Answer: There's really no way to kill a pine tree other than to cut it down and then have the stump and roots ground on site. Pine trees do drop needles and the needles are acidic which changes the soil's pH but it isn't really a poison. Some plants grow best in acidic soils and others prefer alkaline soils. You can plant an acid loving groundcover beneath your pine which would grow high enough to hide the needle and pine cones that drop and still look nice. Carpet bugle (ajuga), prostrate (creeping) rosemary or vinca minor are all good choices.
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