How to Cultivate Ferns in Pots
Growing Ferns in Pots
The cultivation of ferns in pots is best confined to the smaller and less strong-growing species and varieties, and for bringing on young plants for subsequent planting out. To keep the larger kinds in good condition would necessitate steady moving on into bigger and bigger pots until ultimately they become too heavy for easy work, and careful attention to watering. If the pots get too wet and the compost gets sour the fern roots perish, and if they get too dry it checks the ferns severely; and it is difficult to get the pot ball moist again throughout by ordinary watering, as the water travels through the outer part of the compost leaving the centre dust dry. The only way to make sure of getting theevenly moist again is to stand the pots in water until it has soaked right through the root ball.
Plunging the pots as advocated above usually prevents the pots drying right out before they obviously need attention. Suitablemedia are coarse sand, river sand, fine gravel, or coarse peat fibre.
A further advantage of plunging is that the roots are kept at a lower and more even temperature than if the pots are fully exposed, and this will be reflected in steadier growth and healthier plants.
The surface of plunging material can be kept free of algae and liverworts by use of the recently introduced algicides which are now being advertised for that purpose. Mixed with coarse sand and spread over the plunging material between the pots, one application will ensure a clean ‘plunge’ for a season, and this again helps to maintain the health of the plants by allowing free movement of water and air.
The first principle in the potting department: is to maintain scrupulous cleanliness. The potting bench should be kept free of all except the potting materials, and these should 1w kept in tidy heaps.
Pots should be soaked if new, and allowed to dry off before using; dirty pots must be scrubbed out, inside and out, preferably before they are stored and not just before use. Dirty pots carry trouble. I do not like to think how many hours I have spent scrubbing out pots during my time, and I prefer to delegate the job nowadays. Used pots should be put in containers of water to soak as soon as they are out of use, and cleaned as soon as convenient. If plastic pots are used they too should be thoroughly cleaned before use.
Preparing the pots for use, except for the tiny ‘thimbles’ and `thumbs’, consists of providing adequate. In the case of plastic pots this is especially important as all excess moisture has to get away through the drainage holes and cannot evaporate through the pot walls. The object is to keep the drainage holes clear of potting soil, to allow free exit of surplus water.
In the case of plastics, which usually have a series of drainage holes near the edge of the pot base, crushed brick from which the dust has been removed by sieving, or suitably sized stone chippings, are placed in the pot bottom deep enough to cover all the holes — perhaps half an inch deep, finishing off with a layer of smaller chippings over which a layer of sphagnum moss or coarse sievings from compost is placed to prevent the finer soil washing through to clog the drainage.
In the case of clay pots, which usually have a central drainage hole, this may be covered first with a piece of perforated zinc to prevent the entry of worms or other sizeable pests. Over this a piece of broken pot large enough to overlap the hole by half an inch or so, is placed, concave side down. Now a collection of similar pieces is placed, concave side down, to cover the pot bottom adequately, then add smaller pieces to the required depth and finish off as before. Always place the crocks concave side down — like an umbrella, they are intended to shed the water. If left concave side up they will hold little pools of water which will tend to make the compost sour.
Three-inch pots should have half an inch of drainage, up to two inches in the case of six-inch pots, three inches in ten- to twelve-inch pots. This to the top of the moss or other roughage.
Except for use in the smaller pots, three-inch and less, compost should not be sieved through a mesh less than three-quarter-inch; for he larger pots it is better not sieved at all. Well-rotted turfy loam should be pulled into pieces of half an inch to an inch thick, according to the size of the pot. Any weed roots should be removed.
Flaky oak or beech leafmould should be rubbed through a one-inch sieve to get rid of any sticks and stones or bits of root.
Sand should be very coarse: river sand is good. Fine builders’ sand is no use at all, as it causes the compost to cake and prevents movement of water and air.
If peat must be used, a very fibrous or granular grade should be chosen. Fine dust-like peat is worse than useless.
A good standard fern compost is one part by volume of good loam, two parts of leafmould and one part of coarse sand. To each bushel of mixed compost should be added a six-inch potful of granulated charcoal, a three-inch potful of hydrated lime, and a two-inch potful of John Inns base, all thoroughly mixed together. When lime-haters are to be potted, omit the lime altogether. The compost should be moist enough to hold its shape when a handful is squeezed and released, but break up again into crumbs when dropped on the potting bench. If too moist it will pack too hard in the pots, if too dry it will not compact enough.
