Repotting guide

When & how to repot Eleocharis acicularis (Eleocharis acicularis)

Also called dwarf hairgrass, needle spikerush.

More about eleocharis acicularis

About Eleocharis acicularis

Eleocharis acicularis · also called dwarf hairgrass, needle spikerush · tropical

Dwarf hairgrass is a popular aquarium carpeting plant with thin, grass-like blades that spread by runners to form a lush green lawn across the foreground. Grown submerged under good light and CO2 it carpets quickly and dense. A temperate-to-subtropical spikerush, it is one of the most widely used aquascaping foreground grasses.

Mature size: Blades 5-15 cm tall; spreads indefinitely by runners to form a carpet

Watch for — Slow or patchy spread: Poor substrate nutrition. Add root tabs and dose the water column to fuel runner growth.

How to tell eleocharis acicularis needs repotting

Repotting on a calendar is less reliable than reading the plant. For eleocharis acicularis, watch for these signs:

Roots poking out of the drainage holes or coiling visibly around the inside of the pot.
You are watering far more often than you used to because the rootball dries out within a day or two.
Water runs straight through and out the bottom without soaking in.
Top growth has slowed or new eleocharis acicularis leaves are noticeably smaller than older ones despite good light.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot eleocharis acicularis

Every 12–18 months — sooner if roots show fast. Eleocharis acicularis's growth habit — low carpeting grass that spreads aggressively by horizontal runners, sending up tufts of needle-thin blades to form a dense lawn. trim the tops to encourage thicker, lower growth. — sets the pace. Dwarf hairgrass is a popular aquarium carpeting plant with thin, grass-like blades that spread by runners to form a lush green lawn across the foreground. Grown submerged under good light and CO2 it carpets quickly and dense. A temperate-to-subtropical spikerush, it is one of the most widely used aquascaping foreground grasses.

What size pot to step eleocharis acicularis up to

Step up one pot size — about 2–3 cm (an inch) wider. Eleocharis acicularis grows fast, so it will fill that space within a season, but jumping several sizes at once still backfires: the unused soil stays soggy and rots even a vigorous root system. One size at a time, every year or so, is the rhythm.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot eleocharis acicularis

Early spring, just as new growth restarts, is the ideal window for eleocharis acicularis. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting eleocharis acicularis

Time it for spring. Repot eleocharis acicularis in early spring as growth restarts so it re-roots quickly into the fresh soil.
Choose one size up. Pick a pot about 2–3 cm wider with drainage holes. One step only — a much bigger pot stays soggy and rots roots.
Ease the plant out. Water lightly the day before, then tip eleocharis acicularis out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh nutrient-rich planted-tank substrate in the new pot, set the plant so its soil line is unchanged, and backfill, firming lightly.
Water and pause feeding. Water once to settle the soil. Hold off fertiliser for about a month — fresh mix already has nutrients and feeding now burns new roots.

Aftercare

Water eleocharis acicularis once to settle the soil, then let the surface dry before watering again — fresh mix around the roots stays wetter than the old compacted ball, so the commonest post-repot mistake is overwatering. Keep it out of direct sun for a week or two while roots re-establish. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for eleocharis acicularis

Eleocharis acicularis wants nutrient-rich planted-tank substrate. Plant small clumps a few centimetres apart in aquasoil or fine gravel with root tabs. A fertile substrate fuels the runners that knit the carpet together. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting eleocharis acicularis — frequently asked questions

How often should you repot eleocharis acicularis?

Every 12–18 months — sooner if roots show fast for eleocharis acicularis. Repot eleocharis acicularis roughly every 12–18 months, in early spring as growth restarts. It grows fast and circles its pot quickly, so step up one size (about 2–3 cm wider) into fresh nutrient-rich planted-tank substrate. Don't jump several sizes — that soggy excess soil is what rots vigorous roots.

What size pot does eleocharis acicularis need?

When is the best time of year to repot eleocharis acicularis?

Can you put eleocharis acicularis straight into a much bigger pot?

No. Even a fast-growing eleocharis acicularis should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise eleocharis acicularis after repotting?

Not immediately. Wait about 4 weeks after repotting eleocharis acicularis. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.