Updated: September 29, 2022
By Stanton Gill , and Charles F. Schuster


Tulips are a refreshing reminder to customers that winter is almost over. Customers’ desire for color at the end of winter creates a profitable crop for cut flower growers using minimally heated greenhouses and high tunnels. Tulip bulbs can be forced to bloom out of season (from December through May) for early spring sales at Valentine’s Day, Easter, and Mother’s Day. Tulip bulbs can also be grown outdoors in raised beds, allowing them to flower naturally for spring sales.

Bulb Selection

The major groups of tulip flower types are simple petal, parrot, fringed, double flowering, multi-flowering, and lily flowering. Fringed and parrot tulips are considered distinct flower types. The fringed types have a regular tulip bloom with a fringed edge. Parrot tulips, however, have a deeper cut in the bloom edge and are more ruffled overall. Double flowering tulips have a cluster of multiple petals forming the flower head. Multi-flowering tulips have more than one flower per stem. Lily flowering tulips have more pointed petals and usually bloom later than any other type of tulip.

Bulbs are measured by circumference (cm) in a horizontal plane at the middle height of the bulb. The ideal bulb size for tulips is top size 12/+ cm, although some growers use a smaller 11/12 cm size. However, for optimum flower production the 12/+ cm top size is highly recommended because smaller bulbs result in a poorer quality crop with smaller flowers and shorter stems. Bulb orders should be placed with suppliers after Mother’s Day and preferably no later than the Fourth of July weekend. Most suppliers provide the tulips in trays of 500 per variety for a 12/+ size and 750 per variety on the 11/12 size bulbs.

Table 1. Tulips for Field Production - Grouped by Flower Period

Pink Impression Pink early
Red Impression Red early
Van Eijk  Pink early
Othello Purple


Bastogne Red early/mid
Bastogne parrot Red parrot early/mid
Oxford Red early/mid
Oxford Elite Orange/yellow early/mid
Apricot Parrot Apricot parrot mid
Ben van Zanten Red mid
Blushing Beauty Yellow, red blush mid
Don Quichotte Pink mid
Golden Oxford Yellow mid
Gwen White mid
Jan van Nes Yellow mid
Laura Fyii Red/yellow mid
Leen van der Mark Red/white mid
Lucky Parrot Red/white parrot mid
Negrita Favourite Purple mid
Barcelona Pink mid/late
Strong Gold Yellow mid/late
Synaeda Blue Lavender/white mid/late
Avignon Orange late
Big Smile Yellow late
Flaming Parrot Yellow/red late
Grand Style Red late
Ile de France Red late
Lady Margot Yellow late
Maureen White late
Menton Salmon/pink late
Mrs. JT Scheepers Yellow late
Purple Lady Purple mid
Renown Pink late
Texas Flame Yellow/red late
Texas Gold Yelloq late
Queen of Night Black late
Clearwater Pure white very late


