How would you start a garden in hard clay with groundhogs around?

You can start growing before the clay is perfect. Pick a small patch, loosen it when the ground is moist but not soggy, and work in whatever finished compost or leaf mold you can get. Adding organic matter gradually is more useful than trying to overhaul the whole yard at once. A thin mulch of leaves can help too. If you use grass clippings, make sure the lawn was not treated with herbicides and spread them in a thin layer.

Try not to dig or till clay when it is wet, since that can leave it even more compacted. A soil test is a sensible first purchase if you can manage one. Clay does not automatically need gypsum, so it is better to test before spending money on amendments. You could also try a cover crop in an unused area, then cut it down and leave the plant material on the soil.

For the groundhogs, physical exclusion is the part I’d prioritize. A little loose chicken wire may not hold up, so use sturdy welded wire mesh around a small garden area or individual beds. Bury the bottom edge or turn it outward along the ground so digging under it is harder, and make sure the gate has no easy gap. They can climb, so a low fence by itself may not be enough.

That costs more than trying another scent or spray, but it protects the plants directly. If a full enclosure is out of reach, start by fencing the crops you most want to save.

I’d keep the first season small and treat it as a trial. Grow a few things in the soil you have, and improve the beds a little each year with compost and plant residues. Some crops may do fine sooner than you expect, while others may struggle in compacted ground.

Repellents are hit or miss, and planting extra can mean accepting some losses rather than preventing them. If the burrows are leaving large holes or creating a safety problem, check local wildlife rules or ask a licensed wildlife professional about lawful options. Relocation rules vary, so don’t assume it’s allowed.