Salt resistance was compared in populations of Armeria maritima (Mill.) Willd. from salt marshes and from inland sites to investigate which salt-resistance-related traits are present in all populations and which are derived traits of the salt-marsh ecotype. Plants were raised from seeds from six different populations and grown on a mixture of sand and ion-exchange resin at different salinity levels. Inland populations grew better at 40 mM NaCl than with salt-free treatment and survived several months at 200 mM NaCl, and were thus as salt-resistant as many species from brackish habitats. Salt-marsh populations were as salt-resistant as euhalophytes. Growth enhancement by NaCl was related to an increase in shoot:root d. wt ratio, which was shown not to be the result of damage to the roots. Carbon allocation to roots seemed to be reduced as a consequence of a better nutrient supply at elevated NaCl concentrations. In plants from all populations, tissue tolerance of sodium and chloride (500–1000 mmol kg−1 d. wt) was higher than that in glycophytes. Na substituted for K and to some extent Ca and Mg without growth reduction. Betaines were accumulated as cytoplasmic compatible solutes by all populations, whereas proline accumulation was not involved in adjustment to long-term salt stress. The halophytic capacity to load the xylem with Na was found in all populations of A. maritima. However, the allocation of Na to the shoot started at higher salinities in inland populations than in salt-marsh populations. This was presumably due to the Na storage capacity of roots of inland populations being higher than that of coastal populations. Nevertheless, the inland populations of A. maritima were significantly salt-tolerant as a consequence of their capacity to accumulate betaines and allocate Na to the shoot; this might have facilitated the colonization of salt marshes by the species.