Indian bean tree: varieties, care & propagation

Indian bean trees have showy, funnel-shaped flowers that are loved by both humans and pollinators alike. Planted in parks and gardens, these beautiful trees provide shade and support bee populations.

Indian bean trees, also known as common catalpa, catawba, or Indian cigar tree, are poisonous yet stunning flowering trees. Read on to find out all about how to safely plant, care for and propagate Indian bean trees.

Indian bean tree origin and characteristics

The Indian bean tree (Catalpa bignonioides) is native to the south-eastern region of continental North America and can grow up to 18m tall. Admired in parks and gardens as an ornamental tree or shrub, the Indian bean tree’s first flower buds appear in May and they begin to bloom in June. Indian bean tree flowers are showy, trumpet-shaped and white with two yellow stripes down the length of the funnel. There are also purple spots that run alongside the yellow stripes. Successfully fertilised flowers form elongated bean pods. The tree also has a thick, short trunk and a spreading crown. The heart-shaped leaves are large, growing up to 20cm long.

Indian bean trees are generally fast-growers. The only exception here is the slow-growing ‘Nana’ variety, which is perfect for keeping in a pot on your balcony or patio when they are still young. That said, this variety will eventually outgrow these locations.

Beautiful catalpa species and varieties

There are several varieties and species of Indian bean trees, each with its own ornamental value.

• Golden Indian bean tree: Catalpa bignonioides ‘Aurea’ sprouts in late June and early July. The leaves are a golden-yellow at first and later change to a rich green as the summer progresses. After about 10 years, Golden Indian bean trees begin bearing their elegant flowers in July. They reach a maximum height of 10m.
• Northern catalpa: Catalpa speciosa are popular trees for bees, as their large flowers are well-suited for honey production. The first flowers appear in July and produce a lot of nectar.
• Manchurian catalpa: Catalpa bungei is still rare in the UK, yet it has great ornamental value. Its large, green crown provides a lot of shade. As a small tree, it grows 5 to 8m tall. It first blooms in July.
• Yellow catalpa: Catalpa ovata has a broad, round crown. The trumpet-shaped flowers appear from July to August. Also known as Chinese catalpa, these trees grow 10 to 15m tall.

• Southern catalpa ‘Nana’: Catalpa bignonioides ‘Nana’ variety is one of the most popular forms due to its spherical tree crown. However, these trees require annual pollarding. Whilst their large, green, heart-shaped leaves are great for decorating parks and gardens, this variety does not bloom or bear fruit. ‘Nana’ grows up to 3m high and can be kept as a potted plant.

Tip: if you have ever come across an equally magnificent tree with large, blue trumpet flowers, this is most likely the foxglove tree (Paulownia tomentosa). Foxglove trees is a member of the Paulowniaceae family, which belongs to the mint order known as Liamiales, and are distantly related to the Indian bean tree.

Planting Indian bean trees: when, where and how

Indian bean trees can be planted in the spring, starting early in May. They need sunny, warm and sheltered locations with plenty of room to grow. In gardens with lawns, Indian bean trees are excellent for providing shade in summer. Fresh, nutrient-rich soil is ideal, but these trees also tolerate drier and less fertile sites as well.

Before planting a young Indian bean tree, place it in a bucket of water so that the root ball can soak up plenty of water. If planting your catalpa tree directly in the ground, dig a planting hole twice as thick as the tree’s root ball. Then, place the seedling so that the root neck is just above the surface of the earth. Give your tree extra support by tying at least one stake to it. Last but not least, add mulch to the area above the tree’s roots to help the soil retain moisture.

If you decide to plant your Indian bean tree in a pot, you will need the right substrate. Opt for a nutrient-rich soil that is not too well-drained. It is important that the soil holds enough, but not too much moisture. Our Plantura Organic All Purpose Compost is great for this, as it contains clay powder (bentonite) that absorbs and releases water as needed. Before filling the pot with soil, remember to put in a drainage layer of broken clay, pebbles or expanded clay. This allows excess water to easily drain out of the container, thus preventing waterlogging.

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Caring for Indian bean trees

With the right care, Indian bean trees can thrive in the UK too. Luckily for us, these trees are not too demanding, so caring for them is quite simple.

Watering and fertilising

Indian bean trees demand water. For healthy growth, water this tree regularly. Do not allow the soil to get too wet or dry out. In the case of potted plants, take extra care to prevent waterlogging. Empty any excess water from the pot’s tray.

Tip: Catalpa trees are heat-tolerant plants. Nevertheless, the sunnier and hotter the location, the more water they need.

