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  • ✔ Worldwide shipping
  • ✔ Free shipping included
  • ✔ Professional export packaging
  • ✔ Paulownia growing guide included
  • ✔ Root cuttings available for pre-order
  • ✔ Need more information? Contact us at contact@kirigreen.com

Paulownia Seed Sowing Guide

From seed to planting out — the complete step-by-step method for all Paulownia varieties, hybrids and pure species alike. The key to success: light, warmth and a humid greenhouse environment.

7–21 dGermination
8–14 wkSeed to planting
1.5–3 mGrowth year 1
75–85%Germination rate
7–10 yrWood harvest
In this guide

Paulownia seeds are tiny but full of potential. Unlike many seeds, they must never be buried — they need light to germinate. The whole method comes down to recreating a warm, humid, bright micro-climate: a simple greenhouse effect that triggers fast, even germination.

The 3 golden rules

Before anything else, remember these three fundamentals. Get them right and germination follows naturally.

1. Never bury the seeds

  • Paulownia seeds germinate only in the light.
  • Sow them on the surface of the substrate.
  • Press very gently with a fingertip for seed-to-soil contact — nothing more.

2. Light is essential

  • Bright, indirect light or a grow lamp keeps germination going.
  • A windowsill, greenhouse or grow light all work well.
  • Avoid direct, scorching sun — bright but indirect light is ideal.

3. Create a warm, humid greenhouse environment

  • Keep 20–25 °C during the day, 15 °C minimum at night, and ideally no more than 30 °C.
  • Maintain constant humidity — but never soaking wet.
  • Cover to trap warmth and moisture (see the dedicated section below).

What you need

Essential

  • Paulownia seeds
  • A fine, well-draining seed substrate (light potting mix, optionally with a little sand or perlite)
  • Seed trays, cells or small pots with drainage holes
  • A cover: mini-greenhouse lid, clear plastic film, or a transparent box
  • A bright spot: windowsill, greenhouse, or a grow lamp
  • A fine mister (spray bottle)

Optional but helpful Optional

  • A heat mat to hold a steady 20–25 °C in cool rooms
  • A grow light for early sowing or low-light regions
  • Perlite or river sand to lighten the substrate
  • A small thermometer / hygrometer to monitor the micro-climate
Good to know: none of the "optional" items are mandatory. A simple tray on a bright windowsill with a plastic cover is enough to succeed. The extras just make results more consistent, especially in cold or dark conditions.

Creating the greenhouse effect (the most important step)

This is the heart of the method. The "greenhouse effect" simply means trapping warmth and humidity around your seeds while still letting light through. It's what makes germination fast and even.

How to create it

  • After sowing, cover the tray with a transparent lid, clear plastic film or a see-through box.
  • The cover must let light through — never use an opaque cover.
  • Place everything in a warm, bright spot (20–25 °C).
  • Condensation on the cover is a good sign: it means humidity is high.

How to maintain it

  • Ventilate 5 minutes a day by lifting the cover — this prevents mould.
  • Keep the substrate moist but never waterlogged.
  • Re-mist lightly whenever the surface starts to dry.
  • Hold the temperature as steady as you can, day and night.
Watch out: the two enemies at this stage are drying out (seeds stop germinating) and stagnant damp air (mould / damping-off). The daily 5-minute airing is what keeps the balance right.

