Chapter 132 Taxodium distichum, T. ascendens

132.1 Bald cypress, pond cypress

A large bald cypress in the National Arboretum collection. Note that one of the roots has split open, exposing bare wood. This is common on naturally growing trees, so has been kept as a feature on this tree. Link to original image.

132.2 Soil: Moist Deciduous Mix

Ratio: 4 parts bark, 1 part grit, 1 part mushroom compost

Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd). Adding mushroom compost improves moisture retention and mimics natural soil conditions.

pH: ~6.5 (slightly below neutral)

Moisture: Bald cypresses grow best in heavier, high-moisture soil, and can thrive in regularly inundated sites. If they get enough water though, they will adapt to most any soil type.

If the tree is not kept in water, heavy soil is essential since it needs to retain as much moisture as possible. Do not worry about root rot.

Potting and root pruning should be done in spring, just as buds are breaking on the branches and trunk. If the tree is kept in standing water root pruning is advised every year - every 2 years at least.

Pond cypresses live in comparatively higher elevations. They are more common on moist hummocks of land. Their natural growth habit in forests is to grow taller in the center of the grove and shorter towards the edge. From a distance, the forest has a convex dome-shaped canopy.

During the summer both bald and pond cypress need a lot of water. If the pot dries out during the day, put the pot in a shallow bowl with additional water. Alternatively, consider putting the tree in a tray of wet sand to provide additional water without risking root rot.

132.3 Light

Both species of cypress need a lot of light and warmth and should therefore be placed in full sun during the growing season. They do not need any summer shade.

132.4 Cultivation Notes

132.4.1 Potting & Root Pruning

Bald cypresses have strong root growth and the roots become thick very quickly. They are not hard, though, and can be pruned easily. Younger trees should be repotted every two years with root pruning, especially if the growing rootball pushes itself upward from the pot. Older trees can be repotted every three to five years.

Smaller surface roots can be folded and tied with raffia to create “knees” that project above the surface.

Pond cypress is not as likely to grow knees.

Because the trees grow so rapidly, frequent re-potting is necessary.

132.4.1.1 Top & Branch Management

Pruning and wiring: New shoots should not be shortened until they begin to produce lateral ramification. If they are pruned too early, they often die back in autumn. In autumn or early spring branches can be pruned. The Bald Cypress tends to produce a lot of new buds on the trunk, branches and forks. Remove unneeded buds early. Shape the young branches and twigs early; older ones become stiff and brittle. Use twine and guy wires instead of traditional wiring, because wires can damage the bark on fast-growing branches.

Let a branch grow for a season to thicken it, then cut it back the following spring. New growth will sprout at the site of the most recent pruning. Twigs sprout at sharp, acute angles, so it is not difficult to develop a gnarled-looking branch.

Prune throughout the summer. Clip off leaves that sprout from the trunk unless they are to be developed into a branch. Shape the foliage by pinching back new growth.

132.4.2 Feeding

Cypress does well on a standard feeding program, with 18% N, 6% P, 12% K controlled release granules at half normal dose just after spring leaf-out. In late June or early July, and mid-August, feed again with 0.5x Miracle-Grow. Alternatively, feed with slow release shrub and tree fertilizer like Epsoma Tree-Tone, applied at half the recommended rate.

132.4.3 Pests & Problems

Cypresses are very pest-free.

132.4.4 Winter Storage

Bald cypress require winter dormancy, so after the leaves fall, they should remain outdoors. That said, trees in pots are poorly frost tolerant. Trees in smaller show pots should be removed from their container and buried in the ground in a shaded area with ample mulch and protection from wind. The tree will still need occasional watering if we have a dry winter. Trees in larger containers do not need to be unpotted, but still should be buried in mulch to minimize temperature swings.

132.5 Propagation Notes

Bald cypress can be propagated by seeds, but they require specific treatment to get the seeds to break dormancy. Bald cypress cones shatter into irregularly shaped scales that contain the seeds. The seeds are adapted to floating long distances on water, then settling onto soil that is saturated, but does not have actual standing water. They require light to germinate, so should not be covered when planting.

The easiest way to grow bald cypress is to collect unbroken but dry ball-shaped cones in a plastic bag, then breaking them up into scales by gently tapping them with a hammer. Avoid touching the seeds; the resin is extremely sticky and only comes off with paint thinner.

Transfer the broken scales into a new bag and fill will hot tap water. Let soak overnight. Mix 1 part soaked scales with 2 parts moistened sphagnum moss, seal in a bag and let sit at room temperature to warm stratify for 30 days. Refrigerate to cold stratify for at least 60 days.

In early spring (early March here), fill a tub without drain holes with black topsoil to 1 inch below the rim. Drill several drain holes about 1/2 inch below the soil line, and cover them with pieces of window screen to keep them free of debris. The goal is to keep the soil saturated, but still let water drain away from the top 1/2 inch of soil. Saturate the soil with water.

Spread the sphagnum-scales mix from the refrigerator over the surface of the soil and press it into the surface. Place the tub in full sun. Seeds will germinate erratically over 15 months.

Some years my collected cones have higher fertility than others. I have not been able to determine yet what causes good and bad years. I’ve learned just to start new batches each year, and pot up whatever I get.

Chemical treatment is another way to help them break dormancy. This edited quote comes from the Journal of Horticulture and Forestry Vol. 1(2) pp. 022-026 April, 2009 (http://www.academicjournals.org/jhf)

“…The objective of this research was to find an effective method to enhance seed germination of bald cypress, an ecologically and economically important tree species. Bald cypress seeds were hand collected under mature bald cypress trees in southeastern Florida, and…soaking the seeds in a 1% NaOH solution for 5 min and then in water for 24 h had the best germination rate of approximately 50%…Our study has verified that acidity was the chief limitation for germination of the seeds.”

The one year I tried this method I got a very good germination rate. I have not tried it again since the first time.

132.6 Artistic & Styling Notes

Allow the tree ample time to grow and develop thickness of the trunk before cutting back. The tree will look straggly otherwise.

Bald cypress looks good trained into a formal upright, informal upright, slant, or twin trunk shape. Smaller trees make great forest plantings.

Pond cypress are more scraggly, tend to be smaller, and have branches that start almost at the ground and grow along the trunk. They can be styled in the literati style.

132.7 Additional Information

132.7.1 Natural History

Bald cypress is a deciduous conifer that grows on saturated and seasonally inundated soils of the Southeastern and Gulf Coastal Plains of the United States. The bark is gray-brown to red-brown.

Pond cypress looks very similar to bald cypress initially, but has larger coarser needles that look more like a false larch than the feathery leaves of bald cypress. Pond cypress does not branch as freely as bald cypress either, so has a coarser look overall.

The two species have overlapping ranges, but do not overlap as much in the habitat. Bald cypress will be in the swampier areas, pond cypress in the wet uplands.

132.7.2 In Cultivation

Bald cypress can be confused with dawn redwood (Metasequoia glyptostroboides), especially as seedlings. The easy way to distinguish them is that the needles on dawn redwood are opposite, meaning they are positioned directly across from each other on the stem, while bald cypress needles are alternate (staggered).