Sustainable Trees and Shrubs An Introduction to the Sustainable Plant List 1 Planting for Sustainable Landscapes 3 List of Sustainable Trees and Shrubs 8 Index of Common Names 31 Appendix 1: URI Crabapple Tree Disease Evaluations 34 Appendix 2: Tree, Shrub and Vine Selections for Demanding Situations 36 Appendix 3: Cross-reference for Demanding Situations 42 Hardiness Map of New England (USDA Plant Hardiness Zones) 49 An Introduction to the Sustainable Plant List Plant lists are invaluable resources for garden precarious balance of nature in which we play a enthusiasts, designers, nursery trades people and land- pivotal role. Many in our society are looking for ways scape architects. We constantly consult books and to reduce human impacts on the environment. nursery catalogs which list landscape plants, espe- Others lack the time or resources to manage pests or cially those that organize plants by their characteristics maintain shrubs that require frequent pruning or and landscape uses. As times and fashions change, irrigation. These people should find the sustainable new plants emerge, old plants are rediscovered, and plant list an invaluable resource. others lose favor and disappear from these lists. Careful plant selection is the key first step in devel- But one point remains clear: listing plants encourages oping a balanced and self-perpetuating landscape. their widespread distribution and use. The purpose However, plant survival with minimal maintenance is of this publication is to encourage the production not the only issue in sustainability. We are and use of landscape plants that are more sustainable: having more difficulty with invasive those which are not invasive and require reduced exotic plants which inputs of pesticides, water and maintenance. have escaped from managed land- Why Sustainable? scapes, displacing native plants and Not long ago, plants from around the world could disrupting natural be introduced into the landscape and provided ecosystems. The use with the care needed to ensure their long-term beauty of these potential and success. Pesticide use was widespread and its invasives cannot be effectiveness unquestioned, labor for intensive care seen as sustainable was available and affordable, and the supply of except in very con- natural resources was considered limitless. Much has trolled situations. changed in recent decades; we have become painfully This list of sus- aware of the limits of our natural resources and the tainable plants is not SUSTAINABLE PLANT LIST · THIRD EDITION · 1999 1 offered as the entire answer. Proper siting, planting before some of the newer plants are readily available and maintenance are necessary for a plant to prosper in the trade. in the landscape. Therefore, climatic conditions, Many of our favorite plants are not on the list, exposure to sun and wind, subsurface soil and mois- because serious pests threaten their existence or their ture conditions, etc. must be considered when maintenance requirements are too high for them selecting plants for a particular location. Sustainable to be considered sustainable. That doesn’t mean that or not, if one ignores the site and a plant’s cultural we won’t include a few of them in our landscapes. requirements, that plant will suffer. Life would be indeed dull without a rose, but most of us would not want to maintain a half-acre of them. Plants with occasional pest problems or those with relatively minor problems are included on the list with cautionary notes. It is only those plants with life- threatening or chronic pest problems that are omitted from the list, along with seriously invasive species. The list is not intended to eliminate the production of high maintenance plants with desirable traits. Instead, it is intended to encourage the broader distribution of plants which seem to be better suited to satisfying not only our horticultural requirements, but also our environmental concerns. Native Plants There is renewed interest in native plants (those found growing outside of cultivation in this region A List for Professionals during pre-Colonial times) which often are better In preparing this list and the accompanying plant acclimated, less pest prone and more favorable for native wildlife than exotic plants. Native plants are descriptions, we have targeted a professional audience, identified in Appendix 2. However, it should be noted with an expectation that through time, as these plants that many exotic insect and disease pests have been become more available, this information will filter introduced in the past 300 years. They have virtually down to the consumers. Plants on this list are proven eliminated some of our native plants and become performers in Southern New England (USDA Hardiness serious pests of others. In these cases, it is useful to Zones 7a–5b), and many of them can be grown both look to other parts of the world where plants have north and south of here (although the pest complexes evolved resistance to these pests. Even without intro- might change). This list is dynamic and will continue duced pests, some native plants have problems in to change as new plants and pests are introduced and our landscapes where they are far removed from their as we learn more about existing ones. natural environments. A fabulous forest shrub can The list is only a guide. Plants are included which have serious difficulties when sited between a drive- have qualities appealing to designers and plant way and a sidewalk. It is likely that a sustainable lovers alike. Plant descriptions include color, form, landscape will feature many native plants, but we texture and growth habits as well as maintenance think there are many non-natives which should be requirements and hardiness. Many of the plants on the considered as well. list are well known and currently in production, while others need to be grown and distributed more. We are well aware that it will take a decade or more 2 SUSTAINABLE PLANT LIST · THIRD EDITION · 1999 Planting for Sustainable Landscapes Introduction Giving plants a healthy start begins with proper planting. Problems showing up on established plants can often be traced back to poor planting. Traditional planting methods are often passed down through the generations. While some of the old ways are still recommended today, many planting practices are changing to reflect current research and technology. Well-informed landscapers and arborists should be aware of the latest planting and transplanting techniques. This chapter presents the techniques and procedures used to plant and transplant trees and shrubs, and explains how the use of proper planting techniques can improve survival and acceler- ate establishment. Selecting and Purchasing Plants $ THE RIGHT PLANT key to sustainable planting is matching the upon site requirements and planting specifications, plant and the conditions of the planting site. each form has its advantages and disadvantages. A The best planting procedures will not save a Bare root plants have had the soil shaken from plant that is poorly suited for the site. Plants vary their roots after digging. Most bare root trees and naturally in their ability to tolerate site conditions shrubs are purchased by mail order such as extreme heat or cold, wet or dry and planted during the dormant soils, sun or shade. The plant also should season, before roots and buds not outgrow its allotted space. Plants begin to grow. Since there is no should be healthy and vigorous soil on the roots, it is vital that when planted. The condition of the they be kept moist, and if not planted roots in particular affects trans- immediately, that they be stored plant success. The roots should be cold (32°–40°F) with moist packing white and numerous; brown or black around the roots. When planted, roots indicate a health problem. the roots of bare root plants should be spread evenly in the planting hole. $ HANDLING NEW PLANTS Container grown plants have been grown for months or years in rees and shrubs are available the container in which they are sold. from the nursery in one of three Container growing is becoming very popular T forms: bare root, balled and in the nursery trade. Container grown plants burlapped, or container grown. Depending may be planted anytime the soil is workable, but may SUSTAINABLE PLANT LIST · THIRD EDITION · 1999 3 need special attention to correct compacted or circling used to wrap the root ball holds the soil ball together roots. When selecting container grown trees and shrubs, and keeps the roots from drying out. Natural fiber always check the roots. For example, not all plants burlap is biodegradable and may be left in the hole, purchased in containers are container grown. Often though it should be rolled back and completely bare root trees or covered with soil. Some nurseries use treated burlap shrubs are potted in or synthetic burlap which must be removed at plant- containers, grown ing. All twine or rope holding the burlap together for a short time and or tied around the trunk must be removed to avoid sold from the nursery. girdling. Some larger balled and burlapped trees If they are not held come in wire baskets that keep the ball together dur- for at least a year, the ing handling. Although the baskets do not have to roots may not have be removed, it is best to cut the upper rows when plant- established in the ing. This eliminates interference with rakes or lawn container. On the mowers if the tree is planted shallow, and allows roots other hand, if plants to grow and spread freely near the surface. are grown in their container for too Planting long, the roots may have grown in circles. $ THE PLANTING HOLE These roots must be separated and spread nstalling trees and shrubs properly involves more out during planting.