep the roots healthy. Drainage is the other component, so we need to introduce minerals into our soil. To get good drainage I recommend using a mixture of sharp and smooth minerals. Sharp - causes a cutting action that divides the roots as they grow, creating a more fibrous root system. Smooth – allows roots to pass by thus, growing longer and thicker. We want balance in the roots, as the roots will reflect the branch growth on top. Strong (from smooth) but diverse (from sharp) branching is desirable. River sand/gravel is good, but is not readily available for most of us and it may not provide the correct balance we are looking for in smooth / sharp and size. Aquarium gravel is easy to find, is equivalent in size and shape, and is useful for the smooth component. Sharp silica sand about the size of a match stick head or decomposed granite is a good choice for our sharp component. Fine sand can be added if your composted peat does not come with sand mixed in it, as mentioned above. Be sure the mineral medium is rinsed clean and it’s dry. Assuming your composted peat does not have sand in it, mix 2 parts smooth medium, 2 parts sharp medium, and 2 parts sand. Then mix the organic mixture together with the mineral mixture. Be sure it’s thoroughly mixed. Grab a handful of the potting mixture and squeeze it in the palm of your hand. When you release, it should slowly crumble apart. If it sticks together, add more aquarium gravel (or smooth media). I find a 60/40 (organic/ mineral) blend seems to work well in my area. Some use a 50/50 or 40/60 depending, but the crumble test is always good measure.

    -Preparing the root ball for potting - Fill a tub or bucket with water that is large enough to accommodate the root ball. Submerge the root ball and run your hands in a clockwise direction along the outside of the root ball (in my area, the roots tend to run counter clockwise, possibly do to Coriolis effect). Go against the direction of root growth (against the grain). Next, massage the sides and base to free the congested roots. Pull the ball out of the water and rake the roots outward with a small hand rake or your fingers. Trim any roots that are long and leggy. Fibrous roots are desirable, so that they can branch out into your potting medium and not run in a circle around your new pot. Heavy root pruning should be avoided. Removing up to 1/3 is normal, but not ever more than 1/2. The vigor of the tree should be a consideration when root pruning. Heavy root pruning on a less than vigorous tree should be avoided, unless you plan on buying a replacement tree in the near future. If roots are thickly matted on the bottom, use a knife with a fine serrated blade to cut some of the matting. Usually removing an inch will allow the roots to become unraveled.

    Pot selection and potting - Find a pot that suits your taste and compliments the tree, in my opinion. My wife prefers an eye catching dramatic pot, but I find it takes away from the tree. We compromise and have a balance of the two in our landscape (come to think of it, there is more dramatic pots than complimentary pots, but she supports my maple addiction, so it’s all about compromise). Regardless of your taste, be sure the pot has a solid foundation. Tall narrow pots seem to blow over easily. Pots with wide sides and narrow tops look appealing, but they are very difficult to remove when you repot or decide to plant the tree. Do not put a tray under your pot or buy a large pot with a tray built into the bottom. I feel it will trap water at the base and it will not allow the base of the roots to breath, which could lead to root rot (usually shows up as indented wrinkled lines in the bark that runs parallel with the branch). The pot must have an adequate drain hole(s). A wire or plastic mesh can be used to cover the drain hole. (holes in the mesh need to be large enough to fit a match stick through to prevent clogging, but not so large that you are losing potting medium. Craft stores sell plastic mesh / canvas used for thick yarn stitching usually sold 1' square, they are inexpensive and will not rust and can be cut easily using utility scissors. Bonsai suppliers sell the same thing pre-cut into a perfect size, but they are much more expensive) If the pot has 2 or more holes, 1.5 gauge aluminum wire (not galvanized steel) can be run along the bottom of the pot and up through the two drain holes to hold the mesh in place. The wire can be used to secure the root ball, which prevents having to stake the trunk, unless you are using the stake for training or to support a young maple. If the wire is being used to secure the root ball, it should be long enough to bend over the side of the pot, so that it is out of the way while initially potting the tree. Then it can be used to secure the root ball once the tree is in the pot and potting medium is in place along the base and sides up to about half way. Then secure the root ball with the wire by twisting 2 adjacent wires together. Never wrap the wire around the trunk or tightly against the trunk. Great care should be used to ensure the potting medium is added in increments to allow for good compaction and avoid air pockets. Chop sticks can be used to compact the medium in a tight space or around delicate roots. Once the medium is level with the top of the root ball it’s not a bad idea to water and compact the medium again with your fingers or a very small / miniature pointed concrete trowel. Add more medium as necessary to ensure to fill any low spots. Pots that are in a sunny location, I add pine bark chip mulch to the surface to help the roots stay cool.

