Don't worry about it!!! Tree peonies are very resilient, it'll recover and the stems will get woody again, just takes a couple of seasons and it'll be back better than ever. I have one that died down to the ground on its own--it actually grew back from the ground and bloomed that same spring, it's around 4' tall now and had over 40 blooms on it last spring. Just keep an eye on any of the new growth from the ground--if any of the leaves look different than the tree peony that could be a problem. Most sold tree peonies are grafted onto herbaceous roots and they can put up shoots and keep the tree peony from growing roots of its own. If you see any leaves once they start opening that look herbaceous just pinch that stem out as low as you can.

There really isn't a lot that you have to do for any peony to grow. Keep the weeds under control, they don't like a lot of root competition. Keep them from staying too wet, no boggy areas and add some soil around your tree peony if it settles, they can e planted deeper than herbaceous, it's actually better so the nurse root is less likely to sprout. You can add some organic bulb fertilizer in the spring and after blooming later in the summer if you want to but it's not really necessary. Some people use fish emulsion, others swear by adding a bit of compost every year. Anything you'd normally do to keep the soil healthy would probably be a good thing.

Hope you educated your husband on what's not weeds! My husband doesn't even go near my garden beds without me--think he's afraid I'll go Hulk on him if he were to damage anything!