InstaPlant manager Chris Harnett said: "A lot of people want to do something, but if it's to be for April they will have to get their skates on. There's a bit of hype around it."
He said designs used the official silver "C" on top of a gold "W" logo, which avoided the bedding reading as WC. Buckingham Palace has said the princess-to-be should be referred to as Catherine.
Kernock will produce the William and Catherine carpet bed in the nursery in May and install it in Stanley Park in Blackpool in early June, using bedding plants such as Alternanthera dentata, Echeveria elegans, Pyrethrum 'Golden Moss' and Helichrysum italicum 'Korma'.
Business development manager Mark Taylor said another big UK event, the 2012 Olympic Games, could be a missed opportunity because only sponsors were allowed to use the Olympic ring as a logo.
He said: "It's galling. They say the Olympics is going to bring business to the UK, but I don't think that carries through for businesses to make the most of the opportunity." A London 2012 Organising Committee representative said anyone using the ring logo who was not a sponsor would be prosecuted.
Taylor added that the Olympic Development Authority was finalising small planting at the London Olympic village but bedding had yet to be mentioned.
"Display planting has not been done yet with herbaceous and bedding. If they are not going to put bedding in it doesn't bode well for the bedding industry," he said. "We should be hearing about the Olympics now. People should be producing now ready for planting. Lists need to come out soon.
"The Olympics is a shrub planting area and I can't believe it will be covered in shrubs. There's not that much cotoneaster in the country."