Table 2. Tulips for Greenhouse Production - Grouped by Flower Type

Double Early Tulips          
Abba red x x x x
Holland Ballet white x x x x
Largo red x x x x
Margarita lavender x x x x
Monte Carlo yellow x x x x
Mondial white x x x x
Double late tulips          
Abigail dbl Attila   x x x
Angelique soft pink   x x x
Don Camillo dble Don Quichotte     x x
Mount tacoma white   x x x
Upstar pink   x x x
Fringed tulips          
Arma red     x x
Curly Sue purple   x x x
Louvre pink x x x x
Madison Garden deep pink   x x x
Parrot tulips          
Apricot Parrot apricot   x x x
Erna Lindgreen red x x    
Flaming Parrot red/yellow     x x
Prof. Rontgen orange   x x x
Rococo red     x x
Salmon Parrot salmon   x x x
Texas Flame yellow/ red flame     x x
Texas Gold yellow     x x
Webers Parrot pink/white base   x x x
Cloud Nine pink   x x x
H.D. Genscher creme     x x
Silhouette Bouquet red   x x x
Regular cut tulips          
Ad Rem orange/yellow edge   x x x
Attila's Record lavender   x x x
Barcelona pink   x x x
Baronesse pink     x x
Bastogne red x x x  
Ben van Zanten red x x x  
Bright Pink Lady soft pink x x    
Cafe Noir dark purple     x x
Suitable Forcing Periods          
Carola pink   x x x
Cassini red x x    
Charmeur red/white     x x
Cheers creme x x x x
Cherida creme yellow x x x x
Clearwater white   x x x
Deshima red x x x  
Don Quichotte pink   x x x
Dynasty pink/white base x x x x
Dreaming Maid lavender/white     x x
Early Glory pink   x x x
Friso red x x x x
Gabriella soft pink x x x x
Gander pink x x    
Gander's Overture creme/pink flame x x    
Gander's Rhapsody pink/white base x x    
Golden Brigitta yellow x x    
Happy Generation white/red flame   x x  
Holland Beauty pink x x x  
Ile de France red x x x x
Jack Pot dark purple/white   x x x
Jan Reus burgundy red   x x  
Jan van Nes yellow x x x x
Kais. maria Theresia soft pink x x    
Kees Nelis red/yellow   x x x
La Nouba white x x x x
Leen vd Mark red/white x x x  
Leo Visser red/white x x x  
Lucky Strike red/white x x x x
Negrita purple x x x  
Negrita's Favourite purple x x x  
Niigata pink   x x x
Orange Cassini orange x x    
Othello purple x x    
Peerless Pink pink   x x x
Pink Impression pink     x x
Prima Vista red x x    
Primavera pinkish-red x x    
Purple Flag purple x x x  
Purple Prince purple x x x  
Red Gander red x x    
Red Impression red     x x
Rosalie pink   x x x
Royal Virgin white   x x x
Sevilla red   x x x
Shirley white/purple edge     x x
Silver Dollar white x x x  
Stargazer red/white x x    
Strong Gold yellow   x x x
Swinging World pink   x x x
Synaeda Blue lavender/white   x x x
Synaeda Show white   x x x
The Mounties watermelon red   x x x
Washington yellow/red flame x x x x
White Dream white   x x x
White Flight white x x    
World's Favourite orane   x x x
Yokohama yellow x x x x


Precooling Requirements

It is highly recommended that you follow the information provided in the Holland Bulb Forcer’s Guide–5th Edition (see References section for more information). There are two main types of bulbs, precooled and non-precooled.

The Holland Bulb Forcer’s Guide defines precooling as “the dry storage of spring flowering bulbs at temperatures between 35-48 °F after floral initiation and development is completed, but prior to planting.” Precooled bulbs need to be planted fairly quickly upon receipt. If precooled tulip bulbs must be stored for a short period, keep them at the temperature specified by the supplier (usually 40-45 °F). The second type, non-precooled bulbs, are stored at non-chilling temperatures (typically 63 °F) until cooling begins by the final forcer. Non-precooled tulip bulbs can be potted and stored in a dark, cool (33-40 °F) barn or shed for 12-14 weeks. Monitor the stacked crates often to prevent the shoots from growing into the crate above.

Production Methods

Greenhouse—Hydroponic in Crates

Reusable water trays are placed in tulip bulb shipping crates. The trays float in a liner that is inserted in the bulb crates. Two kinds of water trays are commonly used—the egg crate type and the prong type. The prong-type water trays are able to accommodate bulbs of various sizes, whereas the egg crate type comes in two different sizes to hold a particular size bulb.

Precooled bulbs are required for greenhouse forcing. Precooled bulbs are planted into the hydroponic trays and typically placed back into a cooler at about 40 °F for 1-3 weeks depending on cultivar and time of year. This temperature allows for some rooting to take place before the bulbs are placed in the greenhouse for forcing. The tulips can then be grown in a cool (40 °F night) or warm (55 °F night) greenhouse. The warmer the greenhouse, the faster the bulbs will bloom.

Level benches are needed so that the water level is the same for the entire crop. Water is added to the trays so that the level of the water just touches the bottom of the bulbs to initiate root growth. Some bulb suppliers recommend removing the paper skin from the base of the bulb to allow faster root growth, being careful not to damage the root area.

The water in the trays should be changed several times during the growing cycle, either by overflowing the crates when watering or completely changing the water. Be aware that dumping excess water on the greenhouse floor increases the humidity in the greenhouse, thereby increasing the chance of Botrytis problems.

Greenhouse—Soilless Substrate in Crates

The shorter tulip bulb crates are more suitable for growing tulips than the taller lily bulb crates. Place a sheet of newspaper in the bottom of the crate to prevent the substrate from falling out the bottom. Fill the crate with about three inches of moistened substrate. Tulips produce roots at the base of the bulb, so the amount of substrate under the bulb is more important than the depth the bulb is planted. Arrange the bulbs on the substrate in ten rows of six bulbs, or sixty bulbs per crate. The number per crate can vary by bulb size, with as many as 100-105 11/12 cm bulbs being used in some cases. Cover the bulbs with 2 - 3 inches of substrate and then water well. Tips of the bulbs should still be visible after watering the substrate.

