P&PDL Picture of the Week for
May 8, 2006

Dead or Alive?  The Conifer Conundrum

Karen Rane, Sr. Plant Disease Diagnostician, Dept. of Botany & Plant Pathology, Purdue University

This photo of a Fraser fir tree (Figure 1) was taken in April 2006.  The foliage on two branches has turned completely brown (Figure 2), but most of the branches appear healthy.  A slight tan discoloration is visible on some of the needles, but they remain turgid and attached to the branches (Figure 3). Will this tree recover from these symptoms and develop new growth this year?

Definitely not! This tree was cut in November 2005.  After a short time as an indoor Christmas decoration, it was removed and left outdoors (Figure 4).  The foliage has remained green and the branches soft and supple for more than 5 months without a single functioning root. Only when warm temperatures arrive in late spring has the foliage started to lose moisture and turn brown.  Once this process begins, the discoloration will continue to develop until the tree is completely brown and the foliage falls off the branches.  But until a significant portion of the crown turns brown, the casual observer may not notice the subtle change in needle color. 

The same thing happens in landscape conifers when roots are damaged or diseased.  The structure of the needles, and the waxes that coat the foliage, help to inhibit moisture loss and the foliage remains green.  If the root damage occurs when temperatures are cool, then the foliage can appear healthy for several weeks or months after the roots have died.  By the time the foliage begins to turn brown the roots may have been dead for weeks or months.  One clue to determining if a browning evergreen will produce new growth is to check the buds at the tips of the branches – if they are green inside, then new growth may develop in the spring.  If the buds are brown and dry, the tree will not recover.

Click image to enlarge

Cut Fraser fir tree

Figure 1

Cut Fraser fir tree

Figure 2

Cut Fraser fir tree

Figure 3

Figure 4

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service