You've planted a new garden or had a new landscape planting installed and your care is vital to it's success.
Mature plants (grown plants or seedlings that have been started elsewhere and by way of a pot have been transplanted to your yard) require extensive care. Imagine taking a child in his or her early development years and moving them to a new environment, they will require careful attention and care to recognize his or her needs to continue crucial development. The same goes for mature plants.
More attention than less
It's best to pay more attention than assume the plant will be fine. Make it a part of your daily routine to check on your plants the first week after planting. Not all plants leave the nursery healthy and signs or stress are likely to show in the first week after planting. Some stress can be turned around with your help.
Water Water Water
Don't worry about drowning your plants. Plants in the landscape aren't likely to drown unless they're planted in a swimming pool. When a potted plant is watered the water stays in the pot until the plant uses it or it evaporates. When a plant in the ground is watered, the water runs over and through the ground. As the soil dries the plant will need more water until it establishes new roots in its new home. There's no rule of thumb as to when a plant establishes but when you're making daily observations you will notice a plants health improve between watering.
Rain helps but is not enough
Rain water is very helpful in the early weeks of a new planting however it shouldn't be the only irrigation. Rain water will help slow the evaporation and runoff of the water from your hose but it won't be enough for the new plants. So put the rain coat on and get out there.
The First Summer
If you plant in the spring and see no visible signs of stress when you stop your watering routine the plant has established, for now... Greenhouse and nursery grown plants are used to being hooked to an automatic irrigation system. With this they have only just begun getting water and nutrients on their own. A hot dry summer may take it's toll on a new plant because of how easy it's life has been thus far. If you see signs of stress you may need to water at any time in it's first year.
Be careful not to over fertilize in the first season. Use a slow release fertilizer or starter fertilizer. Root growth is the number one priority and most fertilizers will encourage foliage in exchange for root growth. If this happens, the plant may not winter well or make it through a dry season.
Resist the urge to prune in the first season. Remove any dead branches or foliage and cut back old flowers. Pruning can cause unnecessary stress to a plant and stunt growth in other ways. Be ready to prune next year when the plant shows signs of strong healthy growth.