## 1 Introduction  
Peat is the most common growing medium constituent for soilless cultivation of horticultural crops due to its beneficial physical properties and chemical characteristics for commercial plant production [1]. Peat, a non-renewable resource, is formed by the partial decomposition of plants typical of a water-saturated environment with low nutrients and pH, under low temperatures and anaerobic conditions, so it consists of dead biomass with high carbon concentration forming peatland soil [1, 2, 3]. Peat soils are unique ecosystems that account for about 10% of the available freshwater resources [4, 5, 6] and are the most important terrestrial carbon reservoirs on Earth [7]. Peat extraction results in the release of high CO2 emissions due to aeration and mineralization of the peat, which contributes to the greenhouse gas effect [2, 8]. The extensive use of peat for horticulture and the subsequent depletion of peatlands has led to growing environmental concerns about peat extraction [9]. For this reason, the search for sustainable substitutes that can totally or partially replace peat, a non-renewable resource, has become increasingly important. Various materials, such as municipal solid waste, sawdust, biomass waste, digestate, and biochar after proper transformative processes (such as composting, pyrolysis, etc. ), were favorably valued when mixed with peat in horticultural media [10; 11; 12; 13; 14; 15]. Among them, compost is successfully used as a replacement for peat to produce seedlings of tomato (_Solanum Lyopersicum_ L.) in nurseries [16] and plants of tomato and basil (_Ocinum basilicum_ L.) in pots [17]. It has been indicated that compost and peat mixtures are a useful growing medium for the greenhouse production of zucchinis (_Cucurbita pepo_ L.), peppers (_Capsicum annuum_ L.), and tomatoes [18]. The use of good growing media is very important for achieving positive results [19]. Although there are various types of compost that have been evaluated to avoid the consumption of peat, to our knowledge there is no information regarding the use of compost derived from cultivated cardoon (_Cynara cardunculus_ var. _altilis_ DC.) crop residues. Cultivated cardoon is a perennial herbaceous plant with an annual development cycle [20; 21]. Cardoon provides high biomass yields with low nitrogen inputs and drought tolerance, protects the soil from erosion, and its cultivation can lead to the improvement of soil fertility [22]. Nowadays, cardoon has gained interest as a novel crop for multipurpose use that includes energy and biofuels, cellulosic pulps, phytochemicals as well as food and feed [20; 23; 24]. It has recently been reported that cardoon crop residues can also be an optimal growing medium for edible _Pleurotus erysgii_ mushrooms, commonly known as king trumpet [25]. Cardoon is widely considered a strategic crop for bioenergy production while promoting new opportunities for economic improvement in depressed rural areas of the Mediterranean basin, thanks to its excellent adaptation and components of biomass utilized as feedstock for multipurpose applications [22; 24]. The possibility of using compost from cardoon crop residues as a component of cultivation substrates for horticultural crops would allow for a reduction in peat consumption and the conversion of waste into a re-evaluated product, in line with sustainability and circular economy principles. In this regard, positive results were obtained from our investigation on using cardoon-based compost mixed with peat for the production of tomato seedlings [26] and potted plants such as rosemary (_Rosmarinus officinalis_ L.), laurel (_Laurus nobilis_), and cherry laurel (_Prunus laurocerasus_) [27]. Lettuce (_Lactuca sativa_ L.) is considered the most important crop in the leafy vegetable sector of horticultural production [28].