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GARDEN TIPS – written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written October 25, 2015

I occasionally get asked to give a presentation on “putting the yard and garden to bed for the winter.” Fall garden chores are pretty simple and can be designated as “should-do” and “good-to-do”. I am not sure I could give a thirty minute or longer presentation, but here are the “should-do’s” for fall.

RAKE LEAVES: On the should-should do list is raking leaves. If you have a number of trees like I do, the leaves can certainly pile up. They tend to blow around and pile up at my back door and elsewhere in the landscape. As we start to get more dew and moisture, these leaves can mat down and smother the grass and other plants. Get those leaves raked up and consider using them for making compost or tilling them into your vegetable garden soil where they will decompose over the winter and help improve the soil.

MOW THE GRASS: After the stress of a very hot summer, your lawn needs all the help it can get. You should keep mowing if the lawn is growing. Do not mow the grass extra short and then put the mower away. Also, do not leave it extra long, as this can lead to matted grass and favorable conditions for snow mold. (This past spring snow mold fungus showed up in many area lawns and caused significant damage.) Mow at the recommended height of about 2.5 inches until you no longer need to mow. The good news is that as the weather cools, you will not need to mow as often.

TREAT FOR BROADLEAF WEEDS: If broadleaf weeds, like dandelions or clover, have shown up all over your lawn, now is the time you should treat for these weeds with an herbicide spray. However, if you only have a few of these weeds here and there, dig them out by hand or pop them out with a “weed popper.”

Herbicide sprays for broadleaf weeds will not control grassy weeds. Annual grasses, such as crabgrass will die with a hard frost, and need to be controlled next spring with pre-emergent herbicides or “preventers” that will keep the seed from germinating and growing. Perennial grasses, such as Bermuda grass, are not controlled with fall chemical applications.

DIG TENDER BULBS: Many of the tender bulbs, corms, rhizomes, and tubers that we plant in our gardens, including cannas, calla lilies, gladiolas, and dahlias, are tropical plants from warmer climates (Zones 7 to10) where they can stay in the ground over the winter. In cooler climates (Zones 6 and lower) like ours, they should be dug each fall and stored for the winter in a cool, dry protected location where they will not freeze. Some years in our area these tubers and bulbs may survive if left in the ground and heavily mulched. However, if winter brings severely cold temperatures, they will be killed.

To store them, wait about two weeks after frost kills their tops and then carefully lift the tubers, rhizomes or corms from the soil; shake off as much of the soil as possible; rinse them with clean water; and let them dry in a protected dry spot. Place them in cardboard boxes or paper bags using dry sawdust, wood shavings, or peat moss for packing.

You know, maybe I could give a talk on getting your yard and garden ready for winter. There seems to be a lot to do in the fall. More soon on the “good-to-do” fall garden tasks.


GARDEN TIPS – written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published-DECEMBER 12, 2014

Weather-wise, this has been a strange fall. We had a wonderfully balmy October. Frost and cool temperatures were delayed well past October 15th, the average date of the first fall frost. Unfortunately, the extended abnormally warm weather was followed by an abrupt spell of bone-chilling low temperatures.

Many plants were just not ready for the severe cold and may have experienced damage from low temperatures that they could normally withstand in mid-winter. Further complicating the issue was the warmer-than-normal weather that followed this frigid spell. Then, the warm weather was immediately followed by another period of severe cold.

Gardeners knew these departures from the norm could mean trouble for the trees, shrubs, and perennial plants in our yards and gardens. The frost-killed leaves still clinging to trees were a hint that something was awry. The abnormal high and low fluctuating temperatures had prompted gardeners to ask me if they should anticipate dead or injured plants next spring. It is one of those questions that I can not answer with a simple “yes or no.”

First, we have to ask if a particular plant was dormant and ready for winter’s cold. Plants hardy in a particular region physiologically prepare or “acclimate” themselves for impending winter cold based on environmental cues. These two main environmental factors are shortening days and gradually cooling weather that work to slow plant growth until a plant becomes dormant. Each species of plant responds to our local cues somewhat differently because they are adapted to the cues from the environment in their native geographic region. The timing of these cues and the acclimation process can differ from species to species.

