Such a difficult choice;would mine be Albulca nelsonii which I grew from seed and had the most unusual flowers and almond scent or the Angelica gigas who adorned our front garden so majestically,or Aeonium 'zwartkop' which I have as my profile picture,No
Mine would be Rosa' Golden Showers'
The RHS describe it as a deciduous or evergreen shrub or scrambling climber,with usually thorny stems bearing pinnate leaves and solitary or clustered,five petalled flowers followed by showy red or purple fruits.It is a large climber of upright growth with dark stems and glossy foliage. Flowers loosely doubled,fragrant,golden-yellow,paling with age,to 10cm in width.It will grow in clay,loam,sand or chalk s long as it is in a sheltered position not facing north.Making it a plant that most people could grow.
It's colour stands for Joy,Gladness,Friendship,Delight,Promise of a new beginning,Welcome back,Remember me,Jealousy,"I care"
I had yellow roses with freesias and gypsophila in my wedding bouquet
On our anniversary we tend to buy something that we can plant in the garden,so when we moved to where we are now 19 years ago we bought Rosa 'Golden Showers' and planted it next to our front door.Our anniversary is in May and I always get a single bud/flower on my breakfast tray in bed.
It flowers from then until usually October time but the year before last was still flowering in December
So although I buy and grow lots of different plants the plant of MY Centenary reminds me of the wonderful man I married