Is Shiro plum self-fertile or self-sterile?

Shiro Japanese Plum is a self sterile cultivar. It is self-sterile and requires 1 compatible pollination partner flowering within Bloom Groups 1–3 to achieve a reliable commercial fruit set.

Can Shiro act as a pollen donor for other plums?

Yes. Shiro Japanese Plum produces viable, fertile pollen that readily cross-pollinates other compatible plum varieties flowering across its bloom window.

Which bloom group does Shiro plum belong to?

Shiro Japanese Plum flowers in Bloom Group 2 (Early-Spring). It reliably cross-pollinates with compatible cultivars in its own group or immediately adjacent groups (±1 bloom group).

Which plum pollination pool does Shiro belong to?

Shiro Japanese Plum belongs to Pool B (Japanese plum and hybrids). A compatible pollen partner must flower in the same or an adjacent bloom group and belong to the same pool. European and Japanese plum pools do not cross-pollinate.

Curated Pomology Guide · Bloom Group 2

Shiro Japanese Plum
Pollination & Compatibility Guide

Shiro Japanese plum pollination guide: cross-required Pool B status, Group 2 bloom and Methley or Santa Rosa partners.

Pomological Verdict & Botanical Profile

Shiro Needs a Compatible Pool B Partner

Same-Pool Pollen Required

Yellow-fleshed, widely planted. Methley and Santa Rosa both work. Shiro (Japanese) needs at least one compatible pollinizer from bloom group 1–3 to set a reliable crop.

Pollination Pool / Ploidy: Pool B · Diploid
Required Companions: 1 Compatible Partner
Bloom Group: Group 2 (Early-Spring)
Harvest Timing: Early Season

Primary Uses:Fresh EatingCanning

General Notes: Susceptible to black knot

Flowering Period & Overlap Window

Plum bloom groups run from 1 to 5. A useful partner flowers in the same or adjacent group and belongs to the same pollination pool. European plums, gages and damsons are Pool A; Japanese plums and prairie hybrids are Pool B. A tree from one pool cannot pollinate the other.

Flowering Overlap Range for Shiro

Early Overlap

Group 1

Shiro

Group 2

Late Overlap

Group 3

For Shiro, select a compatible plum in the same pollination pool flowering from Group 1 to 3; bloom overlap alone does not bridge Pool A and Pool B.

Compatible Pollination Partners (4)

Test in Checker

Cultivar	Bloom Group	Overlap Type	Harvest	Primary Uses	Interactive Test
Bubblegum Plum (Toka)	Group 2	Full Overlap	Mid	Fresh Eating, Jam	Test Cross
Methley (Hybrid)Guide	Group 2	Full Overlap	Early	Fresh Eating, Jam	Test Cross
Santa Rosa (Japanese)Guide	Group 2	Full Overlap	Early-Mid	Fresh Eating	Test Cross
Toka (Hybrid)Guide	Group 2	Full Overlap	Mid	Fresh Eating, Jam	Test Cross

Incompatible Varieties & Exclusions (10)

These cultivars cannot serve as pollinizers for Shiro because of a different plum pollination pool, a documented incompatibility or another exclusion in the source data.

American Plum

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. American Plum is not one of them — that is a gap in the data, not evidence it is incompatible.

Beauty (Japanese)

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Beauty (Japanese) is not one of them — that is a gap in the data, not evidence it is incompatible.

Burbank (Japanese)Guide

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Burbank (Japanese) is not one of them — that is a gap in the data, not evidence it is incompatible.

Elephant Heart (Japanese)

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Elephant Heart (Japanese) is not one of them — that is a gap in the data, not evidence it is incompatible.

Friar (Japanese)

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Friar (Japanese) is not one of them — that is a gap in the data, not evidence it is incompatible.

Laroda (Japanese)

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Laroda (Japanese) is not one of them — that is a gap in the data, not evidence it is incompatible.

Ozark Premier (Hybrid)

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Ozark Premier (Hybrid) is not one of them — that is a gap in the data, not evidence it is incompatible.

Satsuma (Japanese)Guide

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Satsuma (Japanese) is not one of them — that is a gap in the data, not evidence it is incompatible.

Superior (Hybrid)

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Superior (Hybrid) is not one of them — that is a gap in the data, not evidence it is incompatible.

Valiant (Hybrid)

plum incompatibility groups are only partly mapped, so only cultivars documented as reliable donors are offered. Valiant (Hybrid) is not one of them — that is a gap in the data, not evidence it is incompatible.

Grower Commentary: Shiro's Early Partner Window

Shiro is a yellow-fruited Japanese plum in Pool B and needs a compatible pollen donor. Its Group 2 blossom aligns with the early Japanese plum window; Methley and Santa Rosa are named partner candidates in the pomology record. Do not count a European plum, gage or damson as the second variety. Those trees occupy Pool A and cannot fertilise Shiro even if a printed bloom chart shows the same group number.

A Shiro block needs a plan for both pollen and weather. Early opening flowers face frost, and cool days may leave bees inactive through much of the effective pollination period. Note which companion actually flowers during Shiro's open-bloom days, rather than relying only on a regional seasonal label. If the block sits in a hollow, improve siting before increasing the number of donors.

Yellow fruit makes picking maturity and handling visible, so leave light and access through the canopy. Heavy set after good pollination can produce crowded, undersized plums and bend young limbs; inspect fruitlets after natural drop and thin where needed. A moderately vigorous stock can support a manageable bush or trained form, but avoid specifying Citation on poorly drained ground. Nursery confirmation remains important for hybrid rootstock combinations.