Here is the full list of all 47 Viridi achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Throw one mature plant into the garden
Flower a Sedum pachyphyllum
Grow a Cheiridopsis denticulata to maturity
Grow a Sempervivum to maturity
Grow a Pachyphytum fittkaui to maturity
Flower a Kalanchoe rotundifolia
Flower a Echeveria 'Lola'
Grow a Sedum pachyphyllum to maturity
Grow an Agave 'Blue Glow' to maturity
Grow an Echeveria 'Lola' to maturity
Grow a Kalanchoe rotundifolia to maturity
Grow an Aeonium to maturity
Grow an Echeveria glauca to maturity
Grow an Aloe vera to maturity
Grow a Pachyphytum glutinicaule to maturity
Grow a Pachyphytum hookeri to maturity
Grow an Aloe 'Blue Elf' to maturity
Grow a Kalanchoe thrysiflora to maturity
Grow an Echeveria runyonii to maturity
Grow a Haworthia attenuata to maturity
Grow a Senecio serpens to maturity
Grow an Agave macroacantha to maturity
Grow a Fenestraria aurantiaca to maturity
Grow a Sedum morganianum to maturity
Grow a Pachyphytum oviferum to maturity
Grow a Senecio rowleyanus to maturity
Grow a Lithops optica 'Rubra' to maturity
Flower a Echeveria glauca
Flower a Pachyphytum fittkaui
Flower a Aloe vera
Flower a Pachyphytum glutinicaule
Flower a Pachyphytum hookeri
Flower a Sempervivum
Flower a Aloe 'Blue Elf'
Flower a Kalanchoe thrysiflora
Flower a Echeveria runyonii
Flower a Cheiridopsis denticulata
Flower a Haworthia attenuata
Flower a Senecio serpens
Flower a Fenestraria aurantiaca
Flower a Sedum morganianum
Flower a Pachyphytum oviferum
Flower a Senecio rowleyanus
Flower a Lithops optica 'Rubra'
Throw ten mature plants into the garden
Throw fifty mature plants into the garden
Throw one hundred mature plants into the garden