If the bulbs previously received their entire precooling period, then forcing may begin by moving the crates into a cool (40 °F night) or warm (55 °F night) greenhouse, or holding in a cool area several weeks to grow roots. If coolers are available, bulbs are planted then cooled at 40 °F (or below to reduce shoot growth) for a total duration of 12-16+ weeks depending on the cultivar and time of year. After cooling, forcing may begin. Protect the bulbs from freezing. Keep the substrate moist at all times, while being careful to keep the foliage as dry as possible when watering.

Greenhouse—Raised Beds

An indoor, raised bed can be constructed using pressure treated wood to create six-inch high sides. When constructing raised beds in a high tunnel or greenhouse, consider the space between the beds for maneuvering equipment.

Raised beds are useful for tulip production because they help to improve drainage and prevent disease problems caused by root rots. Do not replant in beds that have had tulips in the past unless you are able to steam sterilize the substrate at 160–180 °F for 30 minutes. During the heat of the summer when a greenhouse is not in use, plastic covers can be used  to solarize (using the sun to heat the soil) the beds for 4-6 weeks.

Growing tulips in raised beds is very similar to greenhouse production of tulips in crates of soilless substrate. Programmed bulbs are used and planted in steam-sterilized soil. Keep the beds well watered and the greenhouse nighttime temperatures between 40 and 55 °F. The warmer the house is kept, the shorter the crop time, but the higher the heating cost.

Field Production

It is easier to plant tulips by digging a trench than it is to plant the individual bulbs. To form a trench, cultivate the planting area 12 inches deep and then shovel the soil to one side of the bed. In field production, tulip bulbs can be planted up to eight inches deep. The deeper the bulb is, the longer the stem will be when pulled at harvesting. If a deeper trench is needed, cultivate the area again and remove more soil. Place the bulbs in the bottom of the trench 6-8 inches deep, leaving about as much space between each bulb as the size of the bulb itself. Cover with soil, being careful not to overturn the bulbs in the process. The loosened soil can be used to create a raised bed over the tulip bulbs. Water the bed well. A preemergent herbicide can also be applied at this time to prevent winter and early spring weed germination.

Low tunnels can be constructed over field grown tulips in early February to force the bulbs into flower in late March, three to four weeks before other field tulips. Low tunnels will also help to protect early crops from deer. Later crops can be protected by placing posts along the sides of the bed and using row cover vertically along each side of the row. Rope zigzagged down the row will support the row cover above the tulips. If the row cover rubs the flowers, the buds will be damaged. For information on how to construct a low tunnel, contact the University of Maryland Extension.


Proper fertilization for tulips used as cut flowers is important. Tulips are not considered high feeders, and the bulbs themselves store many nutrients for the plants’ initial growth. Excessive fertilization can lead to reduced plant height, which may affect marketability. The use of slow or controlled release fertilizers is not recommended as the plant will be harvested before most of the nutrients are released. For field production, use 1.5 pounds of nitrogen per 1,000 square feet at planting, making sure not to allow the fertilizer to come in contact with the bulbs. After bulb emergence in the spring, the application of one pound of actual nitrogen per 1,000 square feet (1.6 oz per 100 sq ft) of row is recommended. The substrate should have a pH of 6.2 to 6.8 for the greatest nutrient avail- ability and plant growth. Adjust phosphorus and potassium to the optimum range based on results from soil tests.

In greenhouse and high tunnel production fertilization should begin after shoot emergence. When the shoots are 2 to 2.5 inches tall use a fertilizer with a 2:1 ratio of calcium nitrate to potassium nitrate after amending the substrate for phosphorus and potassium. Weekly application of this ratio can be used, or a fertilizer injector can be utilized to sup- ply 200 to 250 ppm of N on a constant basis using a well-balanced fertilizer (either 2:1:1 or 3:1:1 nitrogen to phosphorus to potassium ratio) that includes a small amount of phosphorus and potassium. With a soluble salt meter, use the 1:2 dilution method to monitor the electrical conductivity. Acceptable readings should be between 1 and 1.5 mS/cm (mmhos/cm).

