Aspen trees, known botanically as Populus tremuloides, are deciduous trees common to moist forested landscapes with little disturbance. When planted in suburban or urban environs, they can take some extra care and are rarely a long-lived tree, surviving roughly 20 years, according to Colorado State University's website. Cleaning up any winter damage, fertilizing and mulching will all help the tree to perform its best over the coming spring and summer seasons.
Prune away dead or damaged twigs, branches or limbs in the early spring. Prune back to a point of healthy tissue or all the way down to the parent branch, just outside of the slightly swollen branch collar.
Clear up any clippings or debris that have accumulated on the surface of the soil and discard it, as it can be a winter breeding ground for disease and insects.
Spread a 1- to 2-inch layer of compost, well-aged manure or a combination of the two as a topdressing to feed the soil and mimic aspen' natural, forested soil conditions.
Fertilize with a slow-release or organic fertilizer product designed for acid loving plants. Don't use quick-release high nitrogen fertilizer, as this can burn the roots and spur weak and disease-prone top growth. Apply according to product label directions, keeping a foot out from the trunk and extending the fertilizer to the drip line of the tree. Water in well until the soil is drenched to a depth of at least 6 inches.
Lay down a 3-inch thick blanket of organic mulch, such as shredded bark, cocoa bean hulls or wood chips. Mulch will hold moisture in the soil, keep weeds at bay and insulate the roots from warm summer temperatures.