Growing Tulips: Depth, Types and the Ones That Actually Return

Contents

• How to buy tulip bulbs that perform
• How deep should you plant tulip bulbs?
• Site, soil and drainage
• How to plant tulip bulbs step by step
• The tulip divisions and when each one flowers
• Which tulips come back year after year?
• Tulips in pots and lasagne planting
• Deadheading, feeding and when to cut the foliage
• Should you lift tulip bulbs in summer?
• Voles, deer and squirrels
• Tulip fire and bulb rot
• Blind tulips and bulbs that never came up
• Tulips as cut flowers
• Zone and timing chart
• Common mistakes
• Frequently asked questions

How to buy tulip bulbs that perform

A tulip bulb is a pre-packed flower: the bud is already inside, and bulb size decides how big it gets.

Read the size, not just the price

Bulbs are graded by circumference, not diameter: a bulb labelled 11/12 measures 11 to 12 cm around. For garden tulips 11/12 is a solid baseline and 12+ noticeably better in year one. Below 10/11 the flower is clearly smaller and some bulbs make only leaves. Species tulips like Tulipa tarda are naturally small and sold as 5/6, which is not a fault.

What a healthy bulb feels like

A good bulb is firm all round, heavy for its size, with an intact dry basal plate. Put back any bulb soft at the base, mouldy, or carrying small hard black plates on the tunic — those are sclerotia of tulip fire. Buy in late August and store dry at 10–15 °C (50–60 °F).

How deep should you plant tulip bulbs?

Fifteen to twenty centimetres (6–8 in) to the base of the bulb, deeper than most packets say, and the difference shows from year two. The standard three times the bulb's height, about 12 cm (5 in), is enough for one spring but not for keeping them.

Four reasons to go deeper

The bulb splits less. A bulb near the surface sees sharp temperature swings and makes several small offsets instead of one big new bulb. Offsets cannot flower for two or three years, the usual reason for leaves and no flowers in year three.

The soil stays cooler in summer. Tulips come from the mountains of Turkey and Iran, with hot dry summers and cold winters, and a bulb at 20 cm sits several degrees cooler in July than one at 10 cm.

Frost heave cannot lift it. In zones 3 and 4 especially, shallow bulbs work almost to the surface over a couple of winters and dry out in April. The stem also stands straighter: a 70 cm Darwin hybrid planted shallow flattens in the first May downpour.

When shallow is genuinely better

There is a real counter-argument. Cornell University has trialled bulbs in landscape beds since 2009 and reached the opposite conclusion: shallow planting at 5–8 cm (2–3 in) plus mulch gives better return than deep holes. The explanation is moisture: on heavy soil the deeper zone stays wetter all winter, and a wet bulb rots rather than flowers.

Both are right, for different soils. On sandy ground plant 18–20 cm for more years; on heavy clay plant 10–12 cm and raise the bed 5 cm above grade. Spacing is 10–12 cm; tighter looks better but invites fungal trouble.

Site, soil and drainage

At least six hours of direct sun in April and May. What matters is the sun after flowering: a tulip in part shade is lovely in year one and empty in year two, because the leaves never gather light enough to build a new bulb. Under deciduous trees it works, since tulips finish before the canopy closes. Under spruce it does not.

Soil should be free-draining, sandy and humus-rich at pH 6.0–7.0. The requirement is not fertility but drainage: standing water at the spring thaw is the commonest cause of death in cold gardens. Dig a test hole and fill it with water. If it is still there an hour later, build the bed up with 10 cm of coarse sand.

Wind matters too: Darwin hybrids and single late tulips reach 60–75 cm (24–30 in) and snap in an exposed corner.

How to plant tulip bulbs step by step

A hundred bulbs takes half an hour if you dig one trench.

1. Wait until soil is below 10 °C (50 °F): mid September in zone 3, October in zone 5, November in zone 6.
2. Clear weeds and old foliage.
3. Dig one continuous trench for the whole group, 20–25 cm (8–10 in) deep, rather than individual holes. It gives a more even depth.
4. Loosen the base and fork in coarse sand if the soil is clay.
5. Scatter a tablespoon of bone meal per ten bulbs in the base and mix it in. Do not let the basal plate sit against fertiliser.
6. Set the bulbs point up, 10–12 cm apart. The basal plate, the flat pale disc with root stubs, goes down.
7. Backfill in two goes, firming lightly, leaving no air pockets.
8. Water once, about 20 litres per square metre (0.5 in), to settle the soil and start rooting.
9. Label the group, or you will spade through the bulbs in May.
10. Add 5 cm (2 in) of leaf or bark mulch only after freeze-up; mulch on warm soil invites voles.