Harvesting and Postharvest Handling

Tulips are harvested when petals show color, but are not completely colored or open. When harvesting, tulips can be cut or pulled. Crate-grown tulip stems are cut at harvest time. Tulips grown in the field are pulled at harvesting to increase the stem length. If the soil is soft, the bulb usually comes up when the stem is pulled. When pulling tulips, grasp the stem at the soil line and pull straight up. The stem should snap off at the bulb, producing a longer stem. The used tulip bulbs should be discarded after harvest. This pulling method removes the used bulbs from the bed, making bed preparation for the next cut flower species easier. Rotating tulips to another field the following year will help to reduce disease occurrence.

The stems of pulled tulips should be cleaned after picking. Simply swish a handful of stems in a large bucket of water to clean the soil off the stems before placing them in a bucket of water with preservative. If the tulips experience wilting after harvest, any bent stems must be wrapped or somehow supported in the bucket while rehydrating. Otherwise, they will remain bent even after being properly hydrated. Tulips can be stored in a cooler in water or dry at 35 °F for up to one week. If stored dry, they must be supported when rehydrating. Tulips continue to grow after cutting, up to six inches after placing them in a vase.

Table 3. Production Methods

Greenhouse water trays yes no fall season
Greenhouse soil in crates yes no fall season
Greenhouse raised bed yes no fall season
High Tunnel raised bed no yes late fall,early winter
Field raised bed no yes late fall, early winter


Insects: Aphids


Tulips are relatively pest free but aphids can become an occasional problem, especially for greenhouse-forced crops. The two major species of aphids found in greenhouses on tulips are melon aphid (Aphis gossypii) and green peach aphid (Myzus persicae).

Aphids can rapidly become a major pest if left unchecked. Because aphids feed on the plant fluids within the phloem of leaves and green stems, they represent a competing nutrient sink. Heavy aphid populations may measurably reduce plant vigor. Aphids also excrete large quantities of sugar-rich honey- dew on which sooty mold fungus may grow.

Before any attempt is made to control aphids, it is necessary to identify the species. Submit samples of aphids to your local Extension office for identification. After the species is identified, familiarize your- self with its biology on the tulip crop. Note whether it prefers particular species or cultivars of tulips, if it feeds selectively on certain parts of the plant, and how rapidly it reproduces.

Green peach aphid (Myzus persicae)

The color of green peach aphid can range from light green to yellow to gray-green to pink or even reddish. It is a fairly large aphid that most people can see without magnification. The green peach aphid has a pronounced indentation between the base of the antennae on the front of the head. The cornicles (two projections on the rear of the aphid) are long and slender. The color of the cornicles matches the body color of the aphid but the tips of the cornicles are black. This aphid can reproduce very rapidly and populations can explode in a very short time. Control should be attempted early before populations become large.

Melon aphid (Aphis gossypii)

The melon aphid is slightly smaller than the green peach aphid but it reproduces just as quickly. Both melon aphids and green peach aphids have been found to transmit viruses. The color of the melon aphid depends upon its food source. They may vary from slightly green to dark green to various mottled shades of green or even yellow. The antennae are shorter than the length of the body and there is no indentation between the base of the antennae, as found with the green peach aphid. The cornicles of the melon aphid are short and very dark colored.

Insecticidal soaps offer some control against aphids. Applications should be applied at regular intervals for maximum efficacy. Growers that have problems with aphids can also apply foliar or soil drenches of a labeled neonicotinoid. Check the University of Maryland Extension’s Bulletin 363, “Total Plant Management for Greenhouse Production,” to select a recommended systemic pesticide.

If you grow tulips in greenhouses, check the plants before moving them indoors to make sure they are free of aphid populations. Control weeds under the greenhouse benches and directly outside the greenhouse to prevent aphid populations from developing. Aphids can be prevented from migrating into the greenhouse by covering screen vents and doors with a 300-holes-per-inch mesh screening.


Major diseases of tulip in Maryland include tulip fire (Botrytis tulipae), bulb/basal rot (Fusarium oxysporum f. sp. tulipae), bacterial soft rot (Erwinia carotovora), blue mold (Penicillium species), root rot (Pythium species), nematodes, and viruses. Starting with disease-free stock is always the most important step in the growing process. Bulbs should be purchased from a reputable dealer. Most large bulb producers regularly check stock for viruses and other diseases. Inspect bulbs care- fully upon arrival and have suspicious material examined by a lab. The presence of diseases may warrant the rejection of a shipment.

