Mortality within 6 months of planting can be as a result of one of the following: Compost was used at planting and contained nutrients (nitrate and phosphate) which Proteaceae are sensitive to. Compost usually also has a high pH. Most commercially available composts are fairly high in nutrients.  Try to find acid compost or rather not use any. Plants were not watered regularly during the first few months to make sure that they establish their roots well into the soil.  The medium that that plants are grown in should never be allowed to dry out.  The stems of the plants were physically damaged, either by hoeing around the bases of the plants or by weed eater.  Once there is a wound in the stem at ground level, soil borne pathogens can easily enter and kill the plants.  In a very windy area or in a stony soil the plants were not firmed into the soil well enough, rocking/moving of stems may cause wounds. Root disturbance such as weeding, shovelling or walking too closely next to the plant can cause root damage and the plant may die.