Monday, February 2, 2009

The Winter Blast: Which Plants are Coming Through Fine……and which are not

Well, it’s been a few weeks since the worst of our winter blast, but the weather has continued to be cold enough to keep our gardens slumbering. Sigh… it appears that we’ll have to be patient while many plants go through a bit of a “recovery period” before they are as beautiful as in years past. Thank goodness we can count on spring to arrive soon, and even if our gardens aren’t as bountiful as we’d like, they will be lush again in time. And in the meantime we can learn a lot from what has happened. I guess this is kind of an analogy for our current economic times too…

Here’s a bit of what I’ve seen and learned so far:
1) It goes without saying that Tropical and half-hardy plants that overwinter here just fine most years have suffered the most damage or death. (see Agapanthus photo above, which hopefully has roots that managed to survive)

2) A main factor in the amount of damage that a plant has suffered is its exposure to the NE wind, which came blowing in along with the coldest days and nights. I’ve seen a huge variance in identical plant species between ones that are sheltered from that wind and ones that are growing in exposed locations.

3) Many container plants, especially if in an unprotected spot, sustained damage. In severe cases, root death may have occurred. This photo shows my deck containers grouped in the most sheltered corner and surrounded with the "chicken wire-bedsheet" protection method.

4) The warmer-than-average fall, which kept many plants in the active growth stage well into December, is a big factor also. The bitter cold that suddenly arrived was hard on many plants that are typically hardy to low temps, simply because they didn’t have time to acclimate to a gradual cool-down before the big blast.

5) Plants that were already in stress from another source have suffered the most from the cold temperatures, wind, and snow, regardless of their species.
These two Viburnum tinus are planted within 10 ft of one another- the stressed one is hideous while the other still has plenty of normal foliage and flower buds.

6) Hardy broadleaf evergreens didn’t suffer as much from the cold as they did from the heaviness of the snow load, which built up enough on leaf surfaces to break some branches.

7) Deciduous plants fared much better overall, but some have sustained damage to leaf buds or flower buds from the sudden cold, and the degree of damage may not be fully evident until spring growth begins.

8) Most native evergreen plants came through completely unscathed, from Western Red Cedar and Mt. Hemlock, to Salal and Mahonia, to Wild Ginger groundcovers. Even the bent over Sword Ferns, Deer Fern, and others will put on all new fronds after being given a “do-over haircut” in late February, and by mid-spring will look as beautiful as ever.

9) Winter-blooming plants are very late in opening their flower buds, but most look like they’ll have normal blooms. In my garden for instance, Sarcococca have opened almost 3 weeks late, and Hellebores and Mahonia nervosa are still weeks away from their winter glory. Early-blooming bulbs also seem delayed, as I haven’t seen many Crocus and Snowdrop leaves poking out of the ground yet.

10) As I mentioned in a previous blog on this subject (see “Assessing Winter Damage to Plants”), don’t be hasty in trying to correct any winter damage you see. By all means, prune broken branches to nice clean cuts just above the branch collar or strong lateral, but hold off on cutting back tip dieback from broadleaf evergreens. We could still see some cold temps in the next few weeks, and the existing dieback will protect what’s underneath it from any further damage.

Last but not least, remember that most plants are very resilient. This Viburnum bodnantense (Pink Dawn) that was in full bloom when the blast hit, has now put on a new flush of fragrant blooms to cheer me up! And things are starting to stir in all of our gardens, whether evident or not. We’re already starting to see some sunny days accompanied by warmer temperatures, so within a few weeks the first buds will begin to unfold and start to bring spring back into our gardens, along with a spring in our steps!!!

As always, I’ll be happy to assist you in assessing your garden plants, and deciding how/when to take corrective action. February and March are excellent months to do your assessment and planning. And if any of your plants didn’t survive the winter blast, these are good months to choose replacements while local nurseries are having their early spring sales.

If you haven’t yet read my “Season’s Greetings” blog, do check it out for info on my 2009 rates (unchanged) and appointments days, and a special gift for 2007-08 clients!

Hardest Hit Plants:
Phormium (New Zealand Flax)- browning leaves or wholesale dieback from cold, though most roots will survive.
Bananas and other tropicals- top growth turned to mush from cold, though some roots and trunks will survive.
Eucalyptus- broken branches from snow load, some very severe.

Damage Depends on Exposure:
Magnolia grandiflora (Evergreen Magnolia) and Myrica californica (California Wax Myrtle)- some have broken branches from snow load
Bamboo- some leaf tip dieback, some canes didn’t straighten up again after the snow.
Viburnum Tinus and other evergreen Viburnum species- flower bud dieback from cold, some leaf drop in severe cases.
Evergreen Hebes- leaf and twig dieback (see “undaunted” list below for a big exception)
Nandina leaf tip and stem dieback, some broken branches.
Choisya ternata (Mexican Orange)- some leaf tip dieback from cold, leaf drop in some
Daphne odora- leaf tip dieback, but most flower buds are fine.
Evergreen Rhododendron and Azalea- some discoloration of leaf tips and flower buds from wind, a few with leaf drop
Cistus (Rockrose) some leaf tip dieback from cold
Evergreen Euonymus- leaf dip dieback
Evergreen Clematis vines- some leaf and flower bud browning from cold
Trachelospermum jasminoides (Star Jasmine)- some leaf drop
Lavender and Rosemary- older specimens especially suffered broken branches from snow

With a “renewal pruning”, will be as good as new:
Sword Ferns and other evergreen fern species- cut all fronds to ground before new fiddleheads unfold.
Evergreen grasses such as Blue Oat Grass, Pheasant Tail Grass, Carex, etc.- cut browned leaves to the ground or run your gloved fingers through to gently pull them out with a “hand haircut”

A Few of the Undaunted!
Native evergreen species such as Oregon Grape, Salal, Rushes, Wild Ginger, etc.
Most conifer trees and shrubs- their flexible branches and needles usually sloughed off snow load well.
Most deciduous trees, shrubs, grasses, perennials, and vines that were otherwise healthy.
Most spring blooming bulbs.

Cotoneaster lacteus (Parneyi) and other evergreen Cotoneasters.
Osmanthus delavayi

Hebe buxifolia (Boxleaf Hebe)- truly the hardiest member of the Hebe Family- I have yet to see one that looks damaged.
Pachysandra- looked a bit sad in the worst weather, but snapped right back to perky.