Growing Great Peppers and Chiles
Starting from seeds
Start your seeds 6 to 8 weeks before you plan to transplant them into the garden. Peppers grow best when the soil is warmed and daytime temperatures are regularly over 75º F, typically late April or May in Santa Clara County. Temperatures below 50º–55º F cause flowers to abort or the fruits to be misshapen.
Control the environment for your seeds by starting with clean pots and fresh potting soil. Choose containers at least 2 to 3 inches deep, such as recycled plastic plant 6-packs, small recycled pots, or plug trays, with drainage holes. Wash them with a weak bleach solution to remove dirt and pathogens.
Do not fill the pots with dirt from your garden! Even if it has already grown great crops, it may carry soil-borne disease that can kill off seedlings. Seedlings require consistently moist soil with enough air spaces to allow root hairs to flourish. Loosely fill the rinsed containers ¾ full with moist bagged potting mix that includes organic compost and slow-release fertilizer. And, check the back of the seed packet for the expected germination rate, usually less than 100%.
Plant The Seeds
Level the soil in the containers and gently press the seeds onto the moist surface, one per plug or 1 inch apart in larger containers. Sprinkle a quarter inch of soil or vermiculite over the seeds, and moisten the surface. Set the containers in trays to catch drips; recycled plastic food containers work well. Place a clear cover over the container for the first week or until the seeds germinate and you see green sprouts poking through the soil. For small containers, use clear plastic wrap and a rubber band, or recycle the clear plastic covering from your take-out lunch. And don't forget to label the seeds! Used popsicle sticks work fine.
Then control the warmth and light. If your seeding spot gets sufficient light but still feels cold, invest in a plant heating mat — seedlings sprout in much less time on a warm mat. Once the seeds have germinated, make sure they get full sun all day or are exposed to grow-lights. When the first set of true leaves has emerged, thin the seedlings to 1½ to 2 inches apart, so that they do not compete for nutrients and moisture. Seedlings in plug trays should be potted up to larger containers to develop larger root systems.
Peppers and chiles like warm weather and warm soil. So it’s best to keep your new seedlings in a sheltered spot until night-time temperatures are consistently 55º F or above.
Water them frequently, every other day if they’re in the sun. If the pots ever dry out, soak them in a bucket of water to make sure the potting soil gets thoroughly re-wetted. Dry potting soil will shed water without absorbing it, so it can look like it’s wet when it’s not. A truly wet pot will be heavy; a dry pot will be light. Consider transplanting them into larger containers. It will let their roots develop and the larger pots won’t dry out as easily.
Check the seedlings regularly to see if any snails or aphids have found them. Hand-pick the snails. Aphids are soft-bodied insects that can easily be squished with your fingers or washed off with a hard spray of water. For a bad infestation, you can use insecticidal soap.
When you’re ready to plant your seedlings, soak them in a bucket of water to make sure the root ball is thoroughly wet. Remove them from the pot, handling them gently. If the plant is root bound (when you take it out, you see a tight mass of white roots), gently tear them apart a bit or score the rootball with a knife.
Space them 10 to 12 inches apart, with the rootball just below the surface or bury up to 1/3 of the stem. Planting closely helps them support and shade each other. For large-podded peppers, planting two seedlings in the same hole helps protect the pods from sunburn because there will be more leaves. You’ll get more peppers per square foot, plus they’ll support each other and will look lush and beautiful. Sunburn isn’t as much of a problem for small-podded chiles, so just plant them one per hole. For best production from large-podded peppers, pick off all flowers and fruit for 4-6 weeks after planting, so the plant can grow deeper roots and more foliage before setting fruit.
Water them in immediately so the soil settles around the new plants. Mark the plants clearly.
Watering and mulch
Drip irrigation and soaker hoses are great for watering throughout the season. But for the first few weeks, water your seedlings with a hose until they get settled in and their roots start growing. For fast-growing hybrids like NuMex chiles, continue top watering for an extra two weeks.
If your drip irrigation is on a timer, be sure to adjust it as the weather changes, less when it’s cool, more when it’s hot. Use a moisture meter to check the soil moisture. Mulching the plants with compost, straw, or other mulch will conserve water and keep the soil evenly moist. For hotter chiles than normal, stress them by only watering them once a week and letting them get dry in between. This will cause them to produce hotter pods.
Fertilizing and staking
Peppers and chiles need nitrogen for leaf growth and sun protection of pods. Fertilize the plants about once a month. Place the fertilizer about four inches from the stem of the plant (this is known as side dressing). In August you could increase it to every two weeks. Consider adding potassium the first month for fast-growing varieties.
Larger plants may need to be tied to stakes, especially as heavy pods start to develop. Small tomato cages can also be used for support.
Be sure to pick the pods at the right color for that variety. For varieties sold at our Spring Garden Market, the color to pick at is listed on our Peppers/Chiles page. Some are best green and small (e.g. Pimiento de Padrón). Some are good either green or with color (e.g. NuMex, jalapeño, serrano). Some should be picked only after they color up (e.g. many sweet peppers, Thai, etc).
Many peppers and chiles are likely to cross-pollinate and produce impure seed. If you want to save seeds from your plants, contact the UC Master Gardener Help Desk for advice.