How to grow peppers from seed When to Plant : For a head start, plant seeds indoors 6 weeks before the last frost. Peppers can be planted outdoors when frost is no longer a threat and the soil is reasonably warm. Watering : Water regularly, but too much water will result in much milder hot peppers. Soil : Moist, rich, and well drained. Days to Harvest : Can be harvested in as few as 55 days for green and immature, or up to 95 days for red and ripe.