Paulownia from seeds - sowing, the first year, and overwintering in Europe
, Written by Kacper Lorent, 16 min reading
Paulownia grown from seed is one of the fastest-growing trees that can be cultivated from seed. Sow it on the surface of the growing medium, without covering, at 22–28 °C in a bright location - its tiny seeds need light to germinate at all. It germinates quickly, and in its first season can grow from a speck into a knee-high tree or taller. The real test comes later: the first winter. The species is decisive here - downy paulownia tolerates frosts that Fortune's paulownia cannot survive - as is whether the young shoots have time to mature and become woody. Below, we describe how we grow paulownias from seed to tree in different parts of Europe.
| Species | Hardiness of a mature tree | Characteristics | Where to grow outdoors |
|---|---|---|---|
| Downy paulownia (Paulownia tomentosa) | approx. −20 °C | Most hardy, broad crown, purple flowers | Central, Western, and Southern Europe |
| Large-leaved paulownia (Paulownia elongata) | approx. −15 °C | Very fast growth, straight trunk | West and South; in Central regions, only warmer, sheltered locations |
| Catalpa-leaved paulownia (Paulownia catalpifolia) | approx. −15 °C | Slower-growing, compact, narrow habit | West and South; with protection in Central regions |
| Fortune's paulownia (Paulownia fortunei) | approx. −10 °C | Narrow crown, light-colored flowers, most sensitive | Only mild southern regions; container-grown elsewhere |
Which paulownia species should you choose?
All paulownias look similar in their first year: heart-shaped, softly hairy leaves, a thick green shoot, and a growth rate that surprises even people accustomed to exotic plants. The differences appear in winter. Downy paulownia (Paulownia tomentosa), also called the princess tree, is the species that tolerates frost best and the only one we confidently recommend for growing outdoors in Central Europe. In Germany, Austria, and the Czech Republic, it has been grown in parks for over a hundred years.
Large-leaved paulownia (Paulownia elongata) and catalpa-leaved paulownia (Paulownia catalpifolia) are significantly more sensitive. The former grows noticeably faster and has a straight trunk - hence its popularity on plantations in Spain and Italy. The latter grows more slowly but has a more compact form. Fortune's paulownia (Paulownia fortunei) is the most warmth-loving species: outdoors only where winters are mild, and elsewhere as a container plant or an experiment in a sheltered location.
The values given in the table apply to mature, well-woody trees. A first-year seedling is much more sensitive regardless of the species - see the section on overwintering. You can find all four species in the tree seeds section.
How to sow paulownia seeds step by step?
Paulownia seeds are as fine as dust - one packet contains so many that it is easy to sow them too densely. The most important rule is: paulownia germinates in the light. Studies on princess tree and empress tree seeds show that fresh seeds germinate poorly or not at all in darkness. A seed covered even with a thin layer of soil will usually simply fail to germinate.
- Prepare the growing medium. Use a light seed-starting mix, preferably sifted, with added perlite or vermiculite. Moisten it before sowing - when squeezed in your hand, it should release no more than a few drops.
- Sow on the surface. Scatter the seeds thinly, preferably mixed with a little dry sand, and gently press them down with your hand or a board. Do not cover them.
- Keep the moisture in. Cover the container with a propagator lid, plastic wrap, or place it in a ziplock bag. The medium must not dry out even once - the tiny seed has no water reserves.
- Provide warmth and light. A growing-medium temperature of 22–28 °C and a bright spot without harsh sunlight: an east-facing windowsill or an LED lamp. On a south-facing windowsill under a cover, overheating can easily occur.
- Water from below or with a sprayer. A stream from a watering can will wash the seeds away. The safest method is to place the container in a tray of water for a few minutes.
- Ventilate after germination. When the first green dots appear, start opening the lid for increasingly longer periods - this is the best protection against damping-off.
In our range, paulownia belongs to the warm and quick-germinating group. If the seeds have been stored for a long time and germinate reluctantly, cooling can help: several weeks in a moist medium in the refrigerator reduces their dependence on light. However, this is an option, not a requirement. We have compiled the rules for selecting the temperature and growing medium for all exotic species in the guide how to sow exotic seeds. Similarly, eucalyptus from seed is sown on the surface and in the light.
When to sow paulownia?
