Wanganui, Mid Canterbury and West Coast all finished on 26 points but Wanganui had the highest points differential between the sides to scrape through after their 10-6 win over North Otago.
Mid Canterbury had beaten King Country 43-38 and West Coast beat Wairarapa Bush 36-26.
South Canterbury finished top four points clear after their 45-7 win over East Coast in Ruatoria and will host Wanganui next week.
Horowhenua Kapiti travelled to Westport to decide who would take second place and they beat Buller 30-26, scoring three tries to two, to claim top place and gain a home semi-final next weekend in a repeat of Saturday’s game.
In the Lochore Cup, Mid Canterbury finished top and will play Poverty Bay who beat Thames Valley 35-34, both teams finishing on 20 points.
West Coast will play North Otago in the second semi-final.
Heartland Week 8:
Buller 26 (Ellis, Ravudra tries; James Lash 2 con, 4 pen)
Horowhenua Kapiti 30 (Spencer Bishop, Scott Cameron, Willie Paia’aua tries; James So’oialo 3 con, 3 pen). HT: 12-20
East Coast 7 (Hone Haerewa try; Kris Palmer con)
South Canterbury 45 (Loni Toumohuni 3, Vatiliai Tora 2, Leone Nawalu, Glenn Sturgess tries; Willie Wright 3 con, Jared Trevathan 2 con). HT: 7-26
King Country 38 (S Wanden, Jesse Williams, Bavan Brown, Ollie Kay, Keiron Rollinson, Reece Macdonald tries; Macdonald 4 con)
Mid Canterbury 43 (Sam Finau, Willie McGoon, Tom Hanham-Carter, Angus Lindsay 2, Jarred Percival tries; Percival 5 con, pen). HT: 31-24
Thames Valley 34 (Harry Lafituanai, Josh Law, Aaron Carroll 2, Shaun Hill tries; Chris Doak 3 con, pen)
Poverty Bay 35 (Andrew Tauatevalu, Everard Reid 2, Karl McPherson, Ethine Reeves tries; Reeves 5 con). HT: 24-21
Wairarapa Bush 26 (Chris Raymond, Epeli Rayaqayaqa, Nikora Ewe, Eddie Cranston tries; Tim Priest 2 con; James Goodger con)
West Coast 36 (Brad Tauwhare 2, Troy Tauwhare, Isei Lewaqai, Logan Heath tries; Nik Cumming 2 con; Tom Reekie 2 con, pen). HT: 14-19
Wanganui 10 (Tremain Gilbert try; Nick Harding con, pen)
North Otago 6 (Josh Buchan 2 pen)