Monday, January 25, 2016

Winter in the Garden: To trim leaves on PCIs or not?

Kathleen Sayce

A couple of years ago, I posted a comment about having used a dry sunny break in the weather to clip back iris leaves and clean up the garden. Several people reprimanded me for doing so, saying I was taking away these plants' capacity to photosynthesize in coming weeks until the new shoots came into full growth. With PCIs, sometimes that is true, and sometimes it is not. 

PCI "Clarice Richards' stays green all winter; brown leaves are tugged/clipped off in late winter or early spring. 

A storm called an Atmospheric River blew through this week; regionally these are called Pineapple Express storms, which bring warm air, high winds and heavy rain. About 11 inches fell in 3 days, ending with more than 5 inches of rain yesterday, a day so wet that salmon could just about swim in the air instead of the streams. Today the sun came out for the first time in nearly a week.

took photos in the garden of the "photosynthesis-deprived plants" that I trimmed back that fall. My focus in past years for clipping was plants that had brown leaves. Many PCIs have mixed genetic heritages from most of the species in this group, and the degree of browning, if any, varies with those genes.  
Iris innominata has almost completely browned off by mid January. With snow, it will go completely dormant.  

A typical PCI clump in the winter garden, PCI 'Finger Pointing', has a few green shoots and weeds, and a lot of brown. 

Which groups stay the greenest, and can be left alone throughout the winter?  Iris douglasiana-derived hybrids.

Iris douglasiana selections and hybrids with considerable "Doug-blood" stay green all winter long. A few brown leaves are tugged off in late winter or early spring. 

Which groups go the brownest, so that by early winter, the only green leaves are the new shoots?  Joe Ghio's hybrids, and others from his mixed species pool of gene stock. Also, Iris innominata/I. thompsonii plants go brown by midwinter.  

Ghio hybrids typically brown off by early winter. The only green to be seen is weeds, and a few tiny new shoots.

Which groups go completely dormant and lose leaves?  Iris tenax and I. hartwegii. These species' leaves vanish by midwinter. 

Iris tenax vanishes underground by midwinter. Old leaves and winter cress plants will come out when I clean up the oak leaves and spruce cones in a few weeks. 

Spring is coming! Among all the brown leaves and debris, I saw several new shoots on most of my plants. A few have died; one that I though died last fall came back with several new shoots, and the rest have those small green fans we love to see in early spring. 

Now, if the weather stays dry for a few days, I can take my annual soil sample, and start pruning and tidying the garden beds. 

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