Paulownia needs the entire season to build roots and a woody shoot before winter. Therefore, the best time is late winter and spring: from February to April in Central and Northern Europe, and from January to March in the South. Sowing in February requires a grow light - without one, the seedlings become leggy. From March onwards, a bright windowsill is sufficient.
Autumn and winter sowing is possible, but only under a grow light and in warmth. A seedling sown in November will spend the entire winter indoors and will already be a sturdy plant in spring - this is a good solution for people who have supplemental lighting. We advise against sowing in summer, after June: the plant will not have enough time to become woody before the first frosts.
The first weeks: seedlings and pricking out
During the first few weeks, paulownia seedlings grow surprisingly slowly and look inconspicuous: two round cotyledons, followed by the first pair of hairy true leaves. This is normal - the plant is building its roots. Acceleration comes after a few weeks, and from then on paulownia can produce a new, increasingly larger leaf every few days.
Prick out the seedlings when they have two pairs of true leaves. Move them individually into 7–9 cm pots with light, well-drained soil, holding them by a leaf, not the stem - the stem breaks easily, while the leaf will grow back. After pricking out, keep them in partial shade for 2–3 days, then return them to full light. At this stage, the biggest enemy is overwatering: wet substrate combined with a cool night is a recipe for damping-off and root rot.
The first year of paulownia grown from seed - cultivation in a pot
Paulownia grows quickly only when it has space, light and nutrients. In practice, we transplant it 2–3 times in the first season, each time into a pot a few centimetres larger, when the roots emerge from the drainage holes. By the end of summer, a well-managed plant is usually from several dozen centimetres to over a metre tall, with leaves the size of a plate.
Position: full sun, but sheltered from the wind - large leaves tear easily, and the tall, soft shoot can topple over. Move seedlings outdoors only after the last frosts and gradually acclimatize them to the sun over a week. Watering: water generously in hot weather, but always ensure drainage. Fertilizing: from about one month after pricking out until midsummer, use a balanced fertilizer every 1–2 weeks. Stop fertilizing from August - this signals the plant to stop producing new leaves and start hardening its wood. Paulownia fertilized into autumn enters winter with a soft, green shoot that freezes back to ground level.
Plant paulownia in the ground only in the second year, in spring, after overwintering it in a pot. A larger, woody plant has a much better chance than a seedling planted in July. You can find light, well-drained potting mixes in the ready-made potting mixes section.
How do you overwinter young paulownia?
The first winter is when most paulownia seedlings are lost - not because of frost, but because of an unprepared shoot or overwatering in a dark room. In autumn, paulownia loses its leaves. This is normal, not a disease. A leafless plant needs very little water and does not need light, but it must not stand in wet soil.
Southern Europe (mild coastal areas of Spain, Portugal, Italy and Greece): tomentosa and kawakamii can overwinter outdoors as early as their first year, preferably against a wall. Move fortunei in a pot under cover during cold nights.
Western Europe (France, Benelux, Great Britain, Ireland): frost is rarely a problem; winter damp is more often the issue. Place the pot under an eave or in an unheated garage and keep watering to a minimum. From the second year, tomentosa, kawakamii and fortunei can grow in the ground.
Central Europe (Poland, Germany, Czechia, Austria, Hungary): spend the first winter in a cool, bright or dark room at a temperature of 0–10 °C - a basement, garage or stairwell. Water once every few weeks, just enough to prevent the root ball from drying out completely. In this zone, we mainly recommend tomentosa for growing in the ground. Protect young trees with a mound of bark or leaves during their first winters. Even if the shoot freezes, tomentosa usually regrows from the roots in spring, often more vigorously than before.
Northern Europe (Scandinavia, the Baltic countries): growing paulownia in the ground is an experiment even in the case of tomentosa. Growing it in a large pot and overwintering it in a cool, frost-free room is more reliable. We use the same approach - the first winters in a pot, planting in the ground only once the plants are established - for silk tree.
Pruning for “giant leaves”
Paulownia has one trick that gives it a tropical appearance even in a cool climate. If, in early spring, before growth begins, you cut the shoot low above the ground, one or several very strong shoots will grow from the roots, with leaves several times larger than those on an unpruned tree — often more than half a metre in diameter. In England, this is a classic practice in exotic-style gardens.
