Spider Orchids: Meet the Extraordinary Brassia Orchid That Fooled a Wasp

There are orchids that are pretty. There are orchids that are elegant. And then there are spider orchids, looking as though something has escaped from the greenhouse and is making a determined dash across your windowsill.

Their long, narrow petals and sepals stretch out like legs, often decorated with spots and splashes of yellow, green, cream and brown. A flowering spider orchid takes up far more visual space than its pot suggests.

And its resemblance to a spider is more than an amusing coincidence.

The orchid that fooled a wasp

Some Brassia orchids have a remarkable way of getting pollinated: they impersonate a spider.

Female spider-hunting wasps mistake the flowers for prey. As a wasp tries to sting and grasp the flower’s lip, it contacts the orchid’s pollen-bearing structure, which can attach to its head. If it makes the same mistake at another flower, it can transfer the pollen.

Cornell University’s Liberty Hyde Bailey Conservatory describes this extraordinary behaviour. 

The wasp leaves without a spider. The orchid may gain a pollinator.

There is something rather wonderful about a flower that can start a fight simply by standing still.

This story belongs to the natural history of Brassia; it should not be assumed that every cultivated spider orchid hybrid uses exactly the same trick. But it gives those unusual flowers a whole new character.

They are beautiful, certainly. They are also impressively convincing.

What is a spider orchid?

In the indoor plant trade, “spider orchid” usually refers to a Brassia orchid or a hybrid with Brassia in its parentage.

Brassia belongs to the wider Oncidium alliance, a group of related orchids. These tropical American plants often grow on trees, using them for support rather than taking nourishment from them.

Their flowers are the main attraction. Long, tapering flower parts spread out from the centre, giving each bloom an airy, suspended appearance. Several flowers along an arching stem can look like a small procession crossing the plant.

The name “spider orchid” is also used for other orchids around the world, so the botanical or hybrid name on the label is worth keeping. It tells you more about the plant than its common name alone.

The American Orchid Society’s Brassia guide provides an introduction to the genus.

Brassia, Cambria or Oncidium: why the different names?

Orchid labels can make a straightforward purchase feel like the beginning of a family-history investigation.

Your spider orchid might be a Brassia species, a hybrid between Brassia species, or a cross involving Brassia and other related genera.

Some hybrids are sold under the broad retail name “Cambria”. That label groups together a range of orchids, rather than identifying one precise botanical genus or one set of parents.

“Oncidium-type orchid” describes the wider group. It does not necessarily mean that the plant belongs to the genus Oncidium.

The useful thing is to keep the plant’s original label and any care instructions supplied with it. Named hybrids can have different preferences, so general Brassia advice is a starting point rather than a rule for every spidery flower.

The RHS guide to cool-growing Oncidium orchids explains some of the naming changes and the commercial use of “Cambria”.

Do spider orchids smell?

Some do, but fragrance varies between species and hybrids.

The flowers are reason enough to enjoy a spider orchid. If scent matters to you, check whether the individual variety is described as fragrant rather than assuming every plant will perfume the room.

Spider orchid care in a UK home

Those extravagant flowers can make spider orchids look intimidating. Caring for one becomes much easier when you understand its light, watering and growth needs.

The following advice suits many commonly grown Brassia orchids and similar hybrids. Follow any more specific guidance supplied with your named plant.

Give it bright, filtered light

An east-facing window is a useful starting point. A bright west- or south-facing position can also work, provided the plant is protected from strong summer sunshine.

Watch how the light changes through the year. A comfortable winter windowsill may become much hotter in July, particularly close to the glass.

Move plants into brighter light gradually. If growth is weak or flowering is disappointing, consider whether the position is bright enough before reaching for extra fertiliser.

Keep it away from temperature extremes

For many commonly sold spider orchid hybrids, approximately 15°C at night to 25°C during the day is a practical starting range. Exact preferences vary with the plant.

Avoid radiators, cold draughts and contact with chilly window glass. A bright position is useful; a hot, dry blast from the heating is less helpful.

Water thoroughly, then allow some drying

Brassia orchids need regular water, but their roots also need air. Allow the growing mix to dry somewhat between waterings without leaving the plant bone-dry for prolonged periods.

Lift the growing pot to learn how its weight changes as the mix dries. Check below the surface too: dry bark at the top does not necessarily mean the centre of the pot is ready for more water.

