Noxious Cold

Like a good bit of the rest of the US, we were invaded by a particularly noxious and extreme cold usually confined to the northern polar regions. Fierce winds usually keep that cold where it belongs, but on occasion, that cold travels our way. In early December it became apparent that we had bitterly cold weather coming up. The first order of business was to clean out all of the fall plantings in those pots that were due to have winter arrangements, and take the soil level down four inches from the top. The floral foam form would sit on top of that lowered frozen soil. The form would be anchored into the soil with bamboo stakes, or steel rebar. Pounding a stake down through frozen soil is a good bit easier than chiselling out frozen soil. Three weeks worth of installations were accompanied by this relentless cold. Never have I been happier that we do most of our fabrication for the winter pots in the shop stockroom.

The evergreens in my garden have no where to go, and no other option but to endure. A gardener can provide their evergreens with regular water in the fall. An evergreen with juicy stems and needles is an evergreen dressed properly for the weather. Once the ground freezes, the plants will no longer be able to transmit moisture from the roots to the needles. An evergreen that goes into the dormant season dry is poorly positioned to deal with desiccating winter winds and sun, and the inevitable loss of moisture from transpiration. The water that evaporates from the needled foliage of this yew cannot be replaced until the ground thaws.

That many evergreens have needled foliage as opposed to leaves is a survival mechanism, courtesy of nature. Each needle has a relatively small surface area from which moisture can evaporate. Leaves are poor conservators of water, as they present so much surface area to sun and wind. It is no wonder that deciduous trees and shrubs drop their leaves in the fall.  Carrying a full set of green leaves through the winter would most likely be deadly. At the extreme other end of the spectrum, cactus have evolved to have spines in place of those leaves that are so ill equipped to conserve moisture. Those spines do collect water from rare rains, which then drips down to the roots. Water in some degree is essential to the life of plants. I may let plenty of things go in the garden, but I do water. Plants that do not get the moisture they need are stressed and vulnerable plants.

Of course our long run of cold has me worrying about the boxwood. They are broad leaved evergreens. Those leaves readily desiccate in extreme wind and cold. They are prime candidates for winter burn.  A drench of anti desiccant such as Vapor Gard on both the tops and the bottoms of the leaves coats the surface with a waxy natural compound of pine resin that reduces the evaporation rate. It is amazing what a difference an anti desiccant can make. Any evergreen planting I do after the middle of August gets Vapor Gard ahead of the first winter. It is very inexpensive insurance against disaster. The above picture was taken in April of 2014. These 20 year old shrubs were killed outright from the extreme cold we experienced in the winter of 2013-2014. Double digit below zero temperatures for days on end proved too much for them. The 100 inches of snow we had went beyond insulating them to overloading them with branch cracking weight.

A boxwood disaster is rarely apparent before April. That makes it easy to fret over them all winter.

This day was a heartbreaking day. That day in April made it obvious that the west end section of this old hedge had perished. It succumbed to a once in a lifetime extended cold well below its hardiness limit. The entire summer of 2014 I drove by so many hedges of dead boxwood still in the ground.  I could not have looked at dead plants day after day, and month after month, but disbelief, grief and denial can be very powerful.

Do I think the extreme cold spell we have just had will kill my boxwood? Our coldest temperature was 6 below zero. This is not cold enough to kill a zone 5 shrub. It was cold enough to make me dress from top to bottom for bone chilling cold. I limited the time the corgis spent outdoors. One morning at 4 degrees below zero they came in limping after 3 minutes outdoors. Cold feet. But I do not believe it has been cold enough to seriously damage the boxwood.

Once we finished removing the section of dead plants, we placed big Branch pots in front of the bare ends of the boxwood. It would be every bit of several years before the dead spots and sections would recover from this winter. Note that the tulips coming on sustained no damage from the extreme cold. They were completely dormant, and below ground. Sub shrubs such as lavender, that have live branches above ground in the winter, can be very difficult to winter over.

We did finally get the window boxes and 2 pots in front of the shop done up for winter. They feature cut boxwood twigs stuffed into dry floral foam.  After just a few days outdoors, they began to show the signs of leaf shrinkage from evaporation.

Even the backs of the leaves show signs of stress. As long as these cut stems were packed in wax coated boxes, and not exposed to sun or wind, the leaves were glossy and plump. Once exposed to the weather, they reacted as expected. Fortunately boxwood leaves stay green even as they dry.

I am sure we will have burned and dead tips on these plants come spring, but I expect them to recover.  32 degrees this morning-what a relief.

Winter Protection For Boxwood

Detroit-Garden-Works.jpgBoxwood is one of the most versatile and robust growing evergreens available for planting in my zone. There are a number of great cultivars.  Green Velvet matures at 3′ by 3′, and keeps its great color all winter. Green Mountain is virtually identical to Green Velvet, but grows to 4′ tall by 3′ wide. Buxus microphylla koreana, pictured above, is hardy in this full south sun location, and can grow to 5′ by 5′.  The winter color is a dull orangy bronze. Winter Gem boxwood is incredibly hardy, and grows slowly to about 4′ by 4′. The leaves are smaller, and narrower than Green Velvet.

