University of Idaho Arboretum & Botanical Garden

Contact Us

Arboretum

Physical Address:
1200 West Palouse River Drive

Hours:
Open everyday, dawn to dusk, free admission

Contact:
arboretum@uidaho.edu

Mailing Address:
875 Perimeter Drive MS 2281
Moscow, Idaho 83844-2281

Directions

Bulletin Board

Plant of the Month

Japanese Larch Witch’s Broom
Larix kaempferi Witch’s Broom

Location: Grid S11 – West end of the bridge at the south east corner of the upper pond

Witch’s Broom’s are deformities in woody plants that cause a shoot to form a dense mass of congested shoots. They can be caused by various things, including fungi; the parasitic plant, mistletoe; or, sometimes a genetic mutation. If they are a mutation, they can sometimes be propagated by grafting, resulting in a dwarf, shrubby form of the parent tree.

A Witch’s Broom has formed in one of the Japanese Larch in the Arboretum. I looked and decided it is not caused by mistletoe or visible fungi. Therefore, it may be a genetic mutation. The Broom is on a grafted cultivar of Japanese Larch, Larix kaempferi ‘Diana’, which is a full-sized, contorted selection.

I took cuttings (scions is the technically correct term), and sent them to three different growers in Oregon to graft. If any are successful, we will grow some on for a few years to see if they are stable. If so, it may get named, and become commercially available someday. Since the broom appears to be contorted as well, and the parent tree is named ‘Diana’, we are tentatively calling the new plant ‘Twisted Sister’.

Japanese Larch Witch’s Broom, Larix kaempferi Witch’s Broom 10-30-18

Japanese Larch Witch’s Broom, Larix kaempferi Witch’s Broom 11-26-18

Monthly Projects

December has continued the trend of remarkably mild weather in Moscow. I have only had to shovel snow on campus once so far this year—which I see as a good thing! We did get a significant rain storm this week. The weather pattern known as a Pineapple Express, since it brings warm, wet air up from Hawaii, dumped almost an inch of rain on Wednesday. As usual, when that happens the culvert at the bottom of the Arboretum gets clogged up with all the debris that accumulates in the stream bed over the summer. Fortunately, I got to it before it completely overflowed and floods the parking lot. The good news from the storm, is that the grade of the new path at the top of the Arboretum seems to work, water now flows across the main road and out onto the grass, instead of washing down the east side of the road where it used to go.

The rainy weather thawed the ground enough that I have been able to work on propagating plants for next year’s plant sale as well as get to some overdue woody plant pruning.