The plant sale

Most gardens' largest self-run fundraiser is the plant sale. It has a volunteer army, a mailing list, a queue at the gate, and members who plan their spring around it. It also consumes the greenhouse, the horticulturists and the volunteer capacity for weeks.

An auction built as a rival to it will lose, and will take staff attention from the thing that works.

What each is good at

The sale moves volume at a flat price. Hundreds of people buy many plants at set prices, quickly, in person. It is unbeatable at that.

The auction finds the ceiling on scarce things. One rare specimen, one horticulturist's afternoon, one bench, one behind-the-scenes morning — items where a fixed price leaves money on the table because two collectors both want it and only one can have it.

That is the division. Anything you have a hundred of goes in the sale. Anything you have one of goes in the auction.

Three ways to pair them

Inside the sale. A small auction table of the rarest specimens, running online, closing at the end of the sale weekend. The audience is already there and already buying plants, and the rare items get the price they deserve instead of going to whoever queued first.

Adjacent. Opening a week before the sale and closing as it opens, which uses the sale's promotion without competing for the same weekend's attention.

Well away. Autumn or winter, when the greenhouse is quieter, staff have capacity, and nothing else is asking members for anything. For a garden with a large sale this is frequently the cleanest answer.

The one thing not to do

Run a full separate auction in the same fortnight as the sale, staffed by the same volunteers, aimed at the same members. It competes for the same money and the same people, and the sale is the one that will suffer.

The rare-plant table is the best of both

Worth doing even if nothing else changes. Set aside the specimens that are genuinely scarce — a division of something unusual, a seedling of a notable tree, a plant with collection provenance — and run those as an online auction closing at the sale.

• Curator approves each one for propagation and distribution
• Label the provenance, which is what makes it different from a nursery plant
• Photograph it properly, because a plant photographed badly does not sell
• State the size, the hardiness, the conditions it needs and how to care for it
• Say when and how it can be collected, because a plant has a schedule

Capture the sale's customers either way

The most valuable thing the sale produces is not revenue, it is a queue of people who have just spent money on plants — and most gardens take their money and never their email address.

A sign-up at the till, a QR code on the receipt, a card in the bag. Once, at one sale, and the organization's list is permanently different.

Do not raid the sale's stock

The volunteers who grew, potted and labelled the sale's plants did it for the sale. Taking the best specimens for an auction without asking them is how a garden loses a propagation volunteer who has been turning up for fifteen years.

Ask, explain why the rare ones do better at auction, and share the result with them.

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.