# 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=kalm-st-johns-wort Try [black walnut](https://bluewhaletrees.com/tools/companions/index.html.md?species=black-walnut), [flowering dogwood](https://bluewhaletrees.com/tools/companions/index.html.md?species=flowering-dogwood) or [spicebush](https://bluewhaletrees.com/tools/companions/index.html.md?species=spicebush). 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. ## [Kalm's St. John's-wort](https://bluewhaletrees.com/plants/kalm-st-johns-wort/index.html.md) grows in sandy barrens, rocky ground, stream banks and the coast These natives share that ground, so they will look right together and want the same care. - [Common Hoptree (Wafer Ash)](https://bluewhaletrees.com/plants/common-hoptree/index.html.md) (*Ptelea trifoliata*): Small tree, 10–20 ft · shares sandy barrens, rocky ground and stream banks - [Dwarf Hackberry](https://bluewhaletrees.com/plants/dwarf-hackberry/index.html.md) (*Celtis tenuifolia*): Small tree, 15–30 ft · shares sandy barrens, rocky ground and stream banks - [Broom Crowberry](https://bluewhaletrees.com/plants/broom-crowberry/index.html.md) (*Corema conradii*): Shrub, 1–2 ft · shares sandy barrens, rocky ground and the coast - [Golden Heather](https://bluewhaletrees.com/plants/golden-heather/index.html.md) (*Hudsonia ericoides*): Shrub, 1–2 ft · shares sandy barrens, rocky ground and the coast - [Gum Bumelia](https://bluewhaletrees.com/plants/gum-bumelia/index.html.md) (*Sideroxylon lanuginosum*): Small tree, 15–45 ft · shares sandy barrens, rocky ground and stream banks - [Jack Pine](https://bluewhaletrees.com/plants/jack-pine/index.html.md) (*Pinus banksiana*): Medium tree, 35–65 ft · shares sandy barrens and rocky ground - [Showy Mountain Ash](https://bluewhaletrees.com/plants/showy-mountain-ash/index.html.md) (*Sorbus decora*): Small tree, 20–40 ft · shares rocky ground and stream banks - [Grape Honeysuckle](https://bluewhaletrees.com/plants/grape-honeysuckle/index.html.md) (*Lonicera reticulata*): Shrub, 3–15 ft · shares rocky ground and stream banks How far apart: the [planting-distance tool](https://bluewhaletrees.com/tools/distance/index.html.md?species=kalm-st-johns-wort&near=tree) gives the gap between Kalm's St. John's-wort and any tree you name as the next one, by their pages' spacing or half of each crown, added. ## Trees to plant it under Kalm's St. John's-wort takes some shade, so it can live beneath these. - [Northern White Cedar](https://bluewhaletrees.com/plants/northern-white-cedar/index.html.md) (*Thuja occidentalis*): Medium tree, Zones 2–7, 40–60 ft, Price on request. Shares rocky ground and stream banks 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 rocky ground and stream banks in the wild. - [Black Oak](https://bluewhaletrees.com/plants/black-oak/index.html.md) (*Quercus velutina*): Large tree, Zones 3–9, 50–80 ft, Price on request. Shares sandy barrens and rocky ground 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 sandy barrens and rocky ground 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 sandy barrens and rocky ground in the wild. - [Common Hackberry](https://bluewhaletrees.com/plants/common-hackberry/index.html.md) (*Celtis occidentalis*): Large tree, Zones 3–9, 40–60 ft, Price on request. Shares rocky ground and stream banks in the wild. ## Beside it Plants that want the same sun and soil, for a bed, a hedge or a grove. - [Maleberry](https://bluewhaletrees.com/plants/maleberry/index.html.md) (*Lyonia ligustrina*): Shrub, Zones 5–9, 6–12 ft, Price on request. Shares sandy barrens, stream banks and the coast in the wild. Hardy in zones 5 to 7 of the Kalm's St. John's-wort's 4 to 7. - [Canada Buffaloberry](https://bluewhaletrees.com/plants/canada-buffaloberry/index.html.md) (*Shepherdia canadensis*): Shrub, Zones 2–8, 3–8 ft, Price