# Companion species

> Pick one native tree or shrub and see the species that share its ground in the wild, live under its canopy, or want the same sun, soil and climate in a yard.

Blue Whale Trees, a native tree nursery in the United States. Web version: https://bluewhaletrees.com/tools/companions/?species=white-oak&zone=6

Try [black walnut](https://bluewhaletrees.com/tools/companions/?species=black-walnut&zone=6#try), [flowering dogwood](https://bluewhaletrees.com/tools/companions/?species=flowering-dogwood&zone=6#try) or [spicebush](https://bluewhaletrees.com/tools/companions/?species=spicebush&zone=6#try).

Pick one native tree or shrub and see what grows with it. The matches come in three groups. Some species share its ground in the wild, and others live under its canopy or are the trees it can be planted beneath. The rest suit the same yard because they want the same sun, soil and climate. Every match is explained on the page, so you can see why a species is listed.

## White Oak grows in dry uplands and rich moist slopes

These natives share that ground, so they will look right together and want the same care.

- [Shagbark Hickory](https://bluewhaletrees.com/plants/shagbark-hickory/index.html.md) (*Carya ovata*): Large tree, 60–90 ft
- [Common Prickly Ash (Toothache Tree)](https://bluewhaletrees.com/plants/common-prickly-ash/index.html.md) (*Zanthoxylum americanum*): Shrub, 10–20 ft
- [American Chestnut](https://bluewhaletrees.com/plants/american-chestnut/index.html.md) (*Castanea dentata*): Small tree, 15–30 ft
- [Shingle Oak](https://bluewhaletrees.com/plants/shingle-oak/index.html.md) (*Quercus imbricaria*): Medium tree, 40–60 ft
- [Shumard Oak](https://bluewhaletrees.com/plants/shumard-oak/index.html.md) (*Quercus shumardii*): Large tree, 50–80 ft
- [Sweet Birch (Black Birch)](https://bluewhaletrees.com/plants/sweet-birch/index.html.md) (*Betula lenta*): Medium tree, 40–70 ft
- [Lanceleaf Buckthorn](https://bluewhaletrees.com/plants/lanceleaf-buckthorn/index.html.md) (*Rhamnus lanceolata*): Shrub, 3–15 ft
- [Blue Ash](https://bluewhaletrees.com/plants/blue-ash/index.html.md) (*Fraxinus quadrangulata*): Large tree, 50–70 ft

How far apart: the [planting-distance tool](https://bluewhaletrees.com/tools/distance/index.html.md?species=white-oak&near=tree) gives the gap between White Oak and any tree you name as the next one, by their pages' spacing or half of each crown, added.

## Under its canopy

Shrubs and small trees that take the shade a white oak casts and like the same soil. All are rated hardy in zone 6.

- [Mapleleaf Viburnum](https://bluewhaletrees.com/plants/mapleleaf-viburnum/index.html.md) (*Viburnum acerifolium*): Shrub, Zones 3–8, 3–6 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Alabama Azalea](https://bluewhaletrees.com/plants/alabama-azalea/index.html.md) (*Rhododendron alabamense*): Shrub, Zones 6–9, 4–6 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Flame Azalea](https://bluewhaletrees.com/plants/flame-azalea/index.html.md) (*Rhododendron calendulaceum*): Shrub, Zones 5–7, 4–12 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Blackhaw Viburnum](https://bluewhaletrees.com/plants/blackhaw/index.html.md) (*Viburnum prunifolium*): Shrub, Zones 3–9, 12–15 ft, Price on request. Shares dry uplands in the wild.
- [Arrowwood Viburnum](https://bluewhaletrees.com/plants/arrowwood-viburnum/index.html.md) (*Viburnum dentatum*): Shrub, Zones 2–8, 5–10 ft, Price on request. Shares rich moist slopes in the wild.
- [Downy Arrowwood](https://bluewhaletrees.com/plants/downy-arrowwood/index.html.md) (*Viburnum rafinesqueanum*): Shrub, Zones 3–8, 3–10 ft, Price on request. Shares dry uplands in the wild.

## Beside it

Plants that want the same sun and soil, for a bed, a hedge or a grove, with the same size class first. All are rated hardy in zone 6.

- [Black Cherry](https://bluewhaletrees.com/plants/black-cherry/index.html.md) (*Prunus serotina*): Large tree, Zones 2–9, 50–80 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Rock Elm](https://bluewhaletrees.com/plants/rock-elm/index.html.md) (*Ulmus thomasii*): Large tree, Zones 2–9, 70–90 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Northern Red Oak](https://bluewhaletrees.com/plants/northern-red-oak/index.html.md) (*Quercus rubra*): Large tree, Zones 3–8, 50–75 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Mockernut Hickory](https://bluewhaletrees.com/plants/mockernut-hickory/index.html.md) (*Carya tomentosa*): Large tree, Zones 4–9, 60–80 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Pignut Hickory](https://bluewhaletrees.com/plants/pignut-hickory/index.html.md) (*Carya glabra*): Large tree, Zones 4–9, 50–80 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [Red Hickory](https://bluewhaletrees.com/plants/red-hickory/index.html.md) (*Carya ovalis*): Large tree, Zones 4–8, 60–100 ft, Price on request. Shares dry uplands and rich moist slopes in the wild.
- [When these flower and fruit](https://bluewhaletrees.com/tools/calendar/#plants=white-oak,mapleleaf-viburnum,alabama-azalea,flame-azalea,blackhaw,arrowwood-viburnum,downy-arrowwood,black-cherry,rock-elm,northern-red-oak,mockernut-hickory,pignut-hickory,red-hickory), in the bloom and fruit calendar.
- [What to plant under a big tree](https://bluewhaletrees.com/articles/what-to-plant-under-a-big-tree/index.html.md), and how to plant without harming its roots.
- [The habitat around a tree is part of the tree](https://bluewhaletrees.com/articles/habitat-around-a-tree/index.html.md): what keeps its roots alive.
- For the shade under an oak, the [Shade Understory Pack](https://bluewhaletrees.com/bundles/shade-understory/index.html.md) sells five as a set.

