Winter garden watering

>> Saturday, January 26, 2008

We are currently under a high wind advisory. This is not uncommon here in Utah. Pacific storms can throw a lot of nasty stuff at us. Southern California is experiencing very large amounts of moisture being dumped on them and this heavy rainfall creates a weather pattern that generates high winds across the western Utah and Nevada desert which means high winds for us.

Despite the fact that these high winds are the result of heavy rainfall, by the time we get these little blessings from Mother Nature, the wind is dry.

Too much dry wind can adversely affect plants that are not protected by mulch. Wicking action will dry out a plant pretty quickly, which brought up a question that I don’t know the answer to and probably won’t know until this summer. Do I need to water my outdoor plants in winter?

Everything has been mulched well with a blanket of bark chips and leaves to at least three inches thick. Plus, there is ten inches of snow on them, although this is temporary. Shrubs, however, are taller than the mulch cover so their branches are exposed to these dry, winter winds. Is plant moisture being sucked up away from their roots? I guess I would need to dig them up to know for sure. I doubt that I can do this, frozen ground being the serious obstacle it is to digging.

Beds on the south and west sides of the house, shed and fences are most at risk of drying out because of reflected heat. We get foggy mornings and heavy frost and I am sure they add some moisture, but I worry that it isn’t enough.

I really don’t want to start the spring growing season with stressed out plants. I want to do what I can to put these plants in a more favorable position to handle the dryness and heat that is already in store for them from the coming summer.

It seems really odd to me that there is such a thing as ‘winter drought’, but it is real and my research has shown me that winter drought conditions can lead to root injury or death. The worst part is that it could be happening right now without the plants showing any symptoms. According to my local county extension office I wouldn’t know until next season if the plants are dying. They may leaf out and flower just fine in the spring, relying on stored food reserves. Once that energy supply runs out plants weaken and start dying back. Even if a plant isn’t killed outright, it is made more susceptible to insect and disease attack.

With global warming rearing its ugly head, we can’t rely on receiving enough snow cover to protect our plants so it is becoming increasingly more important to mulch well. Shade trees with shallow root systems are especially susceptible to drying out. This includes Norway maple, silver maple, linden, Colorado blue spruce, Norway spruce, and many other evergreens. Shrubs are also vulnerable to winter drought damage, especially those growing up close to the house or in a warmer location. This includes junipers, Oregon grape-holly, and euonymus.

What I read is not encouraging for this year. Watering is supposed to be done when the air temperature is above 40F (some say 32F) with no snow cover and when the ground isn’t frozen. Yeah, right. Let’s see, that would be last month and two months from now. I’ll just have to keep my fingers crossed.

Our clay soil holds water, sometimes a little too well, so this might be a blessing. If you have a more ‘perfect’ soil you should already have watered. Horticulturists used to say it was good practice to insure dormancy by drought stressing plants in the fall and thus decreasing the chance of winter injury. Research since then has indicated that the reverse is true. What you know yesterday may not be true today. Great, another stress point for the gardener.

If the soil can stay slightly moist down to about 12 to 18 inches then plants should fair well despite winter’s drying winds.

Be especially mindful of plants under the eaves of the house. I have noticed a strip about 18 inches wide around the house that is dry after a good rain that I thought was watering everything.

One thing to look for as a sign of moisture loss is cracked soil where roots can become exposed. If you see this condition add some soil to fill in the cracks and add about three inches of mulch and then water, if the temperature is right. You don’t want to water late in the day when night time temperatures could freeze the water directly against the plant base causing more damage. Water early in the day so it has a chance to drain away.

Best methods for watering include: twin-eye or frog-eye sprinkler, deep-root fork or needle, soaker hose or soft spray wand. Give plants a good, deep drink of water letting the water run for 20 to 30 minutes in each area, then move to achieve good overlap. For trees, as a general survival rule, apply 10 gallons of water for each diameter inch of the tree. For example, a two-inch diameter tree, needs 20 gallons per watering.

Newly planted shrubs require more water than established shrubs that have been planted for at least one year. Assuming shrubs are mulched, apply 5 gallons two times per month for a newly planted shrub. Small established shrubs (less than 3 feet tall) should receive 5 gallons monthly. Large established shrubs (more than 6 feet) require 18 gallons on a monthly basis. Decrease amounts to account for precipitation. Water within the dripline of the shrub and around the base. Note: In dry winters, all shrubs benefit from winter watering from October through March.

So, the result of my research on the drying effects of winter winds tells me that it is important to mulch well, water deeply before the ground freezes, and I won’t know if my plants are okay until I see them growing or struggling this spring/summer. Life is full of surprises. Hopefully, this winter will be kind.


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