Assuming you don't use harsh laundry detergent or chlorine bleach in your washing machine, a laundry-to-landscape system can be an effective method of reusing greywater to water trees and plants. At its simplest, removing the discharge hose from the washing machine from the house drain, and connecting it to a longer run of hose that can reach your yard, will enable you to reuse greywater every time you do the laundry. This method has to be manually managed (or you run the risk of creating a bog in your yard from always discharging the water in the same spot) by moving the hose to a different spot with each load of laundry. Care also has to be taken to not let the water that exits the hose from gouging holes in the lawn or plant beds, which can be mitigated by building mulched greywater basins that can deal with that volume of water.
The direct method does have issues, as it could lead to burning out the washer pump, or could accidentally back-siphon dirty water into the washing machine. The ideal method of greywater reuse requires some thought, as a level of filtration or settlement, as well as a method of discharging it either below the surface or in a location where it can slowly filter through the soil without human contact, may be required. If you'd like to implement a larger-scale greywater system in your home, be sure to thoroughly evaluate your options, consult with a greywater professional, and consider investing in a system that complies with local regulations and is appropriate for your needs and your landscape.