When I first started to garden, I understood the design and planting techniques very well. I hadn't really thought about maintenance too much until after I planted my first garden area and realized that maintenance is a very real part of gardening. If you don't like to maintain what you've done, don't garden. Design and planting take just a small amount of time, but maintenance takes a lifetime.
Maintenance is usually composed of simple tasks:
How Much Rain? - The most important step in establishing plants is that they receive adequate water. According to what I've read on the subject, plants need one inch of rain and/or water each week to live and prosper. I feel this statement is a generalization as some plants such as Gaura, Artemesia, and many herbs, prefer dry soil conditions and therefore need less than the one-inch-a-week requirement. Azaleas, rhododendrons, and other broad-leaf evergreens probably do need one inch each week. Other plants need wet or boggy soil, such as Caltha palustris or Marsh Marigold and might need even more rain than that. So, if you have a plant that likes drier soil, such as a sedum, give it only half the amount listed below.
Watering Established Plants - A rain gauge is an essential garden tool for plant establishment. Keep a record of rainfall in your garden journal or on a calendar. If there hasn't been one inch of rainfall for the past week then water your newly-planted plants. From experience I know that the plants at the top of hills, slopes, and berms will definitely require close water monitoring as the plants at the top dry out fast. For plants located on level ground or at the lower levels of a hill or slope, check the soil to see if it's moist or dry. Feel the soil under the mulch; moist soil usually feels sticky and some soil might stick to the fingers. If the soil is moist don't water yet. If it feels dry, water the plant at the water levels listed below.
If any two-year old plants include moisture lovers such as azaleas, astilbes, or garden phlox, then they are watered as well. All three-year old plantings should be established by now and are on their own and not watered except during droughts.
If the weather is hot and windy the new plants may have to be watered more often. If it is windy, the plants may need their leaves misted in between weekly waterings. If the weather is cloudy and cool, the plants may not need as much water.How much water should each plant receive?
For each week there is no rain, the same procedure should be followed for the new plants. This regular watering schedule helps the new plants to produce new roots and grow healthy and strong. Continue this schedule for two years after planting. After the second year, you have an established plant.
Watering after Establishment - After the second growing season, your plants should be well established and should be able to fend for themselves for the first four weeks with no rain. After no rain for four weeks, start watering your plant by thoroughly soaking deeply on a weekly, semi-weekly, or monthly basis, depending on their age and soil moisture requirements.
I don't water plants during the winter, but some experts suggest that all plants should be checked during warm spells during the winter and watered if the soil is dry.
As you can see it is very important to know your plants' soil and light requirements so that you can site them properly and take care of them properly during the establishment period and beyond.
If you have extensive garden areas, perhaps it would be best to hire a landscape maintenance contractor to help you with maintenance.
Unlike watering, normally, trees and shrubs do not need to be fertilized at planting time or on a continuing basis. See the Maryland Extension's information from their Home and Garden Information Center on Fertilizing Trees and Shrubs for specific information.
Some years ago I read an article by Francis R. Gouin, Professor Emeritus, University of Maryland College Park, concerning the need for fertilizing azaleas in the fall. According to Dr. Gouin, azaleas that lose most of their lower leaves in the fall and winter except the leaves at the stem tip surrounding the flower buds are starving for nitrogen. To keep the lower leaves on the azaleas, he suggests fertilizing the azaleas in the fall after the first hard frost. He says that this late fertilization helps to produce bigger blooms and longer shoot growth next spring, and improves winter hardiness. I read many years ago that when azaleas lose their lower leaves, they need more fertilizer. Since then, I feed my azaleas throughout the spring and into the summer. This is the first time I've read that fall fertilization helps too and I'm definitely going to fertilize my azaleas this fall and watch for improved performance in the spring.