Monday, March 12, 2018

Pondering Pacifica Iris and Voles

Kathleen Sayce 
January 27, 2018

It is winter, and for the coastal Pacific Northwest, this means sleeting rain with the occasional snow shower, hail shower, thunderstorm, high winds, and flooding. Bottom line:  Not a lot is getting done outside in the garden. Iris unguicularis puts up flowers every week, only to have the wind and rain smash them flat within days. 

Between rain squalls, I went out to check on Iris hartwegii australis in its planter under the eaves—and it looks quite happy. There are double the number of fans from last year—and I’m hoping for flowers. 

Iris hartwegii australis--happy in its planter under the eaves. The three main shoots of last year are replaced by more than seven this winter. 

Last summer while harvesting iris pods for the SPCNI seed exchange, I saw a vole cleaning seeds from those same pods. It squeaked and dove off. These voracious herbivores do far more damage in my garden than I had previously realized:  
 *   Native West Coast bulbs that keep disappearing? Voles. 
 *  Ditto for Crocus and Lilium. More voles. 
 *  Rainlilies, which poke leaves up one day, only to have them vanish that night? Right again, voles. 
 *  The iris seedling pots and planters that are excavated one night as the seeds are starting to germinate? Yes, voles, expletives deleted. The last probably have some help from squirrels, crows, and jays.

Hypertufa planter with wire mesh cap, and inside,
Pacifica Iris seeds, soaking up winter rain
and getting ready to germinate. 

Voles tend to leave iris flowers and fans alone, but eat seeds and seedlings. I wonder how many species I’ve lost to them? All but two areas of Crocus are gone. As are Tulipa species bulbs—vanished by the dozens. Voles leave Alliums alone, mostly, and so those are doing well, as are the toxic bulbs of Hyacinthina, scillas or bluebells, which thrive here by the thousands. 

There are many potential vole reducing strategies. Mint-oil scented granules are apparently attractive to them; they cart off any that I apply, overnight. Cats aren’t determined enough to keep voles out of flower beds, and I like to birdwatch, so outside cats would defeat that activity. Terriers are excellent rodent hunters, but their indiscriminate digging is discouraging to any gardener. Haven’t figured out how to entice weasels to nest and breed here—though the years when we had resident weasels was also an excellent period for rodent suppression. When we rebuilt my cold frame, we added mesh panels, to protect the plants inside year round, and now finally have thriving, and flowering rain lilies.

I have plotted some strategies and am implementing several:  Wire cages, castor oil based deterrents, and gravel. New lilies went into wire mesh boxes underground, surrounded and capped by inches of gravel. Same for Crocus, Triteliaea, Dichlostemma, and other tasty bulbs and seeds. Pacifica Iris seeds are in hypertufa and stryofoam planters, with wire mesh caps. Over all garden beds, I am spreading castor oil mole-and-vole-deterring granules. 

Vole-resistance:  wire mesh box to bury in ground, and plant edible bulbs inside. For more deterrence, add a layer of gravel on top. 

The potential is what all gardeners want—better odds for a more floriferous garden in coming seasons. We’ll learn how these strategies work in a few months. 

The vole hazard here is probably due to location, which is next to a salt marsh in a temperate climate. Several vole species live in the marshes, and breed from March to October. The loss of even one key predator in a specific area means that voles can breed more quickly. Also, populations tend to peak every three to five years, thus my garden was overrun this year.  


  1. For me they eat flowers and leaves of iris.

    1. Which irises do they eat? and where is your garden located?

  2. I definitely comply with some points that you just have mentioned on this post. I appreciate that you just have shared some reliable recommendations on this review.

  3. Nice post, things explained in details. Thank You.

  4. Thanks for the comments. I wonder if voles are like deer--some deterrents work in some areas, and not in others.