The "Blue Amaryllis"
Photo by Glenn Callcott
Growing medium -- Worsleya needs a loose, airy medium that drains very rapidly and provides plenty of moisture to the roots. For this reason, ordinary soil does not work. A good base medium is porous rock such as scoria, lava rock, pumice or other volcanic rock, approximately 5 to 10 mm in size. Screen it of any tiny particles or very big pieces.
Some organic material may be mixed in to retain extra moisture & nutrients, like fine-grade bark or coco husks. The amount to use depends on the particle size. Coco husks should be no more than 10% of the total volume, fine-grade bark can be 20-30%, and medium grade bark can be 30-50%, especially if using larger sized rocks.
Some have reported success using 100% long-fibered sphagnum moss. I have tried it, and it has worked well so far, but mine have not reached flowering size in it yet.
Transplanting -- I recommend leaving your plant in its pot for 2 weeks after receiving it, so it can recover from being shipped. You may give it some filtered sunlight during this time, with protection from strong afternoon sun. After 2 weeks, you may repot it to a 6-8 inch (15-20 cm) tall pot that has drainage holes at the bottom. Plant it with the entire bulb exposed, and the roots buried. Give it bright, indirect light the first 2-3 weeks, then expose it to direct sun gradually, protecting it from strong afternoon sun for 2-3 months.
Watering -- Water about once a day. Water the entire surface, and use enough water so it runs freely out the bottom of the pot. During periods of slower growth, like during cooler temperatures, you may need to reduce the watering frequency. When you go on vacation, you will need to use an automated watering device - unless you can get someone reliable to water it for you!
Fertilizer -- Worsleya likes regular, light feedings, since the medium it grows in does not hold on to much nutrients the way soil does. You may either feed with each watering using a very dilute dosage, or feed about once a week using a stronger dose. An alternative is to mix some slow-release, pelleted fertilizer into the top inch (2.5 cm) of the surface and let it slowly dissolve with each watering. The disadvantage of this is that the pellets may dissolve at an unpredictable rate - typically slower than they would in soil.
Worsleya can often grow perfectly fine with general-purpose fertilizers, but ideally it prefers a fertilizer that's relatively lower in phosphorous, and higher in potassium and nitrogen. A good "N-P-K" ratio is approximately 15-5-30. The fertilizer should also contain micronutrients (zinc, iron, etc) and calcium & magnesium. Liquid hydroponics fertilizer works well, because it is easily absorbed and doesn't rely on soil microbes to make the nutrients available. I use General Hydroponics Flora fertilizer. A good ratio for this fertilizer is 2 parts "Micro", 4 parts "Grow", and 1 part "Bloom". When flowering begins, use slightly less nitrogen and more phosphorous.
It's normal for an older leaf to occasionally turn yellow and then brown, but if it seems excessive, the roots may be too dry. If you are sure they are not, try increasing the nitrogen fertilizer.
Climate -- Worsleya comes from an area with moderate temperatures and cooler nights, similar to San Diego's climate. Try to protect it from temperatures above 90 degrees F (32°C), or at least give it cooler temperatures at night. In a warm greenhouse, put it on the floor where it is cooler. Outdoors, it can tolerate a couple degrees of frost, but i recommend keeping it above 35 degrees F (2°C), especially the first 2 years. Over about 40% humidity is preferred.
Lighting -- Worsleya likes mostly-sunny conditions, with some protection from strong afternoon sun, especially in warmer conditions. The leaves will naturally arch towards the sun, and should be allowed to stay in this position (don't rotate the pot).
After 2-3 years, repot it to a container about 12 inches (30 cm) tall. Avoid repotting again, as this will delay flowering. It does not mind being pot-bound provided that the roots stay moist.
Feel free to contact me with any questions.
Good luck with it!
Strange Wonderful Things