Wednesday, May 22, 2013

Beat Black Spot; Crown Your Roses

          Right now is prime time to crown your roses.  To get rid of black spot for the summer and make them grow their best, they must be cut to the crown, the solid knotty base below the stems and above the roots, and allowed to grow fresh canes. 
A Betty Boop rose, crowned mid-summer and blooming heavily in September

Cutting them off a foot high, the conventional way to treat roses in mid winter or early spring, leaves black spots on the stems and keeps the infection going.  The same goes for taking the old leaves off as the new leaves start to grow in; the new growth will be spotty before the new roses bloom. 
This applies mainly to tea roses that are not climbers.  Climbers bloom on second-year wood, and you will lose a year of bloom, but you can cut individual canes after they bloom.  Rosa rugosa doesn’t get black spot or molds, but should be crowned and allowed to regrow when it gets too large.
Josephine County, with its mild, wet winters and cool, rainy springs, is a hot-bed for black spot and other fungal diseases.  In Grants Pass, with many roses neglected entirely, photinias spreading the same diseases, and a city-owned pear orchard that was neglected for years and is in the process of being cleared, they are epidemic.
One can crown a rose anytime, and I have been doing so as soon as I saw black spot or mold for the last few years.  I have even crowned them in late fall and midwinter, but that slows re-growth in spring, as the plants get no warmth from the air and must wait another month or two for the soil to warm.  So this year, I crowned them after they broke dormancy and started to grow in early spring, which comes earlier here than most places at this latitude, in mid-February.  Some are already re-growing, only two weeks later.

Joan's rose, about two months after a February crowning
Cutting to the crown means cutting each cane to its base.  Roses hate any kind of dead wood, which blocks new sprouts, and branches that grow from stubs do not grow as well as a cane from the crown.
Crowning roses sometimes means going underground, when they are planted too deep or sink into rotting organic matter, like a stump.  The latter happened to one of my dad’s roses, which I had been cutting only to the ground for several years; it kept growing back smaller and more spindly from such treatment, as its stems were growing from underground stubs, not the crown. 
This year, I was determined to cut all roses to the crown, and dug to find it.  The top of the crown was a good 8 inches below ground, and it went a foot deeper, with thick “arms” reaching for the surface as the years went by, and roots reaching up around it.  Not wanting to dig that far every year, I dug it out and planted it with the crown above ground.  It should live; roses are tough.  (It didn't.  That's all right; roses are cheap.)
You can’t hurt a rose by cutting it, just by not cutting it sufficiently.  Go all the way to the crown for best re-growth and to beat the black spot.  Do it as the new leaves grow in early spring, and you can have clean, pretty roses all summer.  If you don’t, you can do it again as soon as black spot or mildew shows up.  The tea rose is a royal pain; it needs to be crowned.

Rycke Brown, Natural Gardener    541-955-9040

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