This presentation began its’ formulation as a look at what I view as popular misconceptions I have heard over the years, and was designed for beginners – which can probably be better qualified as my alternate view of the theories I have heard. To my surprise, the more experienced growers in the audience to which I gave this presentation were full of questions about these matters, which resulted in this presentation.
The more I look at this, the more I realize that the concepts we all think are principles are really a set of variable guidelines, which are best kept as a guide in the art of growing our plants to their fullest potential, but few of them are good enough to hang your hat on.
Also at the time, I was reading John Catlan’s book 'Under The Mango Tree', which challenged the old theory of “the first pup being the strongest”, amongst other things. I totally agree with him - this ain’t necessarily so, or rather needn’t be so if you think of the factors which might influence this situation. In perusing this book, one of the things I really liked was that John was investigating certain things that he was seeing, and was always prepared to question the knowledge that he has read, or something that he has surmised from previous experience. His writings seem to be a set of ideas gathered from his experiences, which may or may not be applied to any situation he encounters.
So I thought I’d look at the concepts around the matters which influence flowering and pupping, looking at the way we view these processes. Like most growing principles these views have come about through my experiences under the growing conditions I have experienced, what I have read, and discussions I have had with other growers. One thing I have learnt is to always question what you hear or read – and never assume anyone is an expert – but to always listen, watch and research. As with others, my growing conditions are unique to me – it is conditional on my local climate and how I set up my collection, so therefore will not be identical to any other grower. Even growers in your region, though they will mostly have very similar conditions, will never have the same conditions.
A prime example of a popular viewpoint that I disagree with is the often repeated statement that "most bromeliads die after they flower?" This statement does more to discourage interested novices than any other I know. Do orchid collectors say that about cymbidiums, where, after flowering, the back bulbs wither away while the new shoot takes over? Not only does it turn off novices, but it is not a useful view when thinking about growing bromeliads. I have many clumps of plants which I began growing 30 years ago, and they are still alive – and people still say they die after they flower. This viewpoint is also very unhelpful with decisions on if and when to take pups, but more about that later. There are a few other things that I would like to discuss first.
This first of the “growing concepts” I would like to discuss is that of apical dominance, the mechanism that suppresses axillary buds, giving most of the plants resources to the apex (the highest point). I haven’t read much on this subject other than the first Benzing book, but in the 80s not much was known about how this mechanism worked. The principle behind this is that basically a plant gives most of its’ energy to the part of the plant that is highest. (Ref 1) To me the scientific reasons for this aren’t so important – the main thing is how these principles are basically employed by the plants we choose to grow, which is that many plants send most of their energy into growing at the apex, until the cells at the apex turn into the cells that make up a flower. When the apical point turns to flower growth, the old growing pattern can’t continue. As a result the auxins that suppress the growth of offsets are no longer manufactured allowing pups to form. A similar action occurs when all of the pups are removed from a plant that has flowered. The plant is forced to take a different action. But to me, a brief understanding of these principles is very helpful when cultivating bromeliads.
Back to Mr Benzing. He states that there are the following forms of offsets.
1. Precocious basal – more often called grass or adventitious offsets. These have a habit of being produced by a plant for the early period of a plants growth then stop a long time before the plant reaches flowering size. Sometimes they die when the flowering plant dies. If you require a backup plant, remove these when they show signs of producing wider leaves, they may be taken while still having only juvenile leaves, but more care has to be taken while they are at that size. They are quite different to those produced under other pupping systems.
2. Basal offsets – we should all know these as they are the most common form of pupping. They either come straight from the base or are produced on stolons/runners.
3. Offsets higher up the plant, which are most likely to be seen in Vriesea splendens and its’ hybrids. These are often tricky to take off, and many people do not attempt it.
4. Viviparous offsets. Plants produced from the flower spike after flowering.
Particular plants seem to be inclined to use only one or two of these methods, but many times I have seen particular plants use an uncharacteristic method (for that particular species) when subjected to unusual conditions.
While many plants generally only pup after flowering, some plants freely pup without flowering. This is a case of the plant not producing the auxin which suppresses the pups. Some plants are more prone to switching off production of the auxin, or they possibly don’t produce as much before flowering than those that generally don’t pup. External factors can also affect the plant in producing pups when the terminal meristem (the growing point) is damaged due to factors such as heat or physical damage, or the plant simply allows pups to form at stressful times, even when the terminal meristem is not destroyed. Some adventurous growers will even purposefully destroy the terminal meristem (eg. with a screwdriver) to force the plant to produce pups, though this may have unfortunate side effects – it is recommended that you seek advice from someone experienced with this, prior to performing such actions.
