Ramping up for Spring
It has been a WARM winter here in Northern California (Zone 9b). Where our garden beds are located, we’ve seen fewer than a week’s worth of hard frost. Additionally, our irises never really got the memo to go dormant; we have seen sporadic blooms all winter, even from our historic varieties. For us, we have a few concerns about what this means for our summer blooms, as irises do need periods of colder weather to “winterize” and produce spectacular blooms in-season.
Picture taken January 1, 2025
“Remember, “irises like wet feet, but dry knees” - maintaining good drainage in your iris beds is critical.”
We see so much variability in terms of winter care of irises, and the reality is that that is because although we can grow irises in almost every temperate climate, there is no “one-size-fits-all” advice for the best iris care in the world. What may be true in one clime could be false in another, so relying on your local gardeners may be the best source of information. Here in CA, we are fortunate to have the University of California Master Gardener Program, which comprises of university-trained volunteers who specialize in home gardening advice. “In exchange for training from the University, UC Master Gardeners offer volunteer services and outreach to the general public in more than 1,286 demonstration, community and school gardens across 53 California counties.”
When preparing this blog post, I came across this article from Tom Waters of the American Iris Society, which I highly recommend. In it, he details the history of iris domestication and how it relates to winter iris care, which I found utterly fascinating. I'll let you read it, but I wanted to bring to your attention some particular items of interest when it comes to getting irises ready for spring.
Mulching can help moderate temperature fluctuations.
I’ll agree with this. In colder climates than ours, snow acts as a particularly good insulator, to prevent against soil heaving and exposure to winter rot. In more southern climates, this may look like using grass clippings or synthetic mulches. However, like Tom mentions in the article, mulches can bring an additional problem to your perennial beds. This year, one of our nursey beds was plagued with slugs that were able to overwinter in our mulch composite. To combat this, we used an organic mixture of coffee grounds and wood ash. Slugs dislike caffeine, and the wood ash, in addition to deterring slugs, can also inhibit aphids. The wood ash has the added benefit of acting as a slow-release, low-level potassium fertilizer. For our purposes, we noticed an absence of slugs about a week after treatment.
Irrigation may be needed in dry winters.
We definitely needed to supplement the rain with irrigation this winter. Although we saw a heavy set of storms in early winter, this dried up around the new year, and it has only been recently that we have started getting rains again. Remember, irises like “wet feet, but dry knees” - maintaining good drainage in your iris beds is critical.
As we prepare for our first dig (hopefully in March) we are focusing on keeping our rhizomes as healthy and hearty as possible in order to produce plants that will bloom for years to come. We look forward to sharing them with you in the 2025 season!
- Sarah