The 8 steps, from seed to planting out

  1. Prepare & moisten the substrate Essential Before sowing, fill your trays or cells with a fine, well-draining substrate and water it first so it is evenly moist — but never soaking wet. Sowing onto an already-damp substrate gives the seeds the right conditions from the start.
  2. Surface sowing Essential Place 2–3 seeds per cell directly on the surface — do not bury them. Light is essential for germination. Press very gently with a fingertip to ensure seed-to-soil contact.
  3. Misting & covering After sowing, lightly mist the surface with a fine spray to settle the seeds and keep them humid — never a direct jet, which would displace them. You can also water by capillarity (a tray of water under the pots). Then cover with clear plastic film or a mini-greenhouse lid. Ventilate 5 min/day to prevent mould.
  4. Emergence (day 7 to 21) Remove the cover gradually over 2–3 days as soon as the first shoots appear. Keep 20–25 °C by day (max 30 °C), 15 °C minimum at night. Keep the most vigorous seedling per cell — cut the others at soil level with scissors. Thinning optional but recommended for strong plants
  5. Pricking out / potting up (seedlings 5–8 cm) Once the seedlings reach 5–8 cm, transplant them into 9–12 cm pots with the same free-draining substrate. Moisten the cell before lifting the seedling. This time you can bury up to the cotyledons (the first pair of leaves). Water lightly and return to full light at 20–25 °C.
  6. Fertilization (ongoing care) Optional Fertilization is a continuous care step that accompanies growth. From 3–4 weeks after emergence (2 to 4 true leaves): NPK 10-10-10 diluted to 50% of the dose. From the 6th week: full dose. Then switch to NPK 15-15-15 to support growth in pots. Seedlings will grow without feeding, but fertilizer gives stronger, faster development.
  7. Hardening off (10–15 days) Essential Gradual acclimatization is essential before planting out: days 1–4: 2 h outside, sheltered from wind. Days 5–9: 4–6 h with progressive sun. Days 10–15: outside permanently. Bring in only if frost is forecast.
  8. Planting in open ground Once the plants are at least 15–30 cm tall and all risk of frost has passed, plant them in the ground. Well-drained soil, loosened 40–50 cm. Hole 40 × 40 cm. Spacing: 4–6 m for timber production, 2–3 m for windbreak hedges, 1–2 m for dense biomass. Water generously.

Common problems & solutions

Problem Likely cause & solution
No germination after 3 weeks Seeds buried, too little light, or too cold. Sow on the surface, add light, hold 20–25 °C.
Mould on the surface Stagnant humid air. Ventilate daily, reduce watering, improve airflow.
Seedlings collapse at the base (damping-off) Too wet and too warm without airflow. Reduce watering, ventilate more, remove affected seedlings.
Substrate dries too fast Cover not sealing well or spot too hot/dry. Re-mist, check the cover, move out of direct heat.
Tall, thin, pale seedlings Not enough light (etiolation). Move to a brighter spot or add a grow lamp.
Seedlings stall after emergence Often normal in the first weeks. Keep warmth, light and gentle moisture; feeding can help.

Key takeaways for successful sowing

  • Never bury the seeds — sow on the surface, light is essential for germination.
  • Moisten the substrate before sowing, then mist lightly after sowing to settle and humidify the seeds.
  • Create a warm, humid greenhouse environment: transparent cover, 20–25 °C (max 30 °C), constant moisture.
  • Water only by fine misting or capillarity — never a direct jet.
  • Ventilate 5 minutes a day to prevent mould — this is the balance point.
  • Remove the cover gradually once shoots appear; keep one vigorous seedling per cell.
  • Fertilization is optional but boosts growth; hardening off before planting is essential.
  • Plant out once seedlings are 15–30 cm tall, after all frost, in well-drained soil loosened to 40–50 cm.
  • Germination in 7–21 days · seed to planting in 8–14 weeks · 1.5–3 m in the first year.

Happy sowing and a fine harvest!
A question about your project? Contact us at contact@kirigreen.com — we're always happy to help.

Paulownia Growing Guide

Everything you need to successfully plant and grow your Paulownia from root cuttings and bare-root stumps — all varieties, step by step.

In this guide

The root cutting is the most efficient and reliable way to propagate Paulownia. A 12–14 cm root segment holds enough energy reserves to produce a vigorous new plant — with no rooting hormones or special substrate needed. Bare-root stumps take this a step further, offering an already-developed root system and a cut trunk for even faster establishment.

1. Variety overview

Each variety offered by KiriGreen has its own strengths in growth, cold resistance and use. This applies to both root cuttings and stumps.

