How To Ripen Peppers in the Pacific Northwest

What Peppers Want

Peppers are not difficult, but they are picky. In this way they are just like my 18 month old son: as long as he’s doing exactly what he wants he’s the most easy-going boy in the world. But stop him from smearing peanut butter on the cat and suddenly he’s screaming like he’s suffering the world’s worst indignities.

Peppers are the same way. Give them the long, hot days and warm nights they want and they’re easy-to-grow. But ask them to put up with a typical cool Maritime climate and they get downright sulky.

Because peppers originated in the tropics, they are not well-adapted to handle wide temperature swings from day to night or over the course of the season.  Ideal temperatures for growth and fruiting are about 85 degrees during the day and 70 degrees at night.

70 degrees at night. Let that sit with you for a moment and you will appreciate why peppers can be such a challenge to ripen around Puget Sound. We have years, and last year was one, when overnight lows barely climbed out of the 5os, and then for only a few days and in warm microclimates.

Growers further South, towards the Willamette Valley, will likely have less trouble, but the techniques described here will still probably help get consistent ripe fruit in a cooler year.

Mid July - lots of small fruit set

Seeds vs. Starts

In the Pacific Northwest, the question is never “should I sow seeds directly in the ground or use a transplant?” You simply must use starts. Seeds, if they germinated at all outdoors (doubtful), would never grow large enough to produce anything before frost killed off the plant. So, the only thing to ask is, who will be raising those starts: you or a professional plant propagator?

Peppers are not plants to try to start on a South-facing windowsill in the maritime Northwest. If you don’t have a relatively well-equipped space to start peppers, don’t bother starting your own. They need strong light and a warm germination space.

(Read more about my indoor seed-starting set up.)

Peppers grow slowly and cannot be rushed outside, so they’ll take up a lot of time and space under your lights and will tend to get quite lanky and weak if kept in front of a window. If you are growing just a few pepper plants, buy strong, locally and professionally-raised transplants at a local nursery (not Home Depot – ever!) and don’t feel bad about it.

(Read more about selecting quality transplants.)

If you’ve got the space, the lights and either heat mats or a warm indoor area to get germination off to a strong start, peppers are grown out just like tomatoes. I start them at the same time, typically in mid-to-late-February. Conventional wisdom is to start peppers a few weeks later than ‘maters, to allow outside temps to warm up a bit more, but I find the slower growth of peppers gives me that margin.

Whether you grow or own or buy transplants, you want short-season, Pacific Northwest adapted varieties. If you’re starting from seed, just make sure you use a seed house that specializes in cool season crops and read the catalog carefully.

If you’re buying starts, bring a Territorial Seed catalog with you to the nursery. I am not kidding about this, and it’s a good idea when you buy tomato starts, too. Not all varieties on offer at your nursery will be the same as what Territorial is selling, but I’ll bet you’ll see a substantial overlap. For readers in other bioregions, take the best, most extensive and informative catalog targeted towards your region when you go shopping for starts.

Mid-August: peppers at full size

Bumping Heat

The closer you can get your growing conditions to that magic 85-at-day/70-at-night formula, the happier your peppers will be. In the Pacific Northwest, that means you need to go all out to raise soil temperatures and incorporate heat sinks around your plants.

If you have a greenhouse, use it. If you don’t, construct an inexpensive low-tunnel over the area where you’ll be growing your peppers. Put your low-tunnel in place several weeks before you transplant out your peppers. This will give the soil time to warm progressively deeper and act as an effective heat sink.

Soil temperature can be further raised by covering the soil with black plastic a few weeks prior to transplanting. Gardeners who are opposed to plastic use can find biodegradable black paper mulches which will serve a similar function. A very dark compost mulch will also help the soil absorb more heat.

A heat sink is something that will absorb heat from the sun during the day and release it slowly over the nighttime hours. Water is a tremendously good heat sink, which is why places near water tend to have more moderate day-to-night temperature swings than places further inland and why Wall-0-Water type products work.

Anything dark and with a lot of mass acts as a good heat sink, too, which is why black asphalt gets really hot in the middle of summer, and why tender or semi-hardy plants grown against south-facing rock or concrete walls are more likely to thrive.

