Planting and Growing a Catalpa in a Pot

Why Plant the Catalpa in a Pot?

Planting a catalpa in a pot is an excellent idea for many reasons:

• An ornamental tree suitable for small spaces: in a container, the size of the catalpa remains controlled, making it perfect for decorating a terrace or balcony.
• Appreciable mobility: thanks to the pot, it is possible to move the catalpa as needed, particularly to adjust its exposure or protect it during winter.
• Easier maintenance: in a pot, the roots are contained, which simplifies watering, pruning, and monitoring tasks.
• A major aesthetic asset: the catalpa, with its large heart-shaped leaves and clusters of white flowers, adds an elegant and natural touch.

Which Variety of Catalpa to Choose?

Not all varieties of catalpa are suitable for pot cultivation. **It is advisable to choose cultivars with moderate growth**. When purchasing, **also prefer a smaller tree**, which will better adapt to its container, especially since the catalpa has a rapid growth rate. Here are some suggestions:

• Catalpa bignonioides ‘Nana’: also known as the globe catalpa, it is one of the varieties with the least development. It has a compact, spherical habit. Ideal for small spaces, it does not produce flowers, but its dense foliage provides appreciable shade.
• Catalpa bignonioides ‘Aurea’: this variety is distinguished by its bright golden-yellow foliage. In the ground, it can reach a span of 7 meters at ripeness, but its growth in a pot can significantly reduce its dimensions. Its summer flowering, white with a purple heart, is followed by long decorative pods.
• Catalpa bignonioides ‘Variegata’: this variety stands out with its variegated foliage of green and cream white, which brightens the space. With a moderate adult size, it is perfectly suited to pot culture, where its growth will be even more contained. Its white flowering in summer brings an elegant and fragrant touch.
• Catalpa speciosa ‘Pulverulenta’: this catalpa is remarkable for its leaves lightly dusted with white, giving it a delicate and refined appearance. Smaller than the common catalpa, it is ideal for container culture, where it brings a unique charm with its ornamental foliage. In summer, it offers beautiful white flowers with yellow hearts.

Catalpa bignonioides ‘Nana’, Catalpa bignonioides ‘Aurea’, Catalpa bignonioides ‘Variegata’ and Catalpa speciosa ‘Pulverulenta’

When to Plant a Catalpa in a Pot?

The ideal time to plant a potted catalpa depends on the climate conditions:

• In spring: mild temperatures promote rapid root development and vigorous growth resumption.
• In autumn: planting in this season allows the catalpa to establish well before winter, but this method should be reserved for regions with mild winters.

If possible, avoid planting a catalpa in summer to prevent the tree from experiencing water stress, even with diligent watering. In winter, planting is not recommended due to the risk of frost.

Which Pot to Choose for Growing a Catalpa?

For a catalpa to be well-rooted, you need to start by choosing the right pot:

• A suitable material:
  • Terracotta offers good breathability, which reduces the risk of root asphyxiation. However, the soil dries out faster, and you will need to be diligent with watering.
  • Plastic retains moisture better, but beware of water stagnation. Therefore, watering should be done sparingly. Another advantage: the plastic pot is lighter and easier to move.
• A large pot: the pot should be at least 50 cm in diameter and depth, with sufficient volume to accommodate the tree’s root system.
• Good drainage: ensure that the pot has drainage holes to prevent water accumulation, which can cause root rot. Place an appropriate saucer under the pot.

What Type of Substrate Should You Choose for a Catalpa?

A good substrate will ensure the healthy growth of your potted Catalpa. To choose the right one:

• A drainage layer: place clay pebbles or gravel at the bottom of the pot to ensure good water flow.

• A quality potting soil:
  • Use a universal, high-quality potting soil rich in organic matter.
  • Add coarse sand (1/4 sand to 3/4 potting soil) to improve drainage and prevent compaction. Note: exclusively use river or quarry sand.
  • If possible: add a portion of garden soil to structure the substrate.
• Suitable fertiliser: incorporate a slow-release fertiliser or well-ripened compost to provide essential nutrients during the first few months.

How to Plant a Catalpa in a Pot?

Now, slip on your gardening gloves and let’s get practical:

1- Prepare the pot:

• Place a layer of drainage material (clay pebbles or gravel) at the bottom of the pot to prevent water from stagnating.
• Add a first layer of substrate, but do not fill the pot completely, to leave room for the tree’s root ball.

2- Install the root ball:

• Gently remove the catalpa from its original container to avoid damaging the roots.
• Place the root ball in the centre of the pot. Adjust the amount of soil under the root ball so that the base of the trunk (the collar, where the roots begin) is just below the top edge of the pot.

3- Add the substrate:

• Fill the pot with substrate around the root ball, making sure to fill all the gaps. Press down lightly to stabilise the plant, but avoid compacting too tightly to not block air circulation in the soil.
• Water generously to thoroughly moisten the mixture.

4- Install a stake if necessary:

• If your catalpa is young or fragile, plant a stake next to the trunk to keep it upright. Secure it with flexible ties to avoid damaging the bark.

Where to Place the Catalpa Pot?

To ensure your catalpa thrives in a pot, carefully choose its location:

• Bright exposure: place the pot in a well-sunned area that receives at least 6 hours of sunlight per day. This will promote the tree’s growth and encourage abundant flowering. Note that the catalpa also tolerates light shade, but its flowering will be less prolific.
• Protection from the wind: position the catalpa in a spot sheltered from strong winds, which could damage the young branches and dry out the leaves.
• Sufficient space: ensure there is enough room around the pot to allow the branches and foliage to spread freely without constraint.

After Planting: Care and Maintenance of Potted Catalpa

Watering:

• Water as soon as the surface of the substrate is dry, especially during hot or windy periods, as evaporation is faster in pots.
• Ensure that water does not stagnate in the saucer to avoid root rot. Ideally, empty it 10 to 15 minutes after watering. In winter, reduce watering, but do not let the root ball dry out completely.

Fertilisation:

• Apply compost to the surface or alternatively use a balanced fertiliser (type NPK 10-10-10) or liquid every month from March to September.
• In autumn and winter, stop fertilising to allow the tree to rest.

Pruning:

• Regularly remove dead, damaged, or poorly oriented branches to maintain an aesthetic and balanced habit.
• Perform light pruning at the end of winter to stimulate branching and prepare for spring growth.
• If your catalpa is a young plant, shorten the main stems to encourage a more compact and dense development.
• To learn more, check out our tutorial: How to prune a Catalpa?

Repotting:

• Repot your catalpa every 2 to 3 years, ideally in spring, when growth resumes. This allows the roots more space and the substrate to regain its richness.
• Choose a pot slightly larger (5 to 10 cm in diameter extra) to avoid disturbing the roots.
• Gently remove the root ball from the old pot. Remove any damaged roots or those forming a compact mass at the bottom. Add fresh substrate, composed of potting soil, sand, and garden soil, to renew the nutrient supply.

Top-dressing:

• If repotting is not planned, perform top-dressing annually to provide fresh nutrients to your catalpa.
• Remove the top 5 to 10 cm of substrate, taking care not to damage the roots. Replace it with fresh potting soil enriched with compost or organic fertiliser. This also helps to improve drainage.

Winter Protection:

• Place the pot in a sheltered spot away from cold winds, such as along a sunny wall.
• Add a thick layer of mulch over the substrate to limit temperature fluctuations.

Pest Monitoring:

• Regularly inspect the leaves and stems to spot any parasitic pests such as aphids or scale insects.
• If necessary, use natural treatments, such as a black soap solution, to quickly eliminate them.
• To learn more, read our article: diseases and pests of Catalpa.