The catalpa tree (Catalpa spp.) is well-loved and recognized for its height, enormous heart-shaped leaves (up to 12 inches long and 8 inches wide), twisted spreading branches, panicles of creamy white fragrant blossoms, and long dark brown seed pods.
Though its tendency to spring up in odd places and grow rather quickly has earned it a reputation of being a bit of a “weed tree,” plenty of folks love having this large graceful shade trees on their properties.
The flowers are attractive to bees, butterflies, and hummingbirds, and this tree is the sole host for the catalpa sphinx moth. With dense foliage and large leaves, the catalpa provides excellent cover and shelter for a wide variety of song birds and wildlife.
The trees hardiness once made it an important source of lumber, particularly for railroad ties and fence posts. Its seen in many large parks due to its hardiness and graceful shape in the landscape, but as an urban tree the leaf litter can be somewhat problematic near sidewalks and cars.
Growing a catalpa tree from seed is a rewarding process that allows you to add this beautiful, flowering shade tree to your landscape. With its large, heart-shaped leaves and showy spring blooms, the catalpa is an ornamental tree that offers charm and character to any garden. By starting catalpa trees from seed you can grow these hardy trees for a fraction of the cost of purchasing mature specimens.
In this complete guide, we will walk through each step of catalpa tree seed propagation so you can successfully grow these stunning trees from seed yourself
Catalpa trees belong to the Bignoniaceae family and are native to the southeastern United States, There are three main species of catalpa grown in gardens
- Southern catalpa (Catalpa bignonioides): Hardy in USDA zones 5-9. Grows 40-60 feet tall.
- Northern catalpa (Catalpa speciosa): Hardy in zones 4-8. Grows 30-50 feet tall.
- Chinese catalpa (Catalpa ovata): Hardy in zones 4-8. Grows 30-40 feet tall.
Catalpa trees are prized for their showstopping spring flowers, large heart-shaped leaves, and long seed pods. The flowers emerge in late spring in clusters of white and purple blooms up to 8 inches long. The leaves provide dappled shade and turn yellow in fall. The long, slender seed pods develop in summer and persist through winter.
When to Collect Catalpa Seeds
Catalpa trees produce seed pods filled with winged seeds in late summer or early fall. It’s important to collect the seeds when they are mature but before the pods split open. Here are guidelines for harvesting seeds from the three catalpa species:
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Southern catalpa – Collect seed pods as they start to turn brown and crack open in early fall. These seeds do not require cold stratification.
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Northern catalpa – Gather seed pods in late winter just before they split open. Store in a cool, dry place until spring planting. These seeds need exposure to cold temperatures.
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Chinese catalpa – Harvest seed pods as they begin to open in early fall. Seeds can be planted immediately or stored for spring planting.
Check seed pods frequently so you can gather them at just the right time before seeds drop. Place harvested pods in paper bags and allow them to dry for a few weeks before removing the seeds.
How to Plant Catalpa Seeds
Catalpa seeds have a thick seed coat that needs to be softened before germination can occur. This scarification process helps absorb water to trigger the seeds to sprout.
Here are two simple ways to scarify catalpa seeds before planting:
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Sandpaper: Gently rub seeds between two sheets of fine grit sandpaper. Be careful not to damage the seeds.
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Hot water: Place seeds in a heatproof bowl and pour boiling water over them. Let soak for 24 hours before draining.
Once scarified, catalpa seeds are ready for planting. Follow these steps:
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Fill starter pots or trays with a well-draining seed starting mix. Moisture control is important.
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Plant seeds 1⁄4-1⁄2 inch deep. Space multiple seeds at least 2 inches apart.
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Cover seeds lightly with mix and water thoroughly. Keep moist, not soggy.
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Place in a warm location (65-70°F). Bottom heat helps germination.
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Germination occurs in 10-60 days. Thin seedlings to the strongest plant per cell or pot.
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Grow on at 60-65°F until ready to transplant outdoors after the threat of frost.
Transplanting Catalpa Seedlings
Catalpa seedlings can be transplanted into the garden after all danger of frost has passed, when they are about 1-2 feet tall. Follow these tips for transplanting success:
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Harden off seedlings for 7-10 days by slowly introducing them to outdoor conditions.
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Space trees at least 20 feet apart in full sun to part shade. Amend soil with compost as needed.
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Dig holes the depth of the root ball and 2-3 times wider. Score sides with a knife to loosen compacted soil.
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Carefully remove from pots, loosen bound roots, and place in hole. Backfill with native soil, tamping firmly to remove air pockets.
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Water thoroughly and apply 2-3 inches of mulch around base, keeping it away from trunk.
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Stake for support if needed. Remove in 1-2 years once well established.
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Water weekly during first year, aiming for 1 inch per week from rain and/or irrigation.
