The most common landscaping mistakes are planting without a plan, ignoring mature plant size, putting the wrong plant in the wrong spot, and skipping drainage. Impulse nursery purchases produce a yard of singles that never reads as a design. A shrub labeled "grows to 8 feet" planted 2 feet from the foundation becomes a yearly pruning fight, sun-lovers sulk in shade, and zone-inappropriate plants die the first hard winter.
Drainage is the costly one: regrading and drain installation after the fact runs $2,000 to $8,000, while handling it during construction is close to free. Mulch piled against trunks and beds too narrow for the house's scale are frequent offenders too.
The cheapest fix is deciding the whole layout before buying plant one; sketch a few directions with AI landscape design first.