Garden and DIY trading director Matt Compton left "to spend more time with his family" at Christmas. Kemp ran Homebase kitchens and bathrooms for five years before taking on his new role.
From March 2015 Homebase will have 2,500 plants available online for home delivery, up from a trial of a few hundred in 2014.
Horticulture category manager Andy Goddard said affordable specimens with tree ferns and olives at £100-£200 were also a focus.
He said bedding, sourced from Ivan Ambrose, Avoncross and Ornamental Plants, was still 50 per cent of plant sales, but Homebase was not following B&Q and going peat-free.
Homebase said managing director Paul Loft had yet to say when he was leaving after announcing the intention to go last year.
Goddard said Homebase's move to close a quarter (80) of stores would have a "short-term impact on initial volumes" but online will ultimately grow overall sales. Store numbers are currently 304.
Homebase will returns with an Adam Frost-designed garden at RHS Chelsea Flower Show 2015 where it is pushing its Garden Academy apprenticeship scheme and Chelsea plants collection.
Greenfingers is Homebase's chosen charity for 2015-17.
A new 'Sovereign' garden power brand is now available at Homebase and Argos. Garden power buyer is David Gillespie. There are also 17 additions to the Qualcast powered gardening range including a Key Start No Cord Pewtrol Mower.
Homebase has a new amartphone and tablet mobile app and sees more than half of online traffic coming through these devices. Siobhan Fitzpatrick is multichannel director.
David Hedges-Gower is now advising Homebase on its lawn care range. Buyer is Sarah Coldrake.