on request. Shares sandy barrens, rocky ground and stream banks in the wild. - [Sand Cherry](https://bluewhaletrees.com/plants/sand-cherry/index.html.md) (*Prunus pumila*): Shrub, Zones 3–6, 1–8 ft, Price on request. Shares sandy barrens, rocky ground and stream banks in the wild. Hardy in zones 4 to 6 of the Kalm's St. John's-wort's 4 to 7. - [Prickly Rose](https://bluewhaletrees.com/plants/prickly-rose/index.html.md) (*Rosa acicularis*): Shrub, Zones 2–6, 3–8 ft, Price on request. Shares sandy barrens, rocky ground and stream banks in the wild. Hardy in zones 4 to 6 of the Kalm's St. John's-wort's 4 to 7. - [Ninebark](https://bluewhaletrees.com/plants/ninebark/index.html.md) (*Physocarpus opulifolius*): Shrub, Zones 2–8, 5–10 ft, Price on request. Shares rocky ground and stream banks in the wild. - [Creeping Juniper](https://bluewhaletrees.com/plants/creeping-juniper/index.html.md) (*Juniperus horizontalis*): Shrub, Zones 2–9, 1–2 ft, Price on request. Shares sandy barrens, rocky ground and the coast in the wild. - [When these flower and fruit](https://bluewhaletrees.com/tools/calendar/index.html.md?plants=kalm-st-johns-wort,northern-white-cedar,rock-elm,black-oak,mockernut-hickory,pignut-hickory,common-hackberry,maleberry,canada-buffaloberry,sand-cherry,prickly-rose,ninebark,creeping-juniper), in the bloom and fruit calendar. ## Email me when Kalm's St. John's-wort or a companion is ready to order For Kalm's St. John's-wort, Northern White Cedar, Rock Elm, Black Oak, Mockernut Hickory, Pignut Hickory, Common Hackberry, Maleberry, Canada Buffaloberry, Sand Cherry, Prickly Rose, Ninebark: 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 45 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 28 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 45 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. ## Common questions ### What can I plant under a black walnut tree? Under a black walnut, the tool puts first the species on the Morton Arboretum's tolerant lists, such as [pawpaw](https://bluewhaletrees.com/plants/pawpaw/index.html.md), [spicebush](https://bluewhaletrees.com/plants/spicebush/index.html.md) and [flowering dogwood](https://bluewhaletrees.com/plants/flowering-dogwood/index.html.md). It leaves out those Morton lists as sensitive to the walnut's juglone, and Morton warns that any such list is incomplete. ### What should you not plant near a black walnut? Of the trees and shrubs we grow, the Morton Arboretum lists crabapples, hackberries, lindens, rhododendrons, blueberries, larch, yew and red chokeberry as sensitive to black walnut's juglone. Azaleas count among the rhododendrons, and the tool keeps all of them out of a walnut's answer. ### What can I plant under a big tree? Under a large tree, the tool lists up to six shrubs and small trees that take part shade or shade, and species of the forest understory rank higher. Our article on [what to plant under a big tree](https://bluewhaletrees.com/articles/what-to-plant-under-a-big-tree/index.html.md) covers planting without hurting the tree. ### Which native trees and shrubs grow together in the wild? The tool lists up to eight natives that share a natural community with your species and grow wild in one of its states, by the USDA PLANTS Database. The communities are our own tags, and sharing one does not mean two species always grow side by side. ### Can eastern red cedar be planted near crabapples? The University of Minnesota Extension says not to plant [eastern red cedar](https://bluewhaletrees.com/plants/eastern-red-cedar/index.html.md) within a few hundred yards of crabapples, hawthorns, serviceberries, chokeberries or mountain ash, since cedar-apple and related rusts live on both. The tool keeps them out of each other's answers. 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).