Berberis Flowering

Timing of Berberis Flowering in Hays County

by Bob Harms email-here

The flowering of B. trifoliolata (BETR), B. swaseyi (BESW) and hybrid (BESxT) bushes was recorded twice a week from mid February to the end of April, when flowering had ceased on all plants (not just those in the selected sample). Initially, in 2004, a sampling of 20 bushes for each of BETR and BESW was selected, plus 7 bushes that seemed to have one or more characteristics indicative of hybridization. Each potential hybrid had more than three leaflets; most had sessile terminal leaflets. With one exception, a potential hybrid, the plants were evenly distributed along a half-mile route of bottomland, primarily along the edges of oak groves. In the case of hybrids both BETR and BESW plants in their immediate vicinity were selected.

The initial sets were modified as the survey progressed. In 2005 the survey sample had grown to 30 B. trifoliolata plants and 13 blooming hybrids. Although the number of blooming B. swaseyi plants in 2005 remained 20, not all plants of the original 20 bloomed. In 2006 the number of blooming hybrids was 17.

Apparent insect damage led to the loss of all buds from two BESW, so these were replaced by two other plants.
The discovery of two new hybrids led to the inclusion of additional BESW and BETR bushes in their immediate vicinity.
Two of the initial set of hybrids were deemed to be BESW (or at least primarily BESW) and their results were included with the BESW set.
Several plants were added to the BETR set because of floral characteristics not typical of BETR in general.
One BESW bush with unusually late blooms was included.

Also recorded during this period and continuing into the beginning of July were stages of development for buds, leaves, shoots, and ovaries (following anthesis), stages of infructescence, and secondary growth of shoots and buds in early July.

Chart 1 shows the percentages of plants of each set that had at least one flower at the given date. The 2005 results are shown with dotted lines. Chart 2 plots the bloom periods for all three years.

Chart 1

Chart 2: Blooming Periods 2002 — 2006

In 2004 there was roughly a half week of overlap in bloom times for B. trifoliolata and B. swaseyi — March 25-27. Although the winter-to-spring weather was different in 2004 & 2005, it did not seem to play a role in the initial bloom times for either species. By contrast the bloom period for both species was lengthened by roughly a week in 2005, giving an increased period of overlap — March 26-April 2.

But in 2006, an exceptionally warm, sunny and dry winter led to early onset of blooms for both species, but especially for B. swaseyi — resulting in a three week period of overlap, March 8-March 30. And several B. swaseyi bushes had flowers during the peak bloom period for B. trifoliolata. The overlap would probably have been even greater, but the severe drought of early 2006 cut short the bloom period of B. trifoliolata, as all but the first few buds of an inflorescence aborted.

Aborted (dried) buds of B. trifoliolata on March 5, 2006, following successful initial blooms. (Note the green ovaries.)

In all three years the peak bloom times for the hybrids were intermediate between those of the two species. The earlier blooming range for the hybrids in 2005 and 2006 reflects the discovery of early blooming hybrids, which were added to the survey.

Chart 3 shows periods of peak blooming in 2004 — the point at which a bush was judged to be in full flower. For some bushes this stage extended over several dates.

Chart 3