Annona grafting in winter? Do this instead for success

As days shorten and cold fronts roll in, many tropical fruit lovers are stocking up on scionwood for next season’s projects. If you’re eyeing cherimoya, atemoya, sugar apple, or soursop, you’ve likely wondered about Annona grafting in winter. Here’s the hard truth many seasoned growers repeat:

“Grafting in winter will be unsuccessful.”

That short warning saves months of frustration. Annona species are heat-loving, and their graft unions callus best when both rootstock and scion are metabolically active. In this guide, you’ll learn why winter grafts fail, the ideal timing by region, and what to do right now (late fall through winter) to set up a high-success spring. You’ll also get practical tips on scion selection, storage, tools, and techniques—so you’re ready when the weather turns.

Why winter grafting fails for Annona

Annona trees are tropical to subtropical. In cool conditions, they slow down dramatically. When sap flow is low, the cambium—the thin layer of living tissue that must align for a successful graft—doesn’t readily produce callus.

The physiology behind poor winter takes

• Low temperatures reduce cambial activity and callus formation.
• Short days and low light keep rootstocks semi-dormant or stressed.
• Dry indoor air or cold outdoor air dehydrates scions before they knit.

In practical terms, that means a clean cut and perfect wrap can still fail if the plant simply isn’t “awake.” Most reliable Annona grafting happens when daytime temperatures regularly reach 70–85°F (21–29°C) with nights above about 60°F (16°C), and when the rootstock is pushing new growth.

Temperature and moisture targets for callusing

• Day temps: 72–82°F (22–28°C) is a sweet spot for many growers
• Night temps: Consistently above 60°F (16°C)
• Humidity: Moderate to high (60–80%) to prevent scion desiccation

Below those ranges, expect slow or stalled callus and increased infection risk. That’s why winter is a waiting game—unless you can provide controlled conditions.

The best time to graft Annona (by region and setup)

Annona timing varies with climate and microclimate. Plan around your warm-up and the rootstock’s first strong flush.

Calendars by zone (Northern Hemisphere)

• Warm subtropics (USDA 10–11): Late winter to spring as days warm—roughly February to May. Peak window is often March–April.
• Marginal subtropics (USDA 9–9b): Mid-spring into early summer—typically April to June, once nights reliably exceed 55–60°F (13–16°C).
• True tropics: End of the dry season or the onset of the rainy season, when trees transition to active growth but disease pressure is manageable.

Greenhouse and protected culture

If you can hold stable warmth and humidity under cover, you can move the calendar forward. Many growers “bench graft” indoors on heat mats and then harden off as spring approaches. Keep in mind:

• Warm roots matter. Bottom heat (75–80°F / 24–27°C) accelerates callus.
• Gentle light is better than intense direct sun for fresh grafts.
• Aim for steady moisture—avoid both drought and waterlogging.

Species notes

• Cherimoya and atemoya: Generally the easiest for many home orchardists; commonly grafted onto cherimoya rootstock.
• Sugar apple (Annona squamosa): Likes it warmer; time grafts to reliably warm spells.
• Soursop (Annona muricata): Very cold-sensitive; reserve for consistently warm environments.

What to do in winter instead: Prepare like a pro

Winter can be your most productive season—off the tree.

Store scionwood correctly

• Select pencil-thick, disease-free, semi-hardwood scions from vigorous mother trees.
• Cut 6–8 inch sticks, label clearly, and seal both ends (parafilm or grafting wax).
• Wrap in slightly damp paper towel, place in a sealed bag, and refrigerate at 35–40°F (1–4°C).
• Check every 2–3 weeks; rewrap if drying; discard any moldy pieces.

Properly stored Annona scions often remain viable for several weeks to a couple of months—long enough to bridge winter into your ideal spring window.

Build strong rootstocks

• Keep container rootstocks just warm enough to hold health (bright light, minimal cold stress). Avoid pushing heavy growth you can’t maintain.
• Target caliper: Match scion and rootstock where possible. Most Annona grafts do well at 1/4–1/2 inch (6–12 mm) diameter.
• Prune or stake rootstocks now so you have straight, accessible graft points later.