To help your Indian bean tree grow strong and healthy, fertilise trees that are planted out in gardens once a year at the beginning of spring. Use an organic, slow-release fertiliser to provide your tree with all its essential nutrients for the following months. Our Plantura All Purpose Plant Food is optimal here, as it is naturally long-lasting and promotes a healthy soil life.

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Pruning Indian bean trees

The best time to prune Indian bean trees is in autumn. The goal here is to thin them out to prevent them from becoming bald from the inside due to overly dense growth. Use a saw or loppers to remove any dead or diseased wood, taking care not to cut the main shoot or healthy side branches. Annual pollarding is only practised on the ‘Nana’ variety in spring to rejuvenate it.

Caution: remember to wear gloves when pruning Indian bean trees! Touching any part of the tree can cause an allergic reaction to the skin on your hands.

Indian bean tree problems: pests and diseases

Here are some fungi and pests that Indian bean trees are susceptible to.

• Brittle cinder: this fungal disease is difficult to detect. It targets and rots the bottom of the tree trunk and ultimately topples the tree.
• Powdery mildew: Indian bean tree leaves affected by powdery mildew form a white coating on both sides as well as on shoots and buds. Remove affected plant parts immediately.
• Verticillium wilt: this fungus stops the plant’s vascular system from transporting water and thus nutrients around the plant. This causes the leaves to turn yellow, curl and eventually die. This disease is not curable.
• Voles: these rodents feed on Indian bean tree roots, weakening the tree’s roothold. Affected trees then sprout weakly or not at all.

Tip: to prevent fungi spreading further, disinfect garden tools after use, and dispose of affected plant parts in household waste instead of in your garden compost.

Indian bean tree problems: not blooming?

There are several possible reasons as to why your Indian bean tree is failing to form flowers:

• Species: varieties such as the Southern catalpa ‘Nana’ rarely bloom
• Age: Indian bean trees first bloom when they are 5 – 8 years old
• Watering: these trees will not bloom if they are stressed by drought or waterlogging
• Location: Catalpas do not form flowers if they get too much shade
• Fertiliser: Indian bean trees do not tolerate nitrogen-rich fertilisers

Overwintering Indian bean trees

After their first five years of growth, Indian bean trees are hardy down to at least -17° C, some even as low as -30 °C. Younger trees need winter protection. At the beginning of winter, wrap the crown of the tree in a garden fleece. Also cover the soil around the tree’s base with fir branches to insulate the roots. Protect the delicate bark against cracks with a coat of lime. Overwinter potted Indian bean trees in a bright, cool room at a maximum of 10 °C. If you do not have space indoors, feel free to overwinter the pot outside. In this case, just place the container on a polystyrene board close to a house wall and cover it with fleece for insulation.

Propagating Indian bean trees

Indian bean trees can be propagated with seeds or with cuttings. That said, propagating with cuttings takes less work. The following is instructions for propagating Catalpas from seeds and cuttings.

Seed propagation

Wild varieties of Indian bean trees can be propagated by seed. However, this requires a lot of patience. To do so, harvest the ripe seeds directly from the tree in autumn and dry them over winter. In the following spring, it is time to get the Indian bean tree seeds germinating. To start this process, place the seeds in water for half an hour, and then plant them 5mm deep in potting soil at room temperature. Use a low-nutrient growing medium such as our peat-free Plantura Organic Herb & Seedling Compost.

The first shoots will develop after about a month and a half. To accelerate germination, cover the planter with a transparent hood made of plastic or glass – just remember to air it out daily. Once the shoots have formed their first four leaves, repot them into a larger container with nutrient-rich potting soil. Indian bean tree saplings also benefit greatly from the addition of a support and wind protection.

Tip: when repotting, be careful not to damage the plant’s roots, as damaged roots inhibit plant growth.

Propagation by cuttings

Propagating with cuttings starts in July or August. Locate a young shoot that is about 10cm long, and cut it from the tree. Remove all but the two uppermost leaves from the shoot. To reduce the evaporation rate, cut the remaining leaves in half. Then, place the cutting in a container filled with water until it begins to grow roots. Once the cutting has grown roots, plant it in potting soil. Lastly, place the planted cutting in a bright place without direct sunlight. Keep the substrate consistently moist.

Are Indian bean trees poisonous?

Yes, Indian bean trees are slightly poisonous. All parts of catalpa trees, except the seeds, contain catalpin. The leaves and wood also contain coumaric acid, caffeic acid and ursolic acid. Contact with the wood or leaves can cause allergic reactions, and ingestion may cause stomach discomfort.

Indian bean trees are often confused with angel’s trumpet, which are also poisonous. Angel’s trumpets bear magnificently large flowers that exude a pleasant fragrance in the evening and night hours.