i used to use one ... maybe 2.5 to 3 incher ... 12 or 18 inches deep ...

it worked just fine in my arable soil ... read that.. fluffy soil ... no clue if it would work in gooey or clay soils ...

success might depend on the battery life of your portable drill ... or in the alternative.. how much extension cord do you have ... it might help if you had a second battery ...

and to be clear.. i was never planting hundreds or thousands of bulbs ....

ken

oh .. and i recall .. you might want to adjust the drive.. so it just goes thru soil .. but if it hits a root ... the clutch triggers ... i know what i am trying to say.. not sure those words mean what i mean .. lol ...

you dont want to burn up your drill if you hit something underground ...

and i didnt have rocky soil ... i presume the same issue ... immovable object meets rotating drill bit ... rock/root wins

ken

Quite a few years ago, I tried the drill-auger idea, and learned that it isn't for me. I tend to not plant bulbs one at a time -- so I dig out an area at least a foot wide and plant several bulbs (mainly daffodils) in a grouping. Far easier IMO and gives a nice, fuller effect in bloom.

I don’t have the right type of soil. Mine is sandy and just falls back into the hole.

I have in fact planted hundreds of thousands of bulbs, of all sizes at depths to 12 inches. I believe the best method is a sharpened spade and good footwear (steel shank boots are best but not so easy to find in women’s sizes) Carry bulbs in a apron. Jam your spade in the ground, using foot to push in deeper if necessary, and push handle forward. Drop bulb in opening wedge and release. Stomp and continue.

I tried the bulb auger many years ago in the heavy clay (but not rocky) soil in the front garden. It worked OK to get the bulbs deep. To save work, I put the tulip bulb 12” down, added soil back, and then added one or more smaller bulbs that only need to be a few inches deep, and then filled in the rest of the hole with the soil. To plant the small bulbs we have in the side of the ditch, we used the spade wedge approach kitasei2 described. That is very efficient for small bulbs. Since most of the big tulips that we planted are fairly good at returning, planting the big bulbs is not something we’ve had to do in many years now. The shaft of the auger bent after a while and I have no idea where it is now or whether it would still work! My guess is that the auger needs reasonably solid, but not too heavy or too rocky, soil to work well.