Greenhouse growing conditions

What type of fertilizer should I use on perennial ferns/tropical ferns?

Ferns need very little fertilizer. At Casa Flora we use a 20-15-20 water soluble fertilizer. We check our ppm weekly and apply fertilizer as needed. We use about 120 ppm N for our Perennials and 150 ppm for our Tropicals.  If the plants are growing slower during the winter, we adjust our fertilizing accordingly.  We do not recommend using slow release fertilizers, which have been known to burn our ferns.

What light level should I keep for growing ferns in a greenhouse?

1200/2000 fc (foot-candles) of light is required during active growth periods, so shade may be required, especially in the Southern U.S. climates.

What type of soil should I use for growing a 4”/ 1GAL/ 8” hanging basket?

Casa Flora recommends that you use a perennial bark mix or peat-based mix that is well-drained.

How often should I water perennial ferns/tropical ferns?

Allow soil to dry moderately between watering. If conditions are hot, more frequent watering may be necessary to prevent desiccation.

At what temperature should I keep my greenhouse for growing perennial/tropical ferns?

For the first 6 to 8 weeks, a soil temperature of no lower than 65°F/18°C is best; the ideal would be 68° to 75°.  This will help establish the transplant.

What pH should I keep my soil?

pH 5.5 to pH 6.5 is acceptable for most fern varieties.

What type of insects would cause problems on ferns? What pesticide should I use to treat my plants?

We occasionally encounter aphids or caterpillars for which we recommend Orthene or other approved insecticides at half of the recommended rate on the label.  Ferns are sensitive to many pesticides so trial before you use, never apply to a dry fern and be aware that high air temperatures can make the ferns more sensitive.

Why do I have fungus problems? What fungicide should I use to treat my ferns?

Foliage fungus problems tend to occur when the foliage is overgrown, constantly wet, and cool night temperatures prevail.

There are several good fungicides on the market.  The situation you are in will dictate what application rate, type of fungicide and method of application you use. As of now the strongest group of fungicide on the market is group 11. If you are battling a major war with Botrytis due to over watering or humidity you may find that Medallion is your best friend. For preventative purposes, use it as a drench, but If you are treating Botrytis, you must spray. If you are battling Thielaviopsis you will find that it’s best treated with drench using Banrot 40WP. Heucheras are susceptible to Thielaviopsis however using Banrot 40WP can prevent this. Other fungicides such as Decree 50 WDG, Spectro 90 WDG, Subdue Maxx and Root Shield or Plant Shield work well also. Identifying your issue, researching chemicals, prevention and using the correct method of treatment will save you much heart ache and many headaches.

What should I avoid using on Ferns?

Do not spray oil-based products on ferns.



Why are my plants yellow?

Some of the reasons your plants may be yellow are: lack of fertilizer, low light or the wrong pH. Check the rate of fertilizer in which you are applying to your ferns. If it’s lower than 120 ppm you may be under-feeding your ferns.  Usually a rate between 120-150 ppm is best. Sometimes we use up to 200 ppm.  If you have had several days of cloudy and or rainy days in a row this can also affect your growth and color of the fronds.  Always periodically check the pH of your soil (we recommend pH 5.5 to pH 6.5). The information on your soil conditions can tell you important things about the growth of your plants. This may also tell you any inconsistencies in your soil mix.

Why are my ferns gray-green?

Ferns should generally be a vibrant green. If they start to appear a light gray-green color, it means that your ferns need water. If you have just planted the ferns and are trying to force the roots to the bottom of the pot, this is the stage you should water them.  If they stay unwatered for too long at this stage, permanent damage will result.  You can also get this color if you have root damage since the fronds can’t get enough water from the roots.  If the soil is wet or if you have had wet soil for a few days, check the roots to make sure that they are healthy.

Why are my plants not growing fronds or roots?

Your plants may not be growing due to lack of light and/or fertilizer. Monitor the weather, check the light, temperatures and check your fertilizer rate. Also keep a close eye on the application of watering.  Too much water will drown plants and too little will stress them out or kill them.  Most ferns and especially the Heucheras do well when they are allowed to dry out a little in between waterings. This should not be an excessive amount of time as too much stress can cause wilting and make the plant more susceptible to diseases. When the weather is hot for too long, some ferns may go into a dormancy period. When this happens in the summer months the plant will no longer grow new roots or may produce little to no new fronds. The Himalayan Maidenhair Fern, for example, can be susceptible to this kind of heat stress. Try to keep your greenhouse at a more consistent temperature and allow the greenhouse to cool throughout the day and hot afternoons. Also, remember not to over-water.

