Bulb Log 20/06/07

[Cgull49]

Ian,

I've been intrigued by the topic of deep sowing and the positive results you obtain from this method.  I just checked some of my Allium "Purple Sensation" that I sowed last spring and noticed that most of the bulbs were sitting about 3/4s of the way down the pot even though I sowed the seeds on the top of the soil and then covered them with about 1 cm of grit.  They are not very big about 5mm in diameter. There were also some elongated bulbs nearer the top of the pot which I attributed to their being in the process of growing towards the bottom of the pot.  However, with deep sowing the bulbs seem to be bigger at least in the first few years and I'm wondering if it's because the deep sown seeds don't have to grow down to their ideal depth, using up a lot of energy in getting there.  What do you think?

[Heather Smith]

I think experience is the key here. I would tend to note other garderers' experience and that perhaps no seed is routine in its needs. 

Anyone who has findings like this  - could you please share it with all of us (I need all the help I can get when it comes to seed sowing). Even when they germinate I need to know if I should prick out as the first true leaves appear, when the plant is bigger, or leave them until the 2nd year or even longer. I discovered I should have left my Pulsatilla apiifolia seedlings in the seedpot until the 2nd year. I had them pricked out too soon!! Six only have appeared this year.

Those in the know have seeds germinating like mustard and cress and growing on well.

[Ian Y]

Rob, you are correct the seedling bulbs have to use good growing time taking themselves below ground - this energy could be better spent making a biger bulb.
If you do a google search for other bulb logs where I discuss sowing at depth you will find that I discuss the pros and cons of sowing seeds. A reminder of a way to search the Bulb Log:  Go to www.google.co.uk    ( or google.com)
type : site:http://www.srgc.org.uk/bulblog snowdrop      .... substituting what you are searching for for the snowdrop.

The fact is that different bulb seelings germinate in different ways. Fritillarias for instance should only be surface sown and you will find that they send down a small root and the new bulb forms towards the end of this root placing the bulb at depth. With Narcissus for instance the new bulb forms very close to where the seed lies so if that is on the surface that is where the bulb forms, it then has to take it self down into the soil over the next few years.
I take the method of seed dispersal as a guide to which method of sowing will best suit the plant.
Wind dispersed seeds would normally be best surface sown while ant distributed plants are best sown deep.
All bulb seeds will germinate if surface sonw but not all seeds will germinate if sown deep.
I should add that by surface sown I mean sowing the seeds in the normal way and covering with 1cm or so of grit.
Heather makes a good point that if every one reported their results here we could get an excellent source of information. 
For those of you wondering why Maggi is not saying much on the forum just now we are having PC problems - our pc is bust and we only have restricted access to the internet - as soon as I get the faulty hardware sorted out she will be back.

[David Pilling]

Many questions as to what happens to the remnants of the seed (husk?) as it grows.

If seed is sown actually on the surface what tends to happen is a shoot goes up into the air with the husk at the top and often the seed leaves are trapped in it. Do you try to release then by hand, let things take their course, apply some moisture...? sometimes seeds run out of energy at this point and that is the end of them.

If seed is sown lower down then the husk is fixed to the surface or below and the emerging shoot forms a loop into the air. Does that help the leaves emerge? or does it make it harder for the seed to grow?

There are seeds where things work differently, one piece of material emerges, and then splits to form a root and a shoot, for them there's no problem about where the husk goes.

[DaveM]

Just catching up with a few things after being away for the best part of the last month. I'd just like to add to Ian's discussion on the use of rock dust, if I may. Many years ago I visited Mount Etna in Sicily. Whilst talking to one farmer who had many hectares of lemon groves and vines, he said that they welcomed fresh eruptions that deposited a thin layer of fine ash everywhere. This he said would provide much needed boost to the plants over the following few years. The ash from that volcano is basaltic in composition. The vesicular (millions of fine holes throughout the particle) texture of the ash allows water to extract nutrients from the particles - fine dust would be just as good.

Similar 'basic' volcanic rocks such as basalt and dolerite are widely quarried in Scotland, much of it for use as roadstone. These rocks are composed of the minerals feldspar and pyroxene and in some cases some olivine. The feldspar here is calcium aluminium silicate with small amounts of sodium and potassium. Pyroxene is a calcium, iron and magnesium silicate; olivine an iron and magnesium silicate. There's also a wide range of trace elements present. These rocks give rise to rich fertile soils.

I would suggest that granite dust is not as useful as volcanic rock. Granite - such as that which that fine city of Aberdeen is built - is composed essentially of 3 minerals - quartz (i.e. silica), feldspar and mica. When the rock weathers the quartz and mica are little altered and remain as granular and flaky minerals respectively in the soil - they remain effectively inert. On the other hand the feldspar breaks down forming new minerals and allows some of its mineral content to be taken up and used by plants: feldspar in these rocks is essentially a sodium, potassium aluminium silicate; there is a much less calcium than in basalt for example.

Flint grit consists almost entirely of silica, with very few other elements even in trace concentrations.

One final point. A little care has to be exercised when buying rock products, in that quarrymen use 'granite' and one or two other geological terms to describe a number of products, most of which don't are not actually that rock. So do check carefully before buying.

[Ian Y]

Dave
Thanks for this very interesting post, gives me the science behind my observations.