Germinating Seeds in Vermiculite

moulding soil and almond

Yikes! Moulding almond

Some of the seeds in my pots (especially almond) have developed mould, so I had to dump them. They won’t germinated and it’s a health hazard for me, because they live (or try to live) in my bedroom. I thought to try something else to get them to germinate and than I got a date from my co-worker. 😀

Germinating Date Seeds

I got a date seed from my co-worker, who had been to the Green Week in Berlin (a trade fair for agriculture, horticulture and food industries). He had brought a box of three dates from Saudi-Arabia and offered me one. I ate it and kept the seed. He dumped his and I didn’t want to get them off his waste paper basket. So, I only took that one date seed home and soaked it in lukewarm water for four days. They don’t actually need four days, two or three are apparently enough, but I had to wait for the vermiculite.


Vermiculite close-up

Prevent Moulding With Vermiculite

I had done some research on how to germinate date seeds and found a website that recommended vermiculite. That’s a silicate mineral, very much comparable to cat litter. I got a litre on Ebay, just to test it. It comes in different grain sizes, you can see that I took a rather small one.

You put some of the vermiculite into a plastic box (luckily, I discovered 300 ml ice-cream boxes at my supermarket!), add some spoons of water, add the seeds and cover it up with more. Or you just put in more at the beginning, mix it and press the seeds into the vermiculite. Date seeds need a rather high temperature of 25°C (77°F), according to the website I consulted.

Date and Almond Seeds in Vermiculite

Date and Almond Seeds in Vermiculite

I have also put 7 almonds into vermiculite to make up for the rotten ones I dumped earlier. Fingers crossed!

I didn’t plan on growing a date tree, but like with the apples – I cannot resist any seeds anymore!

Addition February 9th:

Take great care not to add too much water or you will see this after some days:

Moulding Vermiculite

Moulding Vermiculite

Some Thoughts about Seeds

Where to get seeds to grow trees from

Risking to state the obvious, I’m just going to say: Don’t buy seeds for trees that either grow in your neighborhood or you can buy fruits of. If you want to try and grow trees from local species, just go on a walk and collect them. If you are into bonsai, you might spot a nice example of an interestingly shaped tree which can inspire you on how to shape your bonsai tree. If you’re more interested in exotic trees, don’t go and buy seeds online. Go to your supermarket and buy the fruit. First of all, you can enjoy the fruit AND you get the seeds which makes it more of a holistic experience (without wanting to sound overly esoteric here). I imagine that when you try to grow trees with children, that it is an interesting experience for them as well to see where the seeds come from and what you can use them for. Obviously, this method only works for fruits, because with nuts the fruit IS the seed. Then just buy/ collect some more (hazelnuts, chestnuts), eat some and use the rest for breeding.

Here’s a table which might help you to find out when which fruit/nut is in season. Green means main season, yellow means low season:

Season Table for Fruits and Nuts

Season Table for Fruits and Nuts

Another argument for using seeds fresh from the fruit is that you might be more successful, i.e. you will have a higher germination rate. I could only compare dwarf pomegranate and pomegranate, because I had dwarf pomegranate seeds in my bonsai starter set and got a fresh pomegranate later, but I think the data speaks for itself (see table below). For some species, using fresh seeds might also have an influence on the germination period. But that would almost literally be comparing apples and pears, because I didn’t have seeds of the same species to compare.

Here are the results of my seeds – germination period of lemons*, pomegranates* and myrtle as well as germination rate.

Latin name
seed or fruit used
no. of seeds germination period germination rate
Dwarf Pomegranate
Punica granatum nana
31 10 to 33 days 23%
Punica granatum
28 9 to 36 days 79%
Citrus x Lemon
fruit (non-organic)
6 5 to 49 days 100%
Citrus x Lemon
fruit (organic)
22 13 to 46 days 88%
Myrtus communis
32 12 to 34 days 31 %

* They might not be done germinating yet, I will adapt the table accordingly, when more seeds germinate. Temperatures above 21°C are highly recommended.

An overview of all seeds I got to germinate successfully can be found here (WIP).


english oak seedling

English Oak (Quercus robur)

With some species, you will find that most texts suggest to use stratification to get them to germinate. As I have just put my medlar seeds into stratification and into soil, I cannot say whether it is really necessary in my experience yet. However, I have tried to get oak (Quercus robur) to germinate without stratification and it worked. I also don’t really believe that it is necessary for medlars, because they are much more common in the Mediterranean than North of the Alps nowadays and I doubt that they get three months of low enough temperatures. Anyway, we will see when my medlar seeds germinate (or not).

“Science Project”: Determining the Germination Period for Stone Pine Seeds

Norman C. Deno’s Seed Germination Theory and Practice

This morning, I came across the book Seed Germination Theory and Practice by Norman C. Deno (available as pdf here). As I have only discovered it this morning, I have not read it entirely and I doubt that I will, because he seems to deal mainly with flower seeds, but he only uses the Latin names.
There is kind of a summary on this page, though, which again I haven’t read in its entirety, I have to admit.
Anyway, the main points I took from browsing both website and pdf is that Norman C. Deno and Brent Walston both don’t believe in stratification to be the solution for all seeds. I liked that idea, firstly because they question all the stuff that is posted and reposted again and again and secondly, because I don’t want to wait for my seeds to rest in the fridge for weeks and months.
As Norman C. Deno apparently “only” tested flower seeds (but thousands of them, mind you) and I want answers for tree seeds, I decided to start my own little “science project”. I put it in quotes, because with the small data I can collect it’ll probably not be very scientific. Anyway, he proposed a method to test several ways to get seeds to germinate which I have tried to reproduce. On page 13 of his book (page 19 in the pdf), he explains how to do it and I mainly copied his method.

