Northern Catalpa (Catalpa speciosa)

Northern Catalpa

Northern catalpa (Catalpa speciosa) is a tree native to the midwestern region of the United States. The latter portion of the Latin name Catalpa speciosa means “showy,” for the tree’s appearance. Northern catalpa is planted as an ornamental tree and grows best in acidic soil and full sunlight.

I. Appearance and Characteristics 

Catalpa speciosa, commonly known as the northern catalpa, hardy catalpa, western catalpa, cigar tree or catawba, is a species of Catalpa native to the midwestern United States.

The Latin specific epithet speciosa means “showy”.

Catalpa speciosa is a medium-sized, deciduous tree growing to 15–30 meters tall and 12 meters wide. It has a trunk up to 1 m in diameter, with brown to gray flaky bark.

The leaves are deciduous, opposite (or whorled), large, heart shaped, 18–30 cm long and 13–21 cm broad, pointed at the tip and softly hairy beneath. The leaves generally do not color in autumn before falling, instead, they either fall abruptly after the first hard freeze, or turn a slightly yellow-brown before dropping off. The catalpa tree is the last tree to grow leaves in the spring. The winter twigs of northern catalpa are like those of few other trees, having sunken leaf scars that resemble suction cups. Their whorled arrangement (three scars per node) around the twigs is another diagnostic.

The flowers are 3–6 cm across, trumpet shaped, white with yellow stripes and purple spots inside; they grow in panicles of 10–30.

The fruit is a long, thin legume-like capsule, 20–40 cm long and 10–12 mm diameter; it turns brown in the fall and often stays attached to tree during winter (and can be mistaken for brown icicles). The pod contains numerous flat, light brown seeds with two papery wings.

The northern catalpa is closely related to southern catalpa, and can be distinguished by the flowering panicles, which bear a smaller number of larger flowers, and the slightly broader seed pods.

II. How to Grow and Care

Sunlight

Northern catalpa performs best in full sun, though it still grows in partial shade. Choose a bright and sunny area for your northern catalpa, where it will receive at least 4 hours of direct light per day. If you choose a location with partial shade, expect flowers to be less abundant than a plant grown in full sun.

Temperature

Northern catalpa is a hardy plant, able to tolerate temperatures as low as -34 ℃. Likewise, it can also survive extremely hot and dry conditions. Once established, the northern catalpa can tolerate drought and some flooding too.

Watering

A young northern catalpa requires regular watering once a week, typically when the soil surface feels dry. Although this plant needs very little water to thrive, the soil must be kept moist for optimum growth, making regular watering essential during the plant’s growing season. Older plants, on the other hand, need less frequent irrigation. Water your northern catalpa at its base and avoid overhead watering, as this can encourage fungal growth and mildew. Avoid overwatering too.

Soil

Moist and fertile soil is ideal for growing the northern catalpa. However, this hardy plant also does well in a wide range of soil types, including sandy, loamy, silty loam, and clay. It’s not picky about soil pH either, as it thrives in both acidic and alkaline soils. Moreover, it can tolerate some waterlogging, as well as extremely hot and dry conditions, especially once established.

Fertilizing

Although the northern catalpa is known for being a tough plant, feeding it with fertilizers will promote healthier growth. A slow-release complete fertilizer is a good start, but you can also use other types, depending on the existing nutrient levels in the soil. For instance, a fertilizer high in nitrogen will encourage foliage growth. However, too much nitrogen may inhibit flower bud formation, so you should only use this if your soil is lacking in nitrogen. The best time to feed your northern catalpa is in late spring. Avoid fertilizing late in the growing season.

Planting Instructions

Growing northern catalpa from an established seedling is a lot easier than planting from seed. plant nurseries and garden centers often have ready-to-plant seedlings available. Spring is the best time of year to transplant the Northern catalpa.

When transplanting, prepare a hole that is twice as deep and wide as the seedling’s root ball. Position the plant so that the top of the root ball is at ground level. Then, spread the roots and fill in the hole with well-draining soil. Once planted, stake the young plant to help it grow upright. Water thoroughly.

Pruning

Regular pruning is a required duty for these trees—both to remove dead or dying branches and eliminate hazards, as well as to manage its size and shape within your landscape. Thinning out the crown also promotes the wind moving freely through the crown, which is important to prevent damage due to high winds.

Pruning a large tree is usually a job for a professional trimmer. Pruning for shape and size is best done during the winter or early spring dormant period.

Propagation

Seed-starting is quite easy for this tree, but northern catalpa can be also propagated by rooting stem cuttings taken in summer after the spring growth is established. Here’s how:

  • Select a disease-free stem tip with flexible new growth and hard older wood beginning a few inches down. Cut it off a 4- to 8-inch section, using sharp pruners. Strip off the bottom leaves, but leave at least two leaves at the top of the cutting.
  • Fill a small pot with a mixture made of equal parts peat moss, perlite, and coarse sand.
  • Use a sharp knife to make two vertical slits in the cutting, from the bottom to a point about one inch up.
  • Dip the cut end of the cutting in rooting hormone, then plant it in the prepared pot. Lightly water the soil, then place the pot in a plastic bag and position it in a shaded location where the temperature is 60 to 70 degrees Fahrenheit.
  • Check the cutting every few days to make sure it remains moist, and periodically tug on the cutting to see if roots are developing. When roots are evident, remove the plastic bag.
  • Move the rooted cutting to a more sunny location and continue growing it, watering when the soil becomes dry, until it is roughly double in size. At this point, it can be planted in the landscape.

