Germination isn’t the simplest of topics. I thought that I had a pretty good idea of how seeds worked. During the course of course of researching the background for this article, however, I realised that I was wrong pretty soon.
I learned, for example, that some seeds will only break dormancy after their coats have been broken by forest fire. And that the oldest germinated seed was 2000 years old!
In this guide I’m going to review some of my favourite propagators, as well as offer some general buying advice. Let’s dive in…
Best Propagators: Quick Guide
|Garland Windowsill Propagator||$$||9/10|
|Vitopod Double-Layer Propagator||$$||9/10|
|Stewart Thermostatic Propagator||$$$||10/10|
|Garland Large Propagator||$||8/10|
|Compact Pop-Up Propagator||$$||9/10|
What is a propagator?
A propagator is a device that creates a closed environment that is ideal for the germination of seeds. The simplest models are essentially trays with removable transparent lids. Of a seed’s three basic requirements – moisture, air (or oxygen) and warmth – a propagator ensures that temperature is maintained at an ideal level and that moisture is retained in the growing area. Some propagators are self-watering.
In trying to understand a certain plant, it’s always worth going back its original, wild environment. Even varieties that have undergone decades and centuries of cross-breeding still closely resemble their wild descendants.
Were you to investigate conditions in nature, one of the things you would notice is that seeds need a degree of stability to germinate. In the same way that seed dormancy can only be triggered when certain conditions are met – usually, but not always, these are warmth and moisture – sprouts (or shoots) will also only grow when certain environmental factors are present.
Heated vs. Unheated
- Heated – One of the main reasons for using a propagator is to overcome the limits of cold outdoor conditions. A heated propagator is essentially the same as an unheated model, the difference being that it contains a “heat mat” built into the bottom of the tray. Some models also include a thermostat.
Unheated – Sprouts can deal with fluctuations in temperature, although it’s important to make sure that an unheated propagator will keep these variations within an acceptable range. It’s important to remember, at the end of the day, that an unheated propagator is just a tray and a piece of plastic. Very often these will overheat during the day, and cool down quickly at night, particularly if they’re in a greenhouse or conservatory in winter.
- Heat mat – Why not just get a heat mat and pop them under your seed trays? This is a fair question and, when germinating lots of seedlings, can be the most viable option. The main benefit is that most heated propagators come with thermostat control (to prevent overheating). When you tot up the costs of buying a mat and a basic propagator, there’s often not much in it.
Features to look for in propagators…
- Size – Whilst it seems self-evident that you need enough space to fit your seedling pots in, there are some concerns beyond the obvious. Bigger propagators don’t heat up as quickly as normal ones. Similarly, there tends to be less chance of seedlings rotting due to condensation in bigger models. If you’re leaving sprouts and seedling untended for longer periods in a greenhouse or conservatory (both of which can heat up quickly), then these points may be worth considering. You also want to make sure it will fit wherever its meant to go…windowsill growers tread carefully!
- Thermostat – Do you want to your propagator to be self-regulating? Higher-end models will usually include a thermostat, which can be either adjustable or non-adjustable. If there’s a possibility that temperatures will be significantly colder at night, then this will be something to look for.
- Ventilation panels – Always make sure that any propagator you buy has ventilation panels! Even thermostats can’t directly lower the temperature underneath transparent plastic if it gets very hot!
Best Heated and Unheated Propagators: Our Top Picks for 2017
***Full Disclosure – Where appropriate, I’ve linked product images to commercial sites and Amazon (see Amazon Disclosure). If you buy from these sites, I earn a small affiliate fee, which helps me keep Urban Turnip going.***
I’ve included three heated and two unheated propagators in this list. The unheated models are at the end of the list.
1. Garland Windowsill Propagator (Heated)
This propagator from Garland really looks the part. It also fits perfectly on a windowsill (18.5 cm/7 in. wide). The “mini propagators”, each with their own ventilation opening, are an added bonus too – there’s no risk of a single polythene sheet or seed tray splitting and having to replace the whole unit.
It’s a plug and play system that uses a carbon heating element to warm the bases of the individual propagators. Because they’re separate from the heating element, there is no thermostat control. Temperature control is by means of the ventilation circles alone. For a cold greenhouse or windowsill, this shouldn’t be a problem (it will mirror natural cold/warm heat cycles). If you’re growing in a room that heats up a lot during the day however, you will likely need to unplug. It will increase room temperature by about 8 degrees (Centigrade).
There is also a smaller unit available that holds four propagators.
2. Vitopod Double-Layer Propagator (Heated)
If you want more space to germinate a range of seeds, and even grow plants in, then this Vitopod double-layered propagator is one of the best on the market. The design incorporates 5 vents (3 for the single-layer model) and the thermostat is fully adjustable, meaning that you can choose your ideal temperature.
The double-layered design also means that humidity levels can be adjusted (by removing or adding the top layer) and that the propagator can double up as a mini-greenhouse. It measures half a metre by half a metre and was voted “Best Buy” by Gardeners’ World.
3. Stewart Thermostatic Propagator
This heated propagator from Stewart is a basic, self-enclosed model that is ideal for those who only need a small germination space. It’s thermostat-controlled and will maintain temperatures between 18°C and 23°C (it has the capacity to heat 15°C above ambient/room temperature). The cover includes two vents for aeration and humidity-control.
As an added benefit, the heater also comes with two trays and two pots. The larger pots are perfect for dense sowing and”pricking out”. Whilst this particular propagator is made with a 22 watt heater, here’s also the option to buy one with 50 watts, the temperature of which can be adjusted in a range of 12°C to 28°C. The 22 watt unit is non-adjustable.
4. Garland High Dome Propagator (Unheated)
If you’re going for an unheated propagator then I suggest you look for a few features. As mentioned in the introduction, you want to make sure there are ventilation holes. Second, durability is a must. It’s so easy to waste money on cheap and flimsy propagators year-after-year. Finally, get one with a high roof (as with this model). It makes temperature control a lot easier (it won’t overheat as quickly and air-flow will be improved) and reduces condensation.
This propagator from Garland fills all of the criteria above and is very reasonably priced too. It’s also very durable and long-lasting and should keep at least a few years. It has drainage holes to help with moisture control or for when you want to sow directly into the seed tray.
5. Compact Pop-Up Plant Propagator (Unheated)
This unique propagator from Sweden has a load of quirky features that make your life as a gardener easier. It’s also amazingly well-built and robust. The spiked cover doubles up as a dibbler. for pushing seed holes into the potting mix, and the tray underneath creates a self-watering system.
The cover can also be lifted by 90 degrees to help you with temperature control and humidity levels. The design of the individual plugs is also interesting. Their cone shape encourages deeper rooting and seedlings can easily be popped out when they’re ready for planting (there’s an indentation on the base of the tray that pushes the plugs out).
Let us know your thoughts! Leave a comment below!
What are your thoughts about my selection? Have you had your own experiences with propagators? Have you tried any of the products on this list? Leave a comment below and let me know!
Image Credit: Planters by Ivan Lian.