How thick was the mulch and how long has been in place? Like all woody plants, the majority of a hydrangea's fine feeder roots are located just below the soil surface because that's where the most nutrients are located, the bulk of the soil moisture and of course, oxygen, which is essential for root health. If the mulch is thick enough and in place for a long enough period of time, the plant's roots will grow up into it to access these essentials.

Do NOT cut them off :-) Just cover with a light layer of compost to keep them from drying out. And try not to pile on the mulch too thick - 4-6 inches is about the max. Even very light mulches like dried leaves or loose straw will compact over winter with rains and snowfall and a dense, thick mulch just presents a challenge to the plant roots to move towards the surface.

hmmmm I wonder which you have? I noticed a similar thing under a 6ft species I have. I do not mulch. The ground there is very clay ridden, so I have added much to amend it. When I moved into this house that area was all rock with HEAVY plastic keeping the rock above ground. Every few feet a hole with huge hostas grew. I found the host roots between the plastic and the soil. Now I see one of my hydrangea doing this--I do not know which one it is anymore. Perhaps this is a maple like growing habit?

I am speaking of the tall one behind the burning bush, to the right of Annebelle.

Looks like a paniculata.

I'm glad you mentioned hostas. I also have a problem with hosta roots growing on top of the ground. The basic soil is clay but has been amended with compost and sand. I don't mulch the hostas because of a problem with slugs. Every year I have had to cover these roots with more soil. The hydrangeas are large and I noticed it is the larger hostas that put out roots on top of the soil. Maybe it is frost heave - which we have plenty of after our -40 degree winters. I don't know any way to avoid this. Thank you to each of you for your thoughts on this problem.

Frost heave is an issue in some areas. There is a hosta forum and they know their stuff. Perhaps they are not planted deep enough. Clay soil is not the optimum but hosta will grow just about anywhere.

This happened to me few days a go. I was cleaning around my limelight hydrangea removing weeds and applying some fertilizer. I noticed a small superficial long root on the surface ; without knowing I cut it off thinking of weed or something like that. later i realized that these are superficial root after reading this post ! i mulched with cow manure around the plant

thanks for sharing

arcy_gw, I agree with Luis that your taller hydrangea is H. paniculata, most likely Quickfire with those lacy loose panicles.

You can do whatever you want with those roots. I've cut my surface ones back to make room for companion plants. The fact that some of these can extend 4-6' out from the main trunk is a bit obnoxious, but I don't blame the plant itself for foraging for nutrients. Just keep dumping 10-10-10 around the base and it won't need to travel far!

Interesting. My BOBO hydrangea also seems to be getting surface roots! I was a bit worried it was a disease or something.

The leaves on my limelight turn yellow with green vein. Any one else have this problem. I have tried a number of things like adding iron, compost and mulch around it but nothing helps. The tree is growing and blooming beautifully and is about twelve years old now. I also have tuns of roots on surface of the soil. Any suggestions?

Correcting iron chlorosis is a process that is slower than watching paint dry so expect to have to wait several week for improvements. I normally see leaf improvements starting in close to 2 weeks and the changes happen faster when I use liquids (iron-chelated liquid compounds) instead of granular amendments. Iron chlorosis starts with light green leaves that turn yellow or even white, all the while staying dark green around the leaf veins. But other mineral deficiencies can have similar symptoms.

If you notice no improvements after -say- two week or two and a half weeks, there may be another mineral that is low or there may be damage to the roots that produces the chlorosis. After no improvements in that time frame, I would check the roots, get a soil test/analysis done asap and add some fertilizer (which you already added this as compost) with lots of secondary minerals (other than the usual NPK) to see if that helps.

Over-watering can also sometimes trigger chlorosis when it rains a lot very quickly in places that do not drain very well. It too goes away slowly.

Unclear what the roots issue may be without a few pictures but -just a comment- some hydrangeas develop adventitious roots near the surface. I cannot see what you see but, I usually cover them with mulch and let them be (they will eventually dry out). If some pest however, is injuring the hydrangea roots then you need to cover and protect the roots and take appropriate action to identify and block the pest in your garden.

Surprising -in a good way- that the plant is growing and still blooming fine if the roots are disturbed!