I live in downtown Toronto and am thinking of planting a Paw Paw tree in my backyard. It would have to go quite close to the foundations of my house and those of my neighbour. Since it is a fairly small tree at maturity, I was wondering if the tree would thrive in an area where the roots will be limited in growth. Conversely, will the roots be a problem by creating leaks in the foundations if they grow under the basements?
What a lovely idea – although the tree may not be as small as you seem to indicate. Pawpaw (Asimina triloba) can grow up to 10 metres (over 30 feet) in height, although in the city is usually from 4.5-6 metres (15-20 feet) high, with an equal spread. Pawpaws adapt well to urban conditions, and are quite low-maintenance, as well as being generally pest- and disease-free. The trees have very long taproots, which are easily damaged. These roots are not considered invasive, so should not damage your home’s foundation. Nor would the roots need extensive “horizontal room” to grow.
However, it is generally recommended that no tree should be planted closer than 3 metres (10 feet) from the foundation of a house, patio, sidewalk or driveway, nor should it be close to underground utilities. The Town of Richmond Hill’s “Planning on planting trees or shrubs on private property?” provides practical advice about issues to consider.
A bit more about this fascinating tree: The pawpaw sends out root suckers, which should be removed if you don’t want a pawpaw patch. If you want fruit, two trees are recommended, as a pawpaw can’t self-pollinate – it requires pollen from a genetically different tree in order to fruit. Beetles and flies (not bees) spread the pollen. Pawpaws like moist but well-drained soil that is slightly acidic. The leaves are large and may be prone to wind damage. The young tree needs partial shade for the first couple of years, although once established, it can do well in a range of conditions, from full sun to partial shade — but best fruit production occurs in full sun.
You might be interested to know that pawpaws are available via the Local Enhancement & Appreciation of Forests (LEAF) Backyard Tree Planting Program. The LEAF website discusses yard and space requirements for trees like the pawpaw. Consider calling LEAF for more practical information about how close to plant the pawpaw to your foundation.
Kentucky State University’s Cooperative Extension Program has published the “Pawpaw Planting Guide”, which provides a good overview of care needed for the trees. See also a good general overview about the tree, from the University of Florida and the US Forest Services – “Asimina triloba. Pawpaw“.
Note that the pawpaw is almost the last tree to leaf out in spring, a trait reflecting its tropical origins, and young leaves can appear chlorotic (yellow), a temporary springtime condition.
Ontarion MNR. Ontario’s Tree Atlas https://www.mnr.gov.on.ca/en/Business/ClimateChange/2ColumnSubPage/STDPROD_102189.html
LEAF. Pawpaw FAQ. https://www.yourleaf.org/pawpaw-faq
Missouri Botanical Garden. Asimina triloba. https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=b500
Chicago Botanic Garden. Pawpaw. https://www.chicagobotanic.org/plantinfo/pawpaw
McClanan M, Pfeiffer DG. Pawpaw, Asimina triloba (L.), in fall. Virginia Polytechnic Institute and State University. https://www.virginiafruit.ento.vt.edu/PawPaw/PAW_000C.html
University of Florida IFAS Extension. Asimina triloba: Pawpaw. https://edis.ifas.ufl.edu/st086
City of Guelph. Featured plant: Paw paw https://guelph.ca/living/house-and-home/yard-and-garden/healthy-landscapes/landscape-planning/paw-paw-asimina-triloba/
University of Illinois Extension. Pawpaw. https://web.extension.illinois.edu/dmp/palette/081019.html
US Forest Service Fact Sjeet ST-86 – Asimina triloba – Pawpaw. https://hort.ifas.ufl.edu/database/documents/pdf/tree_fact_sheets/asitria.pdf