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Planting new hydrangeas in early May, 2024 #867138

Asked May 05, 2024, 6:51 PM EDT

I am planting two new hydrangeas in an area where a cedar tree was taken out completely. The soil in that area is made up of several layers of bark and black mulch accumulated for over 24 years. The arborist said " this is very good rich soil that should provide an excellent place to grow plants , trees, etc." One of my questions is whether we need to amend the soil given the fact that the depth of the soil is way above the clay layer beneath it. Next, I've read that I can use Bayer Three in One as the fertilizer, used for roses when planting them. If so should I use the pellet form or the liquid, and should I apply the fertilizer in the top third of the soil, at the bottom of the soil or at the top base of the plant? Or no fertilizer at all until the next year? What is your recommendation for the fertilizer to use? Please respond prior to 5/18/24, the date for planting them.

Washington County Oregon

Expert Response

Thank you for your questions.  The organic matter in your soil seems perfect.  Hydrangeas do poorly in compacted clay soil. The following is from Ohio, but describes our soil, as well.  https://ohioline.osu.edu/factsheet/hyg-1263

I suggest that you use a fertilizer specifically designed for hydrangeas, since they are formulated to provide the correct pH.  They are available at most garden centers.  Good luck!
An Ask Extension Expert Replied May 08, 2024, 5:05 PM EDT

As you indicated in tour response to get the correct PH level P I should use a fertilizer that is designed specifically for hydrangeas. I will do so. Also I plan to augment my good soil with sand to help with the drainage. Is there a particular sandy loam I should use instead of just plain sand? Please give me an idea how I should fertilize them, amount, at the bottom and top at the time of planting or something different? Please respond before 5//18/24. Thanks.

The Question Asker Replied May 08, 2024, 8:01 PM EDT
Do not add sand!  Water and nutrients flow right through it, leaving nothing for your plants' roots to absorb.  And sand + clay = cement.  Follow package instructions for adding fertilizer.  It should be near roots, but not so concentrated that  it burns roots.  https://depts.washington.edu/hortlib/pal/planting-hydrangeas/
An Ask Extension Expert Replied May 08, 2024, 8:14 PM EDT

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