How Do I Prune a Very Large Lilac Tree?

Discussion in 'HortForum' started by gargavan, Mar 29, 2005.

  1. gargavan

    gargavan Member

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    We have a lilac about twenty feet high with numerous new growth branches sprouting up in the middle of the older growth. They appear to do nothing but consume sap as there were no flowers on them last year and the tree as an whole did not flower much.

    I would like to improve the health of theis tree and promote more flowers but have not been able to find much guidance yet.

    Can anyone help? Should I cut all of the non flowering branches from the middle of the tree as well as cut back some of the older branches?

    Any suggestions would be appreciated.
     
  2. Ron B

    Ron B Esteemed Contributor 10 Years

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    Older lilacs may be grafted, in which case sprouts from the roots would be pruned off. When the shrub is not grafted, these would be kept. Often lilacs here have older trunks that are not persisting well, should be pruned down/out periodically, to be replaced by younger stems from lower down. These newer sprouts that you are describing on yours will flower when they are a little older; few, if any of them should be removed.

    A mature lilac that is not flowering well is having problems, figuring out what, exactly is happening is your best bet.
     
  3. Newt

    Newt Well-Known Member 10 Years

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    Hi Gargavan,

    Some great advice from Ron. There are several reasons why lilacs don't bloom or don't bloom well. They tend to like a more alkaline soil, so if your soil is acidic consider sprinkling a cup of lime around the base every couple of years. It helped mine, but mine didn't bloom for 10 years and had been planted where there had previously been pine trees. If your lilac is located in or near a lawn and receives fertilizer from the fertilizing the lawn, the nitrogen will actually keep them from blooming. Also, sometimes trees grow up around them and block the sun. They need 6 hours or more of sun. Here's some sites you should find helpful, including how to prune an old lilac.

    http://www.ipm.iastate.edu/ipm/hortnews/1993/2-10-1993/lilac.html
    http://www.gardenersnet.com/lilac/lilac02.htm
    http://gardencenter.southernstates.com/lawn_garden_faq/lilactree.shtml
    http://www.heardgardens.com/basicsforlilacs.htm
    http://www.lilacs.com/frames/care.htm

    Newt
     
  4. jimmyq

    jimmyq Well-Known Member 10 Years

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    The lilac may benefit from pruning using the "1/3 method". which is to remove one third of the mature stems to their point of origination each year for the next three years (thereby rejuvenating the entire plant). Afterwards you remove one or two mature stems each season to maintain size and shape.
     
  5. douglas

    douglas Active Member 10 Years

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    Hi
    any chance of a picture
    or do you know what type of lilac it is?

    The 1/3 pruning for 3 years may work/

    Has your weather been a little on the high side? Or the times when you get cold weather changed?

    Most of them do not like to be pampered. ( by us or mother nature)

    Regards Doug
     
  6. sharon77

    sharon77 Member

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    Gotta question for you: my lilac (mature plant) had a couple of rather long (large) branches that just stopped producing anything(leaves, lilacs) this Spring. It just looked completely dead. I cut those branches down because they looked dead. Did I do something wrong to it? It looks a bit lop-sided now. Other than that; I got alot of flowers this year. Think it'll survive?
     
  7. Newt

    Newt Well-Known Member 10 Years

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    Hi Sharon,

    Your lilac should be fine though it's odd that a couple of branches just died like that. You did the right thing and that is how you prune an overgrown lilac. Just be sure to clean your pruning saw or lopper blades with a solution of one part bleach to nine parts water before using it again just in case. Rinse well and wipe dry. You can oil the blades as well. I'd say to watch your shrub carefully. Just in case here's some sites on lilac diesases.
    http://www.ppdl.org/dd/id/bacterial_blight-lilac.html
    http://plantclinic.cornell.edu/treeshrub/lilac.htm
    http://www.ipm.iastate.edu/ipm/hortnews/1993/2-10-1993/lilac.html

    Newt
     
  8. Eyeris

    Eyeris Active Member

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    My problem appears to be the same as Gargavans'. I included a picture of my lilac tree to find out:

    1st- what type of Lilac this is....and

    2nd- if I would benefit from the 1/3 pruning technique mentioned earlier?
    Thanks,
     

    Attached Files:

  9. Newt

    Newt Well-Known Member 10 Years

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    Hi Eyeris,

    I don't see too many sprouts around the base of your tree, but I would suggest you do the 1/3 prune, remove the grass and weeds around the base, topdress with a cup of lime and an inch or compost and scratch those into the soil, being careful not to go too deep and damage roots. Pruning should encourage more sprouts. Do look at the links I gave for pruning.

    I don't know exactly which lilac you have. Maybe someone else will be able to answer that one.

    Newt
     
  10. Daniel Mosquin

    Daniel Mosquin Renowned Contributor UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    Eyeris - for lilac identification, you have one of the best resources in Canada available on your doorstep. The Royal Botanical Gardens in Burlington has one of the best lilac collections in North America. It'd be worth your time to drop in there this upcoming weekend for the second weekend of their Lilac Festival - I'd be surprised if there isn't someone on hand who can help identify your lilac for you.
     
  11. lsod

    lsod Member

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    This info has been so beneficial I've registered to post!
    First of all, thanks for the reminder about RBG...it's been years since I've been there (pre-home ownership and gardenship).
    On the lilac discussion, I pruned last year after blooms hoping to see an improvement and I didn't see much.
    I've purchased a soil test so I can check on that (major clay in our area).
    And the tree (about 12 ft) is in the front yard but this year was the first time I've fertilized the grass (been here for 2 summers now).
    What I am perplexed on right now is I developed a little garden bed around the base of the tree last year, and it constantly gets overrun by new lilac stems growing up out of it. Should I / can I cut these back? Could that be harming the plant/tree?
    Also, I'm not familar with the term grafted.
    A number of us on the street aren't happy with our blooms so I'm wondering if this is just the type of lilacs we have (we've seen others that seem to bloom much fuller & longer, but they apear to be more shrubs than trees).

    Thanks!
    LSOD
     
  12. Newt

    Newt Well-Known Member 10 Years

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    Hi LSOD,

    But you probably don't know if the former owners fertilized.

    Yes, you can cut back the suckers, but keep in mind if you want or need to renovate the shrub you will need to remove the oldest trunks. If you allow some of the suckers to grow they will replace the old ones. It can take 5 to 7 years before the suckers bloom.

    From this site:
    http://www.botany.com/16.gr.htm

    "GRAFT: 1. Method of propagation by which an artificial union is made between different parts of individual plants. The stem or shoot that is inserted into a rooted plant is called the scion; the plant or part of a plant into which the scion is inserted is called the stock or understock. There are many different methods of grafting including flat grafting, split grafting, and side grafting, among others. 2. The point where a scion is inserted in the stock."

    There are many different varieties if lilac that grow to different heights, have different blooms and bloom at different times.
    http://spi.8m.com/care.htm

    There are many other links on this thread that you've probably already read. Do be sure to do a pH test of the soil too.

    Newt
     
  13. lsod

    lsod Member

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    Thanks very much for the quick reply...

    Very valid point on the previous owner. I know they did use a lawn company and fertilizer. Grafting sounds as complex as it would be in human surgery I guess (skin grafting)!

    Appreciate your direction - enjoy your Sunday (oh, and go Oilers go!)

    LSOD
     
  14. Newt

    Newt Well-Known Member 10 Years

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    LSOD, you are so very welcome! Enjoy your Sunday too!

    Newt
     

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