|Sunday, September 19, 2004|
Named after Swedish botanist Andrea Dahl, dahlias (family compositae) were introduced to Europe in late 18th to early 19th century.
In northern India, planting is done between July and September in the plains and between March and April in the hills. Seeds may be sown a little earlier than the planting of tubers and rooted cuttings. At high altitudes, they have to be protected from frost and may not do well in very hot and dry places.
Depending on the height, form and size of the flower, which may range from a button to a dinner plate, dahlias are classified as single, stair, anemone-flowered, cactus, peony-flowered, double-decorative pompon, dwarf-bedding and double giant or fancy.
Dahlias can be grown in separate beds of distinct colours, borders or in pots, but a sunny open site, sheltered from strong winds is required. The ground should be well worked, at least one-and-a-half to two feet deep. They grow in any kind of soil with good drainage but sandy loam enriched with organic manure gives best results.
Dahlias can be grown from seeds, tubers or cuttings. Seeds are sown 2" apart in seed pans or nursery beds and seedlings transplanted when they are about two inch high. But you may not get very true to name varieties from seeds. They may be a mixture of single, cactus and decorative etc. And may grow to different heights as well. Vegetative propagation i.e. by tubers or cuttings is more reliable for show purposes.
A vegetative bud, from which new growth develops, appears on the collar of the last year’s stems. If you had a collection of dahlias from last year and had them stored, along with a portion of the stem (about three to four inches), you may divide the tubers with a sharp knife, in such a way that each part has a growing bud on it or buy them with a portion of the stem showing certain swellings round the ring of stem. These tuberous divisions may be grown in pots or planted. They should be planted at a depth of about three to six inch and the spacing of plants should be equal to their height. They should be staked stoutly at the time of planting to avoid bruising of the tubers later on.
A nice mixture of potted dahlia would be three parts garden soil, two parts sand, two parts leaf mould, two parts farmyard manure and 1/4 part charcoal. Water plentifully soon after planting and then sparingly till shoots emerge out of the soil. Remove all but the strongest shoot. Water liberally as growth progresses and liquid manure may be supplied at regular intervals once the buds appear. A light top dressing with a chemical nitrogenous mixture is good.
For exhibition blooms, rub off the side buds keeping only the middle one. The blooming period may last for about two months. After the flowering is over, reduce the supply of water gradually till the blooms start drying. Cut down about three inch above ground level and store inside a box covered with dry earth, sand and sawdust in a dry cool place.
Dahlias are also grown in ground or pots from the rooted cutting in much the same way as from tubers. If you want to have your own cuttings from the tubers, start the tubers by placing them in a soil compost or moist sand, when the shoots reach two to three inches of height, they should be detached at the base and inserted in a pure sand and taken care of like cutting of other kinds of plants.
Dahlias suffer from few diseases, though they are affected by powdery mildew and mosaic-aphids and thrips. Diseases could be checked by preventing water-logging, over-crowding and growth of weeds. For aphids and thrips, any insecticide like Rogor or Ekatin may be used once in the early stages of growth. You can even spray weak tobacco. Slug can be prevented by sprinkling wood ash or soot around each plant.