Ask Mr. Smarty Plants

Mr. Smarty Plants was bemused by how you planned to use newspaper in your pruning project then realized that you must intend to read it while letting someone else tackle that monster.  Good plan!

Some would wonder why you would need heavy leather gloves to work on a famously thornless species of cactus.  However, you are very wise to use them since Opuntia ellisiana  (Spineless prickly pear) which has no large thorns, is studded with glochids, tiny, nearly invisible thorns which hurt like the dickens and are very difficult to extract from the skin.

The first question you should answer is, "Can I prune this plant in such a way as to provide for the public's safe passage without pemanently ruining the appearance or health of the plant?"  If the answer is no, then your only real option is to move or remove the cactus.  We are often asked about a similar problem regarding yuccas planted too close to walks that have grown and begun attacking innoccent passers-by.  For overgrown yuccas the answer is invariably, "Remove the offending plant."  In this case, you may well be able to prune your sprawling prickly pear.  In time, the plant is very likely to put on new growth on the pruned side of the cactus which will soften and somewhat balance its wounded appearance.  Pruning a large side branch is unlikely to cause the whole plant to topple, though.  You're probably safe in regard to that concern.

Prickly pear pruning is a relatively simple if not slightly hazardous task.  Prickly pear pads are full of water and are very heavy.  So first, remove some of the overhanging vegetation by sawing or simply breaking off some of the pads.  These can be dried for a week or two and new plants started elsewhere.  Once you've removed much of the existing weight of the material to be pruned, make a cut of the main stem a few inches above where you intend to make your final cut.  This is the same technique used on tree limb pruning and you're doing it for the same reason, to avoid stem-splitting at your final cut.  The smoother your final cut, the less likely pathogens will find their way into the open wound and infect the plant.