Here’s the thing. There’s a stump where the new deck post should be, and you’re unwilling to redesign the deck and live with the stump. Well then, cottager, you have three options to get rid of it: A) a rental grinding machine (noisy and potentially dangerous); B) a chemical kick-start to natural decomposition (slow); or C) the manual labour of digging it out (arduous).
A. Grind it out
Noisy, risky, and fast
Rent a small stump grinder (picture a Rototiller with a circ-saw blade) to quickly make mulch of stumps 6″ to 12″ across. Anything bigger will need a large self- propelled machine. These babies spin a massive toothed blade and are tricky to use on sloping or uneven ground. The large grinders are rare in rental yards, so you’ll probably have to hire a pro; even if you could find the machine, a pro would have the stump gone before you could finish the safety check.
B. Induce rot
Slow but easy
A closely cut stump will rot away, eventually. You can speed the process by encouraging fungal growth; just don’t expect your stump to turn to mush by next spring. Drill deep holes into the top of the stump with a 3⁄4″ auger or spade bit. Pour in some nitrogen-rich fertilizer, and top up with water. (Look for a high first number and low second and third numbers on the label: a 30-0-3 lawn fertilizer is ideal.) Cover the stump with mulch or dirt and keep it damp. Rotting out a stump does carry a risk: unfriendly fungi could take hold, jeopardizing healthy trees nearby.
Commercial stump-removal products (difficult to get in Canada because the chemicals can be used in explosives) often recommend burning out a stump after treatment, but the underground fire will smoulder for days, and your neighbours won’t appreciate the noise of circling water bombers when it gets out of hand.
C. Remove it by hand
If you’re not fitness challenged or you have some under-motivated teenagers to occupy, you can remove a stump with muscle power. Begin by digging out as much of the soil as possible with a spade and a pick—a narrow drain spade gets right in between roots. Cut small roots with a bucksaw, but for anything larger, you’ll probably need a chainsaw. But first, blast the roots with a pressure washer to knock off dirt and rocks; you’ll save the chain and keep projectiles from smashing your windows. Don’t forget to scrub the under-side of the roots.
If you left your ox team in the city, some heavy-duty webbing or tow line and a come-along secured to another tree can pull out a stump, once you’ve severed the roots. Try some basic physics too: because a long lever multiplies force, you may be able to shift a massive stump with a log and a fulcrum. You can even gain leverage if you can get a jack, supported by a stout piece of lumber, under the stump. Just don’t cut any part of the stump while it’s under tension—the backlash is dangerous.