Troubleshooting
Grassy Arrowhead problems — and how to fix them
Grassy Arrowhead (Sagittaria graminea) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Aphid infestations on emergent stems
Water lily aphids (Rhopalosiphum nymphaeae) colonise emergent foliage in summer. Knock them off with a strong jet of water into the pond where fish will consume them; avoid pesticides near water.
Overcrowding and invasive spread
Rhizomes spread vigorously; divide clumps every 2–3 years in spring to maintain vigour and prevent smothering neighbouring marginals. In warmer zones, growth can be assertive — use contained baskets to restrict spread.
Leaf scorch in very shallow water
If water level drops and rhizomes are exposed to air during hot spells, emergent leaves yellow and scorch at the tips. Maintain consistent water depth and top up pond levels during summer droughts.
Prevent grassy arrowhead problems before they start
Most grassy arrowhead issues are care-mismatch, not bad luck. Dial in the basics:
Looking for grassy arrowhead in general rather than its problems? Read the full grassy arrowhead care guide — light, water, soil and feeding.
Grassy Arrowhead problems — FAQ
Why is my grassy arrowhead aphid infestations on emergent stems?
Water lily aphids (Rhopalosiphum nymphaeae) colonise emergent foliage in summer. Knock them off with a strong jet of water into the pond where fish will consume them; avoid pesticides near water.
Why is my grassy arrowhead overcrowding and invasive spread?
Rhizomes spread vigorously; divide clumps every 2–3 years in spring to maintain vigour and prevent smothering neighbouring marginals. In warmer zones, growth can be assertive — use contained baskets to restrict spread.
Why is my grassy arrowhead leaf scorch in very shallow water?
If water level drops and rhizomes are exposed to air during hot spells, emergent leaves yellow and scorch at the tips. Maintain consistent water depth and top up pond levels during summer droughts.