Tips for Flower Gardening – Perennials – Methods of Increase

Flower Gardening – Perennials

flower gardening perennials

To become really efficient as a propagator when flower gardening, perennials in particular, takes time and patience. You must expect to learn from your mistakes. Many of these can be avoided, though, if you keep certain basic principles firmly in mind.

Briefly, I would say these are as follows:

  • Propagate only from completely healthy stock.
  • Observe strict hygiene at all times, and when pots, boxes or other containers are used make sure that these are absolutely clean.
  • Use sterilised loam in composts used as growing mediums. Propagate only at the right time of the year for the particular plant you want to increase, bearing in mind the method of propagation to be adopted.
  • Keep as close as possible to the correct temperature and humidity when propagation is being carried out under glass. This is a very important aspect of flower gardening.

Perennials Division

The most usual method of increasing herbaceous perennial plants is by division of the roots. This is an easy task to carry out and should be done in spring or autumn. There is no doubt that autumn is the best time to divide plants which do not establish themselves reasonably quickly, as they then have the advantage of a long growing season ahead. Kniphofias, Oriental poppies, peonies and alstroemerias – which resent being moved in any case and should be left undisturbed as long as possible – are a case in point.

Division, with some exceptions, is only necessary once every three or four years. By that time there will be a marked deterioration in the quality of the growths and flowers of the plants, and the soil will need improving by the addition of compost or other humus-forming material after a long spell without attentions of this kind. You should always take the opportunity to improve the soil when, on rare occasions like this, it is cleared of plants.

Many herbaceous plants can be divided merely by pulling them apart, the portions which are to be replanted having healthy looking roots and at least one shoot. These retained portions should always be from the outside of the plants, the older, woody centres being discarded altogether. Plants which form a mass of roots and which can be dealt with in this way include such favourites as the varieties of Chrysanthemum maximum (the Shasta Daisy), solidago and Michaelmas daisies.

Some plants, though, are made of sterner stuff and different tactics are necessary to cope with these. The large clumps consist of really rough roots and the best way here is to dig around the clump with a spade before lifting it out bodily with a garden fork. Then drive two forks back to back into the centre of the clump and split it by  pressing the fork handles outwards. From then on all will be plain sailing, with any roots which are reluctant to part being cut with a knife.

The parts which are to be replanted should be out of the ground as short a time as possible and they should be covered with sacking or some other material to avoid drying out by sun or wind. For this reason many gardeners like to renovate the border in sections, lifting and replanting, say, one third before starting on the rest. I have never found this necessary if the lifted plants are protected as suggested, but that is not to say that I do not consider it a good scheme to adopt.

In addition to the humus-forming material which I add at this time I apply a dressing of bonemeal, a good all-purpose fertiliser, or both. Bonemeal is an excellent feed but it is slow acting; it will still be there to assist the plants when the general fertiliser has been absorbed.

Softwood Cuttings

These, as the term suggests, are cuttings made from young shoots. They provide a very useful means of increasing numerous hardy and half-hardy herbaceous perennial plants, and suitable growths from which these can be made are normally available in spring and early summer or indeed at almost any time of the year under glass. This or some other means of vegetative reproduction is almost always essential with named, man-made varieties if we want the offspring to have identical characteristics to the parent plant.

To prepare such cuttings the procedure is as follows. Look for healthy, strong looking shoots between 2 to 3 inches long and remove these so that a clean cut can be made just below a node or joint. The lower leaves should also be removed. Pure sand or vermiculite can be used as the rooting medium (and indeed this is often desirable if the plant concerned is known to be what is called ‘shy-rooting’) or a mixture of sand and loam. If pure sand or vermiculite is used as the rooting medium, re-potting will be necessary as soon as the cuttings form roots. Plants which are known to be difficult to root can be treated with a growth promoting, root hormone preparation – available from garden stores – which will encourage the formation of roots, when applied as directed (it is essential that the manufacturer’s instructions should be followed closely). These preparations are obtainable with captan added as a protection against the diseases to which cuttings are prone.

The cuttings may be inserted in the selected rooting medium in either boxes or pots and are best stood in a propagating frame where the atmosphere can be kept suitably moist and the heavy initial moisture losses by the as yet unrooted cuttings can be replaced. Alternatively, insert them directly into the soil in a frame. Shade must also be provided against strong sunshine as in the early stages of growth this also can cause an excessive amount of moisture to be lost through the leaves of the cuttings.

As soon as the cuttings have formed a good root system they will need potting on and hardening off so that they will later be ready for planting in the border during the same season or for planting in the nursery bed for growing on.

Root Cuttings

Propagation by root cuttings is the best way of increasing many thick-rooted perennials like verbascums, Oriental poppies, phlox, anchusa and Limonium latifolium (Statice  latifolia. Some fibrous-rooted plants, like the gaillardias, may also be readily increased in this way. There is great latitude in the time when cuttings may be rooted by this method but for home gardeners spring and early summer, with months of good growing weather ahead, is probably the best time. Some gardeners find it an advantage, though, to put the cuttings in very early in the year, as by late spring hardened off young plants are available for planting outdoors.

To obtain the root cuttings, lift the plants from which they are to be taken and wash the roots. Then cut them into lengths of 1 to 3 inches, depending on the thickness of the particular roots. To ensure that the cuttings will be planted the right way up make the cut at the base end slanting (which provides the maximum rooting surface) or mark it with a distinctive nick. Then insert them in boxes of free-draining compost so that the tops are just covered, water them in and place in a garden frame or in a sheltered part of the garden. With plants like phlox which have thin roots it is usual just to lay them on the surface of the compost and cover with a thin layer of the same mixture. Once the cuttings have made growth they are potted on – or re-boxed – and grown on for subsequent planting out.

It is important to enjoy your plants and make the most of them, and propagation, as any gardener will tell you, is an important part of gardening.  Perennials can be propagated by these three methods, and as I said before, a little time and patience is required.

07. August 2010 by Dave Pinkney
Categories: Perennials, Propagating | Tags: , | Comments Off on Tips for Flower Gardening – Perennials – Methods of Increase


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