Bulbs

Ornamental Bulbs – Spring Planting Guide for Czech Gardens

Spring-flowering bulbs are among the most visually immediate investments a Czech gardener can make. Plant them in October or November and they ask for nothing through the dark months; then from March onward they deliver the first colour of the gardening year before most perennials have broken dormancy.

The term "spring bulb" covers a wide range of botanical structures — true bulbs like tulips and daffodils, corms like crocuses, and rhizomes like some irises. In common horticultural practice they are grouped together because they share the same autumn planting window and the same early spring flowering period. This guide uses the broad definition throughout.

The autumn planting window in Czech conditions

The standard planting window for spring bulbs in Central Europe runs from mid-September to late November. The soil needs to be cool but not yet frozen — typically 8–10 °C at 10 cm depth. In most of Bohemia this means October is the ideal month. In South Moravia, where soils stay warmer longer, planting can run into early November without problems.

Tulip bulbs in particular benefit from a cold period before they flower; they need a sustained spell at or below 5 °C to initiate the flowering sequence. In Czech conditions this happens naturally in the ground. Gardeners in milder climates sometimes have to refrigerate their tulip bulbs before planting, but this is not necessary anywhere in the Czech Republic.

Planting depth: the rule most guides get wrong

The standard instruction to plant bulbs "three times their own depth" works as a rough guide but needs adjustment for Czech soil types. On heavy clay soils, slightly shallower planting — two to two-and-a-half times depth — gives better drainage around the base of the bulb and reduces the risk of rot during wet springs. On light sandy soils, the full three-times depth or slightly deeper provides more stability against heaving.

Specific depths for common species in average Czech soils:

• Tulipa (tulip) – 15–20 cm to the base of the bulb
• Narcissus (daffodil) – 12–15 cm to the base
• Crocus – 8–10 cm
• Allium (ornamental onion) – 10–15 cm depending on bulb size
• Muscari (grape hyacinth) – 8 cm
• Scilla – 6–8 cm

Naturalising versus lifting

Some bulbs naturalise in Czech conditions — that is, they multiply and return reliably year after year without being lifted. Daffodils, alliums, crocuses, muscari, and scilla all naturalise well. Tulips are the exception: most modern tulip hybrids perform best in their first year and decline rapidly. Lifting them each June and storing them dry through summer is the standard approach for maintaining quality displays.

Species tulips — the smaller, simpler forms derived directly from wild populations — are notably more persistent. Tulipa humilis, T. tarda, and T. saxatilis will come back reliably in well-drained Czech soils for five years or more without lifting. They suit rock gardens and the front of sunny borders where the soil drains freely.

Alliums: the underused ornamental

Allium hollandicum 'Purple Sensation' and the giant Allium giganteum are the two most commonly sold ornamental onions in Czech garden centres, and both perform excellently. The spherical flower heads on 60–120 cm stems bridge the gap between tulips finishing in May and the main summer perennial flush in June and July.

A less-used option worth noting is Allium sphaerocephalon, the drumstick allium. It flowers in July — later than most bulbs — and produces dense, egg-shaped heads on 60 cm stems. It naturalises freely in the light soils of central Bohemia and requires no attention once planted. Unlike larger alliums, the foliage is almost invisible by flowering time.

Handling clay soils: practical approaches

Heavy clay is the main constraint on bulb growing in Bohemia. The soil stays waterlogged through winter and into early spring, exactly the period when bulbs are most vulnerable to fungal rot. Three approaches reduce the risk:

1. Sand drainage layer: Dig the planting hole deeper than needed, add 5 cm of coarse horticultural sand at the base, place the bulb, and fill with a 50:50 mix of excavated soil and sand.
2. Raised beds: Even a 15–20 cm raised bed or berm with improved drainage soil dramatically reduces losses on heavy sites.
3. Species selection: Focus on bulbs with natural tolerance for heavier soils — daffodils, alliums, camassia, and fritillarias generally outperform tulips on clay.

After flowering: what to do with the foliage

The foliage of spring bulbs must be left in place until it yellows naturally — typically six weeks after the last flower. During this period the leaves are photosynthesising and replenishing the bulb's energy reserves for next year's flower. Tying the leaves into knots, which is sometimes recommended for neatness, restricts photosynthesis and weakens the bulb. Simply planting later-emerging perennials in front of the bulb area is the tidiest solution.

Buying quality bulbs in the Czech Republic

The main distribution season in Czech garden centres runs from early September through October. Dutch-grown bulbs dominate the market and are of reliable quality. The main thing to check at purchase is firmness — soft spots or visible mould indicate storage problems. Any bulb with a sunken base plate (the flat root end) should be avoided as this indicates the basal plate is rotting.

For unusual species tulips and less common alliums, the specialist bulb catalogue from Tulipany.cz is a useful Czech-market resource, though stock varies by year.