The pot experiment was to determine the possibility of using tall wheatgrass Agropyron elongatum L. 'Bamar' on the growing substrates with sewage sludge and halloysite for degraded land reclamation. This article analyzes the impact of differentiated growing substrates on the phytostabilisation/phytoremediation processes of heavy metals: Cr, Cu, Cd, Zn, and Pb. They involved experimental variants of growing substrates with differentiated addition of halloysite, i.e. 10%, 30%, 50%, and 25%. The reference material was constituted by two control cultivations with growing substrates consisting of sewage sludge and river sand with sewage sludge. The pot experiment results indicated that halloysite had, by improving the growing substrate mechanical parameters, a positive impact on the test plant’s growth rate, which was characterized with lesser variability in the germination level and faster growth rate. Halloysite led to the reduction of soil acidity in relation to the control cultivation substrates, which allows for using this clay mineral as an addition to the growing substrates based on sewage sludge. After two experimental cycles, the studies showed that the growing substrates were characterized with lower heavy metal values than those initial ones recorded for sewage sludge. The addition of halloysite differentiated the phytochemical accumulation of heavy metals in biomass. This gives vast possibilities to shape directions of land reclamation processes and provides the base for field works allowing for the full recognition of the impact of halloysite on the phytostabilisation and phytoextraction of heavy metals.