The Fern Society of Victoria Inc.
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(Ian is a past-president of the Fern Society of Victoria and ran a wholesale fern nursery}
Soil Shade Mulch Feeding Water Wind Acclimatisation Sunny Ferns Shadecloth
If you look at ferns in their natural habitat, you will notice that very few of them grow in very heavy shade or full sun. More often, they grow in filtered sunlight or in areas exposed to morning sun. Gardeners probably more often have disappointing results from overshading in their ferneries than from too much sun.
With regard to the sun, the best situation is in either morning sun, strong filtered light throughout the day, or an hour or two of sun during the day. The afternoon sun in Summer in Victoria is too hot for many ferns to tolerate although, with care, some ferns may be grown successfully in full sun.
The secret is to get the other aspects of their culture right. The ideal conditions for growing most ferns would include strong filtered light; an organically rich and friable soil; mulch; moisture; and protection from excess wind. Most ferns will tolerate one, or maybe two, conditions that are less than ideal if the others are right. Exposure to sun is probably the easiest to work with, while soil is probably the most difficult.
The first thing is to prepare the soil. Heavy soils can be fatal to ferns, combine them with exposure to sun and, instead of establishing a fernery you will have a very successful mortuary. However if you keep replanting regularly, you will develop an excellent relationship with your local nursery and keep the commercial fern growers very happy!
Sandy or poorly draining soils will also require improvement. With heavy or clay soils, the best approach would be to make a raised bed - 20 cm depth is ample for most ferns. If you have a large area to fill, try contacting some of the smaller wholesale nurseries to see if you can take a trailer load or two of their used potting mix - we all have plants we discard. BUT, be careful of weeds and diseases! If a raised bed is not an option then dig plenty of organic matter into the soil. Give some thought to what materials you use as some can have problems e.g. mushroom compost can sometimes have a very high pH, which is not good for most ferns.
If the position is exposed to more than morning sun then establishing some shade is advisable. While some ferns will tolerate full sun they will never look as good as when they are more protected. They will probably be stunted, their foliage will tend to be quite yellow and it will probably burn.
Shade cloth (*refer to the separate section at end of article) is one obvious source of shade. One word of warning; the lighter colours, especially white, are brilliant for flowering plants but not ferns. If, however, there is other shade from trees or buildings (e.g. between a house and a solid fence) then the white shadecloth could be used as supplementary shade.
Another good source of shade, and a more natural one, is to plant some fast-growing large shrubs or small trees. Keep in mind that they may need to tolerate moist soil and a higher humidity. Some of the smaller wattles, bottlebrushes or Melaleucas, or even palms, could be used. Deciduous trees would be useful in that they would allow more light into the fernery in Winter, though of course they would not provide any frost protection.
A third option, in keeping with the fern theme, is to use some of the hardier tree ferns to provide the necessary shelter for less hardy ferns. The Rough Tree Fern (Cyathea australis) NSW Tree Fern (C. coopen), the large, very impressive, robust, and quick growing Black Tree Fern (C. medullaris) from New Zealand, Norfolk Island Tree Fern (C. brownii) or the Highland Tree Fern (C. tomentosissima) a smaller growing tree fern from New Guinea can all be used. Don't forget that tree ferns will grow trunks and, over time, the area underneath them may become more exposed to the sun.
One of the nice things about growing ferns is that they do surprising things because they don't always know-or heed-the rules. I have had self-sown Cyathea australis come up in my front garden which, though one of our common local tree ferns, will be cut very badly by a couple of -3 degrees nights but C. woolsiana and C. celebica, both Northern Queensland ferns, breeze through Winter with little or no damage! Rather ironic!
Organic mulches, liberally applied twice a year, will be very beneficial for any fernery, especially one in a sunny position. As well as retaining moisture, the mulch will provide nutrients and humidity and also help keep the roots cool. At home, I have planted up large areas under mature eucalypts. I have put in raised beds of used potting mix over very poor clay soil. The gum trees have put their roots right through the beds and, during Summer, they take almost all the moisture. The ferns an thriving with most of their roots in the layer of accumulated mulch. Another way to retain moisture and keep roots cool in an exposed fernery is to use large rocks and plant the ferns with their roots underneath the rocks. There are many ferns that will grow naturally in such conditions even in very harsh climates; Pellaea falcata, Doodias, Cheilanthes and some of the Blechnums come to mind.
I never feed the ferns in the ground at home. With regular mulching, I find that they just don't need it. In pots ferns will appreciate regular feeding; half to two-thirds strength liquid fertilizers used regularly or slow release fertilizers can be used. I use Debco's Green Jacket slow release because it is neutral in its effect on soil pH. Some of the other slow release fertilizers tend to acidify the soil a little with each application and after three or four applications the pH can go as low as 4 to 4.5, which will be catastrophic for many plants.