If your goal is to ripen peppers, your best bet is is raise air and soil temperature with a combination of techniques, and incorporate heat sinks to ensure overnight temps stay high too. The only risk with heat-bumping techniques like tunnel cloching, plastic mulching and Wall-o-Water products is the possibility of overheating.

Sadly, season extension techniques aren’t a set-it-and-forget-it proposition. You need to carefully monitor the temperatures inside your cloches, particularly on bright days when temps can climp rapidly. Sudden jumps to 90 or more will likely cause blossom or fruit drop of your pepper plants. Also, the warm, humid environment that can build up inside a low tunnel or greenhouse will create ideal conditions for assorted pests, diseases, mildews and molds. Ick.

Early September - peppers starting to ripening


My experience is that 4 or 6 ripe, full-sized, bell-type peppers off a single pepper plant is a dang good yield. Typical yield for me is maybe 3 ripe peppers and another 3 or 4 green or partially ripened but full sized peppers. Small-fruited peppers are like cherry tomatoes and will give you many more and will tend to ripen more quickly than the full-size versions. Like tomatoes, dates to maturity, flavor, and plant precociousness will vary greatly.

Putting It Into Practice

This is more-or-less what I do. You should adjust exact dates based on your particular microclimate and willingness to fuss over your plants. Some years everything goes a lot faster. Some years, slower. I use peppers that claim a 60 or 70 day to maturity but really, it’s 6 or 7 months from seed to ripe pepper. In seed catalogs, dates to maturity of peppers are typically the time from date of transplant to date of edible green fruit, which always seems a bit deceptive to me.

  • Late February – Start peppers indoors in 4″ pots.
  • Mid-April – Up pot peppers to gallon pots. Make sure final grow out space is prepared with soaker hose, black plastic mulch and buttoned-up low tunnel if not growing peppers in greenhouse.
  • Early to mid-May – Begin hardening peppers off in the greenhouse. Covering the plants with floating Reemay inside the greenhouse further protects them, but at this point I will still shuffle pots inside and outside depending on temperatures.
  • Late May to early June – transplant peppers to final location (note: for me this is almost always the greenhouse.)
  • June – flowering and fruiting starts
  • Mid-July – substantial green fruit set
  • Mid-August – peppers at full size
  • Early to mid-September – peppers fully ripe and harvestable.
  • Early to mid-October – even with protections, plants start to fall apart as temperatures drop rapidly.

Mid-September - many peppers ripe and harvestable

That’s how I get peppers in the Pacific Northwest. It may not be worth it for every gardener, but it’s a fun challenge if you’re into that kind of thing. What do you do?


  1. dr. dave says

    I just read your article on growing peppers. I use bubble wrap on cold soil – large bubbles should heat and insulate better. At planting, I slip white 13 gallon garbage bags over the pepper and tomato standard cages to raise and hold questionable temperatures. Poke some holes in the top of the bags for the first planted week, slit the tops for the second, and slowly peel the bags down towards the soil as weather permits. Clothes pins or binder clips keep the bags in place.

    • says

      I think you’re exactly right on all counts! I’ve had good luck in low tunnel cloches–especially Early Jalapeno. Luckily, peppers will continue to ripen off the plant, so even those green ones can turn red on the counter. Great blog!

  2. Tom Gibson says

    Tall spindly plants with less than 25% possible fruit on them. It would be better to grow them outside in a sunnier location using green or red IRT plastic mulch and a cloche to keep rain off in Fall. The cloche is mostly to keep the plants from getting wet when the rain starts again so you can get another six weeks of production using that combination.

    • says

      Hey Tom – have you found that much improvement in yields using red IRT mulch? I haven’t been blown away by the difference and its more expensive and less durable than standard black plastic. But if you have a method that consistently gets 16-24 full-ripe bell-type peppers off each pepper plant around Puget Sound I will happily do whatever you say.

