Drought vs. Frost

If you could do one thing to preserve the life of a plant you really liked, would you prefer to spend all summer watering it, or to mulch it in fall and cover it with something on the coldest winter nights?

Apparently, most gardeners would choose to spend all summer watering it. Most people have accepted the idea that because plants need water, it only follows that a good gardener should spend a lot of time (and money, in some cases) watering them. In my experience, it’s much less common to encounter gardeners who adapt practical protections for winter cold as part of their gardening regime.

Nature has provided Northwest gardeners with certain limitations on what we can grow. Summer drought is a limitation. Freezing weather is a limitation. We compensate for summer drought by using tons of water to keep our plants healthy. We compensate for freezing weather, by, um, doing nothing, most of the time. The question is, why this discrepancy? Why do we have this subconscious expectation that our garden plants ought to be able to handle all the cold weather our climate has to dish out with no help from us, but it’s OK if they can’t handle the dry weather (a much longer period of time) because then we’ll take care of them? In short, why do we accommodate garden plants for drought, but not for frost?

Consider this example. You have a sunny, well drained area in your front yard where you want to put a shrub, and you have narrowed it down to two possibilities: Hydrangea macrophylla ‘Nikko Blue’ or Grevillea ‘Poorinda Elegance’.

Suppose you choose the Hydrangea, because you don’t want to worry about winter hardiness. What does it need to stay looking sharp? Well, you don’t really have to fertilize it, but it helps if you amend the soil or at least top dress with some rich compost. You’ll also want to mulch it so that the soil will retain moisture. Then you have to water. And water. And water. How often? Once a week would be about right for most gardens: that’s at least 20 times in a typical Northwest dry season (late June through early October). Suppose you have fairly moisture retentive soil: you still probably have to water at least every other week. (Unless you live on the edge of a swamp.) So that’s 10 times every summer to remember to water. And each time you’re probably out there for at least two or three minutes to really give it a good, thorough soak. So there goes, at best, a half hour of your summer, watering. And the next summer. And the next summer, etc.

Suppose you choose the Grevillea: what does it need? It needs to be watered a few times the first summer, but certainly not as much as the Hydrangea—and none at all after the first year. You can probably skip the soil amendments. In fall you mulch with something that will insulate the roots and protect them from freezing—but you’d want to mulch the Hydrangea anyhow. Then when the big arctic freeze is about to come, you cover it with a cardboard box or blanket to prevent it from getting frost damaged. And then when the weather warms up, you take it off. That’s it. It only takes a moment, twice a year. Well, you might get a winter with two or even three big freezes, and have to provide a repeat performance. But on the other hand there are also mild winters when you shouldn’t have to do this at all. On average you’re only expending a few minutes of effort on this every year. And you don’t have to spend any water, or precious summer hours, which we know are all too few in the Northwest anyhow.

Now multiply this by all the plants in your garden, and it’s your choice: spend a whole day watering your plants, once a week, all summer and early fall. Or spend a couple hours – perhaps longer, depending on how many plants you have – covering some of your most special plants with boxes and blankets, just once a year. (And taking them off is even easier, if anything.)

Of course, I know there are automated irrigation systems, and mulching can help the soil retain moisture, etc. But in a climate with reliably dry summers, a situation in which you still save effort by choosing a water hogging plant over a marginally hardy plant is rare. Think about how much money goes into your irrigation system. And mulching the soil, prescribed in both cases, is no more or less difficult either way.

Next time you’re considering what to plant, ask yourself: Is it time to reconsider what the real limitation is on what I can grow in my garden? Perhaps we should get over our somewhat reactionary fear of marginally hardy plants. Perhaps the water hogging plants are the ones to stay away from.

Grevillea ‘Poorinda Elegance’, hardy to about 15°F, needs no water once established in the Pacific Northwest, and is well worth protecting from the occasional cold blast.

10 Comments (+add yours?)

  1. Mark W
    Feb 08, 2011 @ 13:43:19

    My issue with freeze protection is not the time it takes to put up a protective structure, it’s the ugliness of the structure in the landscape and the storage space needed to store the protective structure during summer. But I can see what you’re saying.

    I like to water (for some reason) but I don’t like the cost of it. Larger capacity rainwater storage is on my radar.


