What is the speaker mainly talking about?

For years, it’s been assumed that the indoor environment limits the variety of plants that people are exposed to. Lately, however, plants that are usually only grown outdoors have found their way into indoor spaces. The modern indoor environment can be an ideal setting for a wide variety of outdoor plants. Plants that ordinarily cannot grow in colder outdoor climates can find protection from the cold indoors, where temperatures are easily controlled. Orchids, which were once only found in tropical environments, have begun to thrive in indoor settings. One aspect of the modern home that has made exotic outdoor plants more practical is the modern use of windows. In the past windows were used less frequently in buildings. It is partly because of the ability of 1arge windows to admit large amounts of sunlight and keep the heat in at the same time, that many outdoor plants have been able to make their move inside. It is true that most of the plants that have been successful in moving indoors have been small. Some of the best-adapted varieties are the vines. Although some trees can be grown indoors, it is unlikely that larger varieties can be used. Unfortunately, most homes just don’t have the space to grow a redwood tree.