Synadenium grantii

Growing in Pots, Balconies & Indoors

Synadenium grantii (African milk bush, syn. Euphorbia grantii) is a fleshy shrub-to-small-tree the grower confirms as a houseplant – provided it gets enough light. Grown as a container shrub it is easy and stable; kept too dark, its leaf colour fades.

Quick Details

• Container Size: Start small and pot up with the roots; a 15-30 L (3-8 gal) pot for an established shrub
• Indoor Suitability: A genuine houseplant, but only in a bright position
• Best Spot: Full sun brings the best colour and cold-hardiness; part to light shade is tolerated but needs plenty of light
• Soil & Drainage: Free-draining mix with good drainage
• Watering in Pots: Low – let the mix dry between waterings

Indoors & On the Windowsill

• A houseplant that needs light: The grower confirms it grows indoors, but without enough light the leaf colour suffers – so give it your brightest window.
• Keep it as a shrub: Trained as a shrub it stays more stable and is far easier to manage in a pot than a single-stemmed tree; prune to shape while young.
• Overwintering: Tender – in cold climates keep it frost-free and on the dry side indoors through winter.
• Safety: The milky latex is especially caustic and toxic – wear gloves, wash off any sap at once, and keep well away from children and pets.

On a Balcony or Patio

• Light & wind: Give it the brightest spot the balcony offers; shelter exposed plants from strong wind and stake any tall or top-heavy growth. Walls and paving reflect heat, so pots dry quickly – check moisture often in warm weather.
• Practicalities: A filled pot is heavy once watered, so make sure the balcony can take the weight and stand it where drainage runoff will not be a nuisance.

Choosing the Pot, Soil & Long-Term Care

• Pot & drainage: 15-30 L (3-8 gal) for an established shrub with strong drainage holes; skip a standing water saucer so the roots never sit wet. Terracotta breathes and dries fast, while glazed or plastic pots hold moisture longer.
• Potting mix: A free-draining mix – loam or coir with grit or perlite; good drainage is essential.
• Watering: In a container let the soil dry between waterings; it needs good drainage and resents standing wet.
• Feeding: Potted plants exhaust their soil faster because nutrients leach out with every watering – feed lightly but regularly through the growing season.
• Repotting: Refresh the mix or pot up about every couple of years, teasing out and lightly trimming the roots of established plants.

Grower’s Container Tip

• Grower’s container tip: Grow it as a shrub rather than a tree – it is more stable and easier to care for in a pot. Let it dry out between waterings, and start it in a small pot, increasing the pot size step by step as the roots fill out.

Bloom & Flower Guide

Quick Details

• Bloom Season: Mainly spring, occasionally into summer
• Flower Appearance: Small purple flower clusters at the branch tips
• Edibility: None – not for eating. The milky sap is a strong skin and eye irritant and is poisonous if swallowed

Detailed Blooming Overview

This African milk bush flowers mostly in spring, and now and then into summer, carrying small purple flower clusters at the ends of its branches. As a member of the Euphorbia family, its “flowers” are really the tiny specialised structures (cyathia) typical of the group – modest, but a nice touch on a bold architectural plant.

Flower Characteristics

• Small purple flowers clustered at the tips of the branches.

Bloom Care & Thinning

• Handling safety: Whenever you prune or cut near the flowering shoots, wear gloves and eye protection – the milky latex burns skin and eyes and is toxic if ingested. Keep it away from children and pets.