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Root Pruning: Control Growth from the Roots · Hydroponics Daily

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  Hello, welcome back to Hydroponics Daily, your go-to podcast for everything soilless cultivation.
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  I'm your host, Dr. Russell Sharp, and I have already recorded this podcast once,
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  but realised I didn't have my microphone pointing the right way,
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  and so it sounded tinny and echoey.
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  So now we're going to have lovely, luscious audio, I hope.
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  Today's topic is root pruning, and I said in the last episode about root cuttings
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  that that was a forgotten art.
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  Well this one certainly is definitely a
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  forgotten technique in horticulture it applies
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  to hydroponics as well as growing in
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  soil and soil-based growing media so equally
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  applicable so stay tuned if you're not
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  a hydroponic grower and it's a forgotten art because certainly in horticulture
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  edible horticulture because it was common practice in the victorian times but
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  then with the advent of dwarf rootstocks in top fruits, so apples and pears,
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  cherries, things like this, it wasn't used as much.
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  So before we used dwarf rootingstocks for grafting, and if you don't know what
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  I mean by that, then go to the episodes of this podcast about grafting.
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  But basically it's a dwarf variety that's the.
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  A specific apple variety is
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  grafted onto that keeps the shoots from growing
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  too long they were all invented invented bred discovered by the scientists at
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  east morling where i did my phd down in kent and they're still exactly the same
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  varieties are used to this day very few dwarf rootstocks have been in bred since
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  then um but before they were they were discovered and
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  widely popularized by the team at East Morning,
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  every single apple and orchard used to root prune all their apples and pears in the winter.
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  So they would dig them up and curtail the roots to stop.
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  When it came to growing and some european pear orchards
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  still continue to routinely root prune their trees to
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  control vigor what we call you know too too
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  vigorous growth but the technique is largely abandoned in
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  the uk because of these dwarf rootstocks you can
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  actually graft a pear onto a
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  quince and that produces a dwarf rootstock top
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  fact you won't hear that anywhere else so you
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  can use root pruning to control growth on plants
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  that don't have dwarf root stocks
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  or ornamental shrubs and trees and or
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  where especially useful to do root
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  pruning where if you were to do a stem prune it
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  would produce unsightly wounds so really ornate
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  ornamental plants like magnolia so my next door
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  neighbor for about 10 years she would always
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  massively hack down the stems of her magnolia
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  tree in about february march time because it was
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  spoiling her view as it came into leaf but she cut
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  off all the flowering stems and the tree looked terrible
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  what she could have done was root prune and then she wouldn't
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  have had to shoot prune because the the vigor
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  would be gone but it still produced lovely flowers and fruits our new next door
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  neighbor has now cut the tree down completely so that is a real shame so the
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  reason why they control their it controls shoot growth is because you've got
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  to remember that plants normally have a root-to-shoot ratio of about 50-50.
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  And that can change between species and soil type, but it's normally around
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  50-50. So if you cut it down.
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  If you could cut the tree down completely, suckers would appear straight away
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  and the plant would go really fast to use new stems to try and rebalance that root-to-shoot ratio.
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  But what you wouldn't see below ground is actually the root system would die
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  off as well, because it just can't sustain such a big root system without that
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  massive amount of photosynthesis.
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  And if the reverse happens, so you root prune, then your stems just don't grow
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  as fast, because it can't sustain that size of a tree.
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  Now that's useful as say in ornamental plants where you don't want to producing,
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  don't want to be using damaging stems if you're
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  growing a crop and you imagine you don't want to be pruning the
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  stems all the time for whatever reason because it doesn't look great then
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  perhaps root pruning is for you certainly the
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  main crop is a word
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  that where root pruning is routinely used nowadays is bonsai
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  trees because once you've got that amazing shape
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  in your bonsai tree you want to keep it in a form
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  of almost in a form of stasis you don't want
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  it to be pruning all the time so if you root prune you can
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  stop the stems from growing out you can stop the leaves from expanding and you
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  can keep it almost in that form of stasis so bonsai root pruning the best bonsai
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  growers they always the masters always use root pruning and you'll find that
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  in all the specialized bonsai books.
