Growing guide
How to grow Polystichum
Low-maintenance and tolerant of a wide range of soil conditions, Polystichum complement plant combinations for shade. From small specimens grown in the gaps of a wall, a shady rock garden or in a container for the larger specimens over 1.2m (4ft) tall, there is room for this fern in every garden.
Quick facts
- Easy to grow
- Ideal for shady sites
- Great spring interest from unfurling leaves
- Water well while plants establish
- Great to mix with other woodland plants and bulbs
- Propagated by dividing clumps, using leaf bulbils or through growing spores
All you need to know
Before you get started
Choosing
Look at the available space you have in mind first as Polystichum can grow to a variety of sizes, ranging from Polystichum tsussimense (Korean rock fern) that grows no more than 45cm (18in) to Polystichum munitum (sword fern) that grows over 1.2m (4ft) tall.Consider the individual species characteristics such as evergreen foliage, interesting spring unfurling fronds, and a fern with bronze tinted foliage such as Polystichum setiferum (soft shield fern).
Think about the locations you have to offer in your garden and then which Polystichum will best grow there. For example Polystichum aculeatum (hard shield fern) will tolerate soils that are well-drained (once the plants are established), but many other Polystichum can tolerate moisture retentive (but not waterlogged) soils.
Consider what other plants in your garden Polystichum may look great next to, for example, woodland
These are fleshy, rounded, underground storage organs, usually sold and planted while dormant. Examples include daffodils, tulips, hyacinths, lilies, onions and garlic. The term is often used to cover other underground storage organs, including corms, tubers and rhizomes.
Planting around old tree stumps and logs can often help create a more naturalistic feel, creating what's known as a stumpery, thanks to the Victorian gardeners.
Buying
These ferns are widely available in most good nurseries and garden centres often sold in 3 litre pots although some suppliers have a range of sizes available. For specific cultivars there are specialist nurseries such as Fibrex Nurseries Ltd, Long Acre Plants and Crawford Ferns to name a few.To track down specific cultivars RHS Find a Plant also lists suppliers of Polystichum.
Buying: mail order plants
RHS guide to choosing healthy plants
Planting
Where to plant
Most Polystichum originate from woodlands and therefore prefer shade or semi-shade. They are easy to grow and will thrive in any moisture-retentive soil. They can tolerate dry soils in shade once established.Some can be grown in sunny locations, but the leaves can be scorched by the sunshine and they need the soil to remain moist throughout summer to do well. Plants prefer a sheltered location, away from frost pockets and strong winds.
Allow enough space for your plant to grow as Polystichum can range in size (see Choosing above) depending on species and cultivar. Check the label for their width/spread and allow this gap between plants.
When to plant
- It is best to plant Polystichum in autumn or spring when the soil is naturally moist
- If you buy a Polystichum during the summer, plant it as soon as possible and water it regularly to keep the surrounding soil moist
How to plant
- Begin by trying your new plants in the locations you have in mind before planting. It is often worth placing the plants on the ground and stepping back to take a look to ensure you are happy with the arrangement before planting
- Dig a hole that's roughly the same depth as the pot, and twice as wide for planting
- Firming back the improved soil around the roots. The aim is that, when planted, the compost that was in the container is just covered – deeper planting can cause the base of the plant to rot
- Once planted, water well to help settle the soil and remove air pockets
- Use organic matter such as leaf mould or well-rotted manure as a 5cm (2in) thick mulch around the plant helps condition the soil and replicate the woodland soil Polystichum prefers
Planting Perennials
Ongoing care
Watering
Like most perennial plants, newly-planted Polystichum should be watered regularly and thoroughly, especially during summer, for the first few years until their roots are well-established.Once established, they are fairly tolerant or dry soils compared to other ferns and shouldn’t need regular watering. However on very free-draining soil or during prolonged hot, dry spells you may need to give them some additional water to support continued healthy growth in your garden.
Water to keep the soil moist, ideally applying to the roots and not directly to the fronds or crown as this can encourage rot.
Watering
Feeding
- Polystichum do not usually require feeding when planted in the garden but mulches, such as well-rotted farmyard manure or leamould, will condition your soil and boost to growth
- Where soil conditions are particularly poor, a fertiliser, such as Growmore or fish, blood and bone can be applied in spring
Pruning and training
Propagating
Division
The easiest way for you to propagate hardy ferns is by dividing the clumps. It depends on the growth habit of your fern as to how you can divide it.
Creeping rhizomes (roots)
- In spring, dig up and cut the rhizomes into segments about 5-7.5cm (2-3in) long, ensuring that each segment has at least one growth bud and a small root ball (shoot)
- Pot up individually into peat-free multipurpose compost at the same level at which it was growing. Planting too deep will result in the sections rotting
- Place the pots in a light shady spot and keep the compost moist
Crown splitting
- It can take up to ten years for a multiple crown to develop – where there are several shuttlecock-like crowns (growth points)
- Many nursery-raised containerised plants consist of multiple plants that were initially pricked out and potted up in clumps
- Dig up and tease apart the mature crowns with two forks placed back-to-back to act as levers. Pot up each crown or replant into the ground
Dividing Perennials
Spores
Spores are these dust like particles which usually appear on the backs of the leaves. They are the ferns' equivalent to seeds from which new plants can be grown.
Collecting spores
- The majority of ferns produce their spores in small heaps (sori) or lines on the undersides of the mature fronds
- The sori are pale green when unripe and usually become deep brown or black as they ripen. If the sori are a pale rusty brown, the spores have probably already fallen. However, as spores ripen in sequence (from tip to stem), it is often possible to find both ripe and unripe spores on a single frond, especially in mid to late summer
- To collect spores, place a small piece of spore-bearing frond in a dry paper envelope and keep for a day or so in a warm, dry place. Any spores present will then have settled in the bottom of the packet as a dust-like brown, yellow or black powder
- Before sowing, it is essential to surface sterilise the compost to kill any stray fungal, moss or fern spores else these also grow and smoother the new ferns
- Fill a 7.5cm (3in) plastic pot to within 1cm (½in) of the rim with John Innes seed compost or a 50/50 mixture of coir and sharp sand
- Place a disc of newspaper on the compost
- Pour boiling water gently onto the disc until the water coming from the bottom of the pot is steaming
- Cover the pot with a piece of glass or plastic, or aluminium foil and leave until cold
- Remove the glass and paper disc when you are ready to sow
Sowing the spores
- Sprinkle the spores very thinly over the soil surface of the prepared pot of compost
- Immediately cover the pot with a piece of clear polythene or cling film, secured in place with string or an elastic band
- Label the pot with details of fern's name and date
- If sowing different batches of spores, sow each pot in a different room in order to avoid cross-contamination of ferns
Aftercare
- Place the pot in a cool, lightly shaded place for a month or two by which time a green film on the soil surface will be visible through the cover. This will gradually form into distinct filmy green structures (the prothalli – or a young stage of the ferns)
- After a further month or so the first tiny fronds will appear
- When two-three fronds are visible, prick out the sporelings (as they are now called) and pot fingernail-size clumps into 7.5cm (3in) pots of sterilised potting compost
- Maintain a humid atmosphere by enclosing the pot in a polythene bag, placing in a shady spot away from direct sunlight for a few days, as exposure to dry air can be fatal
- Midsummer sowings may well produce true fern fronds by winter, but autumn sowings may not until the following spring. In one to two years the young ferns will be large enough to be planted out in the garden
Problems
While we think all this information will be helpful to you, we always recommend to read the instruction labels on your plants.
Discover Polystichum
Everything you need to know about choosing the right Polystichum for you.
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