How much can a botanical garden raise with a silent auction?

Short answer: whether plant sale customers were on the list, and whether the catalogue contained anything genuinely rare.

Working it out from gardeners

A garden knows its members exactly and usually has a much larger list it never captured.

• Members, who renew reliably and are genuinely interested in plants
• Plant sale customers — who have just spent money on plants, and mostly not on any list
• Plant societies and garden clubs in reach
• The cost of the horticulture you are funding: a border, a specimen tree, a year of the seed bank

The second input is the one to fix permanently. A sign-up at the plant sale till changes the organization's list for every future campaign, not just this one.

What moves it

Plant sale customers

A much larger list than the membership, made up of people who have just spent money on plants, and mostly uncaptured. A sign-up at the till is the highest-return change a garden can make.

Genuinely rare material

A specimen no nursery can supply, propagated from an accessioned plant with provenance, is bid on by collectors at prices that surprise gardens.

Horticultural expertise in the catalogue

Garden visits, design consultations, pruning and diagnosis. No comparable supplier locally, and the ceiling is staff time.

Plant societies

Organized, passionate, and holding rare material of their own. They donate, they bid, and they bring an audience.

Setting the goal

Name the horticulture — a border replanted, a specimen tree, a year of the seed bank — publish its cost, and report with before and after photographs. Nothing reports as clearly as a bed in March and the same bed in July.

Goal and budget mechanics: fundraising goals and budget.

General information, not legal advice for your garden. Plant patent and trademark rules, phytosanitary requirements, invasive species regulation and any collection or seed-bank agreements you hold are all specific — your curator and counsel decide how any of this applies.