As fall and winter advance, hardy plants continue to acclimate until they reach “maximum mid-winter hardiness,” assuming the temperatures gradually become cooler. Fluctuations between warm and cold periods interrupt the process. During warm periods, plants de-acclimate or lose some of the hardiness they have achieved and then start to re-acclimate when it turns cooler again.

Environmental cues are not the only factors that figure into plants acclimating to cold weather. Cultural conditions that promote late season growth can delay dormancy and the acclimation process. Pruning and fertilizing in late summer or fall stimulate new growth and delay dormancy. Because of our arid climate we still need to water our plants in the fall, but excessive irrigation also encourages growth and slows the process.

Plants weakened from drought stress, insect or disease damage, environmental extremes (such as our extended record heat last summer), nutrient deficiencies, root problems, or physical injuries may not be able to acquire full potential hardiness. The same goes for plants planted in late summer or early fall that did not have a chance to become established fall.

To protect against cold temperature injury experts recommend:

1. Plant trees, shrubs, and perennials that are designated hardy for the area. (This is USDA Zone 6 for most of our region.)

2. Do not prune or fertilize your plants after the first of August.

3. Cut back on the frequency of watering in the fall, but avoid drought stressing your plants.

4. If planting or transplanting trees and shrubs in the fall, wait until they are dormant.

5. Apply protective mulches on tender plants only after the soil has cooled to 40 to 45 degrees Fahrenheit.

Should we anticipate damage on our trees, shrubs, and perennials? My answer is, “Probably, but only time will tell which plants and how severe the damage will be.”

Published: 12/12/2014 12:33 PM


written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published 12/13/13

Brrr… it has been so cold. Gardeners are wondering if the recent frigid weather damaged any of their landscape and garden plants. The answer is “maybe yes and maybe no.” Here are some of the factors involved in cold weather damage to plants.

Hardiness and Acclimation: In autumn, as the days begin to shorten and the temperatures become cooler and cooler, a plant’s potential ability to withstand the cold temperatures of winter increases. Plant tissues become increasingly hardy as the temperatures drop and the plants reach their maximum potential hardiness in mid-winter. This process is called acclimation and involves complex physiological changes within the plant. When frigid winter temperatures are experienced, the time of winter and the temperatures in the weeks preceding the extremely cold weather, as well as the severity and duration of the cold spell, are factors in whether a plant will experience damage.

Maximum Hardiness and Zones: As noted, plants gain their maximum genetically determined potential winter hardiness in mid-winter. This is genetically determined, but is also influenced by weather conditions, plant exposure, and plant health. To see if a particular plant is hardy enough to withstand the extreme cold temperatures typically experienced in their area, gardeners can consult the newest USDA Plant Hardiness Zone Map published last year.

Using weather data from a span of 30 years (1976-2005), the map is based on the average extreme annual minimum temperatures across the country. Each of the 13 zones on the USDA Hardiness Zone map represents a difference of 10 degrees and the divisions of a and b in a zone indicate a 5 degree difference. The Tri-Cities is rated as “Zone 7a” with the average extreme minimum temperature being 0 to 5 degrees and the coldest parts of Benton and Franklin counties are in “Zone 6b” with the average extreme minimum temperature being 5 to -5 degrees.

Trees, shrubs, and perennial plants are rated as hardy in a particular zone based on the coldest temperatures they can survive. For example a Zone 7 plant should be able to survive the average coldest weather experienced in the Tri-Cities… if it has achieved its maximum hardiness through the acclimation process.

Is wind chill a factor?: Humans and animals are subject to wind chill because it is an index created to reflect the heat loss that occurs to warm blooded animals from wind when it is cold outdoors. The wind chill index is not a concern when it comes to plants, but winds can have a drying affect on plants, especially on evergreen plants like pines and rhododendrons. That is why it is important to not let plants go into winter drought stressed and to water trees and shrubs during mild fall and winter weather when the soil isn’t frozen.

Will plants in local landscapes have escaped damage from our recent cold weather? : Winter is far from over so it is hard to predict, but I suspect we may see some damage on certain plants. The plants most likely to have been damaged are Zone 7 (or above) plants, plants that were planted in late fall, and plants that were unhealthy or drought stressed before the frigid weather arrived. One factor that probably limited the damage and aided in the acclimation process was the fairly cold weather we were experiencing before the very low temperatures arrived. For now, all we can do is wait for spring and hope that any damage has been minimal.

