Speaking on the day of the comprehensive spending review (20 October), she said the deal was a "reasonable settlement" because Defra wanted to protect front-line services such as flood defences, animal health and biodiversity.
Kew would see its budget cut for capital and administrative expenses, but not its programmes. The final levels were still being determined, said Defra.
"I hope it will look at how it can enhance its own income," said Spelman. "It has opportunities to generate income. I don't see Kew suffering. We will continue to discuss these matters with Kew. It's a national living treasure."
On quangos she explained: "We have the largest amount of arm's-length bodies, 70. Some are quite small and of no cost to the public purse. With others, their functions have been eclipsed by what has become the department's mainstream role."
She insisted that the cuts were not an option but a must given the "biggest budget deficit in peacetime history". But an 83 per cent uptake in the higher-level stewardship scheme by growers and farmers was "clear evidence of our commitment to become the greenest government ever".
Her department must cut £700m by 2014. The overall reductions, spread across capital spending, resources spending and administration, represent almost a third of its total budget. This will result in 5,000 to 8,000 job losses from a total of 30,000.