In looking at the website, I noticed the author worked and lives in the SE USA. That may be why she recommends a different pruning schedule. you can prune them back in fall, but here in Minnesota, we like the winter interest the dried flower heads provide, so we recommend waiting to prune hydrangeas in late winter / early spring. 'Annabelle' hydrangeas bloom on new wood meaning they bloom on the new seasonal growth (grows up from the base of the plant). Therefore, cut them down to the ground in early spring. This will provide the largest flowers and sturdy stems. If you want smaller flowers, cut them back to 1-2 ft. Make your cut just above a healthy bud. Here is a very good video and also an Extension article.

I disagree with your advise to "cut them to ground in Spring". I cut back to two feet last year and had disastrous results this year; they grew but all over the ground with very few blossoms and almost no branches growing upward. Your method sounds too much like that. Also, liking "to see snow on blossoms" is not a scientific basis for how to cultivate a plant. I expected more of an informed and educated, or experienced answer from this website; not casual observations. Hydrangeas are tricky; the pruning technique has to be specific to the species of plant; not just the weather of the geographic region in which they're planted (or someone's personal preference).

On Annabelle smooth hydrangea (Hydrangea arborescens 'Annabelle') flower buds are produced on new spring growth that emerges from the base of the plant - one of the reasons we prune these plants in late winter / early spring in Minnesota. Winter interest just happens to be a secondary benefit of this.

In late winter / early spring, the plant is also dormant as are pests that may infect a plant via a open pruning wound. Pruning in late winter / early spring reduces the chance for infection.

In addition, pruning in fall in Minnesota signals apical buds to open and new growth to emerge at the time of year when we want plants to move into dormancy for winter. Any new fall growth will freeze. This is why we recommend refraining from pruning trees and shrubs until they are most likely to be fully dormant (late winter / early spring).

To some level, plants also continue to phototsynthesize into the fall. Any parts of the plants that are still green will continue to create photosynthates that are stored in the root system for next year's growth. Waiting to prune in the late winter / early spring takes full advantage of this plant function.

Plants partition stored nutrients to reproduce by producing flowers and subsequently fruit / seeds. Leaving last year's growth intact will increase the stems, foliage and flowers the plant needs to support with the same amount of nutrients, resulting in smaller stems and flowers. Cutting the stems to the ground will result in the plant partitioning more of its stored carbohydrates to produce stronger, sturdier stems and larger flowers. Removing last year's stems will also increase light to the new spring growth emerging at the base of the plant.

I hope you find this answer more satisfactory. If you would like to discuss this further, you are welcome to call me at my office:<personal data hidden>

Thank you, Julie, for the well documented reply based on sound biological and scientific fact. Because of that I am persuaded by your argument that Hydrangea Annabelle is best pruned in Minnesota during the late fall/early spring season. However, pruning to the ground, endorsed in the video link you included, is somewhat shocking to me. My experience last year pruning down to the main stems, or trunks, that are 24 to 30 inches high on my four Annabelles, was a disaster. Mine were cultivated by previous owners almost like a small tree with a single trunk and most, but not all, of the seasonal stem growth originating from that truck, not from the ground, as in multiple stems shooting up directly from the ground (in your video example). That's probably why mine were 8 to 9 feet tall, practically reaching the second story windows. I liked that height but didn't like the lack of leaves and flowers on the lower 4 feet of the plant when in full bloom. So I pruned all the previous season and last year stems back to the main 'trunk'. You can see the results obtained from the pictures included that my seasonal growth was mostly isolated lower stems growing outward to great lengths, with no blooms on one plant and few on the others; instead of many stems sprouting from the trunk and growing upward as I'd planned. The plants grew vigorously but low and long, not many upward growing stems as planned. So now, pruning even that main 'trunk' to the ground sounds risky and most likely to produce more stunted and unpredictable growth, yet again. Can you assure me that won't happen if I cut that main trunk down to the ground? I feel I have already stressed the plants by heavy pruning last year and the folks at Gertens say they need a year or two to recover from that; another heavy pruning, they say, might kill the plants.

Thank you for the photos. They help a great deal. Based on our previous emails, I understand you are looking for a uniform, bushier shrub form with good blooms. Now that I see the planting site, I clearly see reasons that can be affecting your plant performance and will become issues in the future.

The size of the planting bed is really too narrow and it is overplanted. The standard Annabelle Hydrangeas can grow to a mature size and form to 5’ H x 6’ W.  The previous owner most likely pruned these shrubs like small trees to eliminate lower stems from cascading over the bedline and onto the lawn, interfering with mowing and shading out the turf. As you allow the plants to grow to their more natural form, they will most likely begin to block your utilities. By pruning these shrubs like small trees, the previous owner could access to the water spigot and meters, and the plants, for the most part, didn't block the A/C unit. (Heat blowing from the A/C can dry plants and potentially stunt growth).

The above is commonplace because people often plant for an “instant landscape” meaning they don’t space plants based on the mature size / form of the plant, resulting in plants that grow too close together, block access to utilities and structures, and create additional maintenance such as extra pruning and lawn repair.

These are things you'll want to consider as you encourage the plants to grow wider and bushier vs. upward.

Re: the lack of bloom and weak stems you mentioned in earlier emails - foundation plants are commonly shaded by the building which can also cause the plants to be less robust and could affect blooming as well. Foundation plantings also often have drier soil because of building overhangs and grading, and the soil is usually more of a construction quality. Even when topsoil is brought in, we commonly see it simply laid down over the existing soil and not properly incorporated. This can create layers that can result in poor soil conditions for plant roots. While the rock is a fine mulch to use, older plantings may have plastic underneath the rock which blocks moisture from reaching plant roots as well and hampering plant performance. Hopefully, your rock mulch has permeable landscape fabric. Just some things to look out for as you work on this area.

To answer your original question to the best of my ability and based on the information, you could cut the “trunk” to the ground and allow new stems to grow up and around it. Like Gertens, I believe the shrubs may need a season or two to recover and would only prune the other “non-trunk” new stems to about 12” this spring to give you some growth right away. You may also want to investigate the quality of the soil in this area - a soil test would be helpful if you haven't had one done in the past 3-4 years. http://soiltest.umn.edu However, be aware that as your plants grow larger and bushier, you’ll still need to do some selective pruning to keep your utilities clear of plant material, your lawn along the bedline from being shaded out, and thus you may end up reducing some blooming.

IF I were starting over with this site myself, I would renovate the bed. I would remove the rock mulch (ugh - yes I know), the edging and plants, widen the bedline to a minimum of 8 feet deep (distance from the house to the edging, and replant with fewer hydrangeas and some perennials. I attached a quick sketch to demonstrate. You could also just dig up the existing hydrangeas and replant the area with appropriately sized plants that can grow to their mature size and form without the extra maintenance and frustration. You'll want to measure the planting and choose plants that - at mature size - leave a minimum of 18" of space to access the building and space them so the plants just touch. Just some ideas …..!

Feel free to reply or call me with additional questions<personal data hidden>.

Almost forgot - here is a link to our plant selection database that may give you a place to start if and when you decide to alter your planting: http://landscapeplants.extension.umn.edu/
You'll need to create a simple account with a username and password of your choice. (Don't worry - I manage this site and do not send emails to users.)