late starting seedlings
Uli via pbs (Mon, 07 Mar 2022 16:37:51 PST)

Hello Mark,

Your question about how to handle late starting seedlings has been asked
quite often.

There are several things to keep in mind. Warm growing conditions induce
dormancy in winter growing bulbs. Dry growing conditions do the same.
The combination of both may be fatal to young seedlings as their small
bulbs may not be big enough to survive the first dormancy especially if
it was induced prematurely by these factors.

How to overcome this?

Depending were you live, it is important to keep the growing temperature
frost free but as cool as possible for as long as possible into spring.
If you germinate your seed in a greenhouse it is a good idea to move the
seedling pots from the greenhouse to a half shaded sheltered spot in the
garden. Always give artificial shade for a few days after the move.
Greenhouses tend to warm up considerably from March onwards (northern
hemisphere). If this is not possible because of frosty nights it is
important to ventilate the greenhouse as efficiently as possible and to
wet the floor during sunny days in order to increase humidity. Seedling
pots must NEVER dry out. Once growth would be stopped by a dry interval
it will not resume and the resulting bulbs will remain small and weak.

Even outside in the garden it may be useful to apply artificial shading
by using horticultural fleece or shade cloth to cover the seedlings. I
put a wire mesh caging over them to stop birds and other creatures
digging in the pots. The cage will prevent the shade cloth lying
directly on the plants. it all depends on the climate you live in. A
place where the sun is welcome in winter may become to warm in spring so
it may be necessary to move the pots into a shaded or half shaded place.
Shade of buildings with otherwise bright light is a good option.

Fertilizing must not be neglected: It is better to fertilize more often
but with lower concentration. Especially at the end of the growing
season I have found fertilizer very beneficial.

For valuable small seedlings the effort of moving the pots into more
favourable growing conditions and applying artificial shade pays off,
this way most bulbs can be kept green well into May, some even longer.
Follow what the plants tell you: as long as at least some leaves are
still green, keep watering but once all foliage has died down naturally
stop watering. Otherwise rot may set in. Young seedling bulbs should be
left in their pots in the substrate during dormancy. These pots should
not bake in the sun but kept in a shady cooler place in summer.  A
gentle hand watering with a fine rose every 4 weeks or so will prevent
them from becoming too dry. Observe the pots for signs of new growth in
autumn. Again, this depends on where you live. Warm weather delays
sprouting and moist cool weather triggers it.

Last but not least my recommendation for sowing winter growing bulbs is:
not to sow after the end of December. The best results are obtained by
sowing in October. The seed of most bulbous plants can be stored in the
fridge until optimum sowing time.

Bye for now

Uli

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