It is the middle of Winter here and I am getting a lot of locals asking me how to start peppers indoors with a heat mat – or without a heat mat! Growing chilli and capsicum or bell peppers at home is one of the best ways of improving your sustainability and if you can grow your peppers indoors you can extend your growing season significantly.
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How to start peppers indoors
There are some things that peppers need to get growing quickly and give you their spicy fruit. With the right soil, heat and light you will grow healthy pepper plants indoors or out.
There are many reasons you might need to start your pepper seeds inside – our Summers are not as hot or as long as many places, so starting my peppers early in Winter ensures I have nice big plants to plant out when the weather warms up. We cannot grow normal peppers outside even in the Summer, so mine need heat for a couple of months before the weather warms up my tunnel house.
Soil for growing peppers
Peppers do not tolerate being too wet or too dry. When you are starting seedlings, you want the soil to remain consistently moist, but not sopping wet. Soil that is too wet will rot out the seeds or encourage blight ( fungal disease) in plants.
For starting pepper seeds you will need a light, fluffy, well draining soil-free seed starting mix. You can make your own with a combination of peat moss, leaf mold or compost, perlite and vermiculite, or you can buy a specially made mix – this is what I do!
Trays for sowing pepper seeds
You can re-use seed cell trays from other transplants that you have bought – or you can often pick up other peoples empty trays for free if you ask around.
Personally, I use 10×20 inch 50 cell trays and put them in a 10×20 flat that does not have holes in the bottom of it so that I can bottom water (see below) and I sow only 1 seed per cell as this saves pricking the plants out just after they sprout.
Seeds for growing peppers
The BEST thing about growing peppers from seed is the massive range of heirloom and heritage pepper varieties that you can grow. You are no longer limited to the commercially available varieties!
Can Can you grow bell peppers from store bought peppers?
Temperature – how to use a heat mat to start pepper seeds
Peppers need 20-30C / 70-85F to germinate and then a consistent 15C /60F or more to continue growing. The easiest way to do this is to use a garden heat mat or a heated propagation table.
A heat mat is best run with a thermostat so that you don’t cook your seedlings – like this one.
To use a heat mat, you simply place your seed tray full of seed raising mix and seeds on the top of the mat and if you have a thermostat, place it in the soil of one of your seed cells.
You must keep the seed raising heat mat dry, so use a 10×20 flat under your cell/plug tray. Turn on the heat mat and wait for the seeds to germinate.
Alternatives to a heat mat for starting seeds
If you don’t have a heat mat you can place your seeds in one of the following:
- On a sunny windowsill
- In your hot water cupboard
- On top of your fridge
- On the countertop in a nice warm kitchen or laundry
However, unlike tomatoes, once pepper plants have germinated they still require warm temperatures to continue to grow so you will need a warm spot with plenty of light for once they have germinated.
Water for pepper seeds and seedlings
Peppers struggle if they are too wet – they succumb quickly to rot or blight. They will also die quickly if they are left to dry out.
I like to bottom water my seeds by placing them in a try without holes on the bottom and ensuring that the cell tray fits properly so that the cell bottoms are just sitting flat and evenly on the bottom of the bottom tray.
Then you can simply add about 5-10mm or 1/4-1/4 an inch of water in the bottom tray every couple of days and let the soil wick the moisture up to where it is needed.
Alternatively you can mist the soil to keep it moist. Avoid heavy watering from the top as you will displace the seeds.
Light for sprouting pepper seeds
Germinating seeds do not need light. However, once the seeds are sprouted they will need plenty of light. Ideally in a full sun position, or even better directly under some grow lights.
The brighter the light, the less leggy your plants will be.
Potting on pepper seedlings
Once your seedlings are about 15-20cm/6-8 inches tall they will be calling out for more space and more soil. If your frosts are all done by then, you can plant your plants straight in to where they will grow.
If you are needing to continue growing your pepper plants indoors for a little longer, it is time to pot them on to larger pots. This is when I use 10cm / 4inch pots filled with good quality potting mix.
Many people do not realise but peppers, eggplants and tomatoes all grow additional roots out of the buried stems so be sure to bury as much of the pepper as you can when you pot them on. As this will give you better, more fruitful plants in the long run. Just make sure the growing tips are at least sticking out above the top of the soil.
When should I start peppers indoors?
Usually you will start your peppers indoors 8-10 weeks before your last frost date. If you are wanting larger plants to plant out, you can sow your pepper seeds even earlier, as long as you can provide them with ample light and warmth to encourage early growth. Plants without adequate light and warmth will sit in stasis until the sun light hours are long enough for them to take off.
Do you have to start peppers indoors?
No, you can grow peppers directly outside if your season is long enough and warm enough for this. Peppers need consistent soil temperatures of over 20C/70F to germinate – for most places this means they will need to be inside at least until they germinate.
Do pepper plants need cages?
Staking pepper plants may not be a requirement for growing them in your garden, but it has its advantages. Not only does pepper staking help support plants, keeping them upright, but pepper staking can also reduce sunscald on fruits and helps keep them off the ground, where they are susceptible to pests or rotting.
Can you use egg cartons to start seeds?
Egg cartons, egg shells, toilet rolls and peat/coconut pellets all work brilliantly for starting pepper seeds if you cannot access cell trays, or if you are looking for more eco-friendly ways to start your seedlings.
How much light do peppers need indoors?
Peppers need at least 8 hours of direct light each day, the more light the plants get the better they will grow. If you don’t have a sunny spot that gets that amount of direct sun, peppers do respond well to grow lights, try and keep them no more than 10cm/4inches above the tops of the plants.
Be sure to get a full spectrum grow light, I like the adjustability of this design.
Can you grow peppers indoors all year round?
Yes! As long as they avoid the frost – keep the temperatures above 10C/50F overnight and ensure the plants are getting at least 8 hours of direct light each day and your peppers will continue to grow and produce all year long.
The only real limit to growing your peppers indoors all year is how tall you can stake your plants. Keep watering your peppers, and feed them each week with some liquid fertilizer, we alternate between a seaweed fertiliser and a blood meal mix to enjoy fresh peppers even in the middle of Winter!
Do peppers do well in pots?
Smaller pepper varieties will grow well in 8L / two-gallon containers, but bigger plants need at least 20L / five-gallon pots. You can grow peppers in any type of container as long as it’s big enough and has good drainage. Keep the soil moist but not wet and feed them weekly.
If you are wanting to grow peppers this year from seed, these steps will help you germinate your seeds perfectly and grow the best indoor pepper plants.
If you would like help getting the most out of your garden, I would love to help you, find out more here
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