Fertilising guide

How to fertilise Crossvine (Bignonia capreolata)— schedule & NPK

Also called Crossvine, Trumpet Flower, Quarantine Vine.

More about crossvine

About Crossvine

Bignonia capreolata · also called Crossvine, Trumpet Flower · flowering

Crossvine is a native North American woody vine with tendril-like clinging holdfasts, producing striking reddish-orange and yellow tubular flowers beloved by hummingbirds in spring. Semi-evergreen and adaptable, it tolerates a wide range of soils and is hardy across much of the South and Midwest. Excellent on fences, walls, and pergolas.

Growth habit: Vigorous semi-evergreen woody vine that climbs via branched tendrils with adhesive discs; stems develop a cross-shaped pith pattern visible in cross-section (hence the common name).

Watch for — Invasive spread: Crossvine spreads by root suckers and can become difficult to contain in fertile soils. Install root barriers, remove suckers promptly, and prune annually to maintain boundaries. Not considered invasive in its native range but can be vigorous in enriched garden beds.

What fertiliser crossvine actually wants — and why

Crossvine flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.

Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency.

For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for crossvine: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.

How often to feed crossvine, and which months

Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For crossvine:

Generally requires little supplemental feeding in garden soils. If growth is poor, apply a balanced slow-release fertiliser in early spring. Avoid excess nitrogen, which promotes foliage at the expense of flowers. In practice: no routine feeding at all for crossvine — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

The dormant-season rule matters more than the exact interval: skip feeding entirely when crossvine is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.

What strength to mix for crossvine

None is the correct answer for crossvine. The flower-versus-foliage trade-off is the whole point: hold back and you get the display.

Feeding always goes onto already-damp soil, never dry roots — water crossvine first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the crossvine watering schedule.

Signs you are over-feeding crossvine

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for crossvine:

Abundant leafy growth and very few flowers (the classic over-rich symptom).
Soft, floppy stems and a sprawling, leafy habit.
Scorched edges and salt crust if it has been fed in a container.

Signs you are under-feeding crossvine

Effectively never an issue — these plants flower on poverty.
Only on genuinely dead soil: weak, thin growth and few blooms.
A short-lived plant in completely spent container compost.

If the symptoms point at watering, light or roots rather than nutrition, the full crossvine care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

If crossvine has accidentally been fed and is all leaf, a plain-water flush plus a move to leaner soil resets it; otherwise no flushing is needed because you are not feeding it.

Organic vs synthetic feeds for crossvine

Organic options

A thin compost mulch for soil structure is the absolute most; mostly, give it nothing. UK/US: leave it lean — no manure, no liquid feed. Poor soil is the active ingredient here.

Synthetic / liquid feeds

None. Synthetic feeds, particularly anything with appreciable nitrogen, directly suppress flowering in crossvine.

Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.

Fertilising crossvine — frequently asked questions

What fertiliser does crossvine need?

Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency. Crossvine flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.

How often should I feed crossvine?

Generally requires little supplemental feeding in garden soils. If growth is poor, apply a balanced slow-release fertiliser in early spring. Avoid excess nitrogen, which promotes foliage at the expense of flowers. Generally requires little supplemental feeding in garden soils. If growth is poor, apply a balanced slow-release fertiliser in early spring. Avoid excess nitrogen, which promotes foliage at the expense of flowers. In practice: no routine feeding at all for crossvine — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

What strength of feed for crossvine?