Variety Frost Growth/yr Success Parentage Characteristics & use
Pao Tong Z07 (hybrid) −33 °C 2.5–5 m 94–99% P. tomentosa × P. fortunei × P. kawakamii Ultra-hardy hybrid. High-density timber, biomass, agroforestry. The most cold- and heat-resistant of the range. Exceptional adaptability to all climates.
Shan Tong (hybrid) −28 °C 2.5–5 m 94–99% P. tomentosa × P. fortunei The reference hybrid in Europe. High-quality timber, 40% lighter than pine. Even growth, straight trunk. Stump regrows 4–7 times after cutting.
9501 (hybrid) −25 °C 2–4 m 94–99% P. tomentosa × P. fortunei Founding 950x hybrid, versatile and productive. Timber, windbreak hedges, beekeeping, ornament. Very adaptable, from continental cold to warm subtropical.
9502 (hybrid) −25 °C 2–4 m 94–99% P. tomentosa × P. fortunei Productive 950x hybrid. Stable, even growth. Timber, mixed plantations. Good adaptation to varied soils and difficult climatic conditions.
9503 "Oxytree" (hybrid) −25 °C 2–4 m 94–99% P. tomentosa × P. fortunei The most refined 950x selection. Dense plantations, industrial timber, biomass. The most adaptable of the range — from temperate to tropical zones.
Elongata (pure species) −18 °C 3–5 m 94–99% Pure species (P. elongata) Pure species for warm and temperate regions. Ultra-fast growth up to 5 m/yr. Light wood, reforestation, ornament. Decorative pale-lilac blossom in April.
Fortunei (pure species) −20 °C 2–3 m 94–99% Pure species (P. fortunei) Pure species, parent of all modern hybrids. Quality wood, straight trunk. Large leaves, fragrant purple blossom. Excellent drought and pollution resistance.
Tomentosa (pure species) −25 °C 2–3 m 94–99% Pure species (P. tomentosa) The imperial tree. Highly ornamental pure species. Spectacular fragrant purple blossom. Melliferous. Adapts to all soils. The most cold-hardy of the pure species.

2. Root cuttings vs bare-root stumps

Both are excellent starting points — the right choice depends on your project and how quickly you want establishment.

Root cuttings

  • A 12–14 cm root segment
  • The most economical option for volume planting
  • Develops its own roots and shoots after planting
  • Planted inclined at 45°, fully buried
  • Ideal for trials and large plantations

Bare-root stumps

  • A dormant young plant with a developed root system and cut trunk
  • Faster establishment than cuttings or seeds
  • Planted vertically, roots covered, cut section just above ground
  • Ideal for professional, faster-yield plantations
In short: a cutting builds everything from a root segment; a stump already has its root structure and trunk, giving it a head start. The planting principles that follow apply to both — the key difference is orientation at planting (see section 5).

3. Checking your plants on delivery

Your cuttings and stumps arrive ready to plant. On arrival, simply check the following:

  • The cutting or stump is firm and not shrivelled — a sign of good vitality.
  • The bark is healthy, with no black spots or soft, suspicious areas.
  • If you can't plant immediately: keep the material in slightly moist sand, protected from frost (2–5 °C), for a maximum of 2–4 weeks.

4. Soil & substrate preparation

In open ground

  • Ideal soil: sandy-loam; adapts to any well-drained soil. pH 5.5 to 7.5.
  • Loosen to 40–50 cm deep before planting.
  • Add coarse sand or mature compost if the soil is heavy or clay.
  • Avoid areas with a high water table or prone to waterlogging.
  • Organic or plastic mulch: 1 m around the base.

In container / nursery

  • 50% sifted horticultural potting soil
  • 30% river sand or perlite
  • 20% well-decomposed compost
  • Pots of 1–2 litres minimum, with drainage holes. Target pH: 5.5 to 7.0.

5. How to plant

Root cuttings

  1. Dig: make a hole or furrow about 15 cm deep.
  2. Place: lay the cutting inclined at 45°, fully buried, with the top surface 2–3 cm below the soil. Orient the thicker end upward.
  3. Firm: gently firm the soil around the cutting to remove air pockets.
  4. Water: water moderately after planting. Do not saturate the soil.

Bare-root stumps

  1. Dig a hole large enough to spread the roots naturally.
  2. Position the stump vertically, with the root system fully covered and the upper cut section remaining just above ground level.
  3. Fill with loose soil and gently firm around the roots to remove air pockets.
  4. Water thoroughly right after planting, then keep moisture regular during establishment. Avoid permanently waterlogged soil.
Key difference: a cutting is planted inclined at 45° and fully buried; a stump is planted vertically with its cut trunk left just above the surface.

6. Watering, care & fertilization

Watering

  • First 4 weeks: soil slightly moist, never soaked. 1–2×/week.
  • From first shoots: gradually increase water.
  • First 2 years: 20–40 L per plant, 1–2×/week.
  • Heat (> 30 °C): water every evening.
  • From year 3: self-sufficient, except drought > 3 weeks.
  • Sign of shortage: leaves curling and dropping prematurely.

