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Over the past few years, a number of people have written to me with questions about my palm germination method. Here are my answers to some of the most frequently-asked questions.
It is a mineral, similar to mica. It's very lightweight and sterile. It comes in several grades. I prefer the medium grade.
Most good garden centres. If you need large quantities you should be able to obtain large sacks from DIY stores. Vermiculite is also used for roof-cavity insulation.
Some people mix it into compost to create an open texture. Some people pack tubers into it (e.g. dahlias) for winter storage. Personally, I use it as a top-dressing on pots of small seeds such as grasses, conifer seeds and annual flowers. To use as a top-dressing, fill a pot or tray with compost, firm and level it. Water it. Sprinkle the small seeds onto the surface. Then put a quarter to half inch layer of vermiculite over the top. A top-dressing of vermiculite has several advantages over compost or soil: 1) it doesn't contain weed seeds, 2) its very lightweight so easy for the seedlings to push through, 3) there's no danger of it solidifying into a solid crust, 4) it allows light to get through which is needed for the germination of some seeds.
If you are using my method (filling a sealed box or bag with the germination medium), you could use sphagnum moss, moss-peat, coir (coconut fibre) or perlite. I personally don't care for moss, moss-peat or coir since a) the seed roots get tangled into it, b) it's difficult to see what's happening to the seeds in a mossy mass and c) it's unlikely to be totally sterile. I don't like perlite because a) it's dusty and can make the air unpleasant to breath when working with it, b) it's gritty, c) anyone who sells you perlite should be able to sell you some vermiculite so you'd be better off buying that instead.
You've been too generous with the water. You only need very little water. The vermiculite should feel dry to the touch.
Not for fast-germinating, small seeds such as Washingtonia. But for slower germinating and/or large seeds such as Butia, Brahea or Jubaea, you will almost certainly need to add extra water every couple of weeks to allow for absorption by the seeds. But don't overdo it. If that vermiculite feels slimy, you are watering too much!
Yes. Just shake the box and stir the vermiculite around every few days to make sure you aren't getting any completely dry spots.
Not that I am aware of. It is quite possible that the seeds of some palm species may benefit from light. All I can say is that I've never provided light for any palm seeds which I've germinated. The trouble with light is that it promotes algae in the germination box.
It's the British name for a cupboard or small room containing the house's water heater or boiler. If you haven't got an airing cupboard, try to find the warmest location in your house.
Certainly. I regularly use it to germinate most large seeds (say the size of a lentil or bigger). For example: Ginko, Mirabilis (Marvel of Peru), Ipomoea (Morning Glory) and Cycads of all sorts
The principal disadvantage is that any seeds which aren't really thoroughly cleaned will tend to go mouldy. You absolutely must remove all trace of fruit flesh from the seeds and soak them in several changes of water to remove any surface sugars. With some seeds, it is just about impossible to clean them really well at home. If you can't find a supplier of pre-cleaned seeds, you may have to germinate such seeds in a more conventional way - in trays or (better still) deep pots of well-drained compost.
You can pot it up at any length. The sooner the better.
As a general rule, bury it in the compost to about the same depth as the size of the seed. i.e. if the seed is half an inch across, make a hole one inch deep, pop the seed into this and gently cover it with half an inch of compost.
It may be a few weeks before the first leaf pops up. Best to keep the seedling warm at this stage. Water it sparingly. If you over-water, the root may rot, particularly if the seedling is kept in an unheated room.
but mainly, just wait