Another commonly misunderstood concept with growing bromeliads is the conversation about feeding bromeliads. Working as a retail nurseryman, I have long conversations with customers unable to get around the concept of using fertilizers. However with 30 years of growing bromeliads and seeing others in the bromeliad world’s collections, and spending the last 10 years working with the commercial production of bromeliads (longer specifically with tillandsias), I have come to the conclusion that many amateurs underestimate the importance of food. When I think of plant food the primary thing that I have control over is the amount of light that the plant receives. I would like, foremost, to control both light and carbon dioxide, but without a technical setup that is difficult to provide in my circumstances, I cannot control the CO2. But the idea that light is probably the most important plant food, is something we should all look at more seriously. In this respect, optimally, we should grow our plants in the lightest position which doesn’t stress or burn the leaves. This doesn’t mean up against a house facing west where it is in heavy shade for the first 4 hours of the day, medium shade for another 2, then very strong light for the last half. A commercial nursery judges good light, as bright light for as close as possible to all day. This is often very hard to achieve within the confines of a suburban block. It is important to position your plants with regard to those you want to prioritize access to light. There may be those that will lose colour or grow in poor shape that you want in prime light positions, and some plants will grow very slowly unless given access to good light.
Once you have addressed the light issue, then it is time to assess the issue of how to feed and how much food to apply. Food should always be applied in relation to available light and the nature of the plant. Too much food for the available light will result in longer leaves, sometimes poor colour, and a poorly shaped plant. One lady I spoke to recently said that she fed her Aechmea blanchetiana, after which it lost its’ colour – so she stopped feeding all of her bromeliads. After this she had a couple of plants which flowered well, then died. When I explained that this can happen to plants when they use a large amount of their available energy/resources in producing flowers and seeds, leaving too little to produce pups, she was surprised. There is a happy balance of feeding plants with a balanced fertilizer, where the rate of fertilization does not detract from the shape and colour of the plant. The lady then suggested using Seasol, to which I pointed out that Seasol is not a balanced fertilizer, and that when she chose a fertilizer she should look to someone in her area that knows about these things – either a professional nurseryman or an experienced grower should be able to advise what she should use. Both commercially available liquid & controlled release fertilizers can be used on bromeliads with good results. Even coloured foliage plants such as Neoregelias, will grow faster and with more vigour if fed at least a little in their early stages, and if it is done properly they will be magnificent plants. Care should be taken to ensure that Neoregelias have little food left when coming into flower to attain maximum colour. Vrieseas and Aechmeas will have superior flower spikes if well fed – so most growers of show bench plants have fed them well. To produce good plants which look like the ones on the show bench, or in the books, it is necessary to observe and take care of your plants. Most importantly make sure the plant is fed when it is expending energy on flowers, and if you want them to pup will, fertilize them after flowering.
This brings me back to another of the comments I have long heard about bromeliads that like to form a clump first before flowering. In my experience in commercial growing I have come to an observation that this may not be a valid observation in many cases, as many of these same plants flower naturally as single plants when given very good conditions. I have already explained the nature of what I understand of apical dominance and its’ effect on pups, but there is another factor to be considered. The plant uses its’ foliage to convert various elements into usable food. There are many books detailing that a plant will not send up a flower spike until it has the energy to complete the cycle. Of course the larger amount of foliage can produce more effectively the nutrients for the plant to flower. But if a plant is fed well and given the optimum amount of light, it may not need the aid of the clump to provide energy for the spike.
Those orchid growers amongst us have long ago worked out that there are different fertilizers to be used in growing leaves and providing the nutrients necessary to flower – and that it is necessary to have a good plant to act as a food factory to push up that flower spike. Why many bromeliad growers have been so slow to take this up is a bit of a mystery to me. It is possible to have a nice big plant while maintaining shape which will provide a better show when flowering. Also, another thing that local cymbidium growers use is the addition of dolomite lime, correcting the acidity of the soil while providing calcium and magnesium, which is highly beneficial in extending the life of the mix, while adding vital nutrients. I wonder how many bromeliad growers do this, instead leaving their plants in the same pot for years, with a Ph so far out that little of the nutrient added to the pot is available to the plant. (Note that when using substances such as rock type substances and coco peat, there may be less of an issue with ph problems.)