The rules are simple. Prune only plants with a well-developed root system — in practice, from the second or third year in the ground. Prune at the end of winter, not in autumn. Of several new shoots, leave the strongest one if you want the largest leaves. Fertilize and water generously throughout spring and early summer — a large leaf requires a lot of water.
Pruning has two additional benefits. In Central Europe, it solves the problem of frost damage: you remove the shoot that would have frozen anyway. And a plant pruned every year does not flower or set seed — which matters in regions where empress tree self-seeds (more in the questions at the end). If, on the other hand, you dream of purple flowers in spring, leave the tree unpruned: flower buds form as early as autumn on woody shoots and may be damaged by frost during a cold winter.
Most common problems
| Symptom | Most common cause | What to do |
|---|---|---|
| Seeds do not germinate | Covered with soil, too cold, or the growing medium has dried out | Sow again on the surface, in the light, at 22–28 °C, under a lid |
| Seedlings topple over at the base | Damping-off — too wet, lack of ventilation | Remove diseased seedlings, ventilate, water from below, and do not leave water in the tray |
| Seedlings are long, pale, and thin | Not enough light | LED lamp 10–20 cm above the seedlings or the brightest windowsill |
| Leaf edges turn brown in summer | Wind, drying out, or strong sun without acclimatization | Protect it from the wind, water regularly, and gradually acclimatize it to the sun |
| All the leaves fall in autumn | Natural dormancy | Reduce watering and move it to a place for overwintering |
| The shoot is dry in spring, with no buds | Frost damage to a non-woody shoot | Wait until late spring — paulownia often regrows from the roots; cut off the dry part |
If you want to make the start easier, a consistent temperature and humidity help — for sowing small seeds, propagators with a lid are the most convenient.
Frequently asked questions
How quickly do paulownia seeds germinate?
Quickly - paulownia is one of the fastest-germinating trees in our range, provided that the seeds are on the surface, exposed to light and kept warm (22-28 °C). If nothing happens for a long time, the seeds were most likely covered or the growing medium dried out.
Do paulownia seeds need to be covered with soil?
No. Paulownia germinates in light, so the seeds should be scattered on the surface of moist growing medium and only lightly pressed down. Seeds covered even with a thin layer usually do not emerge.
Which paulownia is the most frost-resistant?
Paulownia tomentosa (Paulownia tomentosa). Mature trees tolerate frosts down to around -20 °C, and this is the species we recommend for planting in the ground in Central Europe. Paulownia grandifolia and Paulownia elongata are more sensitive, while Paulownia fortunei is the most sensitive.
Can paulownia be grown in a pot?
Yes, especially during the first 1-2 years and in cold regions. It needs a large pot with drainage, full sun and regular watering. It grows more slowly in a pot than in the ground, and it is easy to move it to a cool, frost-free room for winter.
When should paulownia be planted in the ground?
In spring of the second year, after the last frosts, once the plant has overwintered in a pot and has a woody stem. Seedlings planted in the ground in their first year often do not survive their first winter.
Is paulownia an invasive species?
Paulownia tomentosa is on the EPPO (European and Mediterranean Plant Protection Organization) Alert List and has naturalized in parts of several countries - including Austria, Germany, the Czech Republic, Hungary, Italy, France, Switzerland, Belgium and the United Kingdom. It spreads through tiny seeds carried by the wind, mainly in wastelands, along railway tracks and in cracks in walls. In the garden, this is easy to prevent: regular cutting back to a trunk keeps the tree from flowering, and on flowering trees it is enough to remove the seed capsules before they mature. Do not plant paulownia near natural areas and check local regulations - restrictions may apply in some regions.
When will paulownia grown from seed flower?
Usually after a few years, once the tree reaches a suitable size. Buds form in autumn, and the flowers open in spring before the leaves. Trees cut back to a trunk every year do not flower.
Sources: EPPO, “Alert List: Paulownia tomentosa”; Carpenter and Smith, “Germination of Paulownia seeds in the presence and absence of light”, Tree Planters’ Notes; Grubišić et al., “Light and temperature action in germination of seeds of the empress tree (Paulownia tomentosa)”, Physiologia Plantarum; Cathaia - characteristics of paulownia species and hardiness zones; Royal Horticultural Society, “Damping off”; mr.seed’s own experience from sowings at the warehouse and customer reports from across Europe.