Grow and Care for Prosthechea

Grow Prosthechea in bright filtered light, and water when the mix has dried. Prosthechea is the clamshell orchid, also called cockleshell orchid. It is not a Tampa butterfly orchid.

Give it bright filtered light, water when the mix has dried, and keep the air moving

clamshell orchid is Prosthechea cochleata, an epiphyte. The flattened pseudobulbs store water, so the plant wants a full wet-then-dry cycle, not a constantly damp pot of mix. [1] Give it bright filtered light and moving air. Water about twice a week in warm weather while it is making new growth, then let the mix dry. [2] Flowers are held upside down compared with most orchids: a dark purple, shell-shaped lip sits on top, and yellow-green petals hang below. One stem can open flowers for months, a few at a time. [3] Florida lists wild plants as endangered, so buy a nursery plant rather than lifting one off a tree. [4] If you are tying a plant to live oak or mahogany, that job is on Planting Prosthechea. If the bark in the pot has collapsed, that job is on How to Repot Prosthechea.

Water less in late fall, and leave the flower stem until it has gone brown

After the season’s new pseudobulbs have filled out, cut back on water so the mix dries more fully. Keep the plant above a freeze. Do not cut a green flower stem as if it were spent, because this orchid keeps opening flowers along the same stem.

1. Keep the plant above a freeze. Cold, wet roots on a mount or in a soggy pot stop growth.
2. Once the new bulbs look full, water less often — about once a week in cool weather is a starting point, then judge by how fast the mix dries.
3. When a flower stem shows, return to regular watering so the buds do not blast.
4. Pick faded flowers if you want, but leave the stem until it is brown and dry. Then snip it at the base. Leave firm green leaves and pseudobulbs in place.

What fails when the roots stay wet

Soggy mix, a saucer of standing water, or moss packed around the roots is the usual reason this orchid declines. Healthy roots are firm and pale. Mushy brown roots and a sour smell mean the mix stayed wet too long. Slightly wrinkled pseudobulbs after a dry spell often plump again after one thorough watering; mushy bulbs do not.

1. Empty the saucer after you water. Do not leave the pot standing in water.
2. If the mix smells sour or stays wet for days, the bark has collapsed. Lift the plant and use fresh coarse bark — see How to Repot Prosthechea.
3. If the bulbs wrinkle but the roots are still firm, water once thoroughly, then wait until the mix dries again.
4. Do not answer wrinkled bulbs with a little water every day. That keeps the remaining roots wet.

Not a Tampa butterfly orchid, not a moth orchid, and not a dark hybrid sold as black orchid

A Tampa butterfly orchid is Encyclia. It has yellow, copper, or bronze flowers that move like butterflies, not this plant’s dark shell-shaped lip on top. See How to Grow Encyclia if that is the plant on the bench. A yellow dancing-lady orchid is Oncidium — see How to Grow Oncidium if the lip is a frilly skirt.

A grocery moth orchid is Phalaenopsis. It has broad, thick leaves in a bark pot. See How to Grow Phalaenopsis if the tag says moth orchid. Cattleya is a related corsage orchid with larger flowers — see How to Grow Cattleya if the plant is a large bifoliate Cattleya. Lady of the night is Brassavola — see How to Grow Brassavola if the tag says lady of the night. A dark hybrid sold as black orchid is usually Fredclarkeara, not this species. An old tag that says Encyclia cochleata or Epidendrum cochleatum is still this plant, not a Tampa butterfly orchid and not a reed-stem Epidendrum.

If the mix still feels wet after a few days, wait. Do not water on a calendar while the roots sit wet.