DSC_4001There are lots of other hybrids available.  Vardar Valley is an outstanding hardy cultivar of buxus sempervirens. It matures at 1′ to 2′.  The leaves have a distinctive blue green color.  As it is a slow growing variety, it is not routinely offered for sale at local nurseries.  Most of the boxwood sold in my area is grown in regions where the season is long enough to permit 2 flushes of growth per season.  This means nursery can get a salable product faster.  Boxwood is graded by width-not by height.  A boxwood takes about 7 years to grow to an 18″-24″ size.  This makes them relatively expensive to buy, compared to other ornamental shrubs that grow quickly.

MG 2013 (29)Boxwood is indeed a versatile shrub. They make great hedges, as their growth is uniform, and they are very tolerant of pruning.  That tolerance makes them an ideal subject for living sculpture. Boxwood pruned into spheres, squares, cones and cylinders are striking and delightful.  The large boxwood in this landscape will be kept pruned in spheres.  The small boxwood will be allowed to grow together, and will be pruned flat. This garden will have a much different look in a few years. All of these boxwood are Winter Gem.  The fine textured foliage makes them ideal for pruning into a formal, strictly geometric shape.   DSC_1801Boxwood are quite friendly to other plants.  Provided care is taken in the selection of a cultivar for a specific site, they will stay in bounds. These boxwood rectangles are a beautiful foil for the clipped espaliered crab apples. If the face is pruned on a very slight angle out from top to the bottom, they will stay green all the way to the ground. A boxwood which is hard pruned into a specific shape will stay green on the interior.

boxwood-green-velvet.jpgBoxwood makes a fine tall ground cover under a tree.  They are quite shade tolerant. A small landscape such as this is all the more interesting for a change of level.  These boxwood are a welcome visual intermediary between the ground plane, and a linden which has grown to substantial size. That they are shade tolerant means they can be sited in lots of places.  Naturally grown boxwood make a lovely backdrop for ferns, hostas and shade tolerant perennials.  A boxwood provides a green backdrop for the earliest of perennials to appear in the spring.  The small textured foliage makes them a great companion for the bigger textured hellebores, and European ginger.

Aug 31 2013 (20)A boxwood would go so far to oblige a gardener who wishes to grow them in containers.  They do need large enough containers so there is room to grow.  The root ball of a decent sized and well grown boxwood might be larger in diameter that its leafy component.  Boxwood in containers need special attention to proper watering. They need to be well watered prior to freezing weather.  They will rely on water stored in the stems and leaves to survive they winter, as the water in the container cannot be absorbed when it is frozen.  Boxwood in ground has much more widespread moisture available to its roots, especially given how long it takes for the ground to freeze to any significant depth.  A boxwood confined to a pot needs regular water.

boxwood-hedge.jpgPruning boxwood takes more than a good eye.  A great job invariably involved the setting of level lines.  Relatively level boxwood has a forlorn and unfinished look.  This boxwood has been pruned level with the horizon, even though the driveway drops down to the street.  The boxwood at the bottom of this drive is quite a bit taller than those plants at the top.  Level boxwood has a serene and solid look to it.

August 12 2013 (11)Boxwood can help provide structure to a garden.  This densely growing shrub provides a simple and strong contrast to the garden elements.  This pruning is loosely formal, and softens the stone wall behind them.

Aug 31 2013 (18)I have written about boxwood plenty of times before – I do like them.  It was painful to see how many boxwood in my area were severely damaged or killed outright by our last winter.  Some were crushed by the huge snow loads.  Others in more exposed locations were damaged by the extreme cold.  That cold, in conjunction with sun and wind burned the leaves. Leaves that were completely desiccated, died. It took the coming of the spring weather to see how terrible the damage truly was.  Some of the boxwood at the shop died outright.  The damaged portions will take years to recover.

July 5, 2012 035If you have ever hung a boxwood wreath on a shaded door for the winter, or used cut boxwood in winter pots, you know those stems will dry out, but stay green until the temperatures moderate.  Like many evergreens, by the time a boxwood shows signs of stress, it is too late to remedy the problem.  Now that fall is approaching, I would urge anyone with boxwood in my zone to spray them with an antidessicant.  An antidessicant is a waxy coating with will slow the evaporation of water from the leaves in the winter.

boxwood-spheres.jpgI have heard talk that this winter looks like it may be a very cold winter.  Something like last winter.  Though boxwood is hardy in this zone, extreme cold, sun, and drying winds can damage them.  Though a boxwood may grow out of winter burn, that look is unsightly come spring.  If your boxwood are 15 years old, it will be very expensive to replace dead plants with new plants of the size you already own.  Last winter was dramatic evidence that winter protection for boxwood is a good idea.  photo (43)I recommend Vapor Gard.  It is widely used as an agricultural antidessicant. The main ingredient is pinolene, a natural polymer made from pine pitch.  It can significantly reduce winter burn.  You can buy it, dilute it 1 part to 20 parts of water, and spray it on your boxwood. If you have lots of boxwood, your tree care company can spray this for you.  It is best done on a dry day, before the weather drops regularly into the low forties.  The polymer coating will protect those leaves over the winter, and help them retain moisture.  Vapor Gard is a natural and non toxic spray widely used on crops, including cherries.  It is an easy way to protect your investment. Do read the label-it is not appropriate for every and any plant. I plan to spray all of my boxwood with it soon; one application will protect them the entire winter. The boxwood pictured above from this past spring-heartbreaking.   Interested further?