Fertilization & care

  • First feed when the shoot reaches 20–30 cm: NPK 10-10-10 at half dose.
  • Spring (regrowth): NPK 20-20-20 to boost growth.
  • Summer: NPK 15-15-15. Stop all nitrogen by late August.
  • Weeding within 1 m: essential for the first 2 years.
  • Mulch (10–15 cm): moisture, weeds, root protection.
  • Optional technical pruning (frost-free period): cutting the stem back low encourages a single, straight regrowth.

7. What to expect after planting

Period What happens
Weeks 1–3 No visible sign above ground. The cutting develops its first adventitious roots. No cause for concern.
Weeks 4–6 First buds and small shoots appear at the surface. The cutting has rooted.
Weeks 6–10 Rapid stem development. The main shoot asserts itself. Select the most vigorous one.
Months 3–6 The plant reaches 30–80 cm depending on climate and variety.
End of year 1 In good conditions: 1.5–3 m tall depending on variety and watering.

Selecting the dominant shoot

  • Several shoots may emerge from one cutting. For a straight tree with optimal growth:
  • Select the most vigorous shoot.
  • Pinch or cut the others at their base.
  • Keep only one main stem per cutting.

Frost protection

  • Young shoots are sensitive to late frosts in the first 2 years.
  • Cover with fleece if frost threatens.
  • Frost down to −5 °C kills the aerial shoot, but the plant regrows from the base.
  • Optional technical pruning: in a frost-free period, the stem can be cut back low to obtain a single, straight, vigorous regrowth.

8. Common problems & solutions

Problem Solution
No emergence after 8 weeks Check soil moisture (too dry or too wet), temperature (< 10 °C), or a damaged cutting.
Cutting rot Insufficient drainage or excessive watering. Improve the soil, reduce watering.
Weak, stunted shoot Lack of light, weed competition or compacted soil. Weed and loosen.
Yellowing leaves Excess water, iron deficiency (chlorosis) on chalky soil, pH too high. Check drainage.
Mole cricket attack Insects that cut through roots. Set up water-pot traps around the plants.
Main shoot frozen Normal: remove the frozen stem — one or more shoots will regrow vigorously.
Slow growth in summer Insufficient watering or compacted soil. Increase water (20–40 L) and mulch.
Leaves burnt at the edges Excess fertilizer or water deficit. Leach the soil, reduce NPK by 30%.

9. Annual fertilization plan — Paulownia in open ground

Period NPK fertilizer Dose / plant Frequency Role
Feb–Mar (before regrowth) NPK 20-20-20 soluble 150 g (yr 1: 80 g) 1 application before shoots N: kick-starts growth. P: rooting. K: natural defences.
Apr–May (fast growth) NPK 20-20-20 soluble 100–120 g in water Every 3 weeks High N: 5–15 cm/week growth. P: lateral roots. K: stem rigidity.
Jun–Jul (peak growth) NPK 15-15-15 granular, buried 150–200 g at base Every 4 weeks Balanced N-P-K sustains growth. Promotes trunk lignification.
August (gradual stop) NPK 0-15-30 (no nitrogen) 80–100 g at base 1 application early August Zero nitrogen stops elongation. P+K harden the wood before winter.
Sep–Jan (dormancy) No fertilizer — — Tree at rest. Winter nitrogen causes fragile, frost-sensitive shoots.

10. Key takeaways for optimal success

  • Root cuttings: 12–14 cm segments, delivered ready to plant. Planted inclined at 45°, thicker end up, fully buried.
  • Bare-root stumps: a dormant young plant with a developed root system and cut trunk. Planted vertically, roots covered, cut section just above ground — for faster establishment.
  • Check vitality on arrival: the material should be firm, with healthy bark.
  • Well-drained soil, loosened 40–50 cm. Moderate watering until emergence, then 20–40 L/plant, 1–2×/week for 2 years.
  • Select a single dominant shoot for a straight, vigorous tree.
  • Mulch, regular weeding within 1 m, seasonal NPK fertilization.
  • Protect from late frosts for the first 2 years.
  • Year 1: 1.5–3 m depending on variety. Timber harvest: 7–10 years. The stump regrows around 5 times after cutting.

Happy planting and a fine harvest!
A question about your project? Contact us at contact@kirigreen.com — we're always happy to help.

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