By and large, most trees, shrubs and groundcovers do best when planted in autumn, as well. The chief exceptions to the rule are subtropical plants, like citrus and bougainvillea – these need warm weather to grow. Plant them in fall, and they’ll sulk though winter. One advantage of fall planting is that the soil is still warm from summer, so roots begin growing immediately. 2  The later in fall you wait to plant, the cooler the soil will be, and you’ll lose that advantage.