QBARS - v19n1 Current Bud Damage

Current Bud Damage
by Carl Phetteplace, M.D., Eugene, Ore.

Possibly we in the Eugene area may experience some disappointment at next year's rhododendron blooming season. There seems to be a great abundance of buds on most plants. But on picking some off and cutting them open we found what appeared to be a surprising amount of damage, evidently due to cold. Some varieties, as would be expected, show much greater damage than others. It consists of marked browning of the rachis or of a few or all of the pips, and in some instances branches and pips both are brown. Many griersonianum and all elliottii hybrids seem damaged, although 'Azor' and 'Vulcan' seem unharmed. There is little damage to Fortunei series hybrids, even including the Loderis, 'Loder's White' and the Naomi group. Most Dutch hybrids are unharmed, although I found a few damaged pips on 'Earl of Athlone'. 'Crest' and 'Jervis Bay' escaped, but a little damage was found on both 'Prelude' and 'Carita'. Externally there is nothing abnormal or unhealthy in appearance in any way. There is no foliage damage at all.
This has not been an especially cold year so far, but the cold has come much earlier than usual. And it was preceded by one of the most warm and beautiful autumns, through all of October and beginning November, seen here in a great many years. It was almost the only "summer" we had in 1964. About mid-November there were some frosts, down to about 28° F. here, with some snow. About Thanksgiving there were more similar frosts. About December 20th began a series of cold days and nights with temperatures finally reaching 15° or 16° F. in my garden. None of this would ordinarily have caused bud damage. But probably many plants had not attained dormancy by mid-November following the mild fall. It is not unlikely that this damage occurred not from the colder weather in December but rather from the earlier milder November frosts. On examining these buds the damage looks older than what would have occurred only a week before from the December cold. Of course this is only an impression.
It would be interesting if others, in different areas, would now examine buds in their gardens. It is possible that we may have even colder weather ahead, and yet later observations may show no additional damage has been done. If so, it will emphasize what we already know, that the circumstances preceding and attending a given degree of cold are important factors in the amount of damage (at least to buds); also that a plant of proven hardiness may for some reason be slow in becoming dormant in the fall and sustain more damage than one rated more tender but "smart" enough to become dormant in time.