Dahlias (Fam. Compositae) rival chrysathemums for their variety of form, size of flower (ranging from the size of a paper-weight to that of a dinner plate) and height of the plant. These half-hardy perennials are now a part and parcel of any proud gardenerís collection anywhere. They are able to adjust to a variety of climate except extreme cold or heat.
Dahlias can be grown in separate beds of distinct colours, borders or even in pots. A sunny open site, sheltered from strong winds, is advisable and the ground should be well dug up to 18 in. to 2 ft. deep. Good drainage and sandy loam enriched with organic manure give best results. However, the distance for planting will vary according to the height of the variety ranging from 18 in. apart for dwarf-bedding varieties to 3-4 feet apart for double decorative and giant ones. The following are the well-recognised varieties:
*Single dahlias have a single row of florets with a prominent central disc. These are generally grown from seed.
*Star dahlias have two or three rows of pointed petal with a central disc.
*Anemone-flowered are single dahlias with tubular elongated florets and a central disc.
*Collarette dahlias have flowers with one or more rings of flat ray-florets and an inner ring or collar of shorter florets.
*Peony-flowered dahlias are with two or more rows of ray-florets and a small disc and are graded as large (over 7" across), medium (5-7 in. across) and small (less than 5 in. across).
*Double-Decorative dahlias show no disc and have long broad ray-florets, which are flattish or slightly twisted but usually blunt at the apex. They are graded as:
(i) giant with over 10 inches across blooms
(ii) large with 8-10 in. across flowers
(i) medium with 6-8 in. across blooms
(ii) small with 3-6 in. flowers and
(iii)miniature with less than 3 in. across flowers
*Pompon dahlias have flowers like double decorative but the flowers are less than 3 in. across size.
*Catus dahlias have double flower heads with no disc showing. The ray-florets are usually narrow and pointed with edges twisted. They are also graded as giant, large, medium, small and miniatureóranging from more than 10 in. across to less than 3 in. across.
*Dwarf bedding dahlias are not exceeding 2 ft. in height and can have characteristics of the above-mentioned flower heads.
Dahlias are planted in mid-July to September in plains of northern India; in March-April in the hills; in May-June in Bangalore and in October- November in Chennai. Seeds may be sown about the same time as planting of tubers or a little earlier. While seeds are sown 2" apart in seed pans and the seedlings transplanted when about 2" high, the true-to-name varieties may not come out of them. Vegetative propagation by tubers or cuttings is more reliable and widely preferred.
The vegetative buds, from which new growth develops, appear on the collar of the last yearís stem. While buying new tubers, take care to select the ones showing certain swellings round the ring or collar of the stem. These should be planted about 3-4 in. deep, keeping in mind the distance according to the ultimate height of the plant. Or else dahlias can be raised well from rooted cuttings. Staking with strong stakes is also advisable at this stage only. All the plant shoots should be tied loosely and separately to keep the plant attractive.
Dahlias need much more warmth than chrysanthemums and for good growth temperature not less than 12 degree centigrade would be ideal. For potted dahlias, it would be a good idea to remove them to sunny verandas or other shelters to protect them from frost.
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 dying. Cut down to
about three inch above ground level and store inside a box covered
with dry earth, sand and sawdust in a dry, cool place. They may be
sprinkled with flowers of sulphar.