I believe that there is an over-reliance by many bromeliad growers on the concept of plants being forced into flower, when, for example, orchid growers have long had the view that food and light are the most important factors. I believe this has distorted our perspective. The tales of apple cores and plastic bags, and chemicals like Ethrel may have made us lazy in the way we think of why a plant flowers and why it doesn’t. Of course these triggers are of use, especially when triggering things for a particular reason, eg. shows, or to supply things out of season for commercial purposes. However, the biggest and best flowers come from a plant in perfect health, flowering when the right time has come with all the right resources – primarily food and light but also an NPK based fertilizer – are provided to it, rather than a plant triggered at that time.
On the other hand, if you want to set seed, the use of chemicals to initiate flowers is very useful. There are a few tricks involved in this, and it can be confusing at first. It is easy to time the flowers if they are the same species, though individuals will vary slightly in the time between triggering and anthesis, but different species and genera can take vastly different lengths of time between initiation and anthesis. If you intend to make hybrids, the timing of different species, from initiation to flower, can vary a lot. (There is the possibility of pollen storage to make up for this, but this is another topic.) The timing for plants to be ready for shows can be difficult. The amount of light, affected by clouds, can throw out the expected time of the antithesis by weeks.
The use of Ethrel, acetylene gas or other chemicals can be a dirty word in bromeliad circles, with many critical of its use. Many of those with experience of Ethrel think a plant that has been stimulated into flower will need to be fed well through the flowering process or else it will flower poorly. (I have heard that studies of flower counts on pineapples, fed after flowers have been initiated, do not have a greater quantity of flowers on each spike, so my observations will need further investigation.) Commercial suppliers add fertilizers in the mix to account for this, but collectors should be well aware of this when caring for these plants. I have found those bromeliads that are fed throughout the time between initiation of the flower spike, and the time of antithesis will produce a larger spike. If they are fed well past flowering, they will also throw more pups. Remember that the flowering and seeding process places a great drain on the plants resources, so the plant will be much healthier if these resources are replaced – or the plant may die after flowering – just like the blanchetiana lady experienced.
Some people say that commercially grown plants have been pushed too hard, and will therefore suffer when put out into the real world. To some degree this can be true. However, consumers/collectors should be astute and responsible, like when you buy a car – look to see if it is grown well or soft. If it has been grown soft, and you still want it, slowly harden it off. Commercial growers can feed heavily and produce a nice hardy plant, and responsible growers will attempt to produce a plant which will serve their customer well. They need to produce a plant in a certain time frame, because this affects the price they can afford to sell for – and if it is too expensive, few will buy their product. The amount of care the plant has had (how soft it is) shouldn’t prevent you from purchasing the plant, though it should influence the type of care you give it while acclimatizing it to your conditions. After all – the only reason that some rare plants can be sold at the price they are, is if they are produced in a manner where they grow reasonably fast. It is necessary to assess any plant you buy, and treat the plant accordingly.
A few years ago I grew a xNeophytum Galactic Warrior, which many of you would be familiar with. I grew it in a controlled greenhouse with regular food, both in the watering system and slow release in the pot. It got good light, and a minimum of 14C. Additionally, once every couple of months, after it flowered, I added 3 or 4 prills (granules) of Osmocote to the mix and 3 or 4 to the centre of the vase. In this environment I could take small pups off – with leaves about 3” long, and be assured that they would power away. I got 14 pups from one plant. The 14th pup was every bit as strong as the first. The pups, all rooted very quickly as they were in premium conditions. Over the following years you could not tell which was the first the 7th or the 14th pup. Of course I’m not advising everyone do what I did, in putting prills of slow release fertilizer directly into the vase you may burn a valuable plant and get nothing.
There have been some very interesting articles printed recently on how to encourage pupping by planting bromeliads high in the potting mix, and also removing lower leaves so that pups form around the base more readily (Ref 2 & 3). High doses of fertilizers are then applied to encourage pups to form. In this way some growers have been able to produce quantities of rare plants which may be difficult to self-pollinate, or may not produce pups easily after flowering. Note (again) that it is important to provide heavily fertililized plants with the maximum light levels suited to that plant, not only will it result in stretched leaves without it, but the bromeliad will also need that light to photosynthesize.
‘Under The Mango Tree’ mentions how John attempts to control the growth factors to reduce the anxious wait over where the pup will come from when a plant which has variegation only on one side, he leans the plant over, with that side up, to promote pupping from that side. Using the same principle, mentioned before, of light at the base increasing the chance of offsets, John will increase his odds. Remember though, that the reduction of foliage to create this will reduce the plants photosynthesizing material, therefore reducing the energy available to push out pups. It is all a matter of balance.