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  In some species, root pruning can actually help with plant defense.
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  One example I've got here is the tropical trees in the bean family, the Fabaceae.
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  They produce sulfur-containing compounds in their leaves, which are toxic to
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  bacteria, fungi, nematodes, and insects in response to root damage.
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  And this effect has been hypothesized to occur in other species when root pruned.
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  However, root pruning does also open up a wound and thus a site of infection
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  that could be a route of entry for soil-borne pathogens like Pythium or Phytophthora.
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  And so I would not advise you perform it on species that are particularly prone
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  to rots and heartwood rots, such as birches.
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  Okay so take it on a case-by-case basis now you don't always have to pick the
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  plant out of its container or out of the soil to root prune there are actually
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  containers you can buy air pots have you ever seen these air pots with it look
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  like lots i don't know how you describe an air pot,
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  it's got like little holes in it and it's undulating
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  it's not flat like a normal plant pot
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  and the roots of the plant the idea is that
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  the roots of the plants go out to the sides of the
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  pot and then rather than circling round and round and round they reach
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  the end of the pot and then they're met with a hole and
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  air and obviously roots don't like air and
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  so they stop growing and it's sort of that's
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  almost like a root pruning effect you also
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  get white bags that many tree
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  nursery is growing and the white
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  lets in a bit of light and that again curtails root
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  growth and stops roots circling round and
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  round the square bag that they're grown in rather than a the worst case scenario
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  for a tree is that the roots just circle round and round and round and then
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  you buy the tree from the nursery you put it into the hole you've dug for it
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  and the roots continue to go round and round and round they don't expand and.
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  The very very very poor anchorage of
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  that tree even after say 10 years and it'll
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  topple over and when it topples over you'll see it's just root bound so
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  when you buy a tree that's is the
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  roots are circled or a shrub you're supposed to pull
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  the roots out and it'll cause loads of root damage
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  when you do that but it's absolutely essential because if you don't
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  do that it won't anchor into the soil just continue to
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  go around and around around so root pruning can
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  help with that if you buy trees from
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  a nursery where they've been grown in the soil they're often lifted
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  every year or every two years because they
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  if they're destined to be dug up and
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  transplanted you can't just leave the tree in the
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  ground for five years because its
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  roots will go five meters in every direction and
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  then when you dig it up you'll be left with these really thick roots
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  no and none of the thin nutrient
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  and water absorbing roots will be near the plant that's been
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  dug up and so they'll all be lost and so
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  that's why you find trees and shrubs grown on nurseries will be dug up and almost
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  root pruned every year or every two years for that reason so that when they
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  are eventually dug up for sale they actually have lots of roots near the plant
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  so that's root pruning. Where else is root pruning used?
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  You can root prune mother plants if you're keeping them for vegetative propagation.
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  If you're taking clones or cuttings from mother plants, then you can root prune
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  to just reinvigorate the root ball rather than it becoming root bound.
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  So when you dig up, you can't keep a mother plant just continually in the same
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  growing media for years and years and years.
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  So if you've got any mother plants or any house plants and they're completely
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  root band but you don't want to put them up into a bigger plant pot you just
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  want to keep maintaining them as well as stem pruning you can root prune them
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  just to maintain the plant keep its vigor down and then.
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  Just can control its size i guess the same
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  like large leaf figs you could do
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  the same rather than just hacking at the plant and destroying its
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  architecture that would be a good one fiddle leaf
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  figs as they're called those very ornate very
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  expensive houseplants and then finally the
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  one of the main reasons people root prune is to
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  get root cuttings for plants where root cuttings are the
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  main form of propagation that's been
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  hydroponics daily for today the very very
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  lost art of root pruning maybe we can bring it back and
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  rejuvenate it if you found this useful then
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  please do leave an apple podcast review please make sure you subscribe or press
• 9:33
  the follow button and check out utreema.co.uk for all the fertilizers biostimulants
• 9:40
  and biopesticides you might need on your mother plants your apple plants your
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  bonsais we've got something for you thank you very much for listening.
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  Until next time, goodbye.