Proper watering is vital for ferns growing in a sunny situation. Hand watering while having a long cold drink can be very relaxing after a hard day's work. Otherwise, a well-planned sprinkler system will be necessary. The range of micro-sprays now available is ideal for ferneries as they deliver a fine spray around the plants, which will increase the humidity and they can be easily set up to cater for the individual requirements of any area and of individual plants. They are also easily altered as the area develops - I have recently added extra risers to many of the sprinklers in my ferneries to raise them above the plants that have grown around them. One tip when using micro-sprays - a lot of people turn them on for only 5 or 10 minutes and think they have soaked the garden but because they operate on a very low water flow, for best results it is necessary to run them for about 25 minutes. Then the water will soak right through the root zone of the ferns, instead of having the surface wet but the deeper soil quite dry.
Even In Summer, unless it is particularly hot and windy one thorough watering like that each day or possibly every second day should be more than enough to keep your ferns in prime condition without using an excessive amount of water. The best time to water is early morning or during the evening to reduce the risk of burning the fern foliage and to reduce water loss from evaporation, BUT if the plants need to be watered in the middle of the day then just do it! - it is far better to have a few fronds burn a little from being watered while the sun is on them than to have all your ferns die because you didn't want to water them while they were in the sun, We never water at a set time each day, it is always at need so when the temperature is in the mid to high 20's, the ferneries would normally be watered about three times in four days even with the competition for water from the eucalypts. Sprinklers should be set so they deliver water in droplets, not mist. If you want to humidify the atmosphere, use a fogger fitting on your hose rather than mist through your irrigation system.
Protection from strong wind in summer will also be important as sun and hot wind are a very damaging combination for ferns. The combined drying effect will make it almost impossible to keep any fern looking good. A solid `wall' of any material will tend to compress the wind and increase its damaging effect as it is forced around the wall. Better to break the wind enough to neutralize damage but still allow air movement. Two layers of shade cloth are often the answer.
Before planting ferns in a sunny position they may need to be acclimatized. From mid-autumn to midspring, there shouldn't be any problem planting them straight out in the sun. During the warmer months, because most ferns will have been grown in a shadehouse or hothouse, it will be necessary to harden them by gradually exposing them to more sun over a few weeks - take care with watering and shade the pots during this period! When planting, avoid the middle of a hot spell and try to plant straight after a cool change, when the plants will have a few days of cooler weather to settle in to their new position.
THE FINAL WORD... or, IAN'S LAW ON FERNERIES When developing any fernery, it is absolutely essential that you find a large slab of rock with a suitably sized shallow depression in the top and then place it in a suitably shady corner of the fernery and regularly take a long cold drink, sit on the rock and enjoy your own piece of heaven.
We have many birds enjoying the coolness and moisture in our ferneries, and greedily devouring the smorgasbord they provide. Among many others we get Yellow Robins, a few different Thombills, Tree Creepers, Pardalotes (which nest in earth banks-or my piles of bulk potting mix), Rosellas (that defoliate some of our tree ferns) and Fantails. I have even had a Tree Creeper land on my leg while I was watering recently - doesn't that make a fernery a very worthwhile investment?
The following ferns may be grown in a sunny position, those marked with an asterisk can be successfully grown in full sun if the advice given above is followed. Other species from the list could be tried and some experimenting could be worthwhile.Tree ferns:-
The quoted shade factor is for UV, not visible, light. 70% black and white shade cloths will both give 70% shade of UV light but in the spectrum range of visible light the black will give about 65% shade while the white will only give about 35% shade. Therefore, it can be said that in general, black or dark coloured shadecloths are preferable to light coloured ones. The light under the white shade cloth (though great for flowering plants because they admit visible light containing the whole colour spectrum) would be too harsh for most ferns. However, if there is other shade from trees or houses then white can be used as supplementary shade. A certain amount of shade can also be provided by hanging pots of less shade-loving ferns or other plants (perhaps flowering) from the roof of your fernery.
The other property of white shadecloth which should be considered is frost protection-an extra 2-4 degrees over other colours. I think that this is because when the sun shines on it white transmits more visible light which then heats up the air, soil and plants beneath it and then at night or during overcast weather, because it is reflective, it reflects some of the warmth back in and the cold out.
Probably the pinks would be the best of all. Tests done in Israel on horticultural plastics found that pink produces high levels of photosynthetically active radiation (PAR -the portion of the sun's radiation spectrum that best promotes photosynthesis, thus plant growth). Dark green I personally would not use. It produces low levels of PAR. Green fibreglass, which was widely embraced thirty or so years ago (when it was first available), was found to send ferns white, presumably for the same reason. However, many of us have very successful ferneries covered with it. It must be said that some ferns are more sensitive to the effect of both the intensity and PAR of light than others. I would be interested in seeing what a combination of 50% black over 50% white would do. Would it screen out just enough visible light and just enough ultraviolet light?
If you intend using polycarbonates, fibreglass or similar products in any of the solid colours, you would be well advised to use opal because the white component of these products has a UV blocking property which the clear ones do not have.Go to Top