The Plants of Autumn Foliage

Yellow– and red-leaved flowering shrubs and trees, together with conifers, provide the most noticeable autumn color at the Harvard Forest. The above photograph provides a look at some leaves in mid-October, when the colors are at their peak.

Species in this Photograph

*Hamamelis virginiana L.*
**Hamamelidaceae family**
A tall shrub growing in the understory of forests, occasionally near the forest edges. The alternate leaves have uneven bases. It flowers during the autumn as the leaves turn yellow and fall.

*Viburnum alnifolium* Marsh.
**Caprifoliaceae family**
This is a rather low-growing shrub often seen in forest understory as well along edges in cool moist woods. Its large roundish opposite leaves turn a beautiful wine-red throughout October.

*Viburnum cassinoides* L.
**Caprifoliaceae family**
This is a shrub of medium height with opposite leaves that turn bright red throughout October. It is common in the understory and at the edge of the forest.

*Acer saccharum* Marsh.
**Aceraceae family**
A large and common tree of our roadsides and cool forests on fertile sites. Its opposite leaves with wavy edges and characteristic maple shape turn varying luminous shades of yellow to orange and red from middle to late October.

*Acer rubrum* L.
**Aceraceae family**
This is one of the most common and showy trees in these forests. Its opposite maple-shaped leaves with toothed edges turn varying shades of yellow to dark red from September into October. It commonly grows in the forest understory, on forest margins, in swamps and on the edges of wetlands where it provides an early swath of bright color during autumn.

*Fraxinus Americana* L.
**Oleaceae family**
This is a large and handsome tree of our forests, often found near streams. Its opposite compound leaves turn from yellow to purple-brown in early to mid-October.

*Prunus serotina* Ehrh.
**Rosaceae family**
This tree can become quite large, but is more commonly found as a young sapling in disturbed areas and the forest understory. Its alternate finely toothed medium-sized leaves have a hairy mid-rib on the underside. They turn yellow to pink in mid to late October.

*Vaccinium corymbosum* L.
Ericaceae family
This is a common medium-tall shrub of the forest understory and edges, especially in moist sites. Its small alternate smooth-edged and oval leaves turn a dark red from mid-October into early November. It is also common along pond edges.

*Betula allegheniensis* Britt.
**Betulaceae family**
A fairly common medium-sized tree often associated with hemlock in moist sites and swamp edges, with silver gray to yellow curly bark. Its alternate finely toothed leaves turn yellow in mid-October.

*Fagus grandifolia* Ehrh.
**Fagaceae family**
This large and handsome tree is very shade-tolerant and grows up in the understory of forests, with flat planes of branches and smooth gray bark. Its alternate coarsely toothed leaves turn yellow in mid-October and many are retained especially on smaller trees, even after they turn brown.

*Acer pensylvanicum* L.
**Aceraceae family**
A small shade-tolerant tree often found in the understory of cool forests, with distinctive long white stripes on its green bark. Its large opposite and shallowly-lobed toothed leaves turn yellow in mid-October.

Conifers

Conifers provide the green backdrop during the autumn color changes in New England forests. These are principally white pine and hemlock, although other pines may be introduced in plantations. Larches are the only conifers in these forests which lose their needles completely during the fall. These trees produce an autumn show of bright yellow in the swampy areas where they grow. The European larch may be introduced in plantations or in landscaping, to provide more autumn yellow color.

*Larix laracina* (Du Roi) K. Koch
**Pinaceae family**
This medium-sized coniferous tree is intolerant of shade, and is mostly found in swamps and other wet areas. It is unusual because, although it is a conifer, it is not an evergreen. Its short needles are produced in whorls, and all of them turn yellow in the late autumn and fall from the tree. A very similar introduced species, the European larch, is often planted in yards and parks.

*Tsuga Canadensis* (L.) Corr.
**Pinaceae family**
This large evergreen tree has short single flat needles and is very tolerant of shade. It is common around swamps, in gullies and on north-facing slopes. It drops a small percentage of its needles in the autumn.

*Pinus strobus* L.
**Pinaceae family**
This large evergreen tree is very common in forests throughout this region. It has five needles in each cluster. Each autumn, one-third to one-half of its needles turn yellow-brown and drop.

Red-leaved Flowering Shrubs and Trees

All of these shrubs and trees produce varying amounts of anthocyanins during senescence. Sometimes these pigments are produced uniformly in the leaves, but often distinct patterns.

*Cornus alternifolia* L.f.
**Cornaceae family**
This is a small tree or large shrub often growing along roadsides and forest margins, but also in the understory. Unique among dogwoods, its leaves are alternate in position. The foliage begins to redden in early September, one of the earlier species to change color.

*Pyrus melanocarpa* (Michx.) Willd.
**Rosaceae family**
This low-medium sized shrub grows in the forest understory. Its alternate medium-sized spoon-shaped leaves turn orange to reddish in mid- to late October.

*Quercus rubra* L.
**Fagaceae family**
This large tree is very common in these forests. Its alternate sharply-pointed oak-shaped leaves turn red and then brown from late October to early November. Small trees often retain brown leaves through the winter.

*Cornus stolonifera* Michx.
**Cornaceae family**
This small tree is found in damp forest edges, more commonly near the coast. Its opposite smooth-edged leaves turn a dark wine-red color in late October.

*Quercus coccinea* Muenchh.
**Fagaceae family**
This medium-sized oak is found in drier upland sites in our forests. Its alternate oak-shaped leaves are more deeply divided than those of the red or white oaks. Brilliant red colors appear towards the end of October.

*Amelanchier Canadensis* (L.) Medic.
**Rosaceae family**
A small tree or tall shrub of the understory and forest edges. Its alternate finely toothed oblong leaves turn yellow brown to dull red in mid-late October.

*Nyssa sylvatica* Marsh.
**Nyssaceae family**
A narrow-crowned tree with right-angle branches that is restricted to swamps and adjacent areas in our region. Its leaves are small, oval and alternate, and the handsome foliage turns orange to wine-red in early to mid-October.

*Rhus typhina* L.
**Anacardiaceae family**
This tall shrub or small tree forms clumps from root suckers in fields, forest openings and along roadsides. Its alternate feather-compound leaves turn brilliant red throughout the autumn months.

*Quercus alba* L.
**Fagaceae family**
This is a large and rather common tree in these forests. Its alternate leaves have distinctively round lobes unlike the pointed lobes of red and scarlet oaks. The foliage turns a dull to brick-red in the second half of October.

Yellow-Leaved Flowering Shrubs and Trees

All of these species turn yellow during the autumn, due to the breakdown of chlorophyll and the retention of some carotenoid pigments in their plastids. In a few cases, small amounts of anthocyanins may be produced, sometimes only in a few individuals in a population.