NOTES ON GROWING BROMELIADS FROM SEED
by Andrew Flower, May 1995\October 1996\August 2001.
Most bromeliads are quite easy to germinate, and it is the growing on that can cause problems with some of them. The more complicated to get going are the tillandsias, particularly the grey-leafed “xerics” or “atmospherics,” which are germinated quite differently from the others. There is a special section on Tillandsias that follows discussion of the main group.
This general group includes all plants in the subfamilies Bromelioideae and Pitcairnioideae—including Aechmea, Billbergia, Cryptanthus, Neoregelia, Nidularium, and the terrestrial pricklies such as Puya and Dyckia. Most of the Tillandsioideae group, excepting Tillandsia, are also raised in this group. This includes Catopsis, Racineae, Vriesea and Guzmania, (Those not included are the xeric group of Tillandsioideae, often described as "atmospherics", which comprise nearly all the Tillandsias which do not have a distinct tank formed by their leaves, and the few grey-leaved non-tank Vrieseas which look like Tillandsias. They will be discussed after the main group)
Seeds need light (so they are sown on top of the germinating medium), warmth (aim to keep temperature fairly steady at 20oC to 25oC), and moisture (sow on a damp medium, and keep enclosed).
Sow the seeds in a small container, which is kept covered until germination is complete. I use small seedling trays with a glass lid. Other ways are to use a small plastic pot enclosed in a plastic bag, or a mini greenhouse made out of a margarine container with holes made in the bottom, and the center of the lid cut out. A piece of plastic is then placed over the container and the lid screwed on to keep the plastic in place. Half fill the container or tray with germinating medium. I use any commercial seed-raising mix, to which I usually add fine pumice or propagating sand for terrestrials, or fine bark chips sold for orchid seedlings (about 5mm square) for the epiphytes, to lighten the mix a little. Some people use pure peat moss, or dixonia fibre, some just use damp blotting paper! The right atmospheric conditions are more important than the particular medium—so long as the medium is not too alkaline.
Once the seed has been sown, place the container in a warm place with reasonable light, but not in direct sun which will quickly overheat the container. Indoors it could be on top of the fridge, or near a south-facing window. In the greenhouse you could put the seed under a bench or in some other semi-shaded spot.
Seed which you have not harvested yourself is likely to have picked up some surface contamination—moulds, fungi etc.—which may cause problems by taking advantage of the warm moist conditions you provide and growing all over the seed and smothering it. It is best to sterilize the seed first. The method I use is fairly straightforward, and well worth the trouble. First, soak each batch of seed in a solution of sugar water for 24 hours. This solution is made by dissolving a teaspoon of sugar in a cup of water and adding a drop of detergent. I use small glass bottles (with numbers on them to identify the seed!) or you could use small glasses. By soaking the seed in this sugar-rich solution you encourage any nasties lurking on the seed to start growing. Then you tip off the sugar water and soak the seed in a 50% solution of household bleach (Janola or Chlorodux—which contain Sodium hypochlorite) for 5-10 minutes to decontaminate the seed surfaces. I always soak the seed container, and the glass lids, in bleach for half an hour to sterilize them as well.
Make up a fungicide solution. Benlate or Chinosol are the ones I use. Never use a Copper-based fungicide, as bromeliads are extremely intolerant to heavy metals. Soak the medium with the fungicide solution. Now you are ready to sow the seed. Always place the seeds on top of the medium: they must not be covered. Then water them gently with the fungicide solution, this also helps wash off excess bleach. Cover the seed, and put them away in their germinating position.
Water quality can be a factor, particularly if it is too hard and the dissolved salts are 300ppm or more. But this is normally not a problem with drinking water. If you have the time to collect rainwater, that will be better but not essential. And if you lower the pH to 6 to 6.5 that, too, will be a bonus for the plants but should not be necessary for success. As always, there is an optimum set of conditions to aim for and guide you in the right direction, and the practicality of what you can achieve in your circumstances. The plants are tough, and will usually grow in much less than optimum - just do your best and give it a go!
Wait until the seedlings have formed several nice small leaves. For most of the species these will be quite wide (1 to 3mm) and you can start increasing the fresh air available to the seedlings, and reducing the humidity, by gradually removing the covering over a period of a week or two. The Tillandsioideae such as Vrieseas, Guzmanias and tank-type Tillandsias will usually have very fine juvenile leaves, and can be left enclosed for somewhat longer: until they are 10mm high is a guide. Guzmanias are an exception in that some of them need to be left with the covering on for up to 2 years. If it is necessary to water the young seedlings, always soak the container from the bottom. Overhead misting should wait until after the seedling container is no longer enclosed.
