Crocus care tips for December
Rooting for more plants
Some plants are easy to propagate from root cuttings taken at this time of the year.
Some herbaceous plants (and a few woody ones too) don’t root readily from stem cuttings and do not respond well to regular division. Fortunately though, many can be propagated very easily from small pieces of root. Propagating from root cuttings can also be a good way of getting healthy offspring from a distressed parent. For example, phlox that are debilitated by killer eelworm, can be replaced with healthy and vigorous young plants by taking root cuttings. Unfortunately, this does not work with plants suffering from virus diseases though.
If you want to raise a lot of new plants you will have to dig up the donor plant so that you can select the best roots before replanting. But if you want just one or two new plants, you can locate suitable material on an established plant by simply excavating the soil on one side to expose a proportion of the roots. This is the best way to treat Eryngiums, because they resent root disturbance.
Preparing root cuttings
Wait until the plant is fully dormant before digging it up. In mild areas this may mean waiting until December or even January. Trim back any top growth and remove as much of the soil as you can from around the roots without damaging them. If this is difficult, try plunging the root ball into a bucket of water to wash off the soil and leave to drain. Then select undamaged young fleshy roots, carefully trimming them from the parent plant as close to the crown as possible. The selected roots can then be cut up into sections. Roots of about pencil thickness should be trimmed into pieces about 5cm long for rooting in pots and double this length for rooting direct in the border outside. Using a razor-sharp knife, make a straight cut at the end of the cutting that would have been nearest the crown (the top of the cutting) and an angled cut at the end nearest the tip of the root. In this way you can produce several cuttings from each root and be able to tell which way up to insert them later on.
You can help prevent losses due to disease by dusting the cuttings with a fungicidal powder before insertion. The most convenient way to do this is to gently shake the prepared root cuttings in a polythene bag containing a little of the powder.
Insert the prepared cuttings vertically into pots of cuttings compost with extra grit added for sharp drainage. Each cutting should be planted at 5cm intervals with the top of the cutting (the section with the straight cut) approximately 1.5cm above the surface of the compost. Then cover the compost with a 1cm deep layer of grit. Water well and leave to drain. Place the pots of cuttings in a coldframe or heated propagator set at 10oC.
Herbaceous plants to try
Acanthus, Anchusa, Anemone x hybrida, Brunnera, Catananche, Centaurea, Crambe cordifolia, Dicentra, Dictamnus, Echinacea purpurea, Echinops, Erodium, Eryngium, Geranium endressii, Geranium macrorrhizum, Geranium sanguineum, Gypsophila paniculata, Lamprocapnos, Limonium latifolia, lythrum, Macleaya, Nepeta, Papaver orientale, Phlox (not variegated varieties), Primula denticulata, Stokesia, Trollius, Tropaeolum and Verbascum.
Other plants to try
Ailanthus, Aralia, Bignonia, Campsis, Catalpa, Celastrus, Chaenomeles, Clerodendron, Paulownia, Rhus, Robinia, Romneya and Rubus.
Skinny roots
Some plants, including Aemone, Phlox and Trollius, do not produce roots of pencil thickness, but they can still be propagated from root cuttings, trimmed to about 8cm long. Do not worry about making different cuts at each end, because these will be laid horizontally in the seed tray, before covering with a thin layer of compost.
Trick of the trade
Younger roots are more successful than older ones, so many gardeners swear that you get better results by lifting the plant the year before you intend to take root cuttings and trimming back any thick and unusable roots to the crown. After replanting, new roots are produced which will be the perfect size for turning into root cuttings the following season. Being young and vigorous also means they will root more readily. Another technique is to sink pot-grown plants into a bed of sand, then remove and use any roots that spread outside the pot.
