Friday, April 6, 2012

You Can Grow That! for April

Check out all these great blog posts in the You Can Grow That! site for April! This is an informal project of writers, bloggers, independent garden center owners, and other garden enthusiasts.

Wednesday, April 4, 2012

Rosa banksiae, the Lady Banks Rose: You Can Grow That!

Walking the dogs down the county road at sunset, my son and I came to a stop to identify the fragrance that had suddenly surrounded us. If you’ve been to the county fair, you know the smell of cotton candy. If you had a grandmother that used violet water, you know that faint sweet scent. Put them together, and that was the invisible cloud we had just entered.
“What is that?” he asked.
“The Banks rose in the back yard,” I replied.
“But,” he said.
Yes, I know. The back yard is over five hundred yards away.

Many plants create compounds that volatilize under certain conditions; heat brings out the fragrance of lavender, Brugmansia and Cestrum nocturnum are only fragrant after dark. And many, like the Lady Banks rose, release their aroma at twilight.
You Can Grow That? Pretty much anyone, if living within the hardiness zones, can grow Rosa banksia. If they have enough room.

This is one unusual rose. No thorns. Evergreen. And it only blooms for about three weeks each year. But for those weeks the small blossoms are so abundant you can’t even see the foliage. It climbs by arching and clambering up, over fences, up into trees.
A single plant can cover thirty to forty feet of fence (mine does), or fully engulf a tree. In fact, the largest rose in the world is the Rosa banksia in Tombstone, Arizona, which covers over 8,000 square feet. But it can be pruned. One of my favorite examples is a specimen in downtown Davis (CA), across from Union Bank, which has been trained as a “tree” on two stakes, and has been severely pruned that way for as long as I can remember. It is being kept at about eight feet tall and broad!

The Sunset Western Garden Book tells us that it grows in Sunset Zones 4 – 34, and both zones in Hawai’i. In USDA parlance, that apparently equates to Zone 7a. So here in the Sacramento Valley (Sunset 8, 9 and 14; USDA 9) it is perfectly hardy.

There are three cultivars that I’ve seen, only two of which are in the trade, and not many wholesale growers produce the Lady Banks rose. You may have to search a bit for it.

Rosa banksiae ‘Alba’ is the white, double-flowered form. Flowers are showy, but fragrance is light (some might prefer that).

R. b. ‘Lutea’ has pale yellow, double flowers. It is more fragrant, and less common.

I have the white single-petaled cultivar, R. banksia normalis, which some references say “is believed to be the original wild form.” It is most fragrant of all, and very uncommon in the nursery trade. I got mine at a swap meet of heirloom rose growers in the 1980’s.

Note: a supposed variety called Snowflake has been in the trade for a couple of decades. It is a hybrid with another species, and is easily recognized by the thorns. True Lady Banks rose is thornless. The bloom habit is less abundant, but over a longer period, and it is not fragrant. If you’re expecting the profusion of Lady Banks, you’ll be disappointed. And the thorns are especially nasty.

For more on the Tombstone Rose:

You Can Grow That! is a grass-roots project of independent garden centers, garden bloggers and writers, and other plant professionals!

Monday, April 2, 2012

Bees and systemics: the smoking gun

Two new studies implicate systemics in bee problems
"Field Research on Bees Raises Concern About Low-Dose Pesticides
Erik Stokstad
Five years ago, bees made headlines when a mysterious condition called colony collapse disorder decimated honey bee colonies in parts of the United States. Now bees are poised to be in the news again, this time because of evidence that systemic insecticides, a common way to protect crops, indirectly harm these important pollinators. Two field studies reported online this week in Science document problems. In bumble bees, exposure to one such chemical leads to a dramatic loss of queens and could help explain the insects' decline. In honey bees, another insecticide interferes with the foragers' ability to find their way back to the hive. Researchers say these findings are cause for concern and will increase pressure to improve pesticide testing and regulation."

Don't apply systemic insecticides such as imidacloprid (Merit) to plants that are visited by bees.