Growing substrates are used to provide physical support, as reservoir for water and nutrients, for providing air space for free gas exchange, and also for providing a habitat for beneficial microorganisms. Peat- and coir-based substrates and rockwool are the most commonly used substrates in modern advanced greenhouse operations. This chapter examines the materials commonly used in forming growing substrates and addresses methods and technologies for assessing them. The chapter looks at the use of beneficial microorganisms to create a resilient rootzone and considers the implementation of integrated rootzone management (IRM). Finally, the chapter looks ahead to future trends in this area and provides detailed guidance on further reading.