I am in zone 5, in Kingston, ON. 4 years ago I planted 2 astilbes on either side of a purpleleaf sandcherry tree. It turned out that one of the astilbes was actually an aruncus! It is beautiful, but way too big right beside the tree. I need to dig it out, as it is too close, and is crowding out the other plants. It is very out of place, as you can imagine. My question is, based on the information online, the aruncus is hard to dig out, and will sulk for years if moved. Could you give me any advice? Any help would be appreciated. Thank you.
Sounds like you’re between an Aruncus and a hard place. It will either sulk when moved, or the plants around it will sulk if it stays. If it’s in the wrong spot, diving in and transplanting it to a better area seems the best alternative – or you could transplant something else to give it room. To put the least stress on the plant, it’s probably best to wait to do the move when the weather cools down. Fall is an excellent time for planting or transplanting perennials.
For now, you can reduce some of the transplant stress and prepare the plant for moving by cutting a circle around a large root ball with a sharp spade, but leaving the plant in place. This would also be a good strategy for moving shrubs and small trees like your purple-leaf sandcherry. It severs a good portion of the roots but gives the plant a few weeks to recover from that first shock. Aruncus likes moist soil, so continue to water when necessary.
When the worst of the hot weather is over, choose a cloudy day and finish digging up your plant. Some roots might have continued to grow horizontally, and with soil settling it’s likely you’ll have to recut your original circle. The idea is to take as large a root mass as possible.
Prepare your new bed with the size of this root ball in mind, adding a few inches on all sides. Replant at the same depth (so the soil surface at the top of the root ball is level with – or no higher than – the new planting area). Water well and top with a layer of compost or mulch. Keep an eye on moisture levels, in case we have one of our unpredictable autumn hot spells.
Easy does it, taking it in stages, is the overall message. Hope this helps, and that you and your Aruncus continue to have a long and happy relationship.