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!

Orixa japonica, Rutaceae (citrus) family

Such a lovely shrub, it should be more widely available. In early geological publications, the existence of Orixa japonica was found and placed in the Pliocene period – roughly 2 ½ to 5 ½ million years ago. Areas in Asia where the plant is currently found in the wild was thought to have been, during the Pliocene period, populated with plants that had migrated south from semi-polar regions. (The environmental conditions of the semi-polar areas of the Pliocene period are thought to be somewhat similar to our current north America and Canadian environmental conditions.) Of course, through time, those areas in Asia had undergone long periods of climatic change. What I find fascinating, is that it included known periods of extreme aridity. Not a tolerance we tend to need, with frequency, in the northern regions. Until this year. The survival of Orixa j., throughout these eons of changing conditions, is a testament to the longevity and adaptability of this under-appreciated plant. Even though the current regions of origin are similar in condition - predominately the mountainous ravines and forest hills of Korea, Japan, and China - the cultivated use demonstrates a continued wide range of environmental tolerance as well as a good-natured response to human intervention. 

It was a treat to find it listed, as early as 1784, within private plant collections, and, as a “found” treasure gathered during foreign plant expeditions. With records indicating that Orixa j. has been under western cultivation since the 1870’s, I’m compelled to ask - What happened? Where are they all? Especially given that there are no serious diseases or pests, the fragrant foliage repels hungry critters, and the entire plant is quite tolerant to changing environmental conditions. Hmm. As we all know, plant fashions do come and go. The lack of excitement over the introduction of Orixa j. to western gardeners appears to fall in line with garden and design fashions at the time. When Orixa j. was “newly” available to the western gardeners, exuberantly well-defined explosions of garden color were all the rage. A burgeoning middle class began replacing household vegetable gardens (which were mainly green with a spot of color when fruit was ripe) with external exclamations of their arrival into a better social world (colorful, decorative landscaping). And while Orixa j. has many attributes, flower power is not one of them. As the flower is rather inconsequential with regard to the overall impact of the plant, the impact of the plant on the public remained inconsequential as well. I enjoy the intense herbal scent of the leaves, but some family members, friends, and acquaintances, upon smelling the crushed leaves I jam under their noses, have responded with a not so nice phrase or two. That the foliage scent engenders a love it or hate it response, did not, I’m sure, weigh favorably in the marketability. Such a shame. 

Orixa japonica, pruned

Orixa japonica is frequently used as a hedge plant in Asia. And although it responds beautifully to pruning and shaping, the overall character will still tend toward squattish - wider than tall.   

Orixa japonica - same age as plant in previous photo, but unpruned

If left in a more natural state, an open, slightly mounded, horizontal habit develops. I expect it to max out at, roughly, 8’ – 12’W x 6’ – 10’H. We’ll see, might grow larger than expected. I do like plant surprises. In digging about for growth rate info, reports varied from very fast to moderately slow. My experience, albeit limited in geographic scope, is that it is slow to develop enough root mass to adequately support noticeable top growth. But after 3 to 4 years of wimpy leaf structure and branch development, the top growth starts zooming along, sometimes seeing a foot per year. 

The soil moisture demands for all of our gardens is of increasing concern.We all should be watching our water needs - appropriately balancing plant needs and choices with supply, availability, and cost. For Orixa j., drought tolerance is an accurate appraisal of its capabilities. During 2012's summer of extreme drought and heat, Orixa j. did exhibit extensive scorch along the leaf margins. Thankfully, this is did not appear to harm the overall health and well-being of the plants – plant kudos for that. As the cooler, early fall weather arrived, and brought a smattering of rain, the plants appeared to enjoy resurgence. As they will get no special treatment over winter, I’m going with a wait and see attitude for spring. But - so far, so good.

Orixa japonica, leaf

No matter whether pruned lightly, heavily, or left natural, the leaves are large 3”- 4” wide x 6”- 8” long, a vibrant medium green in color and my, do they have a lovely sheen. Adds great dimension to the overall appearance. The veins are quite noticeable and when planted in full sun, display a delightful tendency to pucker. Fortunately, I have not noticed any decrease in overall health following any leaf puckering. 

