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Early and completely 'shifted' B. swaseyi – was the same in both 2004 and 2005.
Among the very green background plants are B. trifoliolata.

Maroon Shift of Berberis swaseyi Winter Leaves

by Bob Harms  email-here
A striking characteristic of most B. swaseyi bushes is their maroon winter leaf coloration. As noted by Correll & Johnston 1970 "leaflets ... turning a deep red in fall." Not noted, however, is that these same leaflets return to green with warm spring weather, starting in March.

Leaflet cross section.

During the winter months these bushes are often easily identifiable at some distance, clearly contrasting with B. trifoliolata and most hybrid plants, which remain green.


B. swaseyi (left) & B. trifoliolata

But great variation may be noted in the extent of this maroon shift. Not all leaflets are equally affected: some turn completely maroon, some only partially, generally at the outer edges. Some bushes seem unaffected. A comparison of these effects over two quite different winters (2004-5 and 2005-5) would seem to support the following variables:

  1. temperature: a hard freeze seems to be the trigger for the shift, and also a factor in the extent of the shift;
  2. moisture: 2004 had a 'wet' fall & winter; by contrast 2005 brought severe drought and a high percentage of leaflets turned bright red or yellow, then brown and were lost by late winter;
  3. exposure: bushes in deep shade generally did not exhibit this shift – but adjacent plants with the same exposure had differing degrees of color shift;
  4. maturation: recent fall leaves seemed to be unaffected;

    5. Strongly maroon plant together with B. trifoliolata. Unshaded B. swaseyi S15 remained green.
    Winter plants that were the same in both years.
  5. genetics: plants that exhibited both extremes of the maroon shift — i.e., complete strong maroon coloration and virtually no effect at all — reacted the same way in both years.

For the most part winter leaves of the hybrids maintained the same green quality as B. trifoliolata, but a few plants exhibited a somewhat limited maroon shift.

B. trifoliolata & hybrid Hybrid H9 and B. swaseyi S16
Variation in winter hybrid leaves — compared with B. trifoliolata & B. swaseyi.

The maroon shift should not be confused with the redness of new leaves, typical of both species in late summer and fall. These are a bit more red than maroon.

B. swaseyi B. trifoliolata
New leaves resulting from fall rains, Nov. 2004.

Fall/winter leaflets of both species often turn brighter red or yellow prior to falling.

B. swaseyi B. trifoliolata
Leaflets prior to abscission.