Friday, January 22, 2016

Crown your Roses to beat Black Spot

Betty Boop, October 2014, after being crowned in the spring.  Note the black spot starting at the base.  This rose is nearly thornless on young parts, and blooms all summer into late fall.

Roses are starting to break bud and grow leaves, so it is time to crown them, to stop black spot fungus from taking them over and making them pretty flowers on an ugly bush.  The spots are on the stems, and they infect the leaves after they mature.  Removing all the stems, down to the crown, the hard knot of wood from which both roots and stems grow, takes all the fungus off the plant and stops black spot from showing up until late fall.

2016 Betty Boop rose, ready to crown.  Note the purple new growth.  It never quite stopped growing this winter.  

You do not want to crown them in late fall or in winter before bud break, or they won’t grow until months later, as they then feel only the temperature of the soil, and wait until the soil warms up, much later than the air does.  Once the buds swell, the plant is already growing and cannot stop; it will grow new stems and roses very quickly, though they will bloom no sooner than if you did not cut them.

Betty Boop rose buds breaking red, ready to crown.  Notice the black spots starting.


Some roses bud green.  The black spot fungus grows and spreads all winter.

Nearly all tea roses get black spot in this area, as our winters are not cold enough to kill the leave or even stop blooming.   The way we were taught to prune roses in spring in Landscape Management class was to wait until the photinia bloomed, to prevent freezing of tender new growth, and cut them down only to a foot tall, cleaning out spindly growth on what is left.  But I found that black spot took over the plant before it even bloomed, as soon as the new leaves were mature.  And roses start breaking bud before the photinia blooms, earlier in recent years, so leaf growth before that point was wasted, and blooming was delayed.


Betty Boop, cut the classic way roses are normally pruned in spring.  

Our teacher taught us that the way to bring any old, ugly shrub back to youth and beauty is to cut it to the ground.  When I applied this to roses, I found that it works for them, too; it grows back beautiful, with no black spot and great blooms. 


Betty Boop, crowned for the third year.  It was about 10 years old before the first crowning, a large, upright shrub rose; trunks 2-3 inches across, the whole crown about 8".

But cutting to the ground is not far enough if the crown is buried.  If you stop at ground level and don’t cut back to the crown, the underground stubs will grow smaller stems, sometimes several small stems that only crowd the bottom of the plant.  You have to dig down to and around the crown and cut flush with it, filling back in afterwards.  Stems that grow directly from the crown grow back thicker and longer than from stubs, often to their maximum height for that kind of rose.
If that maximum height is too tall for your taste, you can crown it again after the first flush of flowers and it will grow back half as tall and bloom again.  One can crown a rose anytime during the summer and may want to if it grows mold on new growth.  But crowning in fall can cause new growth to freeze while it’s still tender, and might kill it.

January 2016 issue, published online at GardenGrantsPass.blogspot.com  
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