Garden Walk

Labeling your trees so photos land on the right plant

Short version

Five trees: nothing to buy — pick the plant in the app. Around thirty: about $25 of pre-numbered aluminium tags, hung on a loose loop of coated wire. Two hundred: add zones and a stored walk order, and keep a copy of the number-to-plant map outside the garden.

Garden Walk in the Citrus Care app lets you photograph ten trees in a row — or import yesterday’s camera roll at once — and files each photo on the right plant. It never guesses from the leaves: a photo lands on a plant because of something you chose on purpose — a number you wrote on a tag and typed, a code you bound to the plant, a walk order you saved. That only works when every tree carries a marker you can read a year from now. This page is what arborists and arboreta do, with the source next to each claim.

The number is the identity

Every professional system keys on a short, human-readable number on a durable marker. The ISA’s inventory standard calls a physical marker “the surest method of finding a specific tree again that cannot easily be linked to some permanent reference object” — a garden of free-standing trees is exactly that case — and says each tree needs a unique number (ISA, Best Management Practices: Tree Inventories, 2nd ed., pp. 11–12).
Bartlett’s consulting arborists write: “For most tree inventories, we recommend round, numeric brass tags”. QR codes are reserved for engraved arboretum-style plaques, and they tag trees even when they also record GPS.
Arnold Arboretum has decimetre-accurate maps, still hangs a numbered label on every plant, and uses no QR codes.
In the app: type the tag number when you add a plant (the Tags card, or the numeric grid in the picker). A code you scan is an accelerator on top of the number, never a replacement — the number is what you read when the phone is in your pocket.

What lasts outdoors

Numbered aluminium: twenty-plus years. Anything printed or hand-written: a season to three years.

Anodized aluminium tags are guaranteed for 20+ years outdoors.
Pre-numbered 1¼″ aluminium discs cost $21.99–$25.99 per 100 and come in ranges — 1–100, 101–200 and up — from TreeStuff or Gemplers. Buy the range that continues your numbering; do not restart at 1.
Skip plastic tags: they “deteriorate within years and tend to crack and fall off as the tree grows in diameter”.
Printed polyester stickers are UL-approved for outdoor use for up to 3 years, high-tack versions 3–5 (WePrintBarcodes). Marker pen on a plastic label “wore off after about three months” in one grower’s garden — anecdotal, but repeated on every hobbyist forum.
Squirrels “file their teeth on the edges of aluminum tags” and can take the number with them; Bartlett saw no such damage on brass — one consultancy’s observation, so brass is the upgrade, not the requirement.

Where and how to mount

Bartlett places trunk tags “on the least obvious side of the tree at a height of about six feet” with a 2½″ or 3″ coated deck screw angled downward; screws set into sapwood are endorsed by the ISA inventory standard (2nd ed.).
Back the screw out every few years to keep at least an inch of clearance, or the growing trunk swallows the tag.
On stems under 2″ across, use a loose loop of coated wire — never zip ties, which “become brittle and break due to sun exposure”. Loosen or remove the wire as the stem thickens, or it girdles the branch.
Arnold Arboretum hangs labels where they are conspicuous and reachable, on opposite sides of trees with low branches, and gives larger trunks a single label about 12″ above the soil — on a generous wire loop with a “curatorial twist” that keeps the wire from biting the bark.
For a staked tag, leave room between the tag and the ground so mulch does not bury it, and keep it away from the plant’s centre so it stays reachable (Penn State plant records manual).
Remove the nursery stake, ties and tag after planting — “Toss it all” — because they restrict the vascular system as the trunk grows. Your own tag goes on afterwards, loose.
Stickers do not stick to bark: adhesive fails on “rough, porous, textured” surfaces. Put a sticker on a stake, a smooth aluminium blank or a laminated hang-tag instead; a stake plate angled about 30° is easier to scan than a vertical one (QRLog — vendor practice, not a measurement).
The University of Houston files a second photo of every installed tag next to the tree’s record (campus tree-numbering guidelines); the app’s Tags card has a slot for exactly that photo.

Our own suggestion, not arborist guidance: Bartlett’s least-visible side is an aesthetic choice for client trees. If you will scan the tag with a phone, the side you approach from, at a height you can frame while standing, is more convenient. Pick one convention and use it on every tree.

Codes

Any pre-printed QR sticker works — from an office-supply roll, an asset-tag vendor, or a code you already own. The app only compares what it scanned to what you bound; it never opens a link, never stores the code’s contents, and nothing is sent anywhere.
Buy codes of 40 mm or larger so you can scan standing. The often-quoted 10:1 size-to-distance rule is a vendor heuristic, not a standard: a 15 mm code means a 15 cm scan distance — a crouch per tree.
Frame one tag per scan and let it fill the shot: a decoder needs the code, plus the four-module quiet zone Denso requires (Denso Wave), to occupy a large part of the image. A code that is a speck in a whole-tree photo will not read.
Choose matte, high-contrast stock — a silver-etched code on black anodized aluminium scans in sunlight (MyAssetTag).
Sticker rolls only pay off at scale: metal QR tags start at a minimum of 100 (from $249.95 per 100 at MyAssetTag) and polyester rolls ship in increments of 1,000. Below about two hundred trees, numbered aluminium and a typed number is the better buy.
If you print your own — the app can generate an opaque code per plant for you to print elsewhere — use error-correction level Q or H, which Denso recommends “for factory environment where QR Code get dirty”. Level H restores up to 30 % of a damaged code.

Tags go missing — keep the map

Tags blow away, deer chew aluminium and squirrels strip numbers; “you need a backup system in a safe spot” is the one thing every grower agrees on.
In the app, mark a tag as missing on the plant’s Tags card and rebind when you replace it. Profile → “Export spreadsheet (CSV)” writes the plant-to-tag-and-zone map for a spreadsheet, and the JSON backup is the restore path. Both stay on your phone until you choose to share them.

Sources

Every claim above carries its source inline; this is the same list in one place. Forum posts are marked anecdotal.

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