Germination and question about Lachenalia

Tom Mitchell
Tue, 19 Feb 2013 11:02:27 PST

> Rachel Saunders of Silverhill Seeds wrote:
>> I always knew that Lapeirousia seeds needed to be aged for a year, but I did
>> not realise that almost all our bulb seed needed it.  We harvest all our
>> seed of SW Cape bulbous species in the months of September - December. This
>> means that if you purchase them and sow them in your autumn, they are at
>> most a month old. And obviously this is too fresh. In nature the seeds do
>> lie in the heat for about 6 months before the cool weather of our autumn
>> sets in, and then I do think that a cold minimum temperature is important.
>> But obviously one needs heat first followed by cold.
> I have noticed a similar result with seeds I collected in western 
> South America. They have germinated best when I kept them at room 
> temperature over the Northern Hemisphere summer and sowed them in the 
> following autumn.
> In contrast, bulb seeds collected in the N. Hemisphere germinate best 
> here when sown in autumn of the same year. (Some non-bulbous plants I 
> grow for the rock garden, notably Brassicaceae, are immediate 
> germinators best sown in spring.)
> Jane McGary
> Portland, Oregon, USA

Quite a few of the spring-flowering, northern hemisphere species that I collect as seed each year seem to need a period of warm, moist stratification before cold stratification in order to germinate as temperatures rise, in the first spring after they were collected. Both Helleborus and Galanthus, for example, seem to share this requirement. They typically germinate poorly, if at all, the first year, if sown after late summer (though they will often germinate the following spring).

I have accumulated quite a bit of experience of sending fresh seed of Helleborus to friends in the Southern Hemisphere and they report that the seed germinates most reliably if given an artificial period of warm stratification. Peter Leigh, of Post Office Farm Nurseries, kindly provided the following summary for the benefit of southern hemisphere growers receiving fresh Helleborus seed from the northern hemisphere.

July - August: imbibe seed and place in stratifying mix at room temperature
October - November: remove seed from stratifying mix and sow outdoors as usual
June - July: seed germinates

Sowing the seed outdoors immediately exposes the fresh seed to cold temperatures and this seems to inhibit germination.

Presumably the same principle applies in reverse, when sowing freshly collected southern hemisphere seed in the northern hemisphere, especially in the case of species that ripen their seed in late spring or early summer and so are adapted to an initial warm/hot period.

I am usually too disorganised to order seed from Rachel at the 'proper' time of year. A couple of years ago I was in a Romulea phase - am still in it, in fact - and I ordered every species that Silverhill then had available. This was in (northern hemisphere) spring 2011, if memory serves. I sowed all the seed immediately and left it outdoors, protected from rain, as I do with almost all the seed I sow. About a third of the species germinated in (northern hemisphere) fall 2011, as expected on the theory outlined above. Another quarter, roughly, germinated in fall 2011 and a handful have germinated in the last few weeks, in small numbers. The rest I presume will not germinate but I will keep the pots for at least another year, just in case. I guess the message is: be disorganised and order seed 'late' but don't expect one rule to apply to every species of the same genus, even if they all set seed at similar times of year.

Now for my question. I'm entering my Lachenalia phase. Not sure how long it will last. I've just received a bunch of seed of this genus from Gordon Summerfield and am tempted to follow my own advice and sow it all now, leave it outdoors and wait for something to happen. I know that my own advice is usually bad, however, and I wondered whether anyone with specific experience of growing Lachenalia has any suggestions?


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