The first step in lower maintenance is proper design. If a garden is designed well, the plant material chosen will be highly compatible with the microclimates, soil types, topography, and wind exposure of the site. This means the plants will be healthy and will tend to resist or outgrow disease problems. Also, by choosing a more diverse palette of plant material, your garden will not be as vulnerable to disease attack on one species - all of your horticultural eggs will not be in one basket. Additionally, choosing a more biologically diverse planting scheme will tend to attract more beneficial insects into your garden which will attack destructive insects.
It is critical in designing your garden to carefully space the plantings according to their eventual true adult size! Overplanting is the cardinal sin of garden design and it results in the need to continually hack plants back or eventually to remove some, creating much unnecessary maintenance and green waste. It pays to research the new plant introductions carefully or to hire a professional who is well experienced with these plants because much of the literature and nursery advice you get will significantly underestimate eventual size. The cute little puppy of a plant you bring home may become the pit bull terror of your garden!
The quality of installation of your garden also affects the future ease of its maintenance. Proper soil preparation is critical for future health of plant materials. This may range from raised beds of pure organics for acid loving plants to no amendments and careful use of fertilizers for native plants. In sustainable landscaping, the emphasis is on careful attention to soils and choosing plants appropriate to that soil type rather than heavily amending a soil to make it meet the needs of preconceived plant selection. Most organic materials "burn off" quickly anyway and the soil will be back to where it started very soon: a heavy clay soil without ongoing application of mulches will resume heavy, alkaline qualities in our climate. So concentrate amending in limited areas of the garden designed to grow perennials and a small number of acid loving plants. Most shrubs and trees do not need soil amendment or amending of the planting pit.
Finally your garden has been carefully designed and professionally installed; now its up to you to see that it will be properly maintained. You should talk with the designer (and the contractor) so that you understand how the garden was laid out in terms of microclimates and watering zones, how plants should grow and fill out. What potential weed and disease problems to look out for, irrigation scheduling both for the establishment period (which lasts 1-3 months after planting) and for seasonal needs of the established garden. Ask your contractor about referrals for maintenance. You may not be able to afford to have all the maintenance done professionally but he may have on staff or know specialty maintenance people capable of coming in at critical points of the year to help you with perennial care, pest problems, sprinkler maintenance, etc.
In our busy lives we tend to resist further demands on our time and look for ways to get others to do our housecleaning, our car washing, our gardening while we speed to the gym in our car for a workout. Consider slowing down and staying put and having a more intimate relationship with your home and garden. You may find that the chores of weeding, dead heading flowers, mowing the lawn (with a hand mower) pruning etc. allow you to hang out in the garden, get exercise and put yourself in the present moment enjoying flowers, birds, butterflies, the smell of fresh mown grass. Garden maintenance might just become a form of therapy and meditation for getting out of life's fast lane.
Environmental sustainability calls upon us to become more intimately involved with how we use natural resources in our home, businesses and communities. At first glance, this seems a no win situation of either doing without or further complicating our lives but when we meet such life demands with creativity and openness interesting new possibilities arise.