A level results – how much bleach do seed need to surface sterilise them?

As part of their orchid seed research our year 13 (upper sixth) science students have been testing their seed samples to find out how much surface sterilizing they need before sowing in-vitro. Joe’s results here show contamination with both 0% and one 0.5% bleach solution samples but no contamination for 1% or 1.5% bleach. All samples were surface sterilised for ten minutes.

Joe can now confidently test optimum germination conditions and use 1% bleach to prepare the seed.


365 days of orchids – day 694 – Dendrobium harveyanum

The diversity of orchids and their flowers is perhaps their greatest attraction and these dendrobium flowers are some of our most extraordinary.

This wonderful dendrobium is native to Southern China and South East Asia where it grows as an epiphyte at around 1100-1700m in seasonally dry forest. It is semi deciduous and flowers from new and old pseudobulbs together in a fantastic display of its intricate flowers with long filamented edges to the lip and petals. The flowers are produced in sprays similar to the closely related Dendrobium fimbriatum.

Books recommend a cool winter rest for the species and we keep the plant into Warm Asia (min 18C) when in growth and move it to Cool Asia for a rest when the growths are fully mature in late autumn. The cool rest then initiates an abundant summer flowering but this year we have a bonus flowering in November shown above.

When we have kept the plant in Warm Asia throughout the year the flowering has been rather sparse in comparison.

We find the plant enjoys growing in a basket and with its extensive rooting we drop the basket into a bigger one when needed rather than causing lots of disturbance to the roots.

The flowers are sweetly fragrant and last about a week.


365 days of orchids – day 693 – Cattleya walkeriana

This cattleya species is looking an absolute picture at the moment with four flower spikes and eight flowers.

This is an unusual Cattleya and one we have been keen to succeed with for many years. All other Cattleya species (apart from Cattleya nobilor) produce their flowers from the top of the pseudo-bulb but walkeriana produces flowers on spikes produced in the Autumn from the base of the newly matured pseudobulbs. The flowers themselves are also very distinct flowers and it is therefore difficult to confuse this plant with other species.

Cattleya walkeriana grows as an epiphyte in dryish areas often along streams across a broad area of Southern Brazil. It behaves rather as a xerophyte coping with long periods of high temperatures and little rainfall.

In cultivation we try to replicate the hot, dry, bright conditions it experiences in the wild by hanging it in a basket high in the roof of Warm Americas. We water it well when in growth but in the winter give it very little water. This helps us to grow large plump pseudobulbs but avoid and rotting off roots or bulbs in the winter. If you look closely at the basket you will see that it doesn’t contain much composts and no moss so that roots dry out very quickly after watering.

Last year it had two sprays of flowers and five flowers in total so it is making good progress and hope that it will develop into a grand specimen over time.


Year 13 science students devising germination testing investigations

The Mendip propagation laboratory was a busy place again today as A level Science students prepared media for their germination testing investigations. Following the students’ visit to Kew last July to visit Jonathan Kendon they are each working on a different orchid species and are finding optimum germination conditions by varying nutrient levels, agar concentration and pH for seed germination in-vitro.

Today students made up a range of media samples and next lesson they will be sowing seed into these samples. There is great excitement as, of course, we do not know which conditions will suit the particular species being tested.

We will publish some of the students work once it is complete.


365 days of orchids – day 692 – Penilabium struthio

Some orchid flowers last for months while others like the flowers on this miniature asian species only last a day or two. The nice things with short lived flowers is that you are encouraged to have a really good look at them when they do flower or else they are gone.

Penilabium struthio is native to South East Asia and Malaysia and is recorded growing in hot lowland forest near rivers. It has soft leaves suggesting it prefers shaded conditions. Although short lived the flowers is produced successively on short pendulous spikes so the species flowers several times each year. Our largest plant has four spikes and they are co-ordinated so that most of the spikes flower together.

We grow the plant mounted on cork where its flowers can be seen but as the photo shows the flowers point downwards so it is worth picking the plant up and turning it over for a close look.

The flowers are large for the size of the plant (2cm across) and they do have a remarkable lip with a spur.