Why is spirea acting more like ground cover

Question: Good morning,
I have 2 spireas, with yellowish fluorescent leaves and magenta flowers that for some reason died back and have never returned to their 19-24" height. They look healthy but as you can see in the picture they are not more than 5- high and leaves are proportionately smaller.  I would like to try to save them. Help! 

Thank you,

responder: Haley K, UVM Extension Master Gardener Volunteer  Replied May 05, 2023, 12:08 PM EDT
response: Hi Susan, Thanks for reaching out to UVM Extension Master Gardener Helpline. As a deciduous shrub spirea do “die back” aka loose their leaves and enter a dormant period. I’m not sure why they have not grown back to their previous height. In general, if plants are not thriving, it is because they are not getting enough of something or sometimes getting too much. This could be not getting enough sun, over watering, under watering, indirect damage/trauma to roots, lack of appropriate pruning, over mulching etc. From the picture you provided, another expert was wondering about the location too -- these spirea like rich, well-drained soils and full sun. I'm curious if they might be located in the drip zone of the house (I see brick in the background) or getting too much shade? Also, I wonder if/how they have pruned their spirea in the past. To my eyes, it looks like they are heavily mulched and I wonder if it might help to clear away/minimize the mulch that is in direct contact with the plant. Determining what may have caused the decline in the first place, may help determine how it needs to be rectified. Are there any other observations, other than the height, that could give clues as to a potential problem? It could be helpful to fill out the diagnostic worksheet and provide the history of the plants (i.e. how long have they had them, any fertilization they've used, water exposure, sun exposure, any pruning, etc.)  I’ve attached a few resources about Spirea and care. Perhaps after reviewing them, you may get a better idea of what's going on or what you’d like to try to encourage growth. https://hgic.clemson.edu/factsheet/spirea/ https://www.gardeningwithcharlie.com/grow-care-for-spirea/ https://ag.umass.edu/home-lawn-garden/fact-sheets/pruning-shrubs

responder: The Question Asker Replied May 05, 2023, 4:51 PM EDT
response: Hi Haley, Thank you so much for the extensive information. This spirea is in well drained soil, and is on south side of Winooski City Hall, it does not receive supplemental watering. It is beyond the drip zone towards the middle of the garden.I asked Horsfords and they wondered if maybe it needed phosphorus? Sue O’BrienSent from my iPhone On May 5, 2023, at 12:08 PM, Ask Extension <<personal data hidden>> wrote:﻿

responder: An Ask Extension Expert Replied May 08, 2023, 10:43 AM EDT
response: Hi Sue: It's possible. The only way to check the phosphorous level as well as other nutrients is to have the soil tested. You can do that here .  Lisa

responder: The Question Asker Replied May 08, 2023, 1:35 PM EDT
response: Thank you!Sue Sent from my iPhone On May 8, 2023, at 10:43 AM, University of Vermont <<personal data hidden>> wrote:﻿