Preplanting Treatments

Bulbs may be dusted or dipped in fungicides such as thiram (available under many trade names) or thiabendazole (Mertect), to help control diseases such as Fusarium basal rot and Penicillium blue mold.

Botrytis (Tulip Fire)

Tulip fire is caused by the fungus Botrytis tulipae and is the most common disease of tulips during production and in the landscape. Initial symptoms include light tan patches on tulip leaves. These patches are most noticeable on light-colored varieties. Leaves become flecked with small brown (necrotic) spots.

Spots enlarge and coalesce to form large brown patches and cause blight of entire flowers or leaves. Flowers also frequently become infected and display flecked brown to white spots. On colored petals spots appear white and on white petals they appear brown. Under conditions of high humidity, necrotic spots on leaves, stems, and flowers are accompanied by sporulation of the brown-gray fungus. Further infection occurs very rapidly once the fungus begins sporulation; this is the origin of the name “tulip fire.” Infection can also lead to the collapse of leaves, stems, and flowers. The outer bulb scales may also become infect ed and display yellow to brown, sunken, circular lesions. Small, black sclerotia (resting structures of the fungus) may be found developing on rot- ting leaf, flower, stem, and bulb tissue.

Control: Bulbs should be carefully inspect ed by removing the outer husks of the bulb and discolored or spotted bulbs should be discarded before planting. Plantings should be inspected regularly; early detection and hand-rouging is essential for controlling this disease. While inspecting plants, carry a bag for diseased materials. As soon as the disease is detected in a bed, affected plants or parts should be removed. Remove faded or blighted flowers, blighted leaves, or entire plants infected at the base and place them in the bag. Discard infected parts with the trash or burn them. It is best not to remove material when plants are wet because fungal spores (conidia) could be spread during conditions that favor disease development. Entire plants should be removed including the bulb portion below ground if infection is observed at the base of the plant. Overhead irrigation and crowded plants can increase disease incidence. During rainy springs when conditions favor disease development, applications of fungicides may be useful when new growth emerges in the spring. Fungicides should also be used if infections occurred in the previous year. Compounds currently registered for use in Maryland include carbamic acid, chlorothalonil, copper hydroxide, iprodine, and mancozeb. (Always consult the label for dosage rates and safety precautions.)

Bulb and Root Rots

Erwinia carotovora

Infected plants fail to flower or blossoms fall off before they open. Tops may appear water-soaked and collapse. Infected bulbs have a strong odor and are soft and mushy.

Phytophthora cactorum and Pythium species

Bulbs develop soft, gray spots with brown borders near the base of the bulb. Shoots may fail to emerge. If bed has a history of Phytophthora or Pythium infection, then chemical or steam-pasteurized potting mix will be required.

Control: Site management is important for controlling bulb and root rot diseases caused by Erwinia, Phytophthora, and Pythium. These pathogens are favored in moist, shaded areas with poor air circulation and poor drainage. These diseases are highly contagious and control requires the removal and destruction of all infected bulbs. Remove and destroy symptomatic foliage and plant debris in the fall after the tops have been killed by frost. Bulbs should be planted in well-drained soil and watered early in the day. These diseases may also be minimized by avoiding overcrowding and wounding during cultivation. Sanitation is also very important. All equipment should be disinfected between use with 10 percent household bleach, 70 percent alcohol, or one of the commercially available compounds. It is also helpful to control insects and mites because injuries associated with their activity provide sites for infection.

Storage Rots

Fusarium oxysporum var. tulipae and Penicillium species are two diseases affecting tulip bulbs during storage. These diseases are also associated with mechanical injury or damage from mites. Infection is favored by moist conditions. Infected bulbs have a dry rot and bulb scales are often covered with the characteristic blue-green (Penicillium) or pink (Fusarium) colored growth of the fungus.

Normally, Fusarium infections begin in the field and continue during postharvest storage. There are substantial differences in cultivar susceptibility, but it is important to reduce the number of infected bulbs in storage because of the ethylene they produce. This can lead to flower abortion and abnormalities.

Control: Producers need to dig carefully in order to avoid wounding the bulbs. Wounds provide natural entry points for pathogenic fungi. It is also helpful to control insect and mite pests. Producers and suppliers should cull and destroy infected bulbs prior to storage.