If you have voles or squirrels, lay hardware cloth flat over the area and remove it in early spring before the shoots appear. If the bulbs are still in the garage in December, plant them anyway while the ground can be dug. The full autumn sequence is in the flower bulbs guide, with dates in when to plant spring bulbs.

The tulip divisions and when each one flowers

Fifteen divisions by flower form and ancestry, and the division tells you bloom time, height and lifespan. Times are for zone 6; add one to two weeks in zone 5, two to three in zone 4, three to four in zone 3.

April: the early divisions

Kaufmanniana opens first, often early April, only 15–25 cm (6–10 in) tall with wide star-shaped flowers and maroon-streaked leaves. Fosteriana, sold as Emperor tulips, follows with the largest flowers of any division on 30–45 cm (12–18 in) stems; 'Purissima' is the most planted. Single early tulips flower mid to late April on sturdy 25–40 cm (10–16 in) stems and shrug off wind. Double early tulips look like small peonies, but the packed flower holds rain. Greigii flowers late April, with maroon-striped foliage.

Late April to mid May

Triumph is the biggest group in the trade and what you get when the bag just says tulip: 35–50 cm (14–20 in), goblet-shaped, every colour going. Excellent for cutting, but most manage two or three years in a bed. Darwin hybrids are crosses between Fosteriana and the old Darwin tulips, and the most dependable large tulips for cold gardens: 50–70 cm (20–28 in), huge egg-shaped flowers, strong stems. The 'Apeldoorn' series is the most proven of all.

Mid May to early June

Single late tulips are the tallest, 55–75 cm (22–30 in), flowering as the lilacs start. Lily-flowered tulips have narrow blooms with pointed, arching petals on 45–65 cm (18–26 in) stems; 'Ballerina' is citrus-scented. Fringed tulips carry a crystalline fringe on the petal edge. Viridiflora tulips have a green flame up each petal and the longest display of any division, often three weeks. Parrot tulips have deeply cut, twisted petals, spectacular and the most fragile: rain shreds them in a day. Double late tulips are the heaviest. Rembrandt was the historic flamed group, caused by tulip breaking virus; virus-free equivalents now sell as Triumphs, and virus-broken bulbs should never be bought.

Species and botanical tulips

This is where the payoff sits for anyone tired of replanting. The species are small, 10–30 cm (4–12 in), and live for decades in the right spot. Tulipa tarda carries four to six yellow, white-tipped stars per bulb and seeds itself in gravel. Tulipa turkestanica gives up to twelve cream flowers per stem, Tulipa praestans 'Fusilier' three to five scarlet, and Tulipa bakeri 'Lilac Wonder' lilac-pink. Tulipa sprengeri flowers in June, last of all.

Which tulips come back year after year?

Species tulips, kaufmanniana, greigii, Fosteriana and Darwin hybrids. Treat everything else as a one- to three-season purchase, which is fine if you know it going in.

A tulip flowers once per bulb. Next year's flower sits inside a new bulb built under the leaves between bloom and midsummer. Build one large bulb and it flowers again; split into four offsets and you get four tufts of leaves. The double divisions were bred for flower size on Dutch fields where bulbs are lifted yearly, not for persistence in a border.

Honest verdict by division

Excellent. Species and kaufmanniana. Tulipa tarda, T. sylvestris and T. sprengeri also self-seed, and an established patch in sunny gravel only improves.

Good. Darwin hybrids, Fosteriana and greigii: four to six years of strong bloom, then a slow decline.

Fair. Triumph, single early, single late, lily-flowered and viridiflora: two to four years, with fewer flowers each spring.

Poor. Double early, double late, parrot and fringed: replant each autumn, or grow them in pots and for cutting.

To get more years out of what you have: plant deep on free-draining ground, deadhead but leave the stem, feed when shoots are 5 cm tall, and let the foliage stand six weeks. Above all, do not irrigate in summer. A tulip among hostas watered in July rots; one in a dry bed of perennials for full sun will not.

Tulips in pots and lasagne planting

Pots follow different rules, chiefly that you plant far tighter.

Use a pot at least 30 cm (12 in) deep with generous drainage holes. Add 5 cm of expanded clay, then a lean sandy mix rather than peat-based compost, which waterlogs. Set the bulbs 1–2 cm apart, almost touching, so they brace each other. Cover with 10–12 cm of mix.

The pot must stay cold but not freeze into a solid block. In zone 3 or 4 that means a sheltered spot against the house wrapped in bubble wrap, or the pot sunk into a heap of leaves. Water only when the mix is dry. Bring it in during March for earlier bloom, but only to a cool room at 8–12 °C (46–54 °F).

