Watercress is a rapidly growing, aquatic, or semi-aquatic perennial plant which is native to Europe and Asia. It is one of the oldest known leaf vegetables which is eaten by humans and is botanically related to mustard, radish, garden cress, and wasabi.
So can rabbits eat watercress at all?
Lets take a look at its nutritional data and find out more. In particular, we are interested in its phosphorus, sodium, sugar, fat, fibre, and acidic content.
value per 100 g (3.5 oz)
Energy 46 kJ (11 kcal)
Carbohydrates 1.29 g
Sugars 0.2 g
Dietary fiber 0.5 g
Fat
0.1 g
Protein
2.3 g
Vitamins
Vitamin A equiv.
beta-carotene
lutein zeaxanthin (20%)160 μg
(18%)1914 μg
5767 μg
Thiamine (B1) (8%)0.09 mg
Riboflavin (B2) (10%)0.12 mg
Pantothenic acid (B5)
(6%)0.31 mg
Vitamin B6 (10%)0.129 mg
Folate (B9) (2%)9 μg
Vitamin C (52%)43 mg
Vitamin E (7%)1 mg
Vitamin K (238%)250 μg
Trace metals
Calcium (12%)120 mg
Iron (2%)0.2 mg
Magnesium (6%)21 mg
Manganese (12%)0.244 mg
Phosphorus (9%)60 mg
Potassium (7%)330 mg
Sodium
source wikipedia
As you can see watercress contains quite a lot of phosphorus, calcium, acidic content, and a hint of fat, fibre and sugar.
This means that watercress is not as good as you might think for rabbits to eat. It is in fact pretty bad for them due to its high acidic, calcium and phosphorus content. It is not worth feeding to them as it will hurt their tummies if it is eaten. If they eat a little bit of it that would be fine, but it should not be purposely be fed to them.