Greenhouse space is usually limited so we cannot fit in everything we want and must choose just those that most appeal to our needs for bloom, foliage or produce. However there’s also growing something for the sheer fun of it, allowing in plants that may be unlikely to flower, would be a poor show if they should, and can never realistically be expected to crop. Is there anyone who has never sown a date stone, avocado or loquat seed? Each will probably have germinated and given a seedling, this may have grown into a much loved plant. But can these little follies ever really perform and pay for their space or must they remain a curio?
There are not just the limitations of temperature- exotics are unlikely to be hardy and some require higher minimum temperatures than others. We must also consider size. The sole reason you do not regularly see date palms in greenhouses (they are just as attractive as many more popular palms) is that they soon grow too big. And forget producing your own dates- these need intensely hot bright sunlight and are found cropping in very few regions. Likewise for coconuts- even though some may fruit when quite young and relatively small their canopy soon cannot fit anywhere other than in houses of large botanic gardens, these have such enormous leaves.
Now by comparison the avocado tree can be almost compact, nearly hardy and often blooms and crops when quite young and small- but they are scruffy, their rather insignificant flowers have complicated pollination and one tree on it’s own is doomed to celibacy. Likewise for most mangoes, these are tempting, but tender, they come readily from stones, their foliage is prettier than that of avocados but sadly their flowers (unlike a current TV advert’s portrayal) are equally unimpressive and difficult to pollinate. Much resembling a mango seedling is the lychee which is an even greater challenge. Not to germinate, that bit is easy. But it seems very much harder to get them to grow or even survive beyond that first foot or two.
On the other hand the Japanese plum or loquat (Eriobotrya) is a sure grower, even hardy, but notoriously difficult to get to crop properly. This has impressive leaves which perhaps could earn a place for their ornamental value, the small dull flowers are sweetly scented, but fruits- they’re seldom produced, and sadly it’s also a tad vigorous for most greenhouses even when confined to a tub. Likewise the tamarind, a lovely mimosa like tree, small and so elegant to start with, this just cannot be given enough space and heat to ever perform. And I would love to produce chocolate- but cocoa trees require hotter more tropical conditions than most of us can provide and they’ve the weird habit of flowering and cropping directly upon their trunk and branches. So don’t let me stop you trying, as I said every plant is educational and fun anyway- just send me a picture if you should really succeed.