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