How to Grow Dahlia
'Bishop's Children' from Seed
The seed progeny of the legendary 'Bishop of Llandaff' — inheriting the celebrated near-black bronze foliage against which scarlet, tangerine, and apricot single flowers glow like neon; a pollinator magnet, a garden designer's foliage trick, and one of the most dramatic summer plants you can raise from a packet of seeds
The most famous dahlia in the world is 'Bishop of Llandaff' — introduced by Cardiff nurseryman Fred Treseder in 1924, awarded the RHS Award of Garden Merit in 1928, and still one of the most grown and recognised dahlias in Britain. It is celebrated for one specific quality above all others: its foliage. Where virtually every other dahlia produces standard green leaves, 'Bishop of Llandaff' produces deep purple, near-black, metallic-bronze foliage that creates an extraordinary visual effect — fiery scarlet single flowers apparently floating against a dark, moody backdrop that makes the colour appear to vibrate with an intensity it could not achieve against green.
'Bishop's Children' is the seed-raised progeny of that legendary parent, and it inherits the dark foliage reliably. The flower colours, as with any seed-raised population, vary across the colour range: scarlet, tangerine, apricot, rich pink, with various bicolours and two-tone blends. All have open yellow centres that make them immediately accessible to bees and butterflies. At 1m tall, flowering 12–14 weeks from sowing, and producing tubers that can be lifted and kept for a second year's even better display — 'Bishop's Children' offers a great deal from a single packet of seeds.
Quick Facts at a Glance
Plant Type
Half-Hardy Perennial H2, grown as annual
Star feature
Deep purple-black bronze foliage — garden designer's secret
Flowers
Single/semi-double; scarlet, tangerine, apricot, pink; open centres
Height
~1m; flowers July–first frosts; 12–14 weeks from seed
Pedigree
Offspring of 'Bishop of Llandaff' (RHS AGM 1928)
Difficulty
2 out of 5 — fast, rewarding, straightforward
Understanding the Variety
The Bronze Advantage — Why Dark Foliage Changes Everything
The deep purple-black foliage is a garden designer's secret for creating depth. It provides a natural shadow-effect that makes the bright floral colours of scarlet and tangerine appear to 'vibrate' with more intensity than they would against standard green leaves. This is a real optical effect — the contrast between a dark background and a warm bright colour increases the apparent saturation of the bright colour. The scarlet flowers on dark bronze foliage look more intensely scarlet than they would against green, because the eye has less reference for the warmth of the colour. This is why garden designers specifically seek out dark-foliaged plants for "hot" border schemes.
The Bishop of Llandaff Legacy — A Century of Excellence
'Bishop of Llandaff' was bred by Fred Treseder of Cardiff, selected by Joshua Pritchard Hughes (Bishop of Llandaff, 1905–1931), and awarded the RHS AGM in 1928 — within four years of its introduction, which tells you something about how immediately it was recognised as exceptional. 'Bishop's Children' represents seed-grown descendants of this cultivar, inheriting the dark foliage reliably while producing a range of flower colours and forms rather than the uniform scarlet of the original. The connection to this century-old lineage adds a historical dimension to what is also simply a very beautiful plant.
Sowing & Growing On
Fast Germinator — Two Days to Seedling; 12–14 Weeks to Flower
Dahlia seeds germinate with impressive speed in warmth. Once germinated, growth is rapid: pinched and well-managed plants reach flowering in 12–14 weeks from sowing. A March sowing produces July flowers; an April sowing produces August flowers.
-
Sow indoors February–April, 0.5cm deep, at 18–22°C. Sow into seed trays or individual small pots of moist seed compost. Press seeds lightly into the compost and cover with 5mm. Keep at 18–22°C. Germination typically in 5–14 days (sometimes faster). Move to bright, cool conditions immediately after germination to prevent legginess.
-
Pot on when seedlings have 2–3 true leaves. Transplant into individual 7–9cm pots of multi-purpose compost. Grow on in bright conditions at 15–18°C. Keep consistently moist — dahlias are thirsty plants from the outset.
-
Pinch out growing tip at 15cm — essential for bushy habit. Remove the top 2–3cm of the main stem above a leaf pair when plants reach 15cm. This single step produces a multi-stemmed, branching plant that is significantly more floriferous than an unpinched single-stemmed plant. The dark bronze foliage develops its full depth of colour as plants mature.
-
Harden off and plant out late May–June in full sun, rich soil. After all frost. Prepare planting positions with generous compost. Space 60–75cm apart. Water in well. Stake with bamboo cane before the plant needs it — the 1m stems can become top-heavy in full flower.