Ongoing Catalpa Tree Care
Catalpa trees are easy to care for once established. Follow these tips for healthy, vigorous growth:
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Water during drought to keep soil moderately moist. Avoid overwatering.
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Fertilize in spring with a balanced organic fertilizer or compost.
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Prune only to remove dead, damaged, or crossing branches. Avoid heavy pruning.
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Watch for pests like aphids, scale, and caterpillars. Treat with horticultural oil or insecticidal soap sprays.
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Weed and reapply mulch annually. Replace stakes and ties as needed.
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Catalpa trees have shallow roots and should be planted away from buildings, patios, and sidewalks.
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Rotate southern catalpa trees out of landscapes every 15-20 years as they are short-lived trees.
With proper care, catalpa trees started from seed can grow over 2 feet per year, quickly reaching mature sizes of 30-60 feet tall and wide. Enjoy their large, heart-shaped leaves, dangling seed pods, and the spectacular spring floral display these underutilized trees provide in the landscape.
Troubleshooting Common Catalpa Seed Starting Problems
Growing catalpa trees from seeds is rewarding but can pose challenges. Here are solutions to common problems:
Seeds fail to germinate: Scarify seeds, provide bottom heat of 65-70°F, and ensure even moisture. Refrigerate northern catalpa seeds over winter.
Seedlings dampen off: Improve air circulation and do not overwater. Drench soil with fungicide.
Seedlings stunted: Increase light level, repot into larger containers, and fertilize weekly with diluted liquid fertilizer.
Leaves yellow: Treat with iron supplement or chelated iron product. Improve drainage.
Poor transplant success: Harden off gradually, amend transplant holes well, and reduce watering until established.
Leaf spots or distortion: Apply fungicidal soap spray and improve air circulation and drainage.
Pests: Squash bugs chew leaves. Control with insecticidal soap. Tent caterpillars form nests on branches. Remove by hand or apply Bt biological insecticide.
Final Thoughts
Catalpa trees are easy-to-grow, low-maintenance shade trees perfect for today’s smaller gardens. By starting catalpa trees from seed, you can grow these ornamental beauties at a fraction of the cost of buying mature nursery trees. Follow the steps above for collecting ripe catalpa seeds, sowing them properly indoors, and successfully transplanting seedlings into the garden. With proper care as they mature, the catalpa trees you grow from seed will provide enduring beauty, dappled shade, and spring floral displays for decades to come.
Pruning
Catalpas should get regular pruning in youth to ensure good stable growth and good form. Start pruning at one year for new trees. Trim away suckers from the base, and trim large lower branches with a pruning saw to promote a straight, central “leader” trunk.
As the catalpa grows, keep lower branches trimmed to allow for easier maintenance at the base of the tree. Pruning is best done in early spring after blooming or late fall.
Soil
Catalpa trees tolerate a wide range of soil conditions, from acidic to alkaline, wet clay soils, sandy, loam and more. Good drainage is always preferred, but catalpa trees can survive both flooding and extended periods of drought.
How To Grow a Catalpa Tree From Seed With Detailed Description
FAQ
How long does it take to grow a catalpa tree from seed?
Though they grow quickly, it takes about five to seven years for catalpas to reach maturity to the point where they blossom and bear seed pods each year. Some varieties, such as the Haitian catalpa, begin producing flowers in the first two years of maturity.
Do catalpa seeds need stratification?
Seed Stratification: Seeds disperse in the spring and immediately germinate. No stratification period is needed.
Are catalpa trees easy to grow?
Overall Catalpa is a pretty great tree. It’s adaptable to many soil conditions, withstanding wet or dry soils and alkaline or acidic pH. It is a pretty tough plant that can be grown in either sun or part shade. Definitely worth considering if you have the space to compensate it’s size and messy pods.
How to start a catalpa tree?
You can collect the seeds in fall, keep refrigerated, then plant in spring and transplant the seedlings when they’re 3-4 inches tall. Mist lightly with water and they will germinate within 14-30 days. You can direct sow the seed after last frost in spring, or in winter in a cold frame, sunny window or greenhouse.
How do catalpa trees grow?
They can be grown from soft root cuttings or branch cuttings, or from seed. They also reseed freely in most areas where they are established. Catalpa trees grow easily from seeds, which germinate fairly rapidly without any special treatment.
What should you consider when growing a catalpa tree?
The most significant thing to think about when growing a catalpa is the cleanup. Catalpa trees tend to be messy trees that shed a load of large leaves in the fall. Also, in spring, the long seed pods drop and cause more mess. What’s more, the flowers and seed pods can be slippery and need clearing from sidewalks and driveways.
Do catalpa trees reseed?
They also reseed freely in most areas where they are established. Catalpa trees grow easily from seeds, which germinate fairly rapidly without any special treatment. The seeds (from the pods) should be sown in fairly warm temperatures between 60-70 degrees Fahrenheit, and sowed on the surface of a light peaty soil mix, rather than covered in soil.