PACIFIC NORTHWEST (7b–9)

Field Note

August 28, 2026 — Overnight low of 63°F Saturday, then a full reversal: highs of 88–92°F with lows in the low 70s through September 3, rainfall chances under 15% until Thursday. This is the last block of usable heat units before the September decline, and daylength is already down about 75 minutes from the June peak. Florence, KY (Zone 6b).

I write from Zone 6b, where the fall transition is driven by cold. In the Pacific Northwest it is not. Your winter lows are milder than mine — a coastal Oregon grower can go whole winters without a hard freeze — and yet Adenium fail in the Northwest at rates that surprise people who assume mild means easy.

The reason is that Adenium do not run on air temperature. They run on accumulated heat and on light. The Northwest is short on both, and the shortage arrives earlier than the calendar suggests. By late September the marine layer is back, cloud cover is persistent, and effective light drops off a cliff while temperatures stay in a range that keeps the plant metabolically awake. A plant that is awake, wet, and underlit is a plant that rots.

So the fall question in the Northwest is not "when do I protect from cold." It is "how do I keep this plant either properly lit or properly shut down, and never stuck in between."

What Has to Happen Now

Finish repotting while soil is still warm. Root activity follows soil temperature, and Northwest soil temperatures fall faster than most growers expect once the sun angle drops. Get repots done by mid-September. Repot dry, and hold water five to seven days afterward — with your ambient humidity, that hold matters more than it does for me.

Top dress everything else. This is arguably more valuable in the Northwest than anywhere. A compacted, moss-crusted surface layer under Northwest fall conditions stays damp continuously, and that dampness sits against the caudex for months. Pull the top inch, replace it with fresh coarse material, and you eliminate the single most common rot vector in your climate.

Cut nitrogen now.

When to stop fertilizing Adenium: stop all nitrogen-bearing fertilizer roughly six weeks before your average first frost, or when nighttime lows fall consistently below 60°F — whichever comes first.

In the Northwest the second condition is what triggers. Coastal and lowland growers hit consistent sub-60°F nights in early to mid-September regardless of frost date, and that is your signal. Follow with one low-nitrogen, high-potassium feed to firm tissue, then stop.

Decide now which plants get light and which get dormancy. This is the Northwest-specific decision, and it should be made in August, not November. There is no good middle path.

The Two Paths

Path one: real supplemental light. If you are running a grow room, a lit greenhouse, or a serious shelf setup, you can hold plants in active growth through winter. That means real output — a full-spectrum LED delivering meaningful PPFD at canopy height, on a 12–14 hour photoperiod. A shop light three feet above the plant is not supplemental light, it is decoration. If you go this route, keep temperatures above 65°F and water normally, because a lit, warm plant is still transpiring.

Path two: deliberate dormancy. Move plants to a dry, dark or dim space held above 50°F, let them drop leaves, and stop watering entirely. This works well in the Northwest and it is what I would recommend for most growers. Attached garages, unheated but insulated rooms, and dry basements all work if you can hold 50°F.

The failure mode is doing neither — leaving plants in a cool, dim window, watering them occasionally because they still have some leaves. That plant never shuts down and never grows. It just slowly declines until it collapses in February.

Callouts by Sub-Region

Coastal Oregon and Washington (8b–9): you have the mildest temperatures and the worst light. Frost is not your problem. Rainfall and cloud cover are. Get everything under cover before the fall rains set in — an Adenium sitting outside through a Northwest October is receiving weeks of continuous moisture with no evaporative demand. Move earlier than you think you need to.

Willamette and Puget lowlands (8a): you get occasional hard freezes on top of the light problem, so you need both a light plan and a cold plan. Your move-in trigger should be the first forecast below 45°F. In practice that usually lands in early to mid-October.

Inland and higher elevation (7b): your season looks more like mine than like Portland's. Real freezes arrive, soil cools quickly, and your repot window closes around September 10. Treat the Cold Climate timeline as your baseline and adjust from there.

Sowing in the Northwest

Fall sowing works in the Northwest, but only under lights — there is no ambiguity here the way there is in warmer regions. Fresh seed germinates in three to seven days at 85°F on a heat mat, and September-sown seedlings get six to eight weeks of establishment before your light collapses. From there they need real supplemental lighting through February.

If you have the lighting, September sowing produces a noticeably stronger plant than February sowing. If you do not, wait for spring. Damping-off is the other Northwest hazard, and it is media-driven: the flat needs to hold moisture without going anaerobic. Desert Oasis Germination Media is built for that.

Fresh seed from India releases next week, and a Thailand shipment lands mid-September including six Adenium arabicum Thai hybrids.

What Goes Wrong

Slow decline from October through February. The half-dormant, half-lit plant. Pick a path.

Rot with no obvious cause. Usually surface moisture and compacted media, not overwatering per se.

Etiolated, stretched winter growth. Light intensity is too low for the temperature you are holding. Either add light or lower the temperature and force dormancy.

Seedlings that damp off in week two. Media and airflow. Both fixable.

What Changes Next Week

Starting Tuesday, September 1, this publication moves to a Tuesday and Thursday schedule. Tuesday establishes the biological moment; Thursday delivers the specific protocol. September 1 opens the Cold Season series with the four-cohort overwintering trial. September 3 covers repotting and top dress in full.

What We're Growing With

• Desert Oasis Potting Media — fast-draining mix, which matters more in your climate than in almost any other. Full line back in stock next week.
• Desert Oasis Fall Top Dress — the fix for persistent surface moisture.
• Desert Oasis Germination Media — for September sowing under lights.
• Adenium seed — fresh India shipment releasing next week.
  

The full regional breakdown — with specific timing and application guidance for Cold Climate, Pacific Northwest, Gulf Coast, and Western growers — is at americanadenium.com.

Cheers,

Michael