Why isn’t my Himalayan Maidenhair Fern growing roots?

When the weather is too hot for too long, Himalayan Maidenhair Ferns go into a dormancy period. When this happens in the summer months the plant will no longer grow new roots or may produce little to no new fronds.

Why do the plants I received have black spots on them and smell bad?

When we ship, we pre-treat our product with fungicide. However, black rot can still happen during the shipping process due to temperature changes and condensation within the box.  If this happens, we recommend spacing, good air circulation, drying them out and treatment with fungicide.

Why are my fern roots brown?

Unlike most plants, fern roots are supposed to be brown although the tips should be clear and slightly white.

Why my plants won’t grow in the winter?

Buying and planting liners in the winter or early spring (November thru March) will require extra attention.   If you purchase actively growing liners during this period, they will need to be kept above about 65°F/18°C soil temperature and lit for 6 hours during the night (long days) to keep them actively growing.  They should stay vegetative after April 1 without additional lights although heat may still be necessary.  Heat is not enough to produce vigorous top growth; they will need additional lights.

IF YOU SEND A GROWING FERN BACK INTO DORMANCY BY COOL TEMPERATURES AND SHORT DAYS, YOU MUST COOL IT FOR 6 WEEKS 40°F/4.5°C BEFORE IT WILL START TO GROW AGAIN.  Signs of dormancy include yellowing of the foliage, no new frond growth and decreased water requirements.  If you continue to keep a dormant fern in warm temperatures and water regularly, it will very likely die.

If you are not concerned about frond growth until April, then you should maintain soil temperature at a maximum of 40°F/4.5°C.  Cold frames, beds with thermal blankets and unheated greenhouses are good places to overwinter ferns but you need to water carefully and provide rodent control.


Marketing and Selling Your Plants

How can I market ferns?

Marketing ferns goes hand in hand with shade garden promotions. With the limited selection of material available for shade gardens, ferns can add height, texture, and color accents.  There are many ferns suitable for small places, rock gardens, or even for vast sweeps of shady areas. Versatility with ferns is limited only by your imagination.  For our customers in North America, Casa Flora highly recommends the paperback edition of Ferns For American Gardens (ISBN 0-02-584491-1) by Dr. John Mickel.  You will get a feel for the fantastic variety and number of fern varieties and their characteristics – and how they might be deployed to improve your gardens and your gardening sales.  We recommend Mickel’s book as  “…A book that should be on every fern lover’s shelf.”
Sue Olsen has 2 books on ferns. Encyclopedia of Garden Ferns (ISBN 978-0881928198) is a wonderful reference book with most of the ferns you can acquire in the United States. Great pictures and detailed information on the plant. The Plant Lovers Guide to Ferns (ISBN 978-1604694741), co-authored with Richie Steffen, is a smaller, more concise treatment of commonly available ferns in the United States. Again, gorgeous pictures and enough information to make you want each and every one.

In addition, ferns are great for houseplants. As one of the most popular indoor ferns, Boston ferns create a classic feel in any room. Its arching, lacy fronds make it well-suited to hanging baskets. Although has a delicate appearance, a Boston fern can live for decades if you keep it moist and give it moderate light and enough humidity. The variety ‘Dallas’ is more compact and more tolerant of dry air. It’s also a great selling point – and not widely enough known – that Boston type ferns remove toxic pollutants from indoor air. We think this is an outstanding selling point – see below for more information.

Is it true that ferns clean the air?

Yes! NASA’s Clean Air Study documented the fact that Boston Fern not only removes toxic formaldehyde (a carcinogenic air pollutant emitted by every day household products) better than any other plant. It also removes xylene and toluene. Although the study looked only at true Boston fern, it seems very reasonable that other Boston-type ferns have similar properties. So it’s true that a single Boston hanging basket can actually make your home or office a safer and healthier place to live. Plus, its cool and calm vibes will make your office seem less stressful and your home more relaxing. We’ll be posting more information on this topic that you can use for marketing purposes in the Media section soon.

You can find the original NASA report here.

Casa Flora