-
Feed weekly with high-potash fertiliser from first bud and deadhead religiously. Begin weekly tomato-type feeding when the first buds form. Deadhead every spent flower promptly — seed production slows the plant dramatically. With consistent feeding and deadheading, flowering continues from July until the first frost kills the foliage overnight.
Growing On, Cutting & Winter Storage
Cutting for the Vase
Dahlia stems are hollow — they lose water rapidly if not properly conditioned. The professional technique: immediately after cutting, dip the bottom 2cm of the cut stem into boiling water for 10 seconds, then plunge into deep cold water. This seals the hollow stem end and prevents air lock. Change vase water every 2–3 days and re-cut and re-sear stems each time. Vase life is 7–10 days with this method. Cut when blooms are nearly fully open — dahlia buds do not open well after cutting.
Pollinator Magnet
The open single and semi-double flowers with clearly visible golden-yellow centres provide direct access to nectar and pollen for bees and butterflies in a way that fully double dahlias cannot — the dense centre of a decorative or ball dahlia hides nectar from many insects. 'Bishop's Children' open-centred flowers are visited continuously from July to October, providing sustained late-season support as many other flowers finish.
Tuber Lifting and Winter Storage
After the first hard frost blackens the foliage, cut stems to 15cm and carefully fork up the tubers that have formed underground through the season. Allow to dry upside down for a few days (to prevent stem rot). Store in boxes of dry compost, coir, or straw in a frost-free, cool, dark location (a garage or shed is ideal). Check monthly for rot. Replant in May when frost risk has passed. Second-year tuber-grown plants are significantly larger and more floriferous than first-year seed-grown plants.
Selecting the Best from the Mix
Because 'Bishop's Children' is a seed-raised mix, individual plants vary in flower colour, size, and form. Some will produce particularly beautiful colours or combinations. Mark outstanding individuals with a label during the flowering season — these are the tubers to prioritise for lifting and storage. Second-year tubers from selected plants can be divided to multiply a favourite colour.
Hot Border Design
TVerbena bonariensis, whose electric purple heads on wiry see-through stems create a "hot-meets-cool" contrast with the dark dahlia foliage; and Cosmos 'Purity', whose large silk-white single flowers provide high-contrast against the near-black leaves, making both the dark foliage and the fiery flowers appear more intense by comparison. Rudbeckia, Helenium, and Tithonia in amber and orange complete a classic late-summer hot border.
Value Calculation
Dahlia tubers retail for £4–£12 each. A packet of 'Bishop's Children' seeds produces multiple plants, each forming a tuber at the end of year one — so seed sowing is genuinely exceptional value. You can grow so many dahlias inexpensively if you grow from seed! The investment in time (a modest extra 12 weeks) pays dividends across multiple seasons as tubers are lifted, stored, and replanted.
Sowing & Flowering Calendar
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 🌱 Sow indoors |
|
|
|
|||||||||
| 🌿 Plant out |
|
|
||||||||||
| 🌺 Flowers |
|
|
|
|
||||||||
| ❄️ Lift tubers |
|
|
Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| Leggy, weak seedlings | Insufficient light after germination; too warm | Move immediately after germination to the brightest available position. Reduce temperature to 15–18°C — warm conditions without sufficient light produce tall, weak stems. A south-facing windowsill or supplemental LED grow light positioned close to seedlings prevents legginess. |
| Flowering slowing in late summer | Deadheading missed; plant setting seed | Deadhead every spent flower as soon as petals drop — do not allow any seed head to develop. Even one or two seed heads on a plant signals it to reduce flower production. Check and deadhead every 2–3 days through August and September. |
| Stems flopping or snapping | No support; exposed position | Install bamboo canes and tie stems loosely with soft twine before plants reach full height. In exposed gardens, a horizontal netting framework at 50cm height provides the most effective support for multiple plants simultaneously. |
| Tubers rotting in storage | Stored before fully dry; too humid | After lifting, allow tubers to dry completely upside down for at least a week before storing — this prevents stem-rot spreading to the tuber. Store in dry (not moist) compost or coir in a cool, frost-free location. Check monthly and remove any rotted tubers immediately to prevent spread. |
Plant Specifications
The Bishop's legacy — near-black bronze foliage with neon-bright flowers, from a packet of seeds
Sow February–April at warmth, pinch at 15cm, plant in full sun in rich soil, feed weekly from bud, deadhead every spent flower. The dark bronze-black foliage that made 'Bishop of Llandaff' legendary — and the fiery scarlets and tangerines that glow against it like neon against darkness — all from seeds germinating in two days on a warm windowsill. Lift the tubers after the first frost and the investment multiplies into next year's even better display.
Shop Dahlia Bishop's Children Seeds →