Winter can be one of the most challenging times of year for propagating seeds and cuttings. Lower temperatures can slow germination, reduce rooting success and leave growers wondering why their usual propagation methods aren't working. In this guide, Jake explains why winter propagation can be difficult and shares practical tips to improve your success rates throughout the colder months. 

Propagation is a necessary stage of cultivating your own plants; everybody must start somewhere and usually it’s the simple step of placing a seed in the ground, watering it, and hoping something sprouts! Spring and Summer are the seasons where this is easiest and naturally is when most plants in the wild will do their thing and spread seeds so that their offspring have the long, warm, sunny days to grow big and strong before the colder months come through!

However, we that grow in controlled environments and cultivate via protected cropping or hydroponics will often find the need to take cuttings or sprout seedlings in the colder months to grow and harvest our favourite plants all year round.

A lot of people get stuck here because they find they have a much easier time getting cuttings to strike or seeds to sprout in the warmer months but can’t seem to have the same results in the Wintertime despite not doing anything different and the answer as to why is very simple – it’s too cold!

If you’re one of these growers, read on and I’ll be going over why the cold affects this stage of growth, and I’ll also be providing the tips and tricks to really improve your chances when it comes to propagating in Winter!

Why Seeds and Cuttings Struggle In Winter

As I mentioned above, the answer is simply because it’s too cold for seeds to sprout and cuttings to strike roots normally. Specifically, most seeds and cuttings want a soil temperature or rootzone temperature between 22–26°C to successfully germinate/sprout roots.

Additionally for cuttings (and to an extent sprouted seedlings), require at least 70 – 90% humidity as they don’t have roots either strong enough or present yet to take up water and nutrients from the soil. If you’re already using a humidity crib like you would any other time of year, your humidity requirements should already be covered by that, but I thought I would mention that it remains important! A Hygrometer, which measures ambient temperature and humidity, is an excellent piece of kit that can help you keep on top of that.

It takes a lot of effort to grow an entirely new root system if you’re a cutting or crack your shell and grow into a full plant if you’re a seed – and if you’re spending a lot of energy surviving the cold, there’s not a lot left for growing! In Winter, the days are shorter, the Sun is generally not out as much and the temperature is lower, meaning that plants aren’t getting as much energy from the Sun and heat, and therefore don’t have the required energy to process nutrients and grow. 

For plants that have already started growing, this can severely stunt growth rates and maximum sizes, and in our case of trying to get seedlings to sprout or cuttings to take – will outright stop them all together.  Wintertime for all creatures and plants is generally all about conserving as much energy as possible to survive until the warmer months when there will be an abundance of Sunlight, food, and better conditions for growing and continuing the life cycle.

Simply put, your seeds or cuttings don’t detect that it’s the right time of year to grow, so they don’t!

How to Successfully Propagate Seeds and Cuttings in Winter

Luckily, we can trick our plants into thinking it’s whatever season we want it to be by growing our plants in controlled environments indoors!

The number one key component for success in winter propagation is the heat mat!

A heat mat is a heated surface you can place your seedling tray on top of which will provide warmth to the medium that you’ve planted your cuttings or seeds in. Most models have a fixed temperature that raises the soil/medium temperature closer to that sweet spot temperature range (22–26°C) which makes them super easy to use. The Cultiv8 models are a simple, reliable and cheap choice for this application and come in multiple sizes.

For those that like a bit more precision, the Cultiv8s have a Thermostat Controller that can be purchased to increase the functionality, and other brands like Heat ‘n’ Grow and AC Infinity have their own models that have built in Thermostat Controls!

Other Tips and Tricks:

While a heat mat is probably the single most impactful thing you can add to your propagation setup to ensure success in Winter, there are a few other things you can do that as well will also help. You should be propagating indoors regardless of setup, as the insulation of your own home should help with the ambient temperature, and you can go a step further by setting up your propagation inside an enclosed space – such as a spare cupboard or wardrobe, etc. 

Combing an enclosed space with a heat mat and a humidity crib will essentially turn that space into a plant incubator! All the other usual aspects of propagation remain just as important, such as using sanitised equipment, cutting gel (such as Clonex) for cuttings or a good seed-raising mix for your seeds, and a low-wattage grow lamp or grow light on a correct light cycle (18 hours on, 6 hours off).  

It’s also important, as always, to start with seeds that are not old and from good genetic background!

Following all that should significantly improve your success when it comes to raising up seedlings and cuttings in the colder months. Remember – the stronger of a start that you can give your plants, the better the result! If you still get stuck however we encourage you to get in touch with us here at the shop and we’ll make sure to get you on the right track.

Bonus Tips

I thought I’d add in some tips for getting the most out of your plants during Winter once you’ve got them nice and established out of the propagation stage. 

For Those Using Reservoirs:

Plants don’t like their water too cold as it reduces the root zone temperature below ideal levels (18–24°C), and in Winter your Nutrient solution may drop below comfortable temperatures. Ideally, your reservoir needs to be between 18–22°C so having a water thermometer to see where you’re at, and a water heater appropriately sized for your reservoir will keep things in the correct temperature zone, ensuring nutrient uptake is not reduced due to cold water! It’s a bit of an overlooked aspect of growing that people often get caught with in Winter, so if you’re running a setup that uses a reservoir, be sure to factor that in!

Grow Tent Heaters:

Once your plants are out of the seedling phase and have been established in your main grow environment, they’ll be most comfortable with a leaf temperature around 26°C on average. This ideal temperature might be plant specific for you so ensure that you do your research and find a good average temperature dependent on your chosen specie(s).  

In recent years, portable heaters developed specifically for grow environments have become very popular amongst growers to make up for the lack of heat that LEDs put out in the colder months. Heaters like the AeroFlux from Vivosun or the Thermoforge T7 from AC Infinity are compact, smart controlled and directly ducted into your Grow Tent or Growing space, allowing for you to introduce heat when necessary to keep your plants’ leaf temperature at the desired levels. 

It’s important to note that leaf temperature may not be what the room temperature is and you may have to make the room hotter to reach desired levels! You can measure the actual leaf temperature with something like the AC Infinity VPD Thermometer, but in general, just aiming for a room temperature that’s at least the same or slightly warmer than your desired leaf temperature is a great way to grow!

Frequently Asked Questions

Q. What temperature is best for seed germination?

A. Most seeds and cuttings perform best when the root zone temperature is between 22-26°C. Maintaining this temperature range can significantly improve germination rates and rooting success.

Q. Do I need a heat mat for winter propagation? 

A. While not always essential, a heat mat is one of the most effective ways to improve propagation success during winter by keeping the growing medium within the ideal temperature range.

Q. Why won't my cuttings strike roots in winter?

A. Cold temperatures, low humidity, insufficient light and poor environmental conditions can all reduce rooting success during winter.

Q. What humidity should cuttings be kept at?

A. Most cuttings perform best at approximately 70–90% humidity while roots are developing.

About the Author

Jake works with growers every day at Fran's Hydroponics, helping customers achieve better results through practical advice on propagation, environmental control, hydroponic systems and indoor growing. His goal is to make growing easier and more successful for growers of all experience levels.

Grow Strong All Year Round!

So, there you have it! Keeping these important factors in mind and being conscious about the time of year will ensure that you as a grower will know when and how to adapt to changing temperatures and weather throughout the year. At the end of the day, we all just want to see our plants grow happily and paying attention to your temperature in Winter will help you grow your best all year round!