Bulbs in storage must be routinely inspected and the rooms monitored for ethylene. Levels in the storage rooms must not exceed 0.1 part per million. In storage, Penicillium can be controlled with high rates of ventilation and by maintaining a relative humidity of 85 to 90 percent. Tulip bulbs should always be shipped at 63 °F (~17 °C) under a ventilation rate of 150 m3 h-1. With the exception of a 93°F (~34 °C) treatment for early forcing (a process normally completed by the supplier), nonplanted bulbs are never stored above 77 °F or below 32 °F (> 25 °C or < 0 °C).


Stem and bulb nematode (Ditylenchus dipsaci) is the major species affecting tulip. On tulip, infestation is best detected at flowering. The initial symptom is a pale or purplish lesion on one side of the stem immediately below the flower, which bends in the direction of the lesion. The lesion typically increases in size both downward and upward often on to the petals. The bulbs do not show brown rings as with narcissus and hyacinth when cut across. Infestations start at the base of new bulbs. Upon removal of the outer brown scale, soft grayish or brownish patches  can be observed on the outer fleshy scale. Nematodes move out of decayed bulbs into the soil where they overwinter. They may then move into healthy bulbs the next spring. Nematodes require lab tests for identification.

Control: No nematicides are currently labeled for use on tulips in Maryland. Stem and bulb nematode is best controlled by prevention. Many areas (especially Europe) have established legislative laws for Ditylenchus dipsaci as a significant quarantine pest. If infected bulbs are found in a shipment, destruction of the entire contents of the shipment may follow. Hot water treatments for tulip bulbs have been quite effective in controlling nematode problems, but this type of treatment jeopardizes bulb vitality. Many growers report that numerous losses of tulip occur when using hot water treatment to control nematodes.


Viruses known to infect tulips include tulip breaking virus, tobacco necrosis virus, tobacco rattle virus, tobacco mosaic virus, and cucumber mosaic virus. Symptoms of infection consist of stripes or streaks of white or another color in the normal colored petals. A classic example of a virus-infected tulip variety is the “Rembrandt tulip.” Modern tulips exhibiting similar streaking characteristics no longer contain the virus. Leaves of virus-infected plants may appear distinctly mottled. Viruses are persistent in the bulbs and are often transmitted from plant to plant by aphids, especially in situations where plants are crowded and heavily infested.

Control: Bulb suppliers regularly inspect and test for viruses during production. Viral diseases are difficult to control so prevention is a major factor for control. Infected plants and bulbs should be removed and destroyed to minimize spread of the virus. Control of the aphid vectors is also important. Weeds can also harbor various viral diseases and other diseases; therefore, it is important to control weeds in and around production areas.

Physiolgocal Disorders

Frost injury—Frost damage may appear as oblong to oval spots along the veins of the leaves. This injury is not common.

Retarded growth—A result of storage under excessively warm conditions or if bulbs are not fully ripened. Growth may be retarded or suppressed completely.

Sunscald—Occurs in sunny, dry conditions and results in the scorching of flower parts, particularly along margins.

Topple—Some varieties develop water-soaked spots and exude liquid from the main stem. Eventually flowers collapse. This  problem is thought to be due to insufficient ripening of the bulb, especially after wet, cool summer weather and by forcing bulbs in compact soils or at high temperatures.

Control: Prevent high temperatures and pre- mature forcing especially after wet, cool years. If this is a problem, try a different variety that may be less susceptible to this disorder.

Winter injury—If bulbs are planted too late  in the fall in compact, poorly drained sites, roots cannot establish and bulb decay occurs. Shoots may appear abnormal and distorted— be sure to check below-ground portions to examine root development.


Connecticut Agricultural Experimental Station. Plant Pest Handbook Tulip (Tulipa).

Cornell University. “Botrytis Blight of Tulip (Botrytis tulipae)” factsheet. http://plantclinic.cornell.edu/factsheets/botrytisblighttulip.pdf

De Hertogh, August A. 1996. Holland Bulb Forcer’s Guide, 5th edition. Hillegom, The Netherlands: The International Flower-Bulb Center.

The use of brand names in this fact sheet does not express or imply an endorsement by the University of Maryland at College Park College of Agriculture and Natural Resources or University of Maryland Extension. All information provided in this fact sheet is to be used as a guide only. The contributors to this fact sheet cannot be held liable and/or responsible for any damages that might occur.