Frangula alnus
Alder buckthorn, Black dogwood
Also known as Alnus frangula, Rhamnus frangula
- Height × spread
- 2.5m × 1.5m
- Position
- Full sun
- Hardiness
- Very cold to -20C (RHS H6)
- Flowers
- Autumn
Availability
Please ask in store about availability
Many plants are seasonal. Call 01234 567890 to check current stock.
About this plant
This is a large shrub or a small tree. It has quite large, broad, leaves with impressed veins. These turn yellow in autumn. There are red fruits that mature to black which are poisonous. This is an ornamental feature as berries of both colours appear on the plant at the same time. It has a commercial use in that the wood is burned to make charcoal for gunpowder. This likes a sunny spot in soil that has plenty of moisture available. It reaches around 2.5m (8ft) height with 1.5m (5ft) spread.
- Foliage colour
- Green
- Autumn foliage
- Yellow
- Fruit colour
- Black
- Variegated
- No
- Scent
- No
- Shape
- Cone
- Height
- 2.5m
- Spread
- 1.5m
- Season of interest
- Autumn
- Flowers in
- Autumn
- Evergreen
- Deciduous
- Sun or shade
- Likes full sun, tolerates part shade
- Soil type
- Loam (normal), Sandy soil
- Soil pH
- Acid (ericaceous)
- Drainage
- Moisture retentive soil
- Hardiness
- Very cold to -20C (RHS H6)
- Borders & containers
- Borders
- Use for
- Structural, Bee attraction, Butterfly attraction, Bird attraction
- Hazards
- Yes, potentially harmful; Humans: Harmful if eaten
Spring
Spring - late · Outdoors
Feed with slow release fertiliser
Apply a general purpose slow release fertiliser, spreading it around the root area of the plant as it is coming into growth. (Or apply a liquid feed at regular intervals throughout the growing season.)
This is a simple way to provide a nutrient boost as a single annual procedure.
Spring - late · Outdoors
Feed with sequestrol
If plants are acid loving and grown in soil with little acidity, or in a container, or are watered with limey tap water an annual feed with sequestrol (iron chelate) is highly beneficial. Follow guidelines on the packet. Will also 'blue-up' hydrangeas.
For hydrangeas that have good blue flowers in acid soil, this product can be used with alkaline soil to turn the flowers blue. This is most effective when the soil is neutral or just slightkly alkaline.
Spring-Autumn · Outdoors
Water to keep the soil moist
For best results, this plant needs soil that is always moist. Water deeply and regularly as soon as soil appears dry. Even for established plants in the ground, a dry week can cause problems with some soils. Check plants in pots more often, especially in hot weather. Or install an automatic irrigation system which will do the hard work for you, even when you are away on holiday.
Without regular watering some plants never fully regain their beauty.
Planting & general
Outdoors
Water with rain water
This plant needs rain water or soft water (the minerals in alkaline or "hard" water are harmful). This is especially important for plants in pots.
Outdoor planting · Planting
Add root growth stimulant to the planting hole
Mycorrhizal fungi helps roots establish quickly, so they absorb water and nutrients more efficiently. It comes as a powder, granule or gel. Add to the planting hole or container, and to the plant's rootball before planting in the hole. For "bareroot" plants use a gel.
Compost · Planting
Ericaceous compost
This plant requires acidic (ericaceous) soil. Where the soil is not acidic, or when planting in pots, use an ericaceous compost.