As discussed earlier, the flowers are rather inconsequential, but none the less – pretty. Developing in early spring, about two months into active seasonal growth, the small racemes of greenish-white will intermittently grace the branches, midway to 2/3, from the main trunk(s). You may have to nose around a bit to find them as they are often hidden by the large leaves. Plants are dioecious (distinct male and female plants) and fruit will only develop in stands where both are present. I have not had the pleasure to witness the mature seed dispersing but I understand it is quite a sight. Reports indicate that when ready, the seeds will be “thrown” some distance from the plant. What more can I say – how fun! 

For those of us strange gardeners who like to dally about outside during cold that normal people avoid…the winter buds are pretty. They have an almost variegated coloring to the scale edges, much lighter than the main body of the bud scale.

An interesting tidbit I ran across mentioned that an Orixa j. (or in Japan - Koku sagi, if I got it right?!) tea-like mixture was applied to, and used as, a beneficial treatment to the leaf food of silkworms. It was believed to improve the health of sickly silkworms. Also found some interesting human health uses, but those I'll leave to the medically trained...

Amsonia tabernaemontana

Amsonia tabernaemontana is quite a garden trooper. My respect for this plant, commonly called Blue Star Flower, has gained ground this year given its outstanding, and unexpected, performance during this year's drought. Dr. Allan Armitage has been extoling the virtues of this garden plant for years (Thanks Allan!) but did I listen? Not until about five years ago. And I must admit – I’m a little slow but I did, finally, get it. 

Amsonia tabernaemontana is a lovely U.S. native plant with a range that stretches from the lower east coast to the Great Plains, growing in sites from moist shade to dry, full sun locations steeped in limestone. Although right now this is touted as adaptability within this specific species, I think we'll see some separations and/or species re-classifications in the future. 

Early in the spring, Blue Star Flower pokes through the soil surface, the tips resembling large, purplish-green asparagus spears. The 2’ – 3’ stems sport 2” wide, dark green leaves are lovely as they open and develop in spring. But even though I love shades of green - oh - the leaves cannot compare to the icy glow of the pretty, star-shaped blue flowers that sit atop the stems in May.

Amsonia tabernaemontana flowers will fade to a pale, icy blue as they age.

Conditions for good growth and root development are not difficult to provide – these plants are quite adaptable. Again - I have to say, the drought tolerance was quite surprising. If placed in rich soil, the plant will grow very well, quickly developing stem height. And while for many plants that would be a desirable result, for Amsonia tabernaemontana, it will result in a floppy structure - especially given that the plant is tall with a natural tendency to a vase-like shape, plentiful leaves and flowers make the stem weighty at the top. The plants will love you if just placed into a decent site. 

Nice shape!

Full sun is suggested for the best growth but I’ve seen some fantastic plantings in shade as well. If the plants do flop over, whether it’s from too much shade, fast growth, or rich soil, feel free to give them a trim after flowering. Although I, personally, have not felt the need – you can cut them back to within a foot of the ground after flowering to get nice dense, leafy growth. Or if you’re one of those gardeners that just want your plants to present a neat and tidy appearance, and have no need for the seed heads, trimming them back just little may make your life complete. Go for it.

Want more? Division is an easy way to multiply your population of Amsonia tabernaemontana. You won’t need to divide very often (every 8 – 10 years) but when you do, early spring or fall are great times to get your shovel in the ground and split a healthy crown apart. Be sure to include at least one growth point in each division. Propagation via seed is purported to be easy and successful although it does take a few years to develop plentiful flowering. Terminal cuttings (use rooting hormone), taken early in the season, are also an effective method of propagation. 

