The last few nights brought some hard frosts to Wellfield, accelerating the process of leaf senescence in the herbaceous layer. Hostas, which were showing color a few days ago, (a sure sign senescence is well under way) begin to droop quickly as frost crystals rip through cell structures.
The question becomes what should I cut down and when (I wrote an article previously on this topic in broader terms). The temptation might be to clear cut the whole bed and be done with it, however there are a number of plants you will want to leave standing.
Late summer and fall blooming species, such as mums and asters, need to recover some energy after spending their entire energy budget on flowering. Leave them standing at least until the entire stem and leaf system has shriveled up. I tend to leave this material up all winter both for some winter interest, but also to protect the crown of the plant. You could also cut them back on a warm winter day when cabin fever drives you out of doors.
The other category I leave alone until spring are any self seeding plants I want to encourage to drop their load for another go around. I have a stand of Ageratum which has reseeded itself over the past four seasons because I allow it to distribute seed.
Now that you have the answer, cut, slash and burn something – the latter, at your own risk; Wellfield does not condone the slashing and burning of anything! Next time you visit the Gardens, see what plants you can identify that we’ve left alone for winter interest.
Josh Steffen, Horticulture and Facilities Manager