Plant of the Month
Tulip
Tulips
Tulips are a spring essential, adding an extravagant touch to the plot, whether you go for striking tulip combinations of different varieties or stick with one colour to suit the style of your garden. Parrot tulips are especially flamboyant – discover some of the best parrot and fringed tulips to grow.
Botanically, Tulips are divided into 15 divisions chiefly defined by their flower characteristics and sometimes referred to in bulb catalogues. Broadly speaking, their flowers can be described as single or double; cup-shaped, bowl-shaped or goblet-shaped; fringed, parrot or lily-flowered; long, slender-tepalled or star-shaped. When choosing tulips, consider their flowering times, suitability for borders, containers (see below), or a rock garden where the smaller species such as Tulipa tarda AGM or T. kaufmanniana can be best utilised. Some are ideal for naturalising in fine grass; in particular, the low-growing tulip T. sprengeri AGM.
When buying bulbs in person:
-
select the largest bulbs.
-
squeeze them gently to make sure they're firm.
-
avoid any bulbs showing signs of mould.
Hardiness
Hardy.
Soil
Tulips grow best in fertile, well-drained soil in full sun, sheltered from strong winds. All dislike excessively wet conditions; this is particularly true with alpine species which require excellent drainage. Exceptions include Tulipa sprengeri, T. sylvestris and T. tarda which prefer a more moisture-retentive soil with partial shade.
Size
Varies, from 15cm (6in) to 75cm (30in); spread: 15cm (6in)
Watering
Bulbs and plants in the ground shouldn't need additional watering, except in long dry spells during the growing season.
The compost in containers can dry out quickly, so bulbs in containers should be watered regularly throughout the growing season, until the foliage dies down.
Flowers
It is generally best to remove the faded blooms after flowering, so that instead of forming seeds, the plants put all their energy back into their bulb, for a good flowering display the following year.
Deadheading is the removal of flowers from plants when they have faded or died. It is done to keep plants looking attractive and encourage re-flowering.
Deadheading also keeps the display looking its best.
Planting
Incorporate organic matter into the soil before planting to improve both clay and sandy soils, making them much more suitable for tulips. Coarse gravel can also help improve growing in clay soils. Apply Growmore or chicken manure pellets (70g per sq m or 2oz per sq yd) before planting to help nutrient-poor soils.
A neutral to alkaline soil is preferred. Soils with a pH lower than 6.5 may need applications of lime.
To plant new bulbs:
-
Plant from mid- to late autumn – this is later than most bulbs but a late planting can help reduce problems with the disease tulip fire
-
Use only healthy bulbs, discarding any that show signs of damage or mould
-
Plant at least twice the bulb’s width apart, and at a depth of two or three times the bulb's height
Encouraging re-flowering:
Most bedding-type (i.e. not species) tulips are best replaced each year. If left in the ground, they are unlikely to re-flower after their first year.
The alternative to discarding old bulbs and replacing with new is to lift and drythe tulip bulbs after flowering:
-
Deadhead to prevent seed production, and wait until foliage turns yellow before lifting the bulbs (about six weeks after flowering)
-
You need to lift earlier, place in trays until the leaves become yellow and straw-like
-
Clean the soil off the bulbs, and discard any that may be diseased or damaged
-
Allow the bulbs to dry thoroughly before storing
-
Store the bulbs in trays or net bags in a warm, dark, well-ventilated place at 18-20°C (65-68°F), before replanting in the autumn
-
As flowering is uncertain, it is often best to use old bulbs in the less important beds, borders and containers, and use new bulbs for conspicuous areas
-
Dwarf species tulips such as Tulipa kaufmanniana, T. fosteriana, T. greigii and their hybrids often re-flower without lifting. Only lift and divide when clumps get overcrowded.
-
Although not usual, some cultivars growing in warm soils – where they can be baked in summer – may re-flower from year to year, and possibly multiply.
Pruning
Leave foliage to die down until leaves are yellow/brown after flowering. Do NOT tie them in knots
Problems
Failure to flower: Small bulbs or bulbs growing in poor soil may not flower. Such bulbs should be lifted, the bed cleared of other plants, and the soil enriched with a well-balanced fertiliser. Only replant the largest bulbs. Feed with a high potassium fertiliser such as ‘Tomorite’ at weekly intervals after flowering. If the bulbs do not reach flowering size within two seasons, start again with fresh bulbs.
Bulb blindness can also be caused by insufficient ripening of the bulbs during the dormant period. Failure to lift bulbs, or keeping the lifted bulbs at temperatures lower than 18ºC (65ºF), will lead to flowering decline. Unless growing for seed, remove old flower heads to prevent seed pods weakening the bulb.
Excess of small bulbs: Small bulbs may be due to poor soil conditions (see above) or the over-production of offsets due to shallow planting. Replant deeper to discourage this.
Short flowering stem: Once in the ground, tulips require a cold period for flower extension to take place. UK winters are usually sufficient to supply this but, if planting was very late or the winter is particularly mild, then stunted flower stems may be a problem.
Pests and diseases:
Grey squirrels can often dig up bulbs after planting.
Aphids can develop on stored bulbs, as well as during the growing season, and can spread viruses. Holes in leaves and bulbs during early spring may be due to slugs. Stem eelworm is an infrequent problem that can cause distorted growth and malformed flowers.
Brown spots of dead tissue on leaves may indicate tulip fire disease. In severe cases the spots enlarge and extensive areas become brown and withered giving the impression of fire scorch.
Tulip viruses are indicated by streaked and distorted leaves and flowers.
Tulip grey bulb rot is caused by Sclerotium (Rhizoctonia) tuliparum. It is one of the sclerotinia diseases but it is more commonly described as rhizoctonia disease. Prompt removal of infected bulbs is very important and the only means of control. Do not replant bulbs in the infected area for five years.
Bulbs in store can be affected by blue mould rot.
Note: All parts may cause stomach upset if ingested. It is advisable to wear gloves when handling tulips, as contact with any part may aggravate skin allergies.
With thanks to RHS