CO-Horts Blog

Friday, November 18, 2016

Yipee, It Snowed!! But We Still Need to Water...

Posted by Deryn Davidson, CSU Extension, Boulder County

After months of warm and dry weather, parts of CO finally received some much needed precipitation in the form of rain, sleet and snow yesterday. I have to admit, even though I had been hoping for snow for weeks (where was our typical Halloween blizzard?!?) it was still a shock to have to bundle up and drive on those icy roads along the Front Range.

Even though we got that moisture, our landscapes are still not out of the woods. They NEED WATER! That is lawns, perennials and trees. Most people have had their irrigation systems turned off and blown out by now, but you still need to get water to those plants.

Areas across the state received between 0.1 and 1 inches of moisture yesterday. However, not all moisture is created equally. For example, 0.5” of rain is not the same as 0.5” of snow. And in fact, 0.5” of snow is not necessarily the same as 0.5” of snow! 

Unfortunately, figuring out what the snow to water/rain ratio is can be tricky. Like most things, the answer is…it depends. Depending on the temperature, snow will have more or less moisture per snowflake. Have you noticed that when it’s super cold out our snow tends to be really light and fluffy? Or when it has started to warm up in the spring and we get a big snow it’s often very heavy and wet? Depending on when and where you measure your snow can also make a difference. If you measure in an area of high wind, then you are likely to have variable heights (think snow banks and drifts). When you measure can make a difference as well. If you measure as soon as it stopped snowing you will have a more accurate reading than if you wait an hour to measure. Some of that snow may melt or even settle like instant mashed potatoes in a box. Light and fluffy flakes at first, but after sitting on the shelf for months, “Contents may settle. Product sold by weight not volume”.

The point is, it can be quite tricky to get an accurate conversion of snow to water. A general rule of thumb is that 10” of snow is equal to 1” of rain, but hopefully from the examples above you realize that won’t always be the case. It is my understanding that if the temperature outside is 30 degrees, 10” of snow will equal roughly 1” of rain or a 10:1 ratio. However, if the temperature is 20 degrees, the ratio may shift closer to 20:1. And with those warm spring snows, the ratio can be closer to 5:1. There are rain gauges available that can help with this. They have a removable funnel that you keep in place during the warm rainy months (if we’re lucky) and you remove it during the cold snowy months.

From roughly October through March when we have extended periods of dry your landscape needs water. If it doesn't receive any, there is a good chance your plants will experience injury or even death to the root system. In the spring, plants may seems just fine, but once the temperatures begin to rise and the growing season really kicks in the plants may show signs of weakening or die altogether.

So when should you do this watering?? Good question. You want to make sure that you do it on a relatively warm day (which shouldn’t be hard to find this year) with temps above 40 degrees. Water late morning to mid-day when the temperatures are rising, but there is enough time left in the day for the water to fully soak into the soil before nighttime freezing temps return. 

The next question is typically, how MUCH should I water?? Newly planted landscapes are most susceptible to winter drought injury because their root systems haven't had time to fully establish, so keep a closer eye on them. Trees prefer to have water delivered slowly to a depth of about 12" throughout the root-zone (under the canopy to the dripline). You can use a deep-root fork at a depth of 8", soaker hose, sprinkler or watering wand. A rule of thumb is to give landscape trees 10 gallons of water per diameter inch of the tree. Newly planted shrubs (less than a year in the ground) will appreciate 5 gallons, twice a month. Established shrubs can receive 5-15 gallons depending on their size, once a month. 

Mulch is another important part of this equation. Having a nice thick layer of mulch will help the soil retain moisture year-round. You can refresh mulch any time of year.

Remember, the amount of water you put down depends on the amount of natural precipitation your area is receiving throughout the fall and winter months so adjust accordingly. A little extra attention over the winter will benefit your landscape for years to come!

1 comment:

  1. I understand it is difficult to generalize when it comes to watering, especially when you factor in the wind and whether it is an established or newly planted landscape (native or non-native plants). What are you thoughts on supplemental watering needs for native landscaping herbaceous perennials and woody plants? Could you say that supplemental winter watering is more applicable to non-native landscapes that are routinely watered during the growing season than established native plantings or are there also established native plants that you recommend supplemental watering?