West has been head of purchasing at Hillier since 2014. He was head of home and garden at Wyevale/The Garden Centre Group from 2009-13. West left soon after Marshall, when Guy Hands' Terra Firma bought the chain for £276m.
Robertson was acting chief operating officer at Wyevale/The Garden Centre Group and is now running marketing, merchandising brand guardianship and other areas at Dobbies.
Constantinou was also formerly at Wyevale. Other new recruits include Martin Andrews, a former regional manager at Wyevale who was also most recently at Hillier. He is taking a regional manager role at Dobbies. Two more regional managers and others are to be announced.
Marcus Eyles, a former colleague of Marshall's from Country Gardens, will head Dobbies' online offer. He was most recently at Hillview, until September 2016, after selling it his Garden Store group in 2014.
Pippa Hawkins will work on e-learning at Dobbies having pioneered the idea in the sector at The Garden Centre Group.
Marshall said everyone he asked to join him at Dobbies agreed immediately. He wants to recruit more experienced people from the garden centre industry.
Marshall replaced John Cleland at Dobbies this month. Marshall has been in the industry since 1980, starting at Country Gardens and including two stints at Wyevale.
See more in next issue of Horticulture Week.