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April 2, 2008

pruning lilacs

Filed Under cut flowers, tools & techniques, trees & shrubs 

lilacsEXCEPT IN THE warmest zones, where they are basically disinclined to bloom, every garden should include some common lilacs (Syringa vulgaris) or their various beautiful cousins, old-fashioned shrubs that couldn’t be easier to grow. Given full sun, good air circulation (to lessen the incidence of powdery mildew) and proper pruning, they produce profuse numbers of fragrant flowers. If lilacs fail to bloom, it usually means they have been deprived of sufficient sunshine—or pruned at the wrong time. Like other spring-blooming woody plants, the lilac produces its flower buds from late summer through fall for the following year’s display. Prune after, say, July 4th in the north and you risk reducing next year’s bloom. Prune in fall or early spring, and you guarantee that disappointment.
A lilac is happiest if you cut bouquets from it each spring—essentially you are just deadheading it. Though not essential to its health or survival, the lilac isn’t really asking much from you but paying heftily, since the trusses make extravagant indoor arrangements. You work a little, you win. (A tip: before bringing the cuts inside, hammer the bottom few inches of the stem ends on a hard surface like stone to crush them, so they can drink up the water in a vase, or the flowers will wilt almost at once.) Bonus: By harvesting flowers you avoid the unsightly issue of all those large, dried-up flowerheads that hang on tenaciously all year.

Always cut out dead, damaged or diseased wood as it occurs on any shrub or tree, and likewise with suckers that sprout from the base (and may in fact be growing from the rootstock if it’s a grafted plant). Sometimes a lilac needs reshaping. Conventional gardening wisdom says any shrubs can be “rejuvenated” over three years by cutting one-third of its oldest stems to the base each year, but I ask this: Look at your lilac (or any other shrubs) carefully. Sometimes you don’t want to reinvent (a.k.a. “rejuvenate”) the thing but just to tweak it, so look and think, and look some more before the saw comes out. I like the way Jeff Jabco of the Scott Arboretum of Swarthmore College explains the various stages of the pruning process—whether the yearly flower-harvesting kind or the more ambitious undertakings.

If you want to visit my lilac collection, here it is, and to make your cut bouquets last, read on.

Comments

12 Responses to “pruning lilacs”

  1. andrewoowoo on April 2nd, 2008 5:45 pm

    Wonderful blog, Margaret! I toured your garden in 2006 and the experience was more than memorable. What a wild and wonderful and vibrant place. Glad I found the blog!

    -Andrew in Ottawa

  2. margaret on April 2nd, 2008 7:28 pm

    Andrew,
    I am so glad you found me so soon! I haven’t even begun reaching out to garden friends–the site’s just 11 days old, and you are among its first visitors. A very good omen indeed.
    M.

  3. andrewoowoo on April 2nd, 2008 10:03 pm

    M,

    I’ve heard from a number of people via my blog - a sort of reader’s appreciation of all things Martha marthamoments.blogspot.com - that they are eager to hear about what you do next. It was one of these visitors who informed me of the site, which I’ll happily promote. I’ve heard rumours from your MSLO peeps that a new book may be in the works, too? I hope so!

    Your guidance of the magazine was truly wondrous, M. dear, but this new chapter seems ultra exciting! Please see my blog for photos of your garden and a rather loving testament to its beauty.

    I’ll be visiting this blog often.

    -Andrew R.

  4. margaret on April 3rd, 2008 4:45 am

    …and I hope visiting the REAL garden too again someday. Thanks for all the good wishes. We can look forward to spring together.
    M.

  5. mary kate mccarty on April 4th, 2008 11:31 am

    Hello Margaret,
    I’m a friend of your sister, who was my (superb) writing instructor.
    After visiting the Cotswolds in May a few years ago, I am a passionate novice. Lilacs, peonies and hydrangeas are my favs, and fortunately they seem to do well here in Troy, NY.
    I’m planning to plant lilac bushes soon and wonder if you have heard of the Miss Kim variety? I planted one at my Cape Cod home, and it hasn’t done very well there.

    Your site is amazing - so thorough and comprehensive. I’ve recommended it to some friends who have not gardens but “parks” akin to the Cotswolds, and I’ll continue to pass it along.
    Best of luck,
    Mary Kate McCarty

  6. margaret on April 4th, 2008 11:59 am

    Welcome, Mary Kate. I have indeed heard of ‘Miss Kim,’ which is naturally smaller and slower-growing than many of its cousins. Generally lilacs are pretty tough and adaptable, but seashore conditions (sandy soil, salt air, etc.) can be harsh on any plant. Not sure what’s up with it–growing slow, not flowering, dying off in parts? I assume you have given it a sunny location, which it wants to bloom well.
    Do come back and visit–I will open Q&A forums for formal garden help soon on the blog, and there will be new stories posted every day. Happy spring.
    M.

  7. carl ryan on June 25th, 2008 9:56 am

    I have a ? for you, when you pick the lilacs and bring them inside they die so fast, what can we do to slow that dying process down, any suggestions please reply asap, thanks

  8. margaret on June 25th, 2008 12:28 pm

    Welcome, Carl. The details are in the story on this other page, but basically here’s the trick: hammer the ends of the stems (the woody part) to split it so it can take up moisture. Do this outside on some stones or something.

  9. Bonnie on July 20th, 2008 4:19 pm

    This is from your article “Prune after, say, July 4th in the north and you risk reducing next year’s bloom. Prune in fall or early spring, and you guarantee that disappointment.”
    Sooooo - when is the best time to guarantee blooms in the next year. (Eastern Ontario, Canada).
    I see wild lilac blooming profusely in ditches but not my pampered ones.
    Thanks Bonnie

  10. margaret on July 20th, 2008 4:24 pm

    Welcome, Bonnie. Lilacs, like other early blooming/spring-blooming shrubs, should be pruned right after bloom. For me bloom ends around Memorial Day or start of June. You get a little leeway after the blossoms fade, before energy goes into preparing to set next year’s buds, which is why I say July 4 is OK, too, but not after.
    When did yours stop blooming? Figure you have a month after that, but closer to end of bloom is ideal/better.
    Once the buds start forming in high summer and onward, any cutting you do will take off would-be flowers.

  11. a in calgary on August 3rd, 2008 1:49 pm

    Lacking time previously, I’ve just spent a week pruning my lilacs. Some I have taken care of well over the years ..so it was just taking off suckers… But there are some that I left unpruned for several years.. really old lilacs + 50 years old with stems from 3 to 1 inch. These are doing poorly…there was so much deadwood. +60% I had left it there to test a theory that the dead wood would provide support during our very heavy spring snowstorms. But now there was so much that I was alarmed. I know its late in the year to prune but I’m looking ahead a few years… I know its late to be feeding our first frost can come within a month Ha Ha .. but it won’t last.. These lilacs have never been fertilized or even watered much unless there was a severe drought… Is it too late to put a layer of compost down and cover it with mulch?

  12. margaret on August 3rd, 2008 1:54 pm

    Welcome A in Calgary: There is never a bad time to apply compost and mulch, but better not to apply actual commercial fertilizer at this time. Good that you seized the day and got on with your pruning, even now…since you had the time. I know how that goes!

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