Garden · Fruit tree grafting
Grafting compatibility & timing calculator
Grafting lets you grow a specific fruit variety on a rootstock chosen for size control, disease resistance, or soil tolerance, but it only works if the scion and rootstock are genetically compatible, and only if you time the graft to the plant's own dormancy and growth cycle. Get either wrong and the graft simply won't take. This calculator checks compatibility by genus and gives you the collection and callusing timing for your specific graft method.
Compatibility
Compatible
Callusing time: 2–4 weeks
Timing
Collect dormant scion wood in mid to late winter, well before bud swell, and graft while the rootstock is still dormant or just breaking dormancy.
Check for a firm, calloused union at the end of this window before removing any support wrap or tape.
What to actually buy
PUELDU Professional Grafting Tool Kit
A clean, precise cut with maximum contact between scion and rootstock cambium layers matters as much as genus compatibility for a graft to actually take. This kit includes a grafting knife plus tape, labels, and clips in one set, covering the whole process from the cut to securing the union through the callusing window above.
View on AmazonAs an Amazon Associate, ToolBrook earns from qualifying purchases.
Embed this calculator
Paste this on your own site. It includes a small credit link back to ToolBrook.
<iframe src="https://toolbrook.com/embed/garden/grafting-compatibility-calculator" width="100%" height="480" style="border:1px solid #D7DCD2;border-radius:12px;" title="ToolBrook calculator"></iframe>
How this is calculated
Compatibility in grafting comes down to genetic similarity between scion and rootstock, and per Cornell HORT494's grafting and budding reference, that similarity generally needs to be within the same genus. Apple (Malus) and pear (Pyrus), for example, are both in the rose family but are different genera, and don't form a lasting graft union despite how closely related they look. This calculator flags a graft as compatible only when scion and rootstock share the same genus.
Timing depends on the graft type, not just the species. Whip- and-tongue and cleft grafts use dormant scion wood collected in winter and are performed while the rootstock is dormant or just breaking dormancy in early spring. Bud grafting (T-budding or chip budding) works the opposite way: it uses fresh, current-season budwood collected in late summer, grafted onto actively growing rootstock, with the bud itself not forced into growth until the following spring. These timing windows and the general callusing ranges come from Oregon State University Extension's grafting guidance.
Callusing time is when the graft union is doing its real work, forming the vascular connection between scion and rootstock. Don't remove grafting tape, wrap, or wax before that window closes, even if the scion looks like it's taken, the union itself is still fragile.
Sources
Frequently asked questions
Can I graft across different genera with an interstem?
Sometimes, in cases of known compatibility problems, growers use a compatible variety grafted as a middle section (an interstem) between an otherwise incompatible scion and rootstock. This is an advanced technique for specific known problem combinations, not a general workaround for cross-genus grafting, and this calculator doesn't model interstem grafting.
How do I know if a graft actually took?
For whip-and-tongue and cleft grafts, look for the scion staying green and firm, with new growth beginning within the callusing window. For bud grafts, a successful "take" shows as the bud staying plump and green (not shriveled) and the bark around it staying tight, checked 2-3 weeks after budding, well before you'd expect any visible growth.
Does rootstock variety within the same genus matter?
For basic compatibility, no, same-genus grafts generally take regardless of specific rootstock variety. Rootstock variety does matter for other things this calculator doesn't cover, like final tree size, disease resistance, and soil adaptation, which are separate decisions from whether the graft itself will physically take.
What if my graft fails even with compatible genera?
Genus compatibility is necessary but not sufficient. Clean cuts with maximum cambium contact, correctly timed collection and grafting, and keeping scion wood properly cold-stored and hydrated before use all matter as much as compatibility itself. A failed graft between compatible genera is usually a technique or timing issue, not a genetic mismatch.