Published: 12/13/2013 3:41 PM


written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

Every year about this time I check the long range winter forecast for the Pacific Northwest. I hope to get some sort of glimpse into what type of winter is headed our way. Right now the majority of professional prognosticators are predicting a ‘normal’ winter for us when it comes to temperature but an above ‘normal’ winter for precipitation. The problem is that I don’t know what ‘normal’ is for our part of Washington. I’ve lived here since 1980 and I’ve experienced winters that vary from cold and snowy to mild and dreary to very cold and dry. It certainly keeps me from becoming complacent about the weather.

In more recent winters, temperatures have been quite mild and have allowed plants not designated as winter hardy for our area to be planted and grow successfully. If we have a normal winter, damage or even death may occur to these plants. What is considered normal for our region can be discerned from the plant hardiness maps.

The first official USDA Plant Hardiness zone map was published in 1960. The zone map showed ten zones across the US based on the lowest annual minimum temperature. Zones were based on 10 degree gradients. On that first map our region was located in zone 6 (-10 to 0 degrees). Woody landscape plants were rated by their hardiness to indicate in which zones they could be planted and expected to survive the winter. Before that gardeners just had to guess, depend on word of mouth, or consult other gardening references.

In 1990, the USDA decided to update their map and divided the zones even further into ‘a’ and ‘b,’ with ‘b’ being the warmer part of the zone. On that map our region was located in zone 6b (0 to -5 degrees F) and our warmest areas in zone 7a (5 to 0 degrees F). Of course gardeners are always tempted to try something that isn’t quite hardy here, and so far a string of warmer than normal winters has allowed them with success. Some gardeners do like to live dangerously.

The American Horticulture Society (AHS) was asked to draft a new plant hardiness map for the USDA in 2003. They went back to 10 degree gradients and used a digital format, providing higher resolution. The 2003 draft version showed our region in zone 7, designated as 10 to 0 degrees F. The USDA rejected the much criticized 2003 draft and decided to work on the map internally, but it still is publishing only the1990 version.

In 2004 the Arbor Day Foundation used the same extensive recent (past 15 years) climate data as the AHS used and published their own Arbor Day Hardiness Zone map. It is very similar to the 2003 AHS draft version. Both show the warming trend in other areas of the country similar to what our region has been experiencing. On the Arbor Day map we are also in zone 7 (10 to 0 degrees F).

Confusing isn’t it? What it all means to me is that I can feel fairly safe planting trees and shrubs designated as ‘zone 6

or ‘zone 7’. You won’t find me gambling on a zone 8 plant… I still remember the 70

s when climatologists were predicting a mini-ice age instead of global warming.
Who knows what this winter will bring? I never count on the long range forecasters being right, after all even next week’s weather forecast is hard to get right. Just in case we have a cold winter, here are some ways to protect your plants.

1. Mulch marginally hardy plants in mid-November after the soil cools.

2. Hardy plants in containers should be moved into the garage or a sheltered place where their roots won’t freeze. Roots are the least hardy part of the plant. When not growing in the ground, the roots aren’t protected by the insulating properties of the soil and will be subjected to much colder temperatures than they can endure without damage. Leaving them outside and insulating the container or pot won’t work since they aren’t a heat generating organism like an animal.

3. Dig tender (gladiola, begonia, dahlia, canna) bulbs, corms and tubers and store them as recommended over the winter where they will be protected from freezing temperatures. Gambling gardeners sometimes leave these in the ground and mulch them heavily hoping to protect them from the cold and save them the work of digging and replanting.

4. Don’ forget to water your plants as we go into cold weather. Irrigation water has been turned off in all areas so this will mean hauling a hose out to plants. It’s especially important that shallow rooted plants (such as arborvitae, birch, spruce, rhododendrons) and evergreens not be allowed to go dry during the mild fall and winter months. Even if plants are dormant, they can suffer drought stress and damage.

Learn more about the Arbor Day map and see how the zones have changed from 1990 to 2004 at

Published: 11/3/2007 2:32 PM



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