The crown of a plant is where the roots join the stem. Most plants grow best when the crown is planted just at the soil level. There are plants which prefer to sit a few inches below the soil level such as the clematis and plants which prefer to be a bit above the soil as they are particularly susceptible to rot in damp conditions.
Many herbaceous perennials grow by forming multiple stems/leaves around the base (crown) of the plant. Examples of this growth habit can be seen on shasta daisies, hostas, rudbeckias and asters. Throughout the growing season and especially as we head into the fall; what’s going on at the crown tells you when to get out your clippers!
Perennials have very specific growth cycles throughout their season unlike annuals. Annuals typically are almost ready to bloom when you put them in and bloom continuously until they are replaced with new ones for the next season. As perennials live in your garden year-round they need a rest every now and then. That rest doesn’t necessarily coincide with the change of season. Throughout the spring, summer and fall periodic deadheading of the flowers and trimming back of foliage can encourage new growth and perhaps more bloom periods. This is especially true in mild winter regions like mine where perennials aren’t automatically forced into dormancy by freezing cold or snow.
New growth at the crown of herbaceous perennials is your signal that it is time to trim back existing foliage and flowers, freeing up all the plant’s energy to put on new leaves, stems and flowers. In my garden the asters are perfect examples of this principal. While traditionally a fall flowering species, my asters pop their heads up in early spring and are huge sprawling masses by mid summer. They get tired looking and sometimes a bit bug eaten and, as their growth habit is to continue to branch out layering each new flowering stem at the last set of flowers, an individual stem may be 4-6 feet long but only blooming toward the tips. Remember this photo from earlier in the year:
This single plant ends up laying all over whatever is underneath it and the huge rock behind it. I gather up the stems periodically to take a peek ant the base of the plant. When a flurry of new foliage at the crown has begun to show I know it is time to cut back the older stems, flowers and all. It is often heart wrenching! About 3 weeks ago I headed the whole plant back-clipping off each stem individually rather than just grabbing at the base and whacking (my usual M.O.) in hopes of not damaging the new basal growth. Below you see the same plant with a nice healthy basal clump and several new long flowering stems starting the whole cycle again.
The columbine at the front of the long shade bed provides another example. I am not sure I have showed you Aquilegia x cerulean ‘Origami Blue and White’ before so here’s a look at early spring:
These sweet girls not only regrow from the same crown yearly but also throw a good bit of seed so when the original plants finally die out I have plenty of others to move around! They tend toward mildew on their foliage as the fall approaches. The spent foliage will fall to one side a bit and in the upper part of the photo you can just see the new leaves emerging from the crown:
The oldest of the leaves will all pull off easily revealing the new foliage. These are early spring bloomers for me so I will not have encouraged any new flowers by removing the oldest foliage but they will be a bit tidied up while they rest.
Just like everything in nature–one size does not fit all here! Only mild to temperate winter gardeners will want to use these techniques this late in the year. Gardeners with freezing winters, with or without snow, do not want to push any new growth so close to winter and generally leave on the stems of herbaceous and woody perennials to protect the crown from rot–doing their major clean up in spring.
Our mild fall continues and a few things in the garden are thinking it is spring! I have narcissus leaves a foot tall and these fun things are blooming: