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ASSESS EFFECTS OF
WINTER DAMAGE IN EARLY SPRING
Besides the dryness of summer, winter is one of the harshest times of the
year on boxwoods. The most severe stress comes from the combination of cold winter winds
and the ground being frozen, thus not allowing water to move up into the plant. Either one
of these stresses alone is not as dangerous as the two in combination. Winds cause plant
desiccation (drying) and the moisture must be replaced. If the roots and surrounding soil
are frozen, this replacement is not possible. The plant can tolerate frozen roots if there
are no winds to cause excessive desiccation. On the other hand, wind can be tolerated if
the roots are capable of supplying moisture to the top of the plant. The importance of
monitoring winter moisture levels is sometimes not realized until the spring when the
effects of winter dryness is seen in a damaged plant.
Early spring is a good time to assess any damage of the previous winter and take
corrective measures when necessary. The alternate freezing and thawing of the ground will
possibly leave exposed roots which need to be covered with a fresh layer of soil or mulch.
The mulch also provides the all important organic matter necessary for good plant growth.
A reddish-brown rust color is often seen on plants during the winter before spring growth.
Commonly referred to as "winter bum," its seriousness may be evaluated in two
ways. First, feel the plant to determine if the leaves are soft to the touch or whether
they have a crispy, paper feel to them. The latter indicates a level of dryness which may
be terminal, at least for that part of the plant. The second test is to look at the color
of the leaves within the plant. If these deeper leaves are the proper shade of dark green
and are soft to the touch, then the outside leaves are probably showing the result of
maximum exposure to wind and cold. Spring growth, should reestablish the plant to its
normal color. This winter burn condition may very well be caused by lack of
nutrition. That does NOT necessarily mean immediately adding fertilizer.
Getting a soil test is advised since the pH of the soil will determine whether the plant
is able to take up the available nutrients from the soil. The pH advised for boxwood
is around 6.5-7.2. Often the soil becomes too acid and regardless of the nutrients
in the soil OR the amount of fertilizer applied, the plant is unable to take up the
nutrients. The addition of lime will bring the pH back to the proper range and allow
the plant access to the nutrients.
Late winter/early spring is a great time to pluck and shape misshapen plants since the new
growth will quickly provide a uniform appearance and cover any cosmetic work. This is an
ideal time to break out any dead wood. If plants contain winter debris such as dead
leaves, a strong hosing out and cleaning is advised. If plucking results in healthy
cuttings which may be used for rooting, late winter/very early spring is an excellent time
to do this rooting. See PLUCKING and/or
PROPAGATION papers. Late winter is also an ideal
Lime to move plants which need to be transplanted. See PLANTING
paper. Only early fall is a better transplanting time. As soon as major
freezes are over, usually around March I for the middle Atlantic states, transplanting can
begin. Beginning this operation early provides more time for roots to develop before the
dryness of summer stresses the plant. Even though top growth may not come out until May,
root growth will take place any time the ground temperature is significantly above
freezing. One of the surest signs of a healthy plant is a timely overall flush of new
growth. This is normal and should occur. If it does not then a soil analysis may be in
order to determine if nutrient deficiency exists. When grown in well-drained and aerated
soil with good organic matter, the fertilization needs of boxwoods are minimal. The
fertilizer normally applied to a lawn is often sufficient to provide the needs of
boxwoods. If application of fertilizer is called for after a proper soil analysis, a
slow-release type is preferable since it will supply nutrients to the plant over a longer
period of time. Apply around the base of the plant in very early spring before new growth,
being careful not to touch leaves with the fertilizer. An alternate time is in late fall,
after frost has come. The frost will stop any new top growth which otherwise may occur
with fertilization.
Stephen D. Southall
English Boxwoods of Virginia