Malcolm Harrison

Latest posts by Malcolm Harrison

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Posted: 09/04/2014 at 21:44

Welcome Jac to the family of plant lovers and gardeners. You can ask any question you like and you will get so much helpful advice and support. Also a great garden - what are your planting plans for this summer ? Are you interested in Plant Propagation?

Good luck in all you do.


Seed germination - any hope for ones sown too early?

Posted: 06/04/2014 at 15:42
Tootles wrote (see)

Hi folks, in your experience, is there any point in hanging on to trays full of seeds that I planted about 8 weeks ago with no sign of germination? They are in an unheated greenhouse.  I was a bit too keen and think I planted too early. Is it wishful thinking to assume they will just sprout when they are ready? What happens to them when they don't sprout? Do seeds sort of die??  I did tomatoes, chillies, cosmos, dahlias and sweet peas.  Not a cheap mistake!!  That'll teach me!

At the beginning of March I sowed some Dahlia seeds which I had collected last October/November from seed pods in my own garden. I 'overwintered' them in sealed packets in dry, airtight plastic boxes in my garage.  The seeds were sown on multipurpose compost, watered and put in an electric windowsill propagator at a temperature of about 19 deg C.  Most of them had not germinated after several weeks and on examination appeared to have rotted.

Interestingly, some Dahlia seeds bought from a commercial company all germinated quickly under exactly the same external conditions.

So, in your case, I don't think the reason is entirely due to the low temperatures in your unheated GH.

As a member of the RHS I raised the question with them. The Horticultural Advisor suggested that I had sown them a little early  and they could well benefit from cold chilling (cold stratification) for about two weeks before sowing again. I put them in the fridge and the two weeks is now up so I will sow some more this next week and see what happens (it being later also). I have read that even seeds that do not need chilling may germinate more quickly after a period of cold storage.

You may want to try the chilling before sowing now process.  Let me know your results good or bad and we will go from there.

Good Luck.



Beautiful tiny garden

Posted: 04/04/2014 at 14:50
I agree it's amazing what you can do even in a
small space. The combination of Roses and
Dahlias look beautiful as well as the change
of theme at every turn.

Stratification of Seeds

Posted: 27/03/2014 at 20:30

I am interested to know if anybody has tried the technique of stratification (cold chilling of seeds in a fridge at 2 - 5 deg C) before sowing them in Spring in order to break their dormancy and get better more even germination. I am trying this with my Dahlia seeds I collected last Oct/Nov to see if it improves Germination rates.

If you have had good or bad results please let me know. Thank you.


Dahlia Tubers

Posted: 26/03/2014 at 20:01

When a dahlia plant grows to maturity it forms swollen roots called tubers which act as its storage organs for supplying food and water. The tubers can be dug up at the end of the flowering season (Oct/Nov) after the first frosts and stored over winter and planted out again the next Spring - hence you don't need to buy tubers unless you want a variety of dahlia which you might not already have.  

Dahlia seeds are formed in the pod after the flower has bloomed and then lost its petals. You can collect your own seeds from pods when they are mature/ripe as only ripe seed will germinate on sowing the following spring after a winter of dormancy/ 'shut down'.

The choice is up to you - you can grow them either way. However if you don't want to be bothered digging them up and storing the tubers overwinter then just grow from seed and leave the tubers in the ground at the end of the season.


Hanging baskets

Posted: 26/03/2014 at 19:34

Although it can be warm during the day there is still the chance of frost at night. I would still wait until May at least before making up the hanging baskets and putting them out.

My seedlings

Posted: 23/03/2014 at 17:23

Most seeds germinate to produce young seedlings in a temperature range of 15 - 24 deg C. They will then need to be grown on inside if they are frost tender (Half Hardy). If the plant is labelled 'Hardy' on the seed packet then it will tolerate low temperatures and frost and can be grown on in a cold frame/unheated greenhouse (eg: sweet peas).


Dahlia Tubers

Posted: 23/03/2014 at 17:08

I planted most of my Dahlia tubers in pots last year in moist compost and kept them inside at first in a warm place. They then were moved outside when the weather warmed up. The majority of tubers shooted and produced a beautiful and continuous summer-autumn display. This method is the best. I also planted some tubers directly into the soil later in May with successful results. I will be doing the same again this year.

Also, when the shoots are about 3 inches long (before hollow stems develop) you can take stem or basal cuttings and root them in small pots of compost to grow on. These will grow to flower during this summer season and of course come true to type (vegetative propagation).


Growing Sweet Peas

Posted: 23/03/2014 at 16:45

May I ask if they are a Climbing (up to about 6 ft) or Dwarf variety? For a small pot I would suggest growing the Dwarf variety as they do not grow tall and do not need any form of support. It seems you have a climbing variety and therefore support in the form of 6 ft canes/netting/ willow branches is needed and better grown in an open well dug and composted soil. You can make a wigwam of bamboo canes and plant 3-4 seedlings at the base of each cane and attach the first shoots to the bottom of the cane with slip rings- you can buy these from a garden centre in packets of a 100 or so.

Hope this is of help.


Allium Purple sensation

Posted: 13/03/2014 at 21:05
Cathy Raine wrote (see)

I planted my Alliums in sep/oct as instructions in a pot with added grit in a sunny site. I was expecting them to be coming up by now but so far nothing. Have they died or am I to early In expecting to see them?

I think it is a little early yet. I leave mine in the ground over winter and now the strap-like foliage is growing first quite quickly before the flower bearing stems appear.  If you haven't any foliage by now they may have died - did you leave them outside in the pot during all the weeks of rain we have had over this winter? - the bulbs/roots may have rotted in the saturated compost. I would have a look at the bulbs.


1 to 10 of 36

Discussions started by Malcolm Harrison

Stratification of Seeds

Replies: 22    Views: 2507
Last Post: 28/04/2014 at 17:29

Use of Ring Culture for growing Sweet Peas

Replies: 3    Views: 1041
Last Post: 04/03/2014 at 08:26

Viability of Collected Dahlia Seeds

Replies: 3    Views: 1515
Last Post: 03/03/2014 at 17:07

Storing Dahlia Tubers

Replies: 27    Views: 6101
Last Post: 16/11/2013 at 14:22
4 threads returned