Amsonia tabernaemontana problems are difficult to locate. Makes them a treat to grow. I can see the potential for root rot in consistently wet soils but that problem is our fault for poor site choice, not a plant health liability. Try as I might to locate any critter/insect feeding or damage on the plantings – I have not. Again – a treat.

it's been tough

Wow. It has been a tough summer all over - too much rain, too little rain, too much heat, too much heat, and too much heat. If, like me, you live in an area that is suffering from a severe rain deficit - and like me, you could not even begin to match plant needs with hose action – you will be seeing some incredible variances in plant response.

Amsonia tabernaemontana and Amsonia hubrichtii have shown remarkable drought tolerance - especially given my yard's exposure to Round Up over-spray this spring (thank the neighbor). When surrounding perennials went toes up, the Amsonia species were calmly holding their own.

Amsonia hubrichtii with a bit of early Round Up damage showing - otherwise looks great for a drought stricken July.

The behavior of my beloved Phlox paniculata ‘Peacock Series’ ('White' and 'Neon Rose') caused me to rethink that affection as they did not perform well (at all) throughout the months of intensely dry, high temperature conditions. Even those planted in partial shade just couldn’t even pretend to thrive. I watched as the leaves discolored, the plants continually refused to show any response to the water (yes, it was meager) provided. Eventually goodbyes were uttered, as it appeared to be a permanent decline. But to my surprise, and delight, new leaves eventually emerged and, now, continue to develop. Although they still look rather wicked from an overall perspective, growth is happening. I love it when plants surprise me.

Phlox paniculata 'Peacock Series' - Round Up damage from neighboring farm over-spray, followed by drought. Look at it tough it out!

Whether the effects are obvious or a bit more insidious, lots of plants are certainly suffering. Normal treatments need to be modified, depending on plant reactions to the conditions. What changes need to be made? Stick with advised water needs for your area and soil type. Generally for established plants, that means the equivalent to 1” of rainfall per week. For new plants that moisture need rises to the equivalent of about 2” of rainfall per week. During periods of drought, do the best you can while staying within area water guidelines and/or bans.

In the case of fertilizer, as summer blends into fall, the general recommendation is to hold off fertilizing until after normal leaf fall – or in the northern regions, until we’re hit with at least a couple of good, hard frosts. This year, the extended drought has created a period of dormancy extensive enough for the plants to re-leaf, re-bloom (August Magnolia blooms in my Wisconsin yard?!), and/or re-grow (new asparagus spears in August as well) – all, of course at non-usual times. Well…that places severe demand on plant system reserves. As those reserves are depleted, provision of additional nutrients will assist those plants in restoring reserve levels, ultimately reducing plant system stress during the upcoming spring. 

Appropriate timing of fertilizer applications is crucial at this time of the year. For those plants that are sporting a second (or third) set of leaves, get a light application of a balanced fertilizer down and watered in NOW. For those trees and plants that are holding on to this year’s first set of leaves, wait until the generally recommended time - after leaf fall. The worst thing you could do is to encourage any more new growth that will not harden off before winter arrives. Creating additional stress on the plant system is not what we need this, or any, year. 

Disanthus cercidifolius - rallying in August.

  As always, an overall, a planned fertility program is preferred to the shotgun approach (throw everything at anything or anything at everything). Thinking wholistically and planning ahead are invaluable for maintaining your plants. Start with a panel of quality soil tests from various planting areas of your yard - e.g. grasses, ornamentals, trees, vegetables – as all need differing levels of care and potentially different product formulations. Start with the tests, then plan, and execute a fertility program that will get the most out of your plants, and your pocket book.  

Such a Lovely Southern Belle

Magnolia stellata. Lovely star magnolia. What would we do without your spring floral splendor? Although the zone 5 appearance was fleeting this year, the blossoms are always a joy to behold. The fragrance, delicious. 