## Email me when White Oak or a companion is ready to order

For White Oak, Mapleleaf Viburnum, Alabama Azalea, Flame Azalea, Blackhaw Viburnum, Arrowwood Viburnum, Downy Arrowwood, Black Cherry, Rock Elm, Northern Red Oak, Mockernut Hickory, Pignut Hickory: one email per plant when it is priced or back in stock, and nothing else. Each carries a code for 10% off the plants in that order, not shipping or tax.

## How the matches are made

- **Natural communities.** Every species we grow is tagged with the communities it lives in: floodplain forests, swamps and wet flats, stream banks, rich moist slopes, dry uplands, sandy barrens, rocky ground, old fields and edges, the forest understory, the Appalachians and the coast.
- **In the wild.** Up to eight natives that share one of those communities with it and grow wild in one of its states. The most communities in common come first, then the native range most like its own. A species in a yard list is not repeated here.
- **Under its canopy, or trees to plant it under.** Up to six species at least two sizes apart, the smaller one taking part shade or shade: shrubs under a medium tree, shrubs and small trees under a large one.
- **Beside it.** Up to six that share a sun with it, the same size first.
- **The order of a yard list.** Every yard pick shares a zone, a soil and a state of native range with it. A shared community counts two points, and a shared sun or soil one. Under a canopy, a species of the forest understory counts two more, and one that takes full shade one more. Of equal scores, the one hardy in more of its zones comes first.
- **How far apart.** Each yard card links the planting-distance tool with both trees named. The tool gives the gap between them: each one's own spacing from its page, or half of each crown added, unless a page gives a larger distance from other trees. The wild list links the same tool with the chosen tree set, for any next tree you name.
- **Your zone.** With a zone chosen, the yard lists keep only species rated hardy in it.
- **Black walnut.** The 37 species we grow that the Morton Arboretum lists as sensitive to its juglone are left out of its answer, and it is left out of theirs. Under a walnut, the species on Morton's tolerant lists come first and are marked.
- **Eastern red cedar.** The 25 crabapples, hawthorns, serviceberries, chokeberries and mountain ash we grow are left out of its answer, and it is left out of theirs: the cedar-apple, hawthorn, quince and juniper broom rusts live on both, and the University of Minnesota Extension says to keep them a few hundred yards apart.
- **A tree or shrub we do not grow.** The 53 common natives under their own group in the menu take the same tests, with their ground, zones, sun, soil and states of native range from their sources (Silvics of North America, the USDA PLANTS Database, the Woody Plant Seed Manual, the Fire Effects Information System and extension and botanical garden pages). The answer says so, links no page, and offers the sign-up for the companions only.

The communities are our own tags. The states of native range are the USDA PLANTS Database's records, read on 2026-09-23 (2026-10-13 for the common natives we do not grow), as the [native trees by state](https://bluewhaletrees.com/tools/native/index.html.md) tool reads them. Zones, sun and soil are each species' own page, or its record for a common native we do not grow. The juglone lists are the Morton Arboretum's, read on 2026-10-05, which warns that "any list regarding this topic is incomplete and some of the information may be anecdotal." The rusts' hosts are the University of Minnesota Extension's, read on 2026-10-06. [What to plant under a big tree](https://bluewhaletrees.com/articles/what-to-plant-under-a-big-tree/index.html.md) and [the article on juglone](https://bluewhaletrees.com/articles/juglone-what-to-plant-under-a-black-walnut/index.html.md) cover the subject.

Sharing a habitat tag does not mean two species always grow side by side, and a tag says nothing about how far apart to plant them. Use the [planting-site check](https://bluewhaletrees.com/tools/site-check/index.html.md) for the spot itself, and the [growth estimator](https://bluewhaletrees.com/tools/growth/index.html.md) for how much room each one will want in twenty years.

The address carries the companion species tool's inputs, so a link opens it filled in, and Copy link on a result writes one: species (a plant's slug, the last part of its page's address, such as white-oak), zone (a whole number from 2 to 10, to keep the companions to it), sort (featured, name, price-asc, price-desc, height, hardy or fast). For example, [/tools/companions/?species=white-oak&zone=6](https://bluewhaletrees.com/tools/companions/index.html.md?species=white-oak&zone=6).