A pot should be selected barely large enough to accommodate the roots of the fern to be potted. A little compost is dropped over the drainage, then the fern is held with one hand and gently turned about as the compost is added by the other hand, so that it runs down amongst the roots, until the pot is full to the brim. With the first and second fingers of both hands press down the crown of the fern and tap the pot on the bench so that the soil settles, firming it with the thumbs.
When finished the soil should be half an inch below the pot rim, with the fern crown flush with the soil level, so allowing space for watering. Ferns should not be potted very hard; they root more freely in light spongy compost, but they should be fairly firm, and quite steady.
After the preliminary watering, and plunging in the case of the smaller pots, ferns should be lightly shaded and not watered again until necessary. Overwatering of newly potted ferns which have not had time to make new roots leads to rapid souring of the soil with consequent damage to the roots, which actually may die.
When there is some suspicion that the soil is becoming sour and the plants not making any headway, it is as well to repot into fresh soil possibly into smaller pots in order to get the ferns growing again. On the other hand, newly potted ferns, or any for that matter, must not be allowed to dry out, as no ferns, except a few highly specialized species, will tolerate dryness at the root.
Knowing when and when not to water is an acquired skill, based on experience, and must be learned by observation. Feeling the top of the soil is some guide, but if the plants have been insufficiently watered not long before it is quite possible for them to appear quite damp on top and yet be dust dry below. Tapping the pot is quite a good guide in the case of clay pots, using the knuckles or a light wooden mallet. If the pot responds with a dull sound it is damp enough, but if the sound is more resonant it may indicate dryness. Here again experience must be the guide. In the case of plastic pots, the lapping technique is not of much use. Plastic pots need much less watering than clay pots, but for that very reason they should be inspected regularly, especially when the weather is dry and sunny Where both clay pots and plastics are used it is by no means a bad plan to keep them separate on the staging, as it is all too easy to give a drop too much to plastics among clays.
When first I started using plastic pots my staff could not get used to the idea of leaving them alone until watering was necessary, and I lost a batch of two thousand young dwarf rhododendrons and azaleas entirely through overwatering.
I have recently purchased a handy little instrument called a `sprinkle-minder’, which, on being inserted into the soil in a pot, at once indicates on a scale the amount of moisture present and whether watering is required. The use of such an instrument prevents any uncertainty and eliminates bruised knuckles gained through a too enthusiastic performance of the pot-tapping technique.
The advice ‘when in doubt, don’t’ is very sound when applied to watering. If moss is allowed to grow on the pots it can be misleading, its green colour giving the impression that the soil below is quite damp, whereas it may be quite dry. The use of the new materials on offer for preventing moss establishing itself are well worth while, for a dense growth of moss on top of a pot will effectively prevent water getting through, if it gets at all dry.
When a fern gets potbound the soil becomes a solid mass of roots interwoven into a felt-like network impossible to disentangle without considerable damage to the roots, and if not given attention the fern will become stunted. Before this state is reached it is advisable to pot on into a larger size, or plant the fern in the border.
Repotting procedure is to knock out the plant, taking care not to damage the fronds, and then to work out the old crocks or drainage material with the aid of a bluntly pointed stick. Then, provided the root ball is not too wet, it should be rolled to and fro between the palms of the hands. This will loosen the root ball and allow more worn-out soil to be removed and also allow some teasing out of the roots. Then repot into a slightly larger pot so that the crown remains at the correct level, gently working down the soil with the aid of a wooden label or other handy piece of wood, until the plant is potted firmly, but not rammed down too hard.
The choice of a pot only slightly larger is important; if too large a pot is used with the idea of saving repotting again before long, usually the superfluous soil will get sour before the roots have taken possession and the last state will be worse than the first.
The plant may have made a number of crowns and it may be desirable separate these to increase one’s stock. In this case loosen the root ball as much as possible without unduly damaging the roots, then with a sharp knife separate the crowns and gradually work them apart so as to keep as much root as possible to each division. Then pot up the pieces in pots just large enough and no more, having trimmed away any moribund or damaged roots and frond bases; water, and keep shaded for a few days.
The use of a couple of old table forks, back to back, with the prongs carefully inserted between the crowns, sometimes does less damage than cutting and pulling apart.
Repotting can be done at any time except in mid-winter. Spring and early autumn are the best times, but if a plant is looking sickly at any time, it is best to turn it out and give it a fresh start whatever time of the year it happens to be.