Magnolia stellata - morning of bloom

This is becoming such an unusual year that I, somewhat religiously, take my coffee for a walk in the morning, rain or shine, to see what Momma Nature has given and taken away overnight. The other morning, as my coffee and I were enjoying our morning stroll, I was quite pleased to notice that my five-year old Magnolia stellata was sporting four open blossoms. The rest - about 40 or so - were still tight. It was truly an early spring, comfortably enjoyable “ahh” moment.  Drank both it and my coffee in – then wandered to the neighbor’s place to help burn 20 acres of prairie. What a glorious start to the day, a bit of beauty and a bit of fire. Imagine my surprise when I got back – every one of the mag blossoms was out and in full glory. And like almost every other flowering plant so far this year, finished way too quickly. Unbelievable how early and fast the blooms burst, about 6 weeks ahead of the norm and only lasted a few days. Me thinks that this will make for a rather bland mid-summer bloom show. Better start thinking about which annuals to get...

Magnolia stellata, when hardy for the zone to be grown in, are quite an easy and satisfying landscape buddy. They really don’t require much from the human sector other than consistent structural training, a decent setting, and a bit of appreciation. The pruning needed is pretty basic, if you start training early on. Once it develops good structure and branching habits – only a light pruning is needed every year or two. Prune (as with many early spring flowering plants) right after blooming. Don’t wait too long or you’ll be removing next year’s flower buds. Siting magnolias requires a bit of protection this far north. Too much sun, and heat, increases the risk of the buds and/or flowers developing too early in the season. If that happens, our late spring cold zaps will wreak havoc on the buds and flowers - which are not extremely cold tolerant. The buds, if zapped, will fail to develop properly while the flowers will go from vibrantly beautiful petals to brown and gooey in short order. Will that matter in the long run? Not if it only happens once in a while. Magnolia stellata is tough enough for the overall health to rebound fantastically. But let’s be honest – we do grow it for the flowers. Any loss means waiting an entire year for the next show. 

What constitutes good siting? Full sun is best for maximum flowering. But do avoid unprotected, full exposure southern sites to minimize the afore-mentioned damage resulting from that early season warming followed by cold temps and cold, wicked winds. Partial shade does not seem to greatly affect the flowering. All recommendations are for slightly acidic, moist soils - which we don't generally have. And although I have not noticed a fast, dramatic decrease in health and vigor when sited in our higher pH soils, periodic applications of some lovely peat or compost appear beneficial. When in a consistently dry site, growth slows to a virtual standstill. Adequate soil moisture is essential for good growth – be kind with the hose when Magnolia stellata are young. Deep, infrequent watering to the equivalent of 2" rainfall per week is best for young trees, equivalent of 1" rainfall per week for mature trees.

Verticillium wilt and scale are the most common Magnolia problems in zone 5. Verticillium is commonly found in the soils just about everywhere in this area. Be aware of the potential for problems and you won't be shocked if it infects your tree. Disappointed maybe. Symptoms typically appear mid-July or so. Should that stop you from giving them a whirl – nah. It’s certainly not enough to make me stop planting Magnolia stellata. Does Verticillium have the potential to take them out? It can. Or it can just knock them around a bit. Severity varies, but it doesn't go away. If severely infected, you may end up removing the tree as it tends to look rather ragged, fairly quickly. 

Scale is an interesting issue on Magnolias. Seems to run to extremes. Either you have a big problem or you don’t. Often, the horrible end of the infestation spectrum can be attributed to some additional pressures on the tree – winter lighting and/or intense insecticide use. Normally we only have one generation per year this far north. Warmer environmental temps and additional heat and light from non-LED winter lighting may encourage the development of an extra generation per year. As one would expect, more unchecked critters does mean more potential damage. Insecticide use can throw the predator/prey system dramatically off balance as insecticides are made to kill all insects within a targeted spectrum. There is no judgment built into the products. Both problematic and beneficial will be affected. When beneficial insects that prey on scale are reduced, the ability to naturally keep the scale numbers (and damage) in check will also be reduced. This instance is no different than many others - a thoughtful and judicious approach is always a good idea. And controlling scale requires thoughtful, close attention to life cycle stages, appropriate product choices, and responsible application. If an infestation is heavy, expect to spend a few years getting it back under control. Patience and persistence will win the day.

