THE GROWING WORLD OF DAHLIAS
POT TUBERS, THE WAY TO SURVIVE
by Dave Bates
The soil where I grow my plants is quite fine and light, over a clay and pebble sub-soil, so water drains quickly through and then runs off on the sloping subsoil. Plants do not make good tubers, many producing fine whip like roots that are subject to drying out too much during the winter. This is especially the case with the thick stemmed varieties such as the Cupid family, and these often fail with stem rot as well. I suffered many heart breaking Winters and expensive Springs until I was introduced to pot tubers!
Since then, stock losses have been considerably less. Since the plants are restricted, the stems are much thinner than those grown normally. There is less opportunity for them to rot, and as the tubers are left in the pots until propagating time, the soil in which they have grown prevents them from drying out too much. After that, I found many other benefits. I have an 8' by 6' greenhouse and drying space for field tubers in October/November is limited such that it takes a few weeks to get all the tubers lifted and dried. During these weeks, those left in the ground start to deteriorate, and later liftings are the most vulnerable to loss. Pot tubers take far less space and can be left on their sides under the benching. There is no need for air circulation round them and it is possible to lift the entire stock of tubers and move them to the greenhouse in one weekend.
At planting out time, the pots are buried to their rims, they can be pot
thick if space is limited. During the growing season, they must be sprayed on a
regular basis to counteract pests, and foliar fed. Towards the end of the
growing season, a high potash feed should be used to ensure the ripening of
tubers. It is important to watch the health of these restricted plants, any
showing the slightest sign of virus should be rogued and burned before there is
any danger of it spreading. When the plants flower in the crown bud, (there is
no need for stopping), ensure the variety is as labelled as there is no point in
propagating from a wrongly labelled tuber. Around the first weekend of October,
the stems are cut down to about 2", even if they are still green and the pots
dug out and moved to the greenhouse. The major disadvantage of this technique is
that there is little opportunity for stock selection with these plants, but they
should have originated from the best stock of field tubers in any case. I try to
propagate from a mixture of pot and selected field tubers to overcome this
difficulty, but there are always some varieties whose field tubers refuse to
keep. As you recognise these types of varieties it is important to sacrifice
some potential exhibition plants for the following year's stock.
Last updated February 02, 2005
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