Setting Up The Experiment

This is how I did it:
I used 60 pine nuts – bought in the supermarket where they were sold for consumption, but I won’t get pine nuts easily anywhere else. I also needed some paper towel of high wet strength (the one I bought isn’t very strong, but it’s the best I could get), polyethylene bags (I have loads of those, not because I smoke weed, but because the LEGO I buy used comes in them) that can be sealed, a waterproof pen, a plant atomizer  and maybe scissors.

I made four batches of 15 pine nuts, folded each paper towel three times and cut them in a way they would fit into my plastic bags. If you have large enough bags, you might not need to cut the towels. Then you write the name of the plant you got the seeds from and date on the “front page” of the towel. Then you open the last fold of the towel, moisten it with the help of the plant atomizer, put your 15 (or whatever number) seeds onto the wet part, maybe moisten it again a bit and close it. Then you put your package into the polyethylene bag and close it, but not entirely, so that some air circulation is possible and “to insure aerobic conditions”, as Deno puts it.
Afterwards you think where to put it. (Of course, you can think about that when you prepare all the above mentioned stuff.)

I put one bag in the fridge (stratification test), one into the mini greenhouse, one in the cubby and one in the cellar, which probably has a similar temperature to the cubby but less light. I should’ve found some place with temperatures below 4°C, but I didn’t know where. The freezer? Should be more like 0°C or less.
Deno recommends certain brands of paper towel, polyethylene bags and even waterproof marker. The most important point to me seems his concern with the plastic bags. He says to use bags with very thin “walls” to ensure permeability of oxygen. I only had those, so I hope they will work.
Now, I have to wait.


I do hope that at least some of them will germinate, but I don’t know for how long they have been in the bag they were sold in…and if that’s bad for their ability to germinate.
Drying seeds does not have to have a negative effect on them, as Norman C. Deno points out and is even necessary for some of them. I mean, obviously, otherwise stores couldn’t sell seeds. It’s just important to know which can handle it and which can’t. Room for another experiment. I might try apple pips next time. They’re more easily and cheaper available and I can eat the fruit.
Maybe it’s an idea for a kid’s science project, too. It might wanna use a species that germinates quicker like beans or something, though.

Heating Cable for Mini Greenhouse by Romberg – Test

Some days ago, I had taken the temperature in the greenhouse every 10 mins for several hours and shared the ups and downs with my readers. I have since taken the temperature again and again, not always noting it down, but being a bit concerned about it dropping below 19°C, when the ideal temperature for the olives and myrtle is between 22 and 25 °C.
Apparently, the fluctuating temperature didn’t bother the pomegranate seeds, as three have now germinated. However, I researched online for a rather cheap way to keep a constant temperature according to the preferred ones by the seeds. I found a heating cable by Romberg on Ebay for about 13 €. It is supposed to be laid out in the soil. However, as I have several pots in the mini greenhouse rather, that wasn’t possible. So I laid it out beneath, but with some distance between the cable and the greenhouse.

Heating cable in wooden frame

I had built a wooden frame for the greenhouse to stand on, because the window sill got rather warm and by standing on the wooden frame, it wouldn’t come into contact with the window sill.
They actually offer a heating mat for direct contact, but that was more expensive.
And this is what the cable actually looks like:

Heating Cable by Romberg – 3.5 m long

And now for the data. First a chart of the readings without the heating cable, using the normal central heating:

Using Central Heating

And the data from today using the heating cable:

Using the Heating Cable

I think it becomes quite clear that the temperature today was much more stable and ideal. I’m glad I bought it and that I won’t have to leave the heating on all day when I’m at work.

Experiments With Maintaining The Right Temperature In The Mini Greenhouse

I bought a thermometer yesterday, because the old one constantly showed 25°C, which I doubted.

It showed a considerably lower temperature than 25°C. I logged the temperature for some hours manually and experimented with the heating and putting a glass of hot water into the green house. The lowest temperature was 20.4°C and the highest 25.1°C. It would be best to have between 22 and 25, though.
Logging manually is quite annoying, taking the temperature every 10 mins. I wish I already had a Raspberry Pi, because it can do that for you.

Insulation with Rubber Foam

This morning, I started logging again, nonetheless. I had put some rubber foam between the window and the green house in case the windows aren’t completely airtight. I had already thought about getting a heat mat, because my impression was that the temperature was too low on average. But as my calculations showed, it was 22,7°C on average yesterday night. So maybe no need for a heat mat after all.
With the rubber foam and not using the glass of hot water, the result was a bit more even and barely left the ideal zone of between 22 and 25°C:

The lowest temperature was 21.4°C and the highest 24.1°C with an average of 22.9°C.

Bottom Insulation with Board

I have noticed that the window sill (made of some kind of stone) gets really cold when the heating isn’t very strong. So I now put a board underneath the green house to isolate it a bit better. But of course, that isolates into both directions. I would need a semi-permeable material. However, it seems that the temperature already fluctuates less:
The lowerst temperature in this setting was 21.3°C and the highest 23.3°C with an average of 22.4°C.
However, one must not forget to take in account that the sun isn’t shining today. If it was, it would heat the greenhouse even more and I would need the heating less, which heats periodically rather than being at the same temperature at all times. Which is clearly visible from the diagrams.

Using “solar” energy

I googled on how to keep a greenhouse warm, but only found tips on “proper” greenhouses, not ones for window sills. However, I found one solution, which I could modify. I will get some black film canisters, fill them with water and let them collect warmth during the day. I will check whether it is of any effect later.
Another idea was to use Christmas lights, because they emit warmth as well. But I would need electricity for that. I like the idea with the film canisters more. It’s a greener way.