Heptacodium miconioides

One of the first questions I get asked about the ease and beauty of this tree is: How invasive is it? We do associate ease of growth with invasive qualities, often with good reason. But Heptacodium miconioides has not proven to be a problem for any of my planting sites. I love the common name - Seven-son Flower which, more often than not, refers to the structure of the flower. In researching the area of origin (an eastern province of China) there reigned a King with seven powerful sons... such delicious coincidences make life so much more interesting. Today we find that Heptacodium m. is very rarely found growing in the wild. Thank goodness our western gardens were introduced to this lovely plant twice - first in the early 1900's (didn't register with gardeners at this time, for some reason) and again in the 1980's. Both times, the introduction was a result of plant hunting expeditions to China. To come upon this in the wild - what a site it must have been!

Even though it's a late summer/early fall bloomer, it proves interesting throughout the year. Right now, the bark is absolutely beautiful. Almost every branch, from early growth on, has an interesting exfoliating habit. But what I find so engrossing about said bark is that as it ages, the tissue under the exfoliation develops a broad color range. It can sport vertical striations of green, bluish-gray, tan and/or creamy white. Such a pre-spring treat.

Heptacodium miconioides - late winter bark

The habit is relatively vase-shaped, often with sprouting suckers closely arranged around the main trunk(s). The most commonly seen Heptacodium miconioides grooming results in trunks that remain clear and exposed. Hence, the suckers are cleared regularly. May not be a bad idea to encourage a few of the heartier to remain as potential re-populators down the line. 

Conditions for optimal growth and development? Reports say Heptacodium miconioides require full sun and moist, well-drained soils on the acidic side. As a true line pusher, I have planted them in a variety of sites, but, generally the soils have been the alkaline end of the spectrum. And so far, no pH related health issues. The well-drained soils seems to be the best fit. When I have tried Heptacodium m. in a wetter site, root rot attacked. Not so sure about the necessity of full sun though, I've had pretty good success with partial shade siting. Given reports on performance from other parts of the world, I suspect that partial shade siting would be even more successful the further south you roam.

Even in our cold(er) zone 5 climate, expect an early leafing. Generally by mid- to end April the leaves will be tender, but definitely fully expanded. This will be followed, almost immediately, by a couple of days brutally hot, wicked wind - which will rip and scorch the leaves. Not to worry though, it will come back to full glory within a month or so. And my goodness. What big leaves those are! Elongated to about 7" - 8", medium green in color with nicely prominent veins throughout the growing season. Don't expect a powerful leaf show in the fall. Do expect nonstop textural interest.

Heptacodium miconioides - in flower

The habit and leaves are great but I have to admit, I'm a softy for the blooms. Arriving in early fall (zone 5), the flower and fruit are a boon the late season landscape. For us westerners, the common name (Seven-son Flower) comes from the flower structure. The flower heads are comprised of wonderfully fragrant whorls with seven small flowers in each little whorl. Small in size but so large in fragrance - a heady scent reminiscent of jasmine. Not a common outdoor fragrance this far north, to be sure. After the flowers have passed, what follows are beautiful, showy, reddish-maroon fuzzy fruits. I have not tried eating these tiny wonders, mainly because I've not found anything that promotes them as edible for humans. Hmm. More research on that topic needed.

No horrible insect or disease issues have surfaced thus far, although limited longevity has been discussed. I'll keep watch on that. Periodically I see reports of odd cankers and blights but the only concerning health issue I've experienced is root rot. Lab tested, no guess work. Treatment in this instance was definitely experimental - I decided to just move the plant. And it was a wicked mean, early summer transplant. Came back immediately, and within two years was back to the pre-rot size. Seriously - no chemicals used. Barely got watered. Just dug it up and moved it. Yeah, I know. Too easy.

When you're out doing some plant shopping this spring, if you see Heptacodium miconioides, buy one. Or two. Or three. And don't be put off by the rather unattractive container appearance, they look much better, and respond very nicely, once in the ground. Easy, easy, easy. And beautiful.