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How To Grow Ferns

FERNS ARE A GREAT ADDITION TO ANY GARDEN.  Whether you grow your ferns as perennials or annuals or houseplants there are some common care tips that I want to share.
Santa Rosa Tropicals has this great piece on ferns.   Here are some of t

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heir best tips.


At least 63 to 70% shade is required in summer. Some ferns like Boston fern can have a bit more light, but most like some dappled shade.

TEMPERATURE: Fastest fern growth occurs between 73º and 86ºF. Night temperatures are critical for growth and control of fungus. Whereas 50º will not hurt ferns, using 63º as the low will more than offset the increased fuel costs while reducing winter fungus problems.

WATERING: Ferns (with a few exceptions) do not like to have wet feet! Most of them actually like to lightly dry out between waterings...especially Boston Fern relatives, all footed ferns, and in particular the bird's nest and staghorn ferns. [The ferns that will wilt if they dry out include tree ferns, button and brake ferns, maidenhair ferns, lace fern and woods fern]. Misting ferns usually doesn't have any value but if it makes you feel good, go right ahead (but only during the warm part of the year). Note...watch the roots of your ferns. They should all have healthy, light colored ends. Black ends on the roots indicates overwater!

FERTILIZING: Because of the need to grow ferns in a well draining mix, and since most ferns do not store nutrients well, it is best to keep them on continuous feed. A good starting point is 100 parts per million nitrogen using something with ratios close to 15-5-15. Read the label to see that the ammonia and nitrate nitrogen levels supplied are roughly equal. The ppm can be raised if the foliage is too light green in color indicating a need for increased nitrogen. Slow release fertilizers can be difficult to control when the days are short and cool and are not recommended. If your ferns look at all unhappy, try reducing the feed rate.

PESTS: ALL chemicals used to control pests can burn ferns if used improperly. Each must be tested carefully on a few plants and then used only as needed. Repeated use, especially fungicides can cause problems (see note below under stunted or deformed plants). The generally safe pesticides for ferns include: Dipel®. For caterpillars. Tends to leave white residue on foliage, but very effective in eliminating caterpillars and is safe to use. Mavrik® and Talstar®. These are both very effective for caterpillars (worms). They act primarily as repellents. They will also prevent a re-occurrence of scale. Talstar® + Enstar II® or Talstar® + Orthene® are good combinations for aphids and scale. Orthene® (the soluble powder form) seems safe on all except the maidenhair ferns for labeled pests. Marathon works well to control aphids on plants that otherwise attract aphids when they are not on any other plant in sight. Fungicides that are effective for botrytis are Chipco 26019® and Cleary's 3336WP®. Cleary's seems to be more effective when mixed in water that has a Ph around 5.0. We use a few drops of sulfuric acid / tank to reduce the Ph. However, for fungus control in general just lowering the feed levels of those ferns that are particularly susceptible to fungus problems seems to help more than any chemical sprays.

POTTING MIX: Ferns prefer a mix that has a high proportion of organic materials such as peat, yet one that drains very well. There should be a source of calcium and magnesium included and are usually provided by dolomite lime and the irrigation water. Superphosphate can be left out for most ferns. Some potassium nitrate (1/2 pound per yard) helps ferns get started. Most commercial mixes use too much starter feed for tiny ferns.


Boston Ferns and their relatives...

Repotting ferns that are potbound is important if you want to keep your sanity. If you don't, you eventually have to water every day or even twice a day in hot weather since they don't store water well and there is no mix left to hold water.

You just have to be brave and all will be well. If you just want a bigger fern, get the next size pot ready (2" to 4" larger in diameter and not too deep in proportion to width). If you want to divide the plant into smaller plants, have 3 or 4 new pots ready, usually the same size that the fern is in now.

To just move up, don't disturb the roots. Put a layer of new potting mix in the new pot so there will be no more than 1" of space between the top of the plant and the edge of the pot. Trim off all lower fronds and any that are not looking great. Repot filling the sides with new mix.

To divide, trim the fronds extensively. Remove all lower and older fronds. Cut the remaining ones back to half or less of their length(but not all the way off). Take the plant out of the old pot and with a serrated kitchen knife or thin bladed saw divide the plant and root ball vertically into giant pie shaped pieces that are in thirds or quarters.Then take off one to two inches from the bottom of the root ball. Put potting mix into the new pots so there is no more than 1" of space below the edge of the pot when the divided plant is set into the pot.Fill spaces with new mix. Treat these divided plants pretty much as you had been treating the original. When you see new growth you will know the transplant was successful. Try to do this before July 1, so there is plenty of time for the plant to recover.

Rabbit's foot ferns...

The question of repotting Davallia's comes up regularly. They do so well in their first container that almost everyone leaves them there until they form this wonderful ball. Eventually, however, some change is necessary to keep the fern happy.The best time is in December or January before new growth is showing. You have two choices. a) You can cut all the fronds back to the base. Then take a saw and cut the plant into quarters looking at it from the top. Each quarter is placed into a new pot. If the quarter is too tall, the bottom can be cut flat to the correct height. Or try the following which we like a lot...b) Cut all the fronds back to the base. Take something serrated,pointed and sharp and cut an ice cream cone shaped piece out of the center of the plant. Add new potting mix into the space where you removed the cone. Plant the removed cone into a new pot. If too tall you can trim the point of the cone off. (Aha...a new plant for a friend.)Water very little until new fronds appear. Then treat normally, always remembering that the usual problems are too dark, too wet.

PH: One secret to growing those stubborn varieties of ferns is to keep the irrigating water pH between 5.0 and 6.2.

Trouble Shooting Tips

Deformed Leaves...Especially bird's nest varieties but even Nephrolepis will show deformity if kept too wet. Someone will report that the leaf looks like it is being eaten by something, but on further questioning it is noted that the damaged area has very smooth edges, and rather than holes in the leaf, the margins are scalloped. Nephrolepis fronds become constricted somewhere along their length, so that the side leaflets are all short in one area. These are all tattletale symptoms of overwatering.

Burned Edges...If the plant is 'relatively' young, they are hard to burn with salts, but is it is very easy to salt burn pot-bound plants.

Burn spots...Usually spray, either used on that plant or overspray from plants sprayed nearby. In winter it could be fungus on leaves of plants grown with too high feed or wet foliage.








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