Once the seedlings are starting to crowd the container, they can be pricked out and transplanted into seed trays. Plant them in the same mix you use for mature plants, but if possible make the mix a little finer. Space them 3-4 cm apart and grow them on in no more than half the light you would give to mature plants. Once they are again starting to crowd, usually after a year or two, plant them out into small single pots for another year or so before letting them have full light.
“ATMOSPHERIC” or “XERIC” TILLANDSIAS
If the flower has been successfully pollinated, a slender, green seed pod will develop from the ovary at the base of the flower:
Under normal conditions, when the seed is mature the outer capsule will dry off, turning brown before it splits open (dehiscence) and exposes the small wind-dispersed seeds:
Tillandsias need warmth, moisture and light to germinate, just as all the rest of the bromeliads do. Only trouble is, most Tillandsias will soon die if they are sown on the ground! So they need to be sown on something hanging up in the air. Early growers used to germinate then in the greenhouse on a small bundle of twigs (usually Thuja, or some other Cypress, but I used Macrocarpa or any old conifer with no apparent loss of performance. The general idea of using Cypress was because there is something there which inhibits growth of algae, a problem because Tillandsia seed are so slow.)
Sowing seeds on sticks or ponga (tree fern), or small strips of plastic mesh such as shadecloth) in the glasshouse is ok when seed is fresh, and during the summer if they are kept relatively shaded and moist. But you can have difficulty starting them off during winter or with imported seed, because viability decreases rapidly.
I have found that seed and seedlings need a lot higher humidty than used to be thought.
For best results, you need to give the seeds;
Around 20-25oC during the daylight hours, and a little drop at night by about 5oC.
About 14 hours of light per day.
Water if possible by spraying every 3-4 hours for the first 3-4 days, then once each night and evening. Once they have germinated, they must be allowed to dry between watering.
How do you accomplish this? My first device was built around a 2 x 40 watt fluorescent fitting, in the form of a wooden frame 4ft long, 18"deep and 2ft high made of 2” x ½” timber and covered by a couple of layers of PVC sheeting with flaps at the ends which I rolled up during the day to let them get fresh air. The fluorescent tubes were at the top (of course!) and immediately beneath them was a layer of chicken wire.
The seeds were sown on small strips of shadecloth (say 6" x 1") hung from the chicken wire on little hooks. On the floor was a tray with a soil warming cable in it, and by increasing and decreasing the amount of water in the sand I control the humidity. I found that opening the flaps gave too much ventilation (lowered the humidity too much), and I also found that I had to cover the whole thing with a woolen blanket during the winter to keep the temperature up.
Now I have a slightly larger incubator, made of solid timber. You need to have some air exchange going on—I have left about a ¼" gap aound the ballast of the fluorescent tube (I have the ballast sticking up out of the top, and the reflector screwed to the underside of the roof). During the first few weeks I leave the door shut, and the humidity is 100% (so it effectively rains in there just about), then after several weeks I start ventilating a little by leaving the front sliding door up about a half inch. Seed is sown on strips of insect mesh.
Of course you don't have to go to all this trouble. There are much simpler methods - for example you could start the seeds off by enclosing them, on their mount, in a plastic bag hung in a warm place with bright indoor light. I used to do this, and in cold winter months just sat the seedling sticks, in their plastic bags, on a low-heat germinating tray.
I water with a small pressure sprayer, which I leave in the incubator to keep the water at "room temperature," and I reduce the pH to 6.0 with phosphoric acid. I don't think you have to do this, though, but they do prefer water on the the acid side. As I mentioned, when seeds are first sown I water them every 3 hours for a couple of days, then go back to morning and night sprays.
I grow seeds on in a greenhouse, minimum night temperature 7-8oC, under two layers of 35% shadecloth (in addition to normal greenhouse shading) then after a year or two start moving them out into progressively less shade. But I never take them out of the incubator between March and October (that would be around November to April in the northern hemisphere) because it is too cold and the days are too short for the juvenile seedlings.
Seedlings are transplanted onto community sticks when they are about 5-10mm high, 3-4 years old. They are glued with a water-resistant aliphatic glue, or Weldbond "Universal Space Age Adhesive" which is our current favourite! Some growers use a hot glue gun, which is fine.
