Plants & Cold - What to Do?

As gardeners watch the gentle emergence of spring flowering bulbs and the unfurling new leaves of perennials, shrubs and trees with one eye, they are watching the weather with the other. To some, protecting the garden plants from the usual spring extremes is mandatory, a rite of spring. And then there are gardeners like myself – a Darwin believer through and through – who believe that the strong shall survive and the weak rise no more. Reality is somewhere in between those two poles. So what to do - uncover, use more cover, or just leave them alone? My short answer is usually – just leave them alone. Even when I take off my Darwin gardening hat. For those wanting a longer answer, keep reading.

When choosing landscape plants, looking for materials that are cold hardy is not just another exercise to make the novice gardener earn “the dirty garden gloves of pride”. Expect the unexpected from early spring weather. Periodic mid-season warm stretches, sudden drops in temperature, crispy frost and ice coverings in May, raging snowstorms in June. All are historic in my backyard, some - recent history. Plants that are native to the desired planting area, yes - go figure, climatically suitable, will adapt to the varied environmental conditions as needed. Momma Nature taught them how to do so. The how(s) of non-native plant survival depends on many factors. Two that top my list are: 1) whether they are bred or selected from hardy stock for the zone they are planted in and, 2) the overall health going into the current growing season (and a number of seasons before, as well). A hardy and healthy plant will generally be able to bounce back from most weather setbacks thrown its way.

Chamaecyparis obtusa 'Split Rock' with some cold frosting.

Ah, the glories of 50 degrees F days in a northern January. Definitely balm for a winter weary soul, but truly wicked on the plants. Those early warm stretches often induce a plant to leaf out early. And while we’re all happy to see some green, not so early. Please. Especially when a subsequent hard frost or a blast of ice hits. Dead and crispy tissue will follow. Fortunately, plants will generally send out a new flush of leaves that, while they may not be as big, will do their job. Now the ifs: if the overall plant health is good, there will not be any noticeably prolonged damage; if the blooms are hit, expect to lose some if not all of the flowers; if damage is early and light, you may experience a second, minor flush of bloom in late spring; if the fruit blossoms are forming when frost or ice occur, production will be lower. Whew. Lots of ifs. Relax though. Worrying will not produce more of anything this season. Use this as a reason to focus on other aspects of the landscape plantings throughout the year, like improving structure, decreasing turf around plant bases, or maybe just take some time to look at the decorative features. There are some measures that can be taken to protect crops and flowers, if you are willing to invest the time and money. Frost irrigation systems, tarp covers and lights, heaters and fans, sometimes even incantations have been known to work – okay, maybe not that last one. These protection systems can be used successfully when set up and handled appropriately and responsibly. Do be aware that plant material should not be pruned immediately after frost or ice unless it is to remove broken and/or dangerous branches. You can certainly magnify damage by handling ice encrusted plant material.

Surprisingly, the fluctuations in temperatures can actually create situations of slower spring growth or even suspension. Weather changes keep the plants guessing (so to speak) as to what to do - the plant system reacts to the weather changes a bit more slowly at this time of the year. But it is not just the temperature lows and highs that impact plant reactions. Humidity and cloud cover play important roles in how the plants are affected by spring cold snaps. When skies are clear and humidity is low the effects of cold can be somewhat magnified, especially after sunset. Cloud cover helps moderate cold temperatures by deflecting and radiating heat back toward the earth – which is why those clear skies, while gorgeous to view, may assist in doing substantial damage to plant material. When air humidity is higher, that means increased air density. This slows the air temperature changes, moderating the effects of nighttime cold snaps. 

Snow? Please. In our northern area of the country, expect the potential for snow fall until June and be pleasantly surprised if it doesn't happen. A wonderful property of snow is that it can have a great insulating effect on our landscape goodies. If loose or relatively light, the plants will enjoy a nice slow drink as the snow melts. If cover is heavy and compacted, breakage is possible. More often than not though, humans do the most damage. All in trying to be kind and helpful after a snow. If safety demands that you brush snow accumulations off of any plant material – do it carefully and with potential plant loss in mind. As soon as you touch a plant with snow and/or ice cover, you are impacting the plant’s ability to react naturally and adjust to changes.

 Do we ignore the potential impacts? No. Concern about plant health is good – it improves our level of involvement. But to worry about the cold is not a good use of time and not very effective at much of anything.  And really, overall, many of our plants will be okay with anything Momma Nature throws around. Those tulips, daffodils, crocus, and hyacinth that are emerging really love the cold. The peonies poking their eyes up are only checking to see if spring is really here – they will not be shaken by a bit of cold weather, they actually like it. Cold hardy plants with plenty of stored sugar concentrates will survive weather fluctuations like the northern champs they are. So, leave the rake in storage, it’s too early for cleanup. Just relax, sit down, have a cup of tea or coffee, enjoy the sunshine, watch your garden emerge for the new growing season. And if you can’t relax, go sharpen your tools. Or dig around under some leaves (do put them back when you're done) - there is always something going on.

Rumex sanguineus can't wait for spring!