As the others have said, continual link building and constant effort will continue to build your strength. Have you analyzed where your competitors are getting links from? build relationships with local businesses and ask them to link to you.
Also... Think Long-Tail Keywords
My company is primarily a window replacement business. We have the unfortunate situation of being up against major players with huge bankrolls for SEO and advertising. How to compete?
Well, instead of focusing primarily on the major keyword of "landscaping". Try to solve some other issues that may lead into larger jobs.
Examples:
Bed Weeding newcastle, Tree/Shrub Pruning newcastle, mulching newcastle, edging, lawn care, mowing, ect....
Use your blog to create some Tips & How-To's, optimize those blog entries for the long tail keywords and soon enough your blog will be the gateway into your website.
Learn how to target longl-tail keyword searches and how to analyze keyword competition to find the right niche blog posts to create.
Also, don't forget your standard offline marketing practices. As more people gravitate towards SEO it does leave open some traditional ways of getting business.
Also, I would run some PPC campaigns using a platform like unbounce or lander
Good Luck!