Why every new plant goes into quarantine
Almost every serious pest outbreak in a home collection starts the same way: a new plant arrives, looks perfect, goes straight onto the shelf with everything else, and three weeks later the neighbouring Anthurium has silvery thrips scarring and the Alocasia is stippled with spider mite. Nothing was visible on the day of arrival because eggs, first-stage larvae and pupae in the substrate are too small to see. Quarantine is simply time: long enough for anything hidden to hatch, show itself and be dealt with before it can reach the rest of your plants.
On our own benches in York every incoming batch, including plants from long-standing growers, sits in an isolation house before it joins the stock benches. The card this page prints is a home-sized version of the one clipped to those benches.
Choose the right quarantine length
The length depends on where the plant came from and how long pest life cycles take at room temperature. Western flower thrips complete a generation in roughly two to three weeks at 20°C; two-spotted spider mite can go from egg to egg-laying adult in under a fortnight in a warm, dry room. A plant from a UK nursery that runs its own biosecurity programme and ships with a plant passport is reasonably covered by 14 days. A plant from a private swap, a plant fair or a garden centre bench where stock from many sources stands together deserves 21. A bare-root import, which has been unpotted, washed and shipped across borders, warrants 28 days and close attention to the roots.
Set up an isolation zone that actually isolates
Isolation means distance and separate tools. Pick a windowsill or shelf in another room, ideally three metres or more from the main collection, with enough light to keep the plant growing. Give it its own watering jug, its own mister and its own cloth; thrips and mites travel on hands, sleeves and spouts far more often than they fly. Visit the quarantine plant last in any watering round, never first.
Keep the UK Plant Passport
Plants sold by professional operators in Great Britain carry a UK Plant Passport, usually printed on the pot label. It has four parts: A, the botanical name; B, the APHA registration number of the operator; C, a traceability or batch code; and D, the country of origin, for example GB or NL. Copy them onto the card. If a pest or disease problem does appear, those four lines let the seller, and if necessary the Animal and Plant Health Agency, trace the batch. Our plant passport guide explains what each part means.
The first seven days: no repotting
A plant that has spent a day or two in a dark box is stressed. Its roots have been jolted and it has used stored energy. Repotting it immediately adds a second shock at its weakest point, and if it then declines there is no way to tell transit damage from repotting damage. That is why our 7-day live arrival guarantee asks you not to repot during the first week. Unpack it, stand it in bright indirect light away from radiators, water only if the substrate is dry, and use the time to inspect.
What to look for at each check
The inspection matrix on the card covers four places where pests hide:
- Leaf undersides (abaxial surface): fine pale stippling, dusty webbing or tiny moving dots at the leaf base mean spider mite. Use a hand lens.
- Petiole sheaths and new leaves: silvery scars, black specks of frass and slender pale larvae tucked into the sheath of an unfurling leaf are signs of thrips.
- Stem nodes and leaf axils: white cottony tufts or waxy ovals are mealybug, often deep in the junction where the petiole meets the stem.
- Substrate surface: small black flies lifting off when the pot is moved, or translucent larvae with black heads in the top centimetre, are fungus gnats (Bradysia).
Tick each box clean or note what you found, and record the sticky trap count. A rising trap count is often the first clue, before any leaf damage appears. If you find something, treat it and restart the clock from that day; our biological control guide covers predatory mites and nematodes, and the pest release log keeps the programme on track.
Release and the Day-21 repot
Once the final check is clean, sign the release box and move the plant into the collection. This is the right moment to repot: the plant has recovered from transit, you know it is clean, and fresh substrate removes any eggs that might have been in the old nursery mix. Step up by one size into a clear slotted pot filled with a free-draining peat-free blend matched to the genus, and use the repotting calculator to get the litres right.