Polianthes tuberosa

Leo A. Martin leo@possi.org
Sun, 24 Apr 2011 16:44:35 PDT
> I've grown this species for a couple years
> and have yet to get any bloom.


> one of them I potted up in leca stones and kept it on the
> windowsill all winter. It stayed green and healthy the whole
> time, but a few weeks ago it started to decline.


> lots of offsets... and the roots seem very healthy indeed.

Think of this as an evergreen tropical plant that prefers to grow all
year, but will survive winter dormancy with considerable setback.

In my experience it needs a very large pot for best bloom - say 18" / 45cm
across or bigger and correspondingly deep. I find it grows and blooms best
in a soil high in organic matter.

In the ground is much better but it doesn't survive reliably here in
Phoenix, zone 9b. So I use a large container.

It takes a while to build up enough mass to bloom well. In a small pot you
may get a spike every few years. I suspect it would rarely bloom in
anything smaller than a "1 gallon" pot. If the leaves die down from frost
or dormancy it is unlikely to bloom the following summer unless growing
conditions are excellent.

I believe it is considered in the agave family and it has the same growth
habit - a rosette growing for multiple years until big enough to flower,
then dying after flowering (monocarpic) but carrying on from the many
offsets. Until there are plenty of offsets and all the foliage is quite
large there will not be much bloom.

It also requires high summer temperatures (from most people's perspective)
and a lot more nitrogen fertilizer than most people seem to use. If your
growing area is warm enough it will grow all year. Dormancy is certainly
not obligatory and is actually undesirable--an adaptation by the plant to
unhappy conditions. But most people who grow in cold-winter climates don't
have space to overwinter the plant in leaf in a sufficiently warm and
sunny spot.

To further the problem, the bulbs I've seen sold in the last 10-15 years
are all very small and have next to no chance of flowering that year or
the next.

I'm not trying to discourage anybody from growing it--I wouldn't be
without it because of the incredible fragrance. But it needs more care
than most people give it for best results.

Leo Martin
Phoenix Arizona USA

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