Growing from Seed

The seeds found inside the long, tubular pods are remarkably easy to plant and nurture into new trees. It’s not uncommon for the seeds to simply fall into surrounding soil and sprout up as volunteers. These volunteers can readily be dug up and transplanted into a new space.

It’s also an easy matter to collect some of the seeds by peeling a ripened pod apart. The bean-like seeds can be stored for up to two years in the refrigerator before you plant them in spring in a desired location. Or, you can start new plants indoors by planting seeds in pots filled with potting mix in late winter. The seeds should be just barely covered with soil or potting mix. Keep the seeds and growing medium lightly moist in a location with bright but non-direct light until they germinate. After sprouting, move the seedlings to a sunny location and keep them well watered as they are growing.

Seeds started in pots in spring may be ready to plant in the landscape by fall. Or, they can be kept in the pot to overwinter and grow for another season until you’re ready to plant.

Pests and Diseases

Common Pests and Plant Diseases

The only serious pest problem for northern catalpa is the caterpillar of the catalpa sphinx moth, which may badly damage the foliage when it feeds on leaves. The worm rarely does lasting damage to the tree, which usually recovers the following year.

Northern catalpa trees usually do not have serious problems with diseases or insects, though they sometimes have issues with verticillium wilt, leaf spot, mildew, and twig blight.

Common Problems 

Most of the complaints about northern catalpa trees involve its growth habit and messy behavior.

Invasive Roots

Northern catalpa trees have wide-ranging, invasive roots that can infiltrate foundations, sewer lines, buckle retaining walls, or compromise underground swimming pools. For this reason, they should be planted far away from any structures the roots might affect. Large trees may need to be removed if they begin to cause problems.

Messy Growth Habit

Another behavior that you should know about before choosing this tree is the sheer messiness of the species. The spring flowers, beautiful while on the tree, can be a soggy, slippery, smelly mess when they fall onto a sidewalk, deck, patio, or driveway.

The dried seed pods leave a similar mess when they fall, and their sharp points can even cause pin-prick wounds as they plummet from the tree. The huge leaves, though providing excellent shade, require a lot of raking once they drop in fall. And even mild winds can leave your yard covered with sticks and twigs that fall from this brittle tree.

In other words, know what you’re getting into before planting a northern catalpa.

Tree Has Become Too Large for its Space

It’s quite common for homeowners to underestimate the speed with which a catalpa tree can get quite large. And because this is a brittle tree prone to wind damage, it’s not a specimen you want hanging over your home or carport. A tree that is becoming too large can be reduced by a professional tree trimmer, but it’s likely you will need to remove the tree at some point if it is growing in a poor location.

Leaf Drop

A catalpa tree that suddenly drops much of its foliage can be telling you one of several things, some of them quite serious. In some cases, unusually hot, dry weather may cause a temporary leaf drop that, while disfiguring, does not kill the tree. It usually recovers the following year.

But leaf drop accompanied by shriveled, dead branches may be in the early stages of the most serious fungal disease to affect catalpas, verticillium wilt. Like other less serious diseases, verticillium first announces its presence by curling, yellowing leaves, but rather than recovering, the tree’s damage gradually expands from the crown down.

Another cause of leaf destruction is the feeding of catalpa worms—the larval stage of the catalpa sphinx moth. Complete defoliation is possible, but affected trees usually recover entirely the following year.

III. Uses and Benefits 

  • Ornamental uses

The northern catalpa is a coarse tree that can be planted in lawns and rain gardens as a shade tree. It is prized for its fall color as the foliage will turn yellow in autumn months. It is also valued for its resistance to animals and pests. Companion plants of the northern catalpa include the katsura and eastern redbud trees.

In the UK it has gained the Royal Horticultural Society’s Award of Garden Merit (confirmed 2017).

  • Other uses

The wood is soft, like white pine, and light, weighing only 26 pounds per cubic foot when dry. It also does not rot easily; in earlier years it was used for fence posts and less than successfully as railroad ties. More modern uses that highlight the wood’s beautiful grain include furniture, interior trim and cabinetry. Catalpa has one of the lowest shrinkage/expansion rates of any U.S. hardwood. Only northern white cedar and redwood have lower shrinkage/expansion rates, and not by much. The wood’s unique properties make it excellent for carving and boatbuilding. Often regarded as a weed tree, its wood is under-appreciated and underused.

Northern Catalpa (Catalpa speciosa) Details

Common name Northern Catalpa
Botanical name Catalpa speciosa
Plant type Native Plant
Hardiness zone 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b
Growth rate Medium
Harvest time Fall
Height 40 ft. 0 in. - 70 ft. 0 in.
Width 40 ft. 0 in. - 70 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color Orange
Leaf color Brown/Copper