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 hundred mature plants into the garden
Flower a Echeveria runyonii
Flower a Echeveria glauca
Flower a Pachyphytum oviferum
Flower a Aloe 'Blue Elf'
Flower a Aloe vera
Throw fifty mature plants into the garden
Flower a Haworthia attenuata
Flower a Pachyphytum hookeri
Flower a Senecio serpens
Flower a Pachyphytum fittkaui
Flower a Senecio rowleyanus
Grow an Agave macroacantha to maturity
Flower a Sempervivum
Grow a Sempervivum to maturity
Flower a Kalanchoe rotundifolia
Flower a Kalanchoe thrysiflora
Grow an Agave 'Blue Glow' to maturity
Grow a Kalanchoe thrysiflora to maturity
Grow a Kalanchoe rotundifolia to maturity
Flower a Fenestraria aurantiaca
Grow an Aloe 'Blue Elf' to maturity
Flower a Sedum morganianum
Flower a Cheiridopsis denticulata
Flower a Pachyphytum glutinicaule
Flower a Echeveria 'Lola'
Grow a Sedum morganianum to maturity
Flower a Lithops optica 'Rubra'
Flower a Sedum pachyphyllum
Grow a Haworthia attenuata to maturity
Grow a Sedum pachyphyllum to maturity
Grow a Pachyphytum glutinicaule to maturity
Grow a Cheiridopsis denticulata to maturity
Grow a Lithops optica 'Rubra' to maturity
Grow a Fenestraria aurantiaca to maturity
Grow a Senecio rowleyanus to maturity
Grow a Senecio serpens to maturity
Grow a Pachyphytum hookeri to maturity
Throw ten mature plants into the garden
Grow an Echeveria runyonii to maturity
Grow an Echeveria 'Lola' to maturity
Grow an Aloe vera to maturity
Throw one mature plant into the garden
Grow a Pachyphytum fittkaui to maturity
Grow a Pachyphytum oviferum to maturity
Grow an Echeveria glauca to maturity
Grow an Aeonium to maturity