Tuesday, January 20, 2015

Black Spot? Crown Your Roses


These were crowned in late fall 2011, blooming in June 2012

          Spring has sprung midwinter again this year, almost a month earlier than last year, which was about a month ahead of normal.  A cold snap in November gave way to a warm December, and shifted winter and spring about 6-8 weeks early for hardier plants.

Betty Boop, November 2013.  Notice the black spot beginning to show beneath.

This year, spring started by the end of December, when bitter cress and groundsel started blooming.  They and dandelions are already making seed.  Some roses started breaking bud by mid January, and I’ve started crowning them. 

Betty Boop, February 2014, ready to be crowned.  Note the red new growth sprouting all over.

To “crown” a rose is to cut it to the crown, the hard knot of wood above the roots, rather than cutting it off at the knees.  This removes all black spot fungus on the plant, which infects canes as well as leaves.  It also looks more natural and thus more beautiful than growing from cut canes, producing thick canes from the crown, rather than weaker ones from stem buds.   Crowning roses in spring can keep black spot at bay until late fall, if it shows up at all.

Betty Boop, crowned.  This year's canes were all 1 inch or less wide.

Black spot is endemic in Grants Pass because there are so many roses and our mild wet winters never let them go fully dormant.  The leaves and stems grow the fungus all year.  Outside of town, it is possible to eliminate it with hygiene; in town, it is in the air everywhere.
I used to cut rose canes to the ground or the crown, whichever was higher.  But underground canes produce small, spindly growth.  It pays to dig down around the crown and cut every cane to the hard ball of the crown.  It is easier when it was done the year before.  Sometimes, a rose can sink into the soil because of an old stump rotting away below it.  If it has sunk too far, it’s best to replace it.
A rose can be crowned at any time during the year; it’s hard to kill one by cutting it.  Crowning when it’s half-way to blooming is apt to shrink the plant, which is good when the rose wants to be 6 feet tall and you would prefer 3.  If your rose gets hit by mildew from excessively wet weather later in the year, don’t hesitate to crown and let it restart.  In warm weather, it will jump up and bloom in a month.
Crowning in late fall to mid-winter may delay regrowth in the spring by several months, as the plant feels only soil temps, which lag far behind air temperatures.
Not every rose should be completely crowned every year, only regular tea roses.  Climbers grow their flowers on two-year-old wood, so only the bloomed-out canes should be cut out, and the new canes allowed to bloom.  Rosa rugosa has heavily textured leaves that don’t get black spot, and should be crowned only when it gets too big for its space.
Revised Jan-Feb 2015 issue, online at GardenGrantsPass.blogspot.com and at the Mail Center, 305 NE 6th
Gardening is easy if you do it naturally.  Litter is tagging, marking the territory of the disorderly.

Rycke Brown, Natural Gardener          541-955-9040        rycke@gardener.com