Lasagne planting

Three layers in one pot gives six to eight weeks of bloom instead of two, the largest bulbs deepest, pushing past the smaller ones.

1. Add drainage, then mix to 22–25 cm (9–10 in) below the rim.
2. Lay the bottom layer of late tulips, such as 'Queen of Night', and cover with 5 cm.
3. Lay the middle layer of daffodils or Triumph tulips, offset from those below. Cover with 5 cm.
4. Lay the top layer of crocus or species tulips, cover and water once.

Allow 15–20 bulbs in a 35 cm pot. Potted tulips rarely flower again.

Deadheading, feeding and when to cut the foliage

The six weeks after flowering decide next spring.

Pinch off the spent flower as soon as the petals drop, but leave the stem and every leaf: a seed pod sends energy into seed, not a new bulb. The exceptions are T. tarda, T. sylvestris and T. sprengeri, which you let seed.

Feed twice: bone meal in the base of the trench at planting, and bulb fertiliser when shoots are 5 cm tall. Nothing after flowering, and a nitrogen feed in June only gives floppy leaves.

When you may cut the leaves

Only once they have yellowed completely, six to eight weeks after bloom, so late June to mid July. Cut in May and you halt bulb formation.

The answer to the scruffy stage is planting, not shears. Set tulips behind perennials that rise in May: daylily, catmint or hosta, as covered in the guide to planning a flower bed. Water 20 litres per square metre a week if spring runs dry, then stop.

Should you lift tulip bulbs in summer?

No, not as a rule. Lifting, drying and storing is Dutch field practice transplanted into a garden. Bulbs come through a zone 3 winter in the ground perfectly well, and handling risks the basal plate.

Four cases are exceptions. If the soil is heavy and wet in summer, lift in early July as the leaves yellow and replant in October. If the bed goes over to annuals, lift the whole plant with leaves attached and let them die back in the shade. If a clump has crowded itself, lift in July and discard anything under 3 cm across. After tulip fire, do not put tulips back there.

Store bulbs dry, airy and dark at 15–20 °C (60–68 °F), in paper, never plastic.

Voles, deer and squirrels

Tulip bulbs and buds are prized eating, and three animals do most of the damage.

Voles

The worst, and the only one that can empty a bed without a visible trace. Meadow and pine voles eat the bulb from below through their runs, and what you find in April is an empty shell or nothing. Zero emergence across a whole group is almost always voles. Only physical exclusion works: line the trench with 13 mm (0.5 in) hardware cloth as a basket, base and sides, rim 5 cm above grade. Coarse gravel round each bulb helps too.

Deer and rabbits

Deer eat buds and leaves, not bulbs. A browsed bed shows stems bitten off at 10–15 cm with a ragged, frayed end, because deer have no upper incisors and tear rather than cut. A clean angled cut is rabbit. A 150 cm (5 ft) mesh fence is the only sure answer. Better to plant near the house and give the open yard to daffodils, which neither deer nor voles touch.

Squirrels and chipmunks

Squirrels dig up newly planted bulbs for a few weeks each autumn, drawn by loose soil and scent. Firm the soil, water, and hold off the mulch. Wire laid flat and lifted in early spring settles it; once the ground freezes the digging stops.

Tulip fire and bulb rot

Tulips have few diseases, but the two that matter persist in soil for years.

Tulip fire (Botrytis tulipae)

Shoots come up twisted and distorted, often with leaves stuck together. The leaves carry small pale brown to grey-brown spots with a darker rim and a watery yellow-green halo, which run together into large withered areas. In damp weather a fuzzy grey mould grows over the dead tissue, flowers spot brown and rot fast, and small hard black sclerotia the size of pinheads form.

Infection starts from sclerotia on the outer bulb scales or in the soil, where they survive several years, then spreads on airborne spores. Dig out the whole plant with its bulb and the soil around it and bin or burn it, never compost. Do not plant tulips there for three years, space more widely, and never water over the leaves.

Grey bulb rot (Rhizoctonia tuliparum)

This one shows as nothing at all: bulbs fail to emerge, usually in distinct patches, while neighbours look fine. Dig them up and the bulb is grey and shrivelled from the top down, with felted white to grey-brown fungal mats between the scales and flat black sclerotia on the surface, 1 to 10 mm across. Sclerotia last at least three to five years. Remove the bulbs and surrounding soil, and plant no tulips, hyacinths or crocus there for five years.