      • Tom says

        I have seen dramatic results using the IRT plastic and high tunnels. The biggest obstacle to getting peppers and eggplants rocking is soil temperature. Black plastic can only indirectly heat the soil whereas any of the IRT plastics turn sunshine into a radiator heating the soil to as much as 20 degrees warmer than the surrounding uncovered soil. That assumes that we actually get some sunshine. Even cloudy days do something but the last couple of years some of the best farmers I know were six weeks later than usual with their crops and then it all came in at once. OK if you are selling to markets but kind of sucky if you are a CSA operator/member. Being able to provide layers of protection, high tunnel/cloche, ground cover, mulch all add and multiply the heat energy of the sun. Can anyone promise you peppers in June every year? Not without a pretty large investment. It helps to choose from anywhere from 6-20 varieties that have a mix of harvest dates and to use plants that are being started now and moving to at least gallon sized pots for planting by May/June.

        • says

          Good to have your perspectives on this, Tom. I’d like to see a comparison on the effect of IRT v. black plastic (when black plastic is applied correctly, in tight contact with the soil) on soil temperature at a consistent depth – say 4 or 6 inches. It sounds like we have similar timing on our plants – I’m into gallons for transplanting by May as well – and actually agree on the importance of stacking protection. That said I’ll be damned if I can imagine having full ripe peppers anytime in June. My timeframes as listed come from my notes over the past few years so it’s probable that my perspective on pepper ripening timing is skewed towards the cool and cloudy we’ve had lately. Assuming you’re in Camas, I’m also 200 miles north of you. :) I know IRT plastic reflects the “late-summer sun spectrum” light back up on the plants and, in theory, encourages fuller and speedier ripening – does this actually happen, in your experience? What kind of full-sized, ripe-on-the-plant yields are you getting per plant before cold weather knocks your peppers out?

          • Tom says

            That is a pretty good article. Here is what I thought was important for us people here in the PNW suffering from some really crazy late Summers etc. “The benefit of IRT mulch is highest early in the season. Late-planted crops don’t usually show a yield improvement with IRT compared to black plastic. Cloudy cool weather can also lead to very little difference in yield between IRT and black mulch. Since IRT costs more than black plastic, it is best suited to early plantings of tomatoes, peppers, and vine crops.”

            Early in Virginia is probably like March. Early in Portland or Seattle could mean July some years if you plant by the weather. A few years ago we had a week of weather in the 90s followed by snow the next week. The last two years we had Junuary and everybodies crops were weeks late. There is no panacea but I am a firm believer in being prepared to provide as many layers of protection as possible in order to have a reliable supply of food. I hope it doesn’t happen but I am not counting on the trucks to keep showing up loaded with food grown as far away as China, Peru and Israel. I have talked to people that used the red IRT plastic and they all had bad weed problems with it so I recommend the green. Literally, up to a 20 degree difference compared to surrounding soils.

  3. Mary W. says

    Thanks for the tips! Those temps are warmer than indoors in my house, even! So it looks like I will be buying starts and trying to keep them warmer. Do you have any suggestions on how large of starts I should be seeking? The really big ones around here cost $12 (at least last year they did), and at an expected 6 fruits per plant its some pretty expensive peppers! But do the big ones have more, or less chance of adjusting and doing well?

  4. Sue says

    Definitely a “your mileage may vary” sort of thing, that. We’re rural and find that black mulch of any sort is a wonderful haven for voles. Still trying to recover from that debacle. And we’ve also found that for us, in our location, wall-o-waters become wall-o-slugs.

  5. Deborah Aldridge says

    I just bought some mini bell peppers at the wellness fair, and am going to plant them this week to see if they will come true from seed. I love peppers, so I’m glad I live in the subtropics. Our only problem is that we have to shelter bell peppers from afternoon sun, because they will scorch. Not a problem, though. In the summer, I just plant them on the east side of the house. They are so easy to grow here, it’s unbelievable. I think I would go crazy in the Northwest trying to grow things I love like summer squash and peppers.

