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Growing in the Green: Scaevola’s ‘star’ power

March 15, 2011  By Melhem Sawaya

This is the second in a series of vegetative crop production features.

This is the second in a series of vegetative crop production features.

Scaevola is an attractive plant with star-like flowers. It multiplies on a vine at a moderate growth rate. Scaevola is a versatile plant that can be used in hanging baskets from 10” to 16.” The larger the container, the better, because scaevola requires plenty of water.


Scaevola can also be grown in mixed planters, 4” pots, window boxes, and as the ultimate annual groundcover that will turn a flower bed into a carpet of blue flowers. In my opinion the number one use is as a bedding plant where a large mass of blue flowers is desired, and where moisture lasts longer between waterings than in hanging baskets or other containers.

Scaevola is a day-neutral plant, but the ratio of flowers to vegetative growth increases drastically when light intensity is higher or the plant perceives more foot-candles. Vegetative growth, however, is not inhibited, but only slows down.

 p18_3987-DSC3346- p18_3987-DSC3347-
Scaevola Bombay White

 Scaevola New Wonder

 p18_3987-DSC3356-  p18_3987-DSC3353-
 Scaevola Scala Blue

 Scaevola Blue Falls

 p18_3987-DSC3351-Pink p18_3987-DSC3344-
 Scaevola Bombay Pink

 Scaevola Blue Print

Light: Scaevola is a light-loving plant and does not mind the heat as long as it is watered on a regular basis. Scaevola grows at low light levels, but for a high-quality plant, light levels should be between 5,000 and 10,000 foot-candles.

Temperature: Scaevola can survive at temperatures as low as 0ºC and as high as 50ºC as long as the plant roots are moist. There is a direct relation between light levels and temperature in growing this crop. With high light levels, scaevola will grow nicely at high temperatures. But if light levels are low, for example between 600 to 2,000 foot-candles, then temperatures should be dropped to 17ºC, or spindly growth will result.

Nutrition: Scaevola is a vigorous plant, so adequate fertilization is necessary in order to avoid leaf yellowing. The optimal ratio is as follows: nitrogen-3, phosphorus-1, potassium-3, calcium-2, magnesium-1, and soluble trace elements.

The EC of this fertilizer is directly dependent upon your growing media and the way you water. In other words, test your media before fertilizing and then fertilize accordingly.

The target is an EC of 1.0 mmhos with one part soil and two parts distilled water. A pH of 5.8 is optimum. As well, the addition of iron chelate (1 gm/10 L) will help in greening the yellow tips. If the whole plant is yellow, it could be root problems, a lack of fertilizer, or that it has been wet for too long.

A remedy for correcting yellow plant tips is as follows: 100-200 gm of 21-7-7 and 10 gm iron chelate per 100 L of water. A note of caution: if applied overhead, a rinse of the leaves is a must or phytotoxicity of the leaves most probably will occur. The best way to rinse is with a sprayer filled with clear water, because the goal is to rinse the leaves only and not dilute the treatment.

Water: Scaevola can be watered heavily during spring and summer, but during fall and winter it should be watered lightly since it does not like to be wet for a prolonged length of time. As well, scaevola has a semi-waxy leaf, which requires a high level of nutrition, necessitating frequent fertilizer applications – overwatering must be avoided.

Medium: A soil mix that drains well is a must for growing scaevola during fall and winter. A mix of 80 per cent peat and 20 per cent perlite should work very well. Scaevola will do much better if the starting media pH is 5.5 rather than the regular 5.8.

Planting: Scaevola liners can be planted into 6” to 16” baskets, 4” pots, window boxes, wall bags and used as bedding plants. The liner should be watered lightly upon planting, and only to the depth of the liner. Sick liners should not be planted, but if not discarded, they should be treated and revived before planting. Discarding them after planting is an expensive process. As well, treatment in the liner stage is more effective and more economical.

Here is a guide for the number of liners required per pot size and approximate crop time from liner to finish.


The crop time varies with the time of year and the number of pinches you do. Scaevola does not stop growing when it flowers, so finishing time also depends on the size of plant you like to ship.

Pinching: Scaevola is a plant that needs to be pinched at least three times for hanging baskets, and once for 4” pots. Experiments applying ethrel on scaevola improved branching significantly, and delayed flowering, which will speed up the vegetative growth. Ethrel could be used for timing purposes, spraying the crop at different stages to give flexibility in finishing dates.

Spacing: Plants can be grown pot to pot as long as we are performing enough pinches. Spacing as soon as the plant starts touching is very important or else weak, spindly growth will result. A suggested spacing is as follows.


Again, spacing depends greatly upon the finish size that you require.

Growth regulators: We mentioned the experimental use of ethrel for branching and management of flowering. Bonzi improves the quality of the finished product significantly – low concentrations of frequent applications of any growth regulator are preferable, especially when you are trying to shape a plant rather than stop it. Many of the recommendations from the U.S. are based on experiments done in Florida, which has completely different weather conditions from those experienced in the northern parts of the U.S. or in Canada. Use with caution.

A drench of 0.5 ml/L Bonzi gives a very good growing habit –  tight but still growing. The flowers will last much longer. Another application might be needed if the crop did not ship on time.

A note of caution: if you are growing 4” pots of scaevola that are normally used as bedding plants, an  application of Bonzi or Sumagic has to be done two weeks before shipping, especially if the product is shipped in early May. Plants that are treated with Bonzi or Sumagic just before shipping will not grow properly when planted in the garden. For hanging baskets or any container that is not to be transplanted, treating with Bonzi or Sumagic and shipping in one or two weeks is really a benefit for long shelf quality.

Disease: Scaevola is not prone to a specific disease. As is the case in many varieties, any disease could infect it. The healthier the plant, the less susceptible it is to diseases. The best disease control is prevention. The second best defence is to use your eyes to watch for abnormalities, identify the disease, and treat it with the specific chemical for that disease.

(A colleague recently made the following comment: “The plants really grow when they hear your footsteps.” WiFi and other remote gadgets are a disaster if overused in plant production.)

Insects: Thrips find scaevola irresistible, because they love those blue flowers! Regular pinching and growth regulator use will eliminate the flower haven for thrips. Chemical treatments, then, will be more effective because thrips can’t hide since there will be fewer flowers to conceal them from the spray treatment. Of course, biocontrol is much more widely used and works when applied properly.

Physiological: Scaevola is a fast-growing plant. It is a teenager that is hungry most of the time! Regular fertilization is a must to keep up with its fast-growing habit, or yellowing will occur.

Yellowing could also happen if is has been wet for too long. This will tie up iron and damage the roots, and the plant will not have the means to pick up fertilizer.

Scheduling scaevola varies significantly with different cultural practices and the enviroment, but by following the guidelines we talked about, you won’t be too far from your targeted product. To achieve the ultimate program that would fit your operation, apply the following records and you will be able to adjust, improve upon or repeat the crop you had this year.

  • Planting date.
  • Size of liner and condition.
  • Number of liners per container.
  • Temperature.
  • Light conditions (in general), or how many layers of baskets are above, if any.
  • Fertilization type and concentration.
  • Any specific problems or setbacks.
  • Date of shippable stage, not shipping date.

Be objective and listen to customer response to your product.

Write next year’s program and changes by the end of this year, since your memory can fail.

We mentioned these 10 steps in the brachyscome plant production article, and will mention them again as we continue the rest of the crops – this is only to stress the importance of these steps.

Melhem Sawaya of Focus Greenhouse Management is a consultant and research coordinator to the horticultural industry. Comments on this or any other article are always welcome; please e-mail, or visit or .

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