Buckley Design Associates in London said it has been overwhelmed by wealthy Russian, Middle-Eastern and City clients wanting luxurious projects in the capital and Surrey. These range from £40,000 to £200,000.
Owner Declan Buckley said business is "booming". He added: "The lower end of the market is much tougher because the onus on price is so strong. The quick-makeover market has been badly hit because people just don't have the spare cash, but it's not all bad for the smaller-scale designer.
"Practices targeting less urban areas have not been so badly stung as those in built-up areas because £20,000 will pay for acres of soft landscaping in rural areas. In city-centre gardens you often need costly structural work that swallows up budgets."
Bowles & Wyer partner John Wyer said competition and ever tightening budgets prompted his practice to pull out of mid-market projects between £20,000 and £80,000. What used to make up around 30 per cent of turnover now accounts for just five per cent.
"That market has been badly hit since the credit crunch, but there are tentative signs of improvements in the South East," said Wyer.
James Steele-Sargent, who runs Arun Landscapes, likened the lower end of the design market to "frontier territory" with firms "fighting for survival". Driveway and patio companies are muscling into this market, causing fierce competition.
"These companies are trying to sell metre-squares of paving and are not interested in overall design," said Steele-Sargent. "That is hitting designers, especially as clients often don't know the difference between landscapers and builders."
The higher end of the market is holding out but clients paying £300,000 for a garden are much more money-conscious, he added.
"Bad weather has slowed projects and wiped out profits of many designers. People are spending money but not as much. All we need is a drop of sunshine to make people more carefree, and we need more 'emotional sales' - people spend three times as much on design linked to children's parties, weddings or other family occasions."
Designer Ann-Marie Powell said: "We are busier than ever but we are in a minority and it's not as straightforward to earn a buck. Clients have higher aspirations for a lower budget, so we have to be careful with suppliers."