Another of my little experiments that I did was with regard to monocarpy, but I must say a little about concepts associated with bromeliads that I have issues with, which also relate to monocarpic plants, before that.
1. The fallacy that the habitat of a plant is its optimum environment. So often I have had people assume that they can know the habitat by the description in books. We can only get a brief idea from these descriptions. Sometimes plants only occupy patches of terrain, existing in certain micro-climates in these areas. Even when you visit these areas, it is fine to say how you saw it on a particular day, or week, but what is it like for the rest of the year?
2. That it is impossible to recreate its natural habitat – or possibly even to understand it – even when you’ve been there. Though never discard this, or any information, as it may provide clues if you have issues with growing the plant in your conditions.
A number of years ago I was concerned with some plants which were in the Tillandsia limbata, T. utriculata group. These plants were not of a great commercial value, because at the time I couldn’t say that I’d got a single pup from the 20 or so I’d flowered. When I was down to 20 or so I did some reading, and Dr Benzings Biology Of Bromeliads came in handy again. Particularly the bit about how the monocarps have big inflorescences and set lots of seed. I thought about this for a while, and I developed a stategy to tackle this “problem”. I assumed that the plant expires from a lack of energy, giving its’ energy to the spike and seed in preference to pupping. So the auxins were not switched off in time for the plant to be able to initiate offsets. So I set about cutting the flower spikes as they came up, as well as feeding the plant heavily to encourage the pups to form. I was keen, cutting the spike as early as possible to save the maximum energy from being wasted in the flowering process, for the plant to devote to pupping.
Later my experiment was in full swing, it took a turn I didn’t envisage. When I cut off the spike, it then developed another shoot from the usually dormant buds at the base of one of the lower scape bracts. I then cut it lower down chasing each shoot as they continued to appear. Soon the plant expired, using all of its’ energy trying to flower. However I didn’t give up. After wasting a couple of plants, I found that there is a point at which the plants did not try to form another spike at the base of the cut spike. In the case of the T.aff. limbata, it was as the flower buds were starting to form. From anecdotal evidence I believe the point at which the plant will opt to initiate pups, rather than make another attempt at flowering, may vary in different bromeliads. Some people have said to me that they couldn’t bear to cut the spike off their lovely bromeliad as they would like to see their monocarpic plant flower, get the seed, and grow the seed. My aim was to have, within three years, the offsets from these supposed monocarpic plants in flower while having a backup of another to cut the spike off and produce more from offsets. I achieved this and had the best of both worlds, enjoying the flower on one pup as it matured while having another where I could remove the spike to keep more pups going.
There are a number of supposedly monocarpic plants which I have found to produce pups simply by feeding them heavily during the flowering process. Often I have had collectors tell me that a plant cannot be a particular species due to the fact that I, or other growers, have produced pups on the plant. Even on one of the internet chat groups some very knowledgeable people insisted that plants such as Tillandsia guatemalensis were monocarpic, based on how the plants grew in the wild. We are not growing our plants in the wild, and often would not like our plants to look like many do in the wild. I believe that monocarpy is a tendency in particular plants, not a principle, and that it is possible to counter the factors which influence this. If the plant is dying after flowering, it is likely to be because of the effort necessary to produce the flowers and seed. Feeding may just be the answer.
All of the concepts I have talked about may seem obvious at first, but many growers may have not considered them together. There are many books and articles which explain these concepts in greater depth, and give an analysis of feeding rates, etc, for you to experiment further. To grow our plants better, we must provide our plants with the ability to function at their best, giving them energy, primarily from light and carbon dioxide, as well as a balance of NPK, minerals and trace elements. These elements work together, providing energy which is (mostly) pushed upwards. When it can’t move upwards it initiates another eye and/or produces seed. If the new growth is removed it should produce another eye or multiples – to say it dies after flowering is not looking at the functioning of the plant. Our role is to control and provide the conditions to maximize the potential of our bromeliads. To do this we must observe and react accordingly.
1. Benzing, Dr David. The Biology Of Bromeliads. P.101
2. Dunstan, Bruce. “Variegated Alcantareas”, Bromeliaceae, The Bromeliad Society Of Queensland.
3. Dunstan, Bruce. “Alcantarea Propagation By Adventitious Pups”, Bromeliaceae, The Bromeliad Society Of Queensland.
4. Catlan, John. “Bromeliads Under The Mango Tree”.
Thanks to Bruce Dunstan and Peter Tristram for their support in preparing this article.