Six Secrets to Successful Ferns

Shanti Claycamp

At Casa Flora, Inc., we grow more than 100 varieties of ferns. Proving the adage that “what’s old is new again,” these ancient plants are quickly growing in popularity because they provide a unique and beautiful natural texture to gardens and landscapes. Armed with a few growing tips, both greenhouse growers and gardeners will come to appreciate the relative ease of growing an eye-catching fern crop or garden.

1. Hardiness zone. Check the zone allocation for the fern and make sure it matches the area where the plant is being sold.

2. Moisture levels. Though a bit trickier, this involves balancing both growing media and watering technique. Most ferns prefer the soil media to be moist without being sopping wet or completely dry. When preparing a well-drained media of perlite, bark and peat moss, the goal is to encourage even aeration and moisture retention between each watering.

3. Shade. Most ferns grow best in full or dappled shade. Adequate shade will produce lush, dark green foliage. We recommend 65% to 75% shade, depending on your location. (Less may be needed in the winter when the days are shorter.) Sunscald on the tops of the leaves, or stiffly upright and light green growth are all symptoms of too much sun. If any of these occur, add more shade. A few ferns—such as ostrich fern (Matteuccia struthiopteris)—can grow in full sun if adequate water is provided to prevent drying out.

4. Fertilization. Ferns are relatively light feeders compared to many other foliage plants. They prefer a balanced fertilizer, such as 20-10-20 or 20-20-20, with micronutrients applied at approximately 200 ppm nitrogen. Too much nitrogen can cause tip burn on the roots and leaves if the plant becomes dry. Tropical ferns are more sensitive to fertilizer residue on the fronds from a liquid feed and may react to rates as low as 200 ppm nitrogen, so be sure not to overfertilize.

5. Watch for potential signs of pests. Although ferns have relatively few pests and diseases, catching potential threats early is always important. The main fern pests include non-selective caterpillars and fungus gnats. Watch for moths in the greenhouse and use bug zappers to attract them before they lay their eggs. Fungus gnat larvae are often a sign that the fern is staying too wet and watering may need to be reduced.

6. Winter habit. Many perennial ferns—also known as hardy ferns—lose their foliage in the winter, but will rebound in the spring. Deciduous ferns can be cleaned up and stripped of their dead growth as soon as the foliage dies back. You can mound the foliage over the crown. Mulch may be applied to the crown if extra winter protection is needed. Semi-evergreen ferns should not be trimmed until spring since the extra foliage that dies back will act as a mulch to help protect the crown, and the bit of green left on the leaves will help it recover faster in the spring. Evergreen ferns should not be trimmed at all until the new leaves start emerging. If some of the leaves have suffered cold damage, they can be trimmed at any point.

With these simple growing tips, you will find growing outdoor ferns to be relatively easy and will provide years of enjoyment to the end consumer. GT


Shanti Claycamp is the fern specialist for Casa Flora, Inc.