Headline figures were that RHS membership rose 20,000 to 448,977 while income was up 4.7 per cent to £76.5m. Expenditure was up 8.3 per cent to £71.1m. President Sir Nicholas Bacon said: "One of the problems with British horticulture had been its disparate nature with no consistency of approach across the various horticulture bodies. This has led to little political influence."
The action plan, launched in 2015, changed this, he added. "I am delighted to say that our director-general Sue Biggs chairs that group and things are most definitely happening."
Biggs said this is "one of the most exciting periods in the society's 212-year history" because of the £160m Strategic Investment Programme (SIP). She highlighted the fifth RHS garden, due to open in 2019 and being masterplanned by Tom Stuart-Smith as well as Christopher Bradley-Hole landscaping, a new retail front-of-house building designed by Carmody Groarke and a science building at Wisley.
Revenue expenditure on the SIP was £2.2m in 2015-16 plus £1.5m capital spend on "masterplanning, architects and consultants' fees". Largest single capital projects spent on were Harlow Carr's car park and substation (£0.8m).
Accelerated depreciation from a 50-year lifespan from 2014 of shop and plant centre buildings to be demolished at Wisley in 2019 to make way for the new buildings helped gardens expenditure increase £2.2m to £20.1m.
Staff numbers rose from 614 to 643 full-time and 184 to 207 part-time. Staff costs increased to £25.36m from £22.75m. There were seven staff paid more than £100,000 against two in 2015, with the top earner, Biggs, on £190,000-£200,000, up from £170,000-£180,000.
The RHS saw "significant growth in online plant sales" supplied by Crocus. Increased show ground rental helped lead to a 4.5 per cent increase in shows expenditure to £15.7m. Moving the science and collections department to the members and marketing departments partly contributed to a rise of £2m in costs to £4.6m for that area.
Treasurer Alistair Muirhead said: "We need to employ a significant part of both our investment researches and our future annual operating surpluses to meet an investment programme of this scale. We need to raise additional funds from donors and external funding bodies, and this will be a crucial part of our efforts in 2016."
The major risks to the society identified in the report were SIP expenditure, followed by weather causing variations in income.
An RHS representative said: "Since the formation of the leadership team, the net surplus has risen steadily from £3.1m in 2008-09 up to £9.3m in 2013-14 and £7.4m in 2014-15, and £5.3m in 2015-16. This lower number reflects the increasing investment we have previously announced including Horticulture Matters, which has increased the number of apprentices and the pay we have given to all of our horticulturally qualified professionals, and we also have more staff to deliver this major investment programme."
Meanwhile, Jekka McVicar is set to be named a new RHS vice-president at its AGM at Wisley on 27 June. Sarah Raven, James Alexander-Sinclair and Dennis Espley are set to be elected to the RHS council. Five ordinary council members - James Alexander-Sinclair, George Anderson, Dennis Espley, David Haselgrove and David Morrison - are retiring. Their places will be filled by election for a term of five years.