    Planting on top of clay soil - I live in an area with clay soil about 6" below the surface. I have great success growing Japanese Maples in my area despite the less than desirable soil conditions. I build up my landscape beds using my mix of organic matter (composted peat moss and pine bark fines 3:1 ratio. The composted peat moss I buy has up to 20% sand mixed in it, otherwise add sand to the mixture). Building up the beds will not only provide good drainage, but it will create an elevated stage for you plantings to stand out. Digging a hole will only create a clay bath tub for your maple, which will bring a permanent end to the growing season.

    I prefer to use small pine bark chips (1-2 inch long) as mulch applied 1.5†to 2†deep. Never pile mulch up against the trunk of the tree. I believe the pine bark chips allow for good water penetration by reducing the amount of water run-off. The mulch will allow the roots to breath. Also, the peat along with the pine bark mulch feeds the tree and, as it breaks down, it will help improve the clay soil below. I do not recommend using dyed mulch or shredded mulch. In my opinion dyed mulch does not add any organic matter and it increases the risk of fungus and disease. Shredded mulch tends to mat together which increases water run-off and decreases the roots ability to breath. I think it’s always a good idea to apply a fresh coat of mulch over the root base in late fall to protect the roots from the cold winter. There may be a better option for mulch available in your area, but keep the ideas above in mind when selecting mulch.

    Hope you find this helpful,

    JT
     
  15. sasquatch

    sasquatch Active Member

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    I am about to try out a "gritty mix" for 15-20 of my maples. It consists of equal parts of pine bark, gavel/chicken grit, and turface (expanded clay) that have been screened to remove fines and particles over 3/8"

    This mix is supposed to have excellent drainage while holding a good amount of usable water for the plant. One of the benefits of his mix is that only the pine bark (1/3 of the total soil volume) will ever break down, and this will take several years before there is any loss of fine pore spaces. Most soil mixes with peat, compost, and other organic materials will break down within a single growing season, reducing drainage and increasing the likelihood of saturated soils.

    This gritty mix is very popular on the gardenweb forum that focuses on container plants. The gardenweb forum has dozens of pages of discussion on the topic of proper soils for container plants and specifically about maples. I am surprised that the ideas discussed over there are not in use by maple growers on these forums. I do see that some commercial nurseries pot 2-5 gallon maples in 100% bark nuggets.

    The materials pose a challenge for many people to find, but things were fairly easy for me. I sourced pre-screened fir bark that is used for Orchid soil from a local company for $50 a yard. The gravel is available prescreened to remove fines and chunks over 1/2" from the landscape supply yard for $15 a yard, and turface (thich can be the hardest component to find)is sold locally by John Deere landscape supply. Turface is commonly used on baseball fields to prevent mud in the infield, and is available in 50lb bags for $8-10. Diatomaceous earth is a good substitute if Turface can't be found.

    Here is a link to a very, very long thread discussing soils and water movement
    http://forums2.gardenweb.com/forums/load/contain/msg031557203792.html?150<BR>

    Here is a link to many links discussing the gritty mix
    http://www.google.com/search?hl=en&....,cf.osb&fp=a4183349b9a276ea&biw=1280&bih=622

    Is anyone else growing in a "non-conventional" growing medium? Does anyone find that the standard "potting soil" mixes sold in garden centers and in landscape supply centers to be inadequate for the needs of their maples? It seems like the gritty mix may be a solution to a problem that few people complain about. Are we ignoring the reality which may be that our maples are suffering in silence, and not living up to their potential? Or is this just the new fad for the the gardening hipsters?
     
  16. emery

    emery Renowned Contributor Maple Society 10 Years

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    Thanks Sasquatch, that's an interesting post by Al, very useful.

    I use kitty litter which is made from sepiolite to add grit. (Although there are a few baseball leagues in France, it's maybe not that easy to get Turface!) I've used it for some years now and find it doesn't break down at all, or maybe only very slowly. Quite cheap too, IIRC 1.50 EU per 5 kg bag. I wish I had a source for pine bark. I put larger caliper through the shredder but it mostly falls through, so has a hard time breaking up.

    Gomero, oddly my experience jibes with both your contradictory conclusions ;), but at different stages. Initially seedlings do better in taller containers, no doubt because there isn't that much root, and as it develops it stays clear of the saturated zone. But when these are sized up to 1 or 2 liters, depending on root development, growth is usually retarded in a tall container and the plants do much better in wider, flatter pots. (I'm talking about AP, AJ, AS seedlings; many others that very quickly build large root mass do fine in deeper containers).

    I don't use any kind of sand except some in seed trays. My experience with sand and pseudomonas is not good. No doubt what works in one climate doesn't work in another; but here and in much of the UK we get really a lot of wet during the winter, with frequent freezing and thawing. Some sources to recommend "sharp sand" which I believe is widely available in the UK at DIY outlets.

    I just received a fab gift, about 200 2 liter and 100 1 liter pots! Also a couple of hundred godets (small starter pots, can't find the English word) but I think they're too small for maples.

    Actually an interesting question (to me) would be what size starter pots that people use.

    -E
     

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