    • says

      Yeah, I have been known to have a little zone envy. I do wish we could grow citrus and avocado – both huge favorites of mine. But I just keep telling myself, “I love kale!” :)

  6. Ein Middlebrooks says

    Thank you so much Erica. I seeded my first ever peppers and tomatoes yesterday. So I don’t have a clue what I’m doing. :-). They are on the heat mat in the greenhouse. I think I should cover the trays to trap the heat in, and also bite the bullet and get lights. Something I’ve never seem anywhere is how high above the trays do you put the lights? Once they germinate of course.

    • says

      Not to worry, your peppers and tomatoes have a pretty good idea what to do. :) Cover the trays until you see sprouts, then uncover. If your greenhouse is heated and warm enough, the direct light of the sun outside will be better than artificial light. But temps will be too low for pepper growth in a NW area greenhouse for another few months unless you have sufficient supplemental heat. If you get florescent lights, you want them as close to the plants as possible – maybe an inch or two away. Fluorescents shouldn’t get hot enough to scorch leaves. I have had tomatoes grow up into the tubes (I don’t recommend this, I’m just saying that I keep them close).

  7. says

    Great post. You wrote:”If you are growing just a few pepper plants, buy strong, locally and professionally-raised transplants at a local nursery “. Amen, amen.I finally did that last year and wonder why it took me 40 years, :). There is no shame in admitting defeat in some matters.

  8. Danny says

    Zone 7…Upper foothills of the Sierra…Good read on peppers. I have noticed that they do like the heat. Seems like every year I put them in the ground way too soon, before the soil heats…Problem is that timing can be tricky. Last week it was 80’s plus for several days with night time temps. in the high 50’s and 60’s. Nice. Today its raining and temps. are in the 60’s and nights will drop to the 40’s. Not so nice. So this year I have kept them back in the hot house, like you, in 4″ pots (getting ready for the 1 gal. soon). These are from seed (March 1st) and they are 4-5″ tall with 2-3 sets of leaves…Hot house two days ago was 97 degrees, so ventilation is a must, etc. etc……You have a very informative blog and you have a follower.

  9. Haley says

    Hi all!
    i’m wondering if there’s been a conversation on this blog about trimming the early flowers off pepper plants before (or at) transplant date. I have read in some other literature that folks trim the first flowers or buds off their pepper plants for better production later. Is this recommended in the PNW? And does the size of the pepper plant at transplant determine if you should trim flowers back or not? I have many peppers being hardened off now in a hoophouse under reemay. They will soon be planted in a low tunnel with plastic mulch and reemay to help keep soil/air temps warm at night. They are in 4” pots currently and about 12-16 inches tall (they need OUT of those pots, I know :-) and are producing lots of flowers. They were germinated in a nice warm, cozy hothouse for the past 2 months and grew unpredictably fast. They are not extremely leggy though. Just lots of blooms. So, should I trim all the flowers back for better production later in the season? Or do I just take advantage of the early blooms for an early harvest? HELP :-) Thoughts are welcomed….!

  10. says

    One trick I use in growing these peppers is to use and open greenhouse sort of thing. I surround my pepper area with 6mil plastic in a big square about 4 feet high. It keeps the wind off and heats the inside up about 10 degrees even on partly overcast days. I’ve yet to not have peppers in the last three cold summers.

  11. Richard says

    Hi Erica…thanks for the tips on peppers. I live on the Columbia R. in Morrow County, Or. Much different weather from the Puget Sound area, but I’m trying to grow some hot peppers. I’ve got a couple Habanero plants and a couple Caribbean Hot Chilis going now, (in gallon black pots) and they’re flowering like crazy. Got a few peppers already turning colors, although their size is really small. And lots of blooms falling off. Is this due to the cool rainy weather we’re having? And do I need to protect them from the really high temps we get in the Col. Basin? It’s not unusual to be over 100 degr for a week at a time in Aug or Sept.

  12. Norm says

    Thanks for this article! I wish I had read it several months ago! Oh, well. There is always next year! One thing I would like to know is how to monitor and adjust temps in a low tunnel (48″ at peak). I can’t stand there opening and closing the tunnel every hour if temps climb, and if I leave it open on the ends the temp drops from 90 to 70 in a matter of minutes. I know green houses have fancy temperature louvers, but what do tunnel growers do?

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