Ordinary wet bulb rot

The commonest of the three, and a growing problem rather than a disease. The bulb goes soft and brown and smells sour, often with a pale fuzz, and the cause is standing water at snowmelt. Raise the bed and add grit.

Blind tulips and bulbs that never came up

A blind tulip made leaves but no flower, a different problem from a bulb that never emerged.

Tulips as cut flowers

Plant tight for cutting, 5–6 cm (2 in) apart, and slightly shallower than in a bed, 12–15 cm (5–6 in), because deep bulbs give a gritty stem at harvest. Choose Triumph, Darwin hybrid or single late for long straight stems. A standard raised bed takes 100–200 bulbs; see raised bed gardening.

Cut when the top of the bud has coloured but before it opens, so you get the whole show in the vase. Pull the whole plant with the bulb attached for maximum stem length, or cut above the lowest leaves.

Harvested at that stage, tulips last nearly two weeks. To hold them a couple of days, stand the stems in newspaper somewhere cool and dark, with no water. In the vase use cold water, a couple of centimetres, and turn it daily: tulips keep growing and bend to the light.

Zone and timing chart

Planting time is set by soil temperature, not the calendar. Bloom times are for Triumph; early divisions run two weeks ahead, late ones two weeks behind.

In zone 3 and cold zone 4 the division matters more than technique. The tall late classes do not finish before summer arrives and hand you small bulbs for next year. Stick to low early divisions and species tulips against a south wall.

Common mistakes

• Planted too shallow. Twelve centimetres buys one spring, not several. Fifteen to twenty on free-draining soil halves the splitting.
• Planting in August. Warm soil starts the bulb too early and invites fungal trouble. Wait for 10 °C (50 °F).
• Foliage cut in May. The new bulb is built under those leaves over six to eight weeks. Cut early and next year brings leaves, not flowers.
• Tulips in an irrigated bed. They need a dry summer rest. Among hostas watered in July, the bulbs rot.
• Doubles and parrots sold as perennials. They are one-season bulbs: buy them for the effect, or choose Darwin hybrids.
• Mulch on warm soil. Leaves and bark spread straight after planting draw in voles.
• Replanting after tulip fire. Sclerotia stay in the soil for years. Change site for three years, five for grey bulb rot.

Frequently asked questions

How deep should you plant tulip bulbs?
Fifteen to twenty centimetres (6–8 in) to the base of the bulb on free-draining soil, deeper than the 12 cm most packets suggest. The depth means cooler summer soil, less splitting into offsets and straighter stems. On heavy clay plant 10–12 cm and raise the bed instead.

When should you plant tulip bulbs?
Once soil is below 10 °C (50 °F) and while the ground can be dug: mid September in zone 3, late September in zone 4, October in zone 5 and November in zone 6. The last sensible date in zone 6 is mid December, and a bulb planted then flowers late but flowers.

Which tulips come back every year?
Species tulips such as Tulipa tarda and Tulipa sylvestris, kaufmanniana and greigii types, Fosteriana like 'Purissima', and Darwin hybrids like 'Apeldoorn'. Expect four to six years from Darwin hybrids and ten or more from the species. Triumph manages two to three, and doubles and parrots are effectively annuals.

Why did my tulips come up blind with only leaves?
Most often the bulb split into offsets too small to flower, which is normal in Triumph and double divisions after year one. Other causes are too little sun, foliage cut before it yellowed last summer, or shallow planting. Feed at emergence and move to a longer-lived division.

Should you dig up tulip bulbs after flowering?
No, not as a rule. Bulbs come through a cold winter well in the ground, and handling risks the basal plate. Lift only if the soil is heavy and wet in summer, if the bed goes over to annuals, or after tulip fire. Then store dry and dark at 15–20 °C.

How far apart do you plant tulip bulbs?
Ten to twelve centimetres (4–5 in) in a bed, which is 40–60 bulbs per square metre for solid colour and 25–30 among perennials. For cutting go down to 5 cm, and in pots almost touching. Tighter spacing in a bed raises the risk of tulip fire.

When can you cut back tulip leaves?
Only once they have yellowed completely, six to eight weeks after flowering, so late June to mid July. Remove the spent flower as soon as the petals fall, but leave stem and leaves. To hide the scruffy stage, plant tulips behind daylilies or hostas, which fill out in May.

What is eating my tulip bulbs underground?
Voles, which gnaw the bulb from below through their runs and leave an empty shell or nothing. Squirrels dig up newly planted bulbs for a few weeks in autumn, and deer take buds and leaves but never the bulb. Only 13 mm hardware cloth around the bulbs stops voles.

A reminder of when bulb planting opens in your zone goes out in our newsletter with the rest of the autumn jobs.