When watering is needed, wet the mix thoroughly and let excess water drain away before returning the plant to its decorative planter. Empty any water that collects inside the outer pot.

There is no dependable “every seven days” rule. Pot size, growing medium, temperature and active growth all affect how quickly the plant uses water.

Feed while the plant is growing

Use a specialist orchid fertiliser, following the product’s dilution and frequency instructions.

Reduce feeding when growth slows rather than assuming the plant needs the same amount throughout the year. Occasionally water without fertiliser, letting the water run through and drain away, to help limit salt build-up around the roots.

Consider humidity and airflow together

A warm, dry position beside a radiator can make water loss harder to manage. Humidity affects how quickly both the plant and its growing medium lose moisture, so it also changes watering needs.

Allow gentle air movement around the plant and avoid leaving foliage persistently wet.

When should you repot a spider orchid?

Repot when the growing medium is deteriorating or the plant has genuinely outgrown its container. Roots appearing outside the pot do not, by themselves, mean something is wrong.

For Brassia, the American Orchid Society recommends repotting when new shoots have begun producing new roots. This gives the plant an opportunity to establish itself in fresh medium.

Use an airy orchid mix suitable for the plant and a pot with good drainage. Choose enough room for healthy roots and developing growth without surrounding a small root system with a large volume of damp mix.

A clear inner pot can make inspection easier, but good drainage and a suitable growing medium matter more than appearance.

Why are the pseudobulbs wrinkled?

The swollen structures at the base of a spider orchid are called pseudobulbs. They act as storage organs, helping support the plant between periods of growth.

Wrinkling can occur when the plant has been too dry. However, damaged roots can produce a similar result even when the growing mix is wet.

Before adding more water, check both the medium and the roots. 

Older pseudobulbs need not look as plump as newer ones. Keep healthy older growths rather than removing them simply because they look less tidy.

A thirsty-looking orchid can still have wet feet.

Why are the new leaves folded like a concertina?

Pleated or “accordion” growth can develop when a thin-leaved orchid cannot obtain enough water while its leaves are forming.

Irregular watering or prolonged dryness may be responsible, but root damage can also prevent water uptake. Check the roots before assuming the answer is to water more often.

The existing folds generally remain. The aim is to improve conditions for the next growth, rather than drenching the plant in apology.

The [American Orchid Society’s leaf-problem guide](https://www.aos.org/orchid-care/troubleshooter/leaf-problems) explains these possible causes.

What should you do after flowering?

Once the flower stem has finished, cut it near its base with clean scissors, taking care not to damage the surrounding growth.

Keep the pseudobulb and look for new shoots around the base of the plant. These develop into the growths that can support future flowers.

Healthy roots and developing shoots are encouraging signs, even when there is nothing particularly spectacular happening above them.

The next display begins long before a flower spike appears.

How do you encourage a spider orchid to flower again?

Start by checking the light, roots and newest growth.

A plant may survive in a position that is too dim to support strong flowering. Equally, unreliable watering or damaged roots can hold back development, however bright the windowsill.

Give the orchid time to develop healthy new growth, adjust care to its named variety and avoid making several dramatic changes at once. More fertiliser will not compensate for struggling roots or unsuitable conditions.

There is some patience involved. Orchids have never shown much interest in our preferred schedules.

Do spider orchids catch flies?

No. Spider orchids are not carnivorous plants. They do not catch flies, eat insects or spin webs.

Their spider-like appearance may help some wild Brassia species deceive a pollinator, but your houseplant is not an insect trap.

It is simply very committed to the look.

Choosing a spider orchid online

When buying a spider orchid, look beyond the flower colour. Check:

- The botanical or hybrid name.
- Whether the plant is in flower, in bud or currently not flowering.
- The growing-pot size and approximate height.
- Whether a decorative pot is included.
- The care information supplied with the plant.

A flowering plant offers an immediate display. A plant that is not flowering offers the pleasure of watching its growth develop. Clear product information helps you choose the experience you want.

Explore our Cambria and Oncidium orchid collection.

Spider orchids reward a closer look. Their flowers are unusual enough to start a conversation, and their growth becomes just as interesting once you know what to watch for.

Then there is that wasp story.

It is one thing to admire an orchid on your windowsill. It is quite another to realise that its wild relatives can persuade a passing insect to pick a fight with a flower.