Assemble and sanitize your kit

• Razor-sharp grafting knife or replaceable-blade utility knife
• Parafilm or buddy tape for sealing scions
• Stretch grafting tape or rubber strips for firm pressure
• Isopropyl alcohol for tool sanitation
• Labeling supplies and pruning seal if needed

A winter “dry run” helps too. Practice straight, smooth cuts on prunings so your hands are confident when the window opens.

Techniques that boost Annona graft success

You’ll find many viable methods—choose based on caliper match and your comfort.

Match technique to material

• Cleft graft: Great for topping rootstocks or when scion is smaller than the stock.
• Veneer (side) graft: Excellent for adding a variety to a growing limb without removing the leader.
• Bark graft: Useful on larger stocks once bark is slipping in spring; not ideal in cool weather.

Whatever you choose, the fundamentals don’t change:

• Make smooth, flat cuts to maximize cambial contact.
• Align cambium on at least one side if diameters differ.
• Apply firm, even pressure with tape; then seal completely to prevent drying.

Seal, shade, and wait

• Wrap scions fully in parafilm to lock in moisture.
• Provide light shade for the first 1–2 weeks, especially in bright climates.
• Don’t disturb the union. Resist “peek” checks—watch the scion bud for swelling instead.

Aftercare checkpoints

• 2–4 weeks: Look for callus and swelling buds.
• 4–6 weeks: If growth pushes, gradually relieve binding pressure to avoid girdling.
• Remove any shoots from below the graft to direct energy into the scion.

Troubleshooting quick hits

• Scion dried out: Improve sealing; increase humidity; graft earlier in the day.
• Union blackened or mushy: Sanitize tools, reduce water stress, use fresh scions.
• Slow callus in borderline temps: Add bottom heat or wait for a warmer spell.

Buying, selling, and timing Annona scions

Winter is prime time for buy/sell/trade activity—but timing delivery to your climate is everything.

How to choose quality scions

• Freshness: Look for recently cut wood with green cambium.
• Caliper: Pencil-thick pieces graft easily and hold moisture better.
• Variety authenticity: Buy from reputable sources; label immediately upon receipt.

Receiving and holding scions

• Open the package, check for mold, and rewrap in slightly damp paper if needed.
• Seal and refrigerate promptly. Avoid the freezer.
• Plan your grafting window backward from your climate’s warm-up so stored scions aren’t held excessively long.

Region-first scheduling

If you’re in a cooler zone (9–9b), request scions later in winter so they’re fresh in April–May. Warmer zones (10–11) can request deliveries earlier, targeting February–March grafts.

A quick case comparison

• January attempts (outdoor, Zone 9b): 0–20% typical takes due to cold snaps and slow callus.
• April attempts (same yard, highs 75–85°F): 70–90% takes with the same varieties and techniques.

Your mileage will vary, but temperature and rootstock vigor drive most of that difference.

Your winter action plan

Turn the “off-season” into a preparation advantage:

1. Inventory varieties and rootstocks; set your spring targets.
2. Order scions to match your climate window; store them correctly.
3. Prep tools and practice cuts on pruned branches.
4. Stabilize rootstocks—good light, no cold stress, balanced moisture.
5. If you have a greenhouse, set up a warm, humid bench-grafting station with bottom heat.
6. Block your calendar for a 2–3 week warm period when you can graft and monitor.

Conclusion: Wait now, win later

Annona grafting in winter is a losing bet outdoors, but that doesn’t mean you’re sidelined. Use the cold months to source top-tier scions, prepare vigorous rootstocks, and dial in your tools and technique. When your weather hits that 70–85°F groove and the rootstock is flushing, your take rates will reward the patience.

Ready to plan your spring grafts? Request our Annona timing checklist and cultivar planning worksheet, or reach out for a quick consult on your zone and setup. What varieties are you most excited to add to your collection this season?