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(updated Feb 2020) Today I will be writing a guide on planting pepper seed indoors in winter, and I will also share some tips on how to successfully grow peppers in a short cool growing season!
I grow peppers in the Pacific Northwest in gardening zone 8b. We have a cool, short growing season, so it is hard to find peppers that do well here. I am including a couple of varieties that have done well for me here.
Oda Peppers: These are the most beautiful royal purple color. Worth growing for the sheer beauty of the color! Thin walled and yummy for snacking or salads.
These have grown really well for me and are worth growing just for their beauty. They have a thin white wall and their flavor is not my favorite. But if you are looking for a stunning variety to grow, this is my favorite for that!
King of the North: This is a short season pepper and it has done really well for me, both for flavor and productivity. Turns red when fully ripe. Very productive large fruits. The photo below, I took the first week of June last year in my unheated greenhouse.
Purple Beauty: Purple Beauty has become a fast favorite. It produces well and early for me, and keeps up well with King of the North. Tastes great too!
If you haven’t checked out my Seed Starting 101 Series: Essential Seed Starting Equipment post, it outlines what type of soil I use and all the other equipment I use in this process.
When I am planting pepper seed, I use the fat end of a chop stick to indent the soil about a quarter inch. If I feel confident that my seed is still good, I will put two seeds in. If the seed is older or you got it in a swap, and you don’t know how old it is, you might do better to put 3 or 4 seeds in.
Lightly bury the seed and press it down so the seed is in contact with the soil all around. Then I give each one a good soaking spray with a spray bottle. You want all the soil above and below the seed to be damp, for the seed to germinate.
You might also want to check out my Seed Starting 101: Winter Sowing article, that explains how to use milk jugs as mini greenhouses so you can start your seed outside in the dead of winter.
After you are done planting pepper seed, spray down the seeds well, place a plastic dome cover over your plant flat, or cover with saran wrap. You want to keep all the humidity inside until the seeds germinate.
Place the flat on a heating mat, as peppers need very warm soil to germinate. Once the majority of the seeds have germinated, you can remove the plastic cover and place the seedlings under a grow light.
Spray down again gently if it looks like the seed is drying out, or, water by adding water to the tray and letting the 6-packs absorb water from the bottom.
Once the seeds have germinated and you have removed the cover, you want to now move your heat mat and flat so that they are under grow lights. Now is also a good time to put a small fan on your seedlings. If you don’t have an oscillating fan, try to move the fan so it is aiming from different directions, a couple of times a day.
The fan helps with air circulation, to prevent fungus and disease from developing in the warm moist environment. It also makes for much stronger plants as they will develop stronger stems.
When the second set of true leaves develop, thin the plants down to just one plant for each cell. Keep the lights within an inch of the top of the plant. As the plants grow, move the light upward with the plant.
When the plants get large enough to either not fit under your lights, or just get to crowded in the tray, it is time to transplant them to a larger pot. I like to move them into Solo Cups at this time as they are a little deeper than most of the standard small 4″ pots available. Make sure you snip some drainage holes into the bottom of the cups though.
If you plan to grow them in larger pots for the season, you could transplant them directly into those pots at this time. I usually do not have space to do that yet, since I usually keep around 3 dozen pepper plants going for the summer. So transplanting them to the Solo cups is kind of an intermediate phase for them.
Usually by the end of March or early April, I then transplant again into the larger permanent 3 gallon pots that they will live in for the rest of the summer, and they get moved into my unheated greenhouse.
Before you move your pepper plants from indoors to outside, it is critical that you harden them off properly. Without hardening off your seedlings, they will go into shock and may not recover. See my article for a guide on How to Harden Off Your Seedlings.
Peppers do not do well if the temperature gets below 50 degrees. So until the temperatures get warmer than that, especially at night, you must keep them in a sheltered location or bring them in at night.
Even if you are moving them to a greenhouse, it is a good idea to keep a thermometer in the greenhouse with an alarm that will let you know if the temperature drops below this so you can take proper precautions.
When you are doing the final planting of your pepper plants, whether it is in pots or in the ground, my secret tip is to add a little sulfur to the bottom of the hole. Peppers like it a bit acidic, and I learned this trick from Dick Raymond in his Joy of Gardening book .
You can buy sulfur powder for plants, and just put a pinch in, or even throw a few match stick heads in there. I also add a bit of crushed egg shell and a bit of Epsom salt for a bit of a calcium and magnesium boost. Stir this all together at the bottom of the hole with some soil, and then plant your pepper plant, and water well.
Peppers (and tomatoes) love heat, and it is often something we lack in our short cool growing climate.
One thing I do to make my pepper plants happy, is I grow them all in pots. The roots stay warmer up out of the ground, and this makes the plants happier and more productive. This goes for hot peppers as well as sweet bell peppers.
I also grow peppers in an unheated greenhouse, which helps tremendously. Just providing them cover at night when the temps get cool, really helps them out.
If this is not an option for you, consider placing your pots up against the south side of your house, or place them on a patio which retains the heat of the sun during our cool nights. This extra heat really makes the plants happier and healthier!
Typically I move my peppers and tomatoes into my unheated greenhouse around April 1. The picture above was taken at the end of April a few years ago, and I already had many blossoming. The greenhouse provides them with just enough extra warmth during the day, and cover from the cool nights.
I do keep watch on the weather after they move to the greenhouse. If the weather should get below 40, I would provide additional cover inside the greenhouse, by laying a sheet over the plants.
We have such a cool short growing season here in the PNW, planting them in pots and keeping them in the greenhouse for the summer, has allowed me to have more productive harvests.
I like to spray my peppers and tomatoes once a month with a water solution containing 1 TBSN of Fish Emulsion fertilizer, and 1 TBSN of Epsom Salts, thru the growing season until most of the fruit has set. Other than that, water regularly and you should be all set for a bumper crop of peppers this summer!