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Fwd: Cold Snap 2007 Update

Got this missive from Missouri Botanical Garden. Nice advice on
dealing with freeze damage.
Begin forwarded message:

> View this email in a browser.
> Dear Members,
> Three weeks after the great Spring Freeze of 2007, were seeing
> encouraging signs of recovery throughout our gardens, reaffirming
> our faith in the remarkable resiliency of plants and nature.
> The question on everyones mind is What can I do to help my trees
> and shrubs recover? Like a broken record, the answer remains that
> the best option for now is to continue to exercise patience and
> restraint where pruning and fertilizing are concerned until the
> full extent of dieback has been determined. Provide water if
> rainfall is lacking. The growing season is in full swing and most
> plants respond best to one good soaking per week, with the classic
> 1-1= inch as a standard benchmark.
> To maintain even moisture levels and regulate soil temperatures,
> cover root zones with a shallow 2 to 3-inch layer of mulch if this
> has not yet been done.
> Only in recent days has new growth begun to push out from Japanese
> maples, magnolias, oaks, ginkgos, and other trees suffering
> extensive damage. Fast-growing trees such as hard maples are
> recovering more quickly than slower-growing species such as oaks.
> In many cases, well-established younger trees are recovering faster
> than older specimens of the same species. This is normal, given the
> circumstances. Older trees that were healthy prior to the freeze
> still have an excellent prognosis and should show marked
> improvement by the end of May.
> Some Saucer and related hybrid magnolias suffered damage to stem
> tips that has caused variable dieback that will require corrective
> pruning once we fully ascertain whats alive and whats dead in the
> weeks ahead. Loebneri hybrids, including the popular Leonard
> Messel and Merrill fared surprisingly well with only minimal
> damage.
> While new growth is a welcome sight, I am concerned about some
> Japanese maples. The first growth of many varieties froze and has
> dried up; if not pruned off, it will eventually fall off. There may
> also be hidden damage to the vascular tissue beneath the bark that
> could result in additional dieback when summer stresses arrive in
> full force. I expect pruning to remove dead wood and restore
> aesthetic balance will be necessary later this summer and possibly
> for years afterward. This freeze event was one that will weed out
> marginally hardy plants, and there could be some casualties.
> Many callers are also concerned about azaleas, crape myrtles, and
> Bigleaf hydrangeas. Damage to azaleas has been highly variable,
> with some varieties showing minimal injury, near-normal flowering,
> and vigorous new growth. Flowers and buds that froze on the more
> tender varieties should be left to fall off naturally rather than
> pulling or pruning it off and risking inadvertent damage to live
> tissue present at the base of frosted growth.
> Crape myrtles were at such a vulnerable stage of growth that many
> were killed to the ground when their sap froze and expanded,
> damaging vital cambium tissue. This will be a shock to gardeners
> who have become used to large specimens, courtesy of the string of
> unusually mild winters in recent years. All dead wood should be
> removed as soon as new growth appears. Though crape myrtles bloom
> on new growth and we look forward to their showy displays, the most
> severely damaged varieties may not sprout before June and could
> show poor flowering this summer.
> Bigleaf hydrangeas (Hydrangea macrophylla) are marginal shrubs
> whose popularity has also benefited from recent mild winters. I
> have yet to see a specimen this spring that has not suffered
> extensive damage to their old growth and anticipate few, if any
> flowers on most cultivars this summer. New growth has already
> occurred from the base of most varieties, so dead stems can be
> pruned back any time now. This summer should be a good test for the
> new generation of remontant (repeat-blooming) cultivars said to be
> capable of producing flowers on new wood. Well find out if they
> stand up to all of their advance media billing and prove productive
> under this most challenging of weather circumstances.
> Roses present unique challenges also, especially to inexperienced
> growers. Most of the popular new landscape shrubs will recover
> nicely, provided they were well-established before the freeze. Many
> roses that bloom on old growth, including most climbers, have
> suffered loss of flowering wood and will have few, if any, blooms
> this year. Considerable pruning of dead growth and training of new
> shoots this summer will be necessary to re-establish a sturdy
> framework of stems to support future growth. For roses that flower
> on new growth, especially hybrid teas, the issue of survival may
> come down to whether gardeners left mulch in place or succumbed to
> the temptation to remove it prematurely before the traditional
> average last frost date of April 15. With blackened stems all the
> way to the mulch and soil lines, there may still be live dormant
> buds below grade mustering the energy to answer the call to active
> growth. The only way to find out is to wait and see and only
> experienced growers may have the patience to do so. When pruning is
> done, look for the tell-tale ring of live green cambium tissue and
> absence of darkened and discolored interior wood when examining cut
> stems. Otherwise, it may be necessary to cut further down on stems
> until unblemished tissue is revealed. Begin to fertilize roses once
> pruning is completed.
> Its apparent that some herbaceous perennials fared better than
> others. For plants with only minimal injury its best to leave the
> partially green leaves for now and remove only dead growth.
> Perennials will benefit from a light fertilization at this time to
> speed their recovery.
> Many gardeners have expressed concern about iris, peonies and
> daylilies. Its apparent that the Garden benefited from the heat
> island effect, as our iris and peony collections fared remarkably
> well and we look forward to showy displays to greet our Mothers
> Day visitors. Likewise, were expecting normal displays from our
> daylilies later in summerweather provided, of course!
> Its important not to let down your guard, so scout your garden
> regularly for new signs of trouble and take corrective action
> promptly. Insect and disease pests may take advantage of the
> weakened condition of recovering plants to gain the upper hand.
> Injured plants can ill afford additional setbacks. Proper
> identification of symptoms is the first step in remedying problems.
> Take advantage of our walk-in Plant Doctor diagnostic services,
> staffed by trained Master Gardeners. This service is available
> daily except Sunday between 10 am and 3 pm in our Kemper Center for
> Home Gardening. If treatment is necessary, consider hiring a
> certified consulting arborist to provide professional services.
> Seek out qualified arborists certified by the International Society
> of Arboriculture. Some can be found in the Yellow Pages under Tree
> Service or they can be located through the society web site http://
> www.isa-arbor.com/findArborist/findarborist.aspx.Be sure to select
> an arborist employed by a private tree care firm rather than a
> utility or municipality.
> Chip Tynan
> Missouri Botanical Garden Answer Man
> William T. Kemper Center for Home Gardening
> P.S. For specific inquiries, call the Gardens Horticultural Answer
> Service, Monday through Friday, 9 a.m. to noon, at (314) 577-5143,
> or visit the Gardening Help section of the website at www.mobot.org.
> Click here if you do not want to receive further emails.

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