  2. Arlene Mikelsons
    Feb 08, 2011 @ 18:24:11

    I prefer to cover rather than water because I know that water could become (has become in some places) a community problem.

    That said, I believe that many people would rather water because it is pleasant to stand outside on a sunny day, looking at your plants and watering them.

    It is definitely NOT pleasant to rush outside long after dark (when I usually realize that it is going to be very cold at night) and rush around in the freezing wind trying to cover a plant.

    I try to stick with native plants since I don’t really like to worry about either issue.



  3. desertnw
    Feb 08, 2011 @ 23:08:45

    Mark, good point. This was more of a thought/logic exercise than anything else, and I might have chosen better examples. I get bored of watering though; maybe I’ve just spent too much time in my life doing it already.

    Arlene, what, you don’t like to rush outside when it’s 37 degrees and windy and dark? I thought that was something all Northwesterners loved to do… just kidding. Well you’re right, the best plants are those that can take both drought and cold and anything else in stride. It’s just hard to stop myself when there are so many exciting plants that are almost hardy…



  4. David C.
    Feb 14, 2011 @ 08:46:31

    I have been enjoying your website and blog, esp past trips to interior NW locales and the SW, of course!

    On this topic, we have some people here called “arcticists”, who push Albuquerque’s climate into far colder, wetter realms. Their ideal landscape is USDA Z 3-5, like Jackson Hole or Duluth. This year, our historic, record cold must be making them happy, until their aspens and bristlecone pines suffer in May. They are the opposite of some gardeners in Austin TX who fail by pushing zones to grow tropicals.

    Am seeing some plant damage (1st in 40 years on most), but many successes. For small plants, protection is fine. But my vote on larger plants that get frozen is to either just suck it in and replace, or try something else!


    • desertnw
      Feb 14, 2011 @ 20:40:48

      What’s just happened in NM/west TX is truly amazing and verging on apocalyptic (I’ve seen some damage pics from El Paso). Probably most of the palms I photographed in Albuquerque and Las Cruces are dead outright!! I guess everyone has to find their own balance as to how much risk they want to take, but I pretty much agree with you – to me the prospect of a 40′ year freeze is a caution against planting something that will grow to be enormous in that time frame, but not so much of a concern for smaller shrubs/perennials/groundcovers etc that are easily replaced if they croak.

      We would probably also agree that both ABQ and Seattle have a long ways to go in pursuing/discovering the most appropriate and best adapted plant selection for our respective regions.


  5. James NE Portland
    Feb 27, 2011 @ 21:50:39

    I like the point you make and I fully agree that people don’t ever think it’s a big deal to have to water or fertilize, but to insulate? You become the talk of the neighborhood. Look at how much work people will put into a lawn.

    My policy now after 3 consecutive hard winters is to stick with the hardier shrubs in general ( although most still a little borderline), but have a few that I am willing to baby because they are extremely special. This way I minimize the workload during the winter. I was curious what you use to protect a full size grevillea? I find grouncovers and trunking plants like bananas and treeferns to be easy but I never really thought how you protect a large shrub short of mulching the crown.


  6. Ian
    Feb 28, 2011 @ 12:25:19

    James, I would throw an old blanket over it – or a blanket plus a sheet of plastic – and pin it down at the corners with rocks or bricks. That’s just for a couple weeks, not for the whole winter. Of course once something gets bigger than 4-5′ tall/wide, protecting plants from cold gets more difficult.


  7. Heico
    May 11, 2013 @ 02:12:51

    Hello James,

    Would I be able to use your picture of Poorinda Elegance on ebay and my website to sell them in Australia.

    I am finding it hard to source a copyright free picture.

    Kind regards



  8. Ian
    May 11, 2013 @ 09:51:39

    Heico, sure, go ahead. Thanks for asking – most people don’t. But they should.


  9. Heico
    May 12, 2013 @ 15:17:59

    Thank you Ian.

    That made my day easier.

    We cannot send plants overseas, but if you know anyone in Australia who you would like to bless with a voucher for “buy one get one free” for up to the value $200.00 (Except for Northern Territory, Western Australia and Tasmania. Government restrictions wont let us send to there), please email me their email address and I will email them a voucher.

    My website is http://www.plantinspirations,com.au if they want to have a look around in our online store

    Have a great week



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