Very similar to tomatoes. Start inside at least 6 weeks before last frost (around 4/1). Ideal temperature for germination is 85° (use a heating mat). Days to germination: 5-14. Once leaves appear, grow plants at 72°. Plant seedlings outside late May into fertile garden soil (with lots of compost or decomposed manure) at a spacing of 18” apart. Stake plants if space is limited. Tomatillos are susceptible to several fungal diseases (including Early and Late Blight and Verticillium Wilt). To prevent blight, keep foliage dry by 1) Pruning plants to allow for good air circulation 2) Water with drip irrigation/soaker hoses. Crop rotation is also key to preventing diseases. Ideally, plant in a spot that has not had any Solanaceae crops (tomato, peppers, eggplant, potatoes) growing there for 4 years.
Fruits are ready for harvest when husk is papery and split. Ripe fruits may also be picked up off the ground. Store fruit with husk on, but remove and wash before eating. Soaking in water can help remove sticky coating left by husk.
Tomatillos are relatively easy seed-saving crops. They are primarily self-pollinated but may be crossed pollinated by insects when different varieties are planted next to one another. You can just save seed and see what you get! Always harvest seed from the best plants. It is best, but not totally necessary, to collect seeds from a minimum of 6 plants. Collect ripe tomatillos and cut and squeeze out seeds. Rinse and dry seeds on a screen or wax paper.