Yields are typically lower than in plasticulture. Another method uses a compost sock. Plants grown in compost socks have been shown to produce significantly more flavonoids, anthocyanins, fructose, glucose, sucrose, malic acid, and citric acid than fruit produced in the black plastic mulch or matted row systems. Similar results in an earlier study conducted by USDA confirms how compost plays a role in the bioactive qualities of two strawberry cultivars. Strawberries may also be propagated by seed, though this is primarily a hobby activity, and is not widely practiced commercially. A few seed-propagated cultivars have been developed for home use, and research into growing from seed commercially is ongoing. Seeds (achenes) are acquired either via commercial seed suppliers, or by collecting and saving them from the fruit. Strawberries can also be grown indoors in strawberry pots. Strawberries won't grow indoors in winter unless aided by a combination of blue and red LED lights. In southern lands, such as Florida, winter is the natural growing season and harvesting begins in mid-November. The Kashubian strawberry (Truskawka kaszubska or Kaszëbskô malëna) is the first Polish fruit to be given commercial protection under EU law. It is produced in Kartuzy, Kościerzyna and Bytów counties and in the municipalities of Przywidz, Wejherowo, Luzino, Szemud, Linia, Łęczyce and Cewice in Kashubia. Only the following varieties may be sold as kaszëbskô malëna: Senga Sengana, Elsanta, Honeoye that have been graded as Extra or Class I. Manuring and harvesting Most strawberry plants are now fed with artificial fertilizers, both before and after harvesting, and often before planting in plasticulture. To maintain top quality, berries are harvested at least every other day. The berries are picked with the caps still attached and with at least half an inch of stem left. Strawberries need to remain on the plant to fully ripen because they do not continue to ripen after being picked. Rotted and overripe berries are removed to minimize insect and disease problems. The berries do not get washed until just before consumption. Soil test information and plant analysis results are used to determine fertility practices. Nitrogen fertilizer is needed at the beginning of every planting year. There are normally adequate levels of phosphorus and potash when fields have been fertilized for top yields. To provide more organic matter, a cover crop of wheat or rye is planted in the winter before planting the strawberries. Strawberries prefer a pH