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