Although the Dahlia is a tender plant, it is easily managed in a greenhouse, or in a frame resting on a hot-bed.  The seed may be sown as early as January, but unless sufficient space is at command to keep the plants stocky as they develop, it will be wise to wait until February.  A sowing in the month last named will produce plants forward enough to bloom at the usual time.  Even March will not be too late; but whatever time may be chosen, when the start has been made it must be followed up with diligence, so as to avoid giving any check from first to last.  Sow thinly in pots or pans filled with ordinary light rich compost, and cover the seed with a mere sprinkling of fine earth.  When the first pair of leaves attain the height of an inch, pot off each plant singly close up to the base of the leaves.  It is not advisable to throw the weakly seedlings away; these are the very plants which are most likely to display new shades of colour and they are worth some additional trouble.  Although weak at the outset, they may, by judicious treatment, be developed into a thriving and healthy condition.

When potted, place the plants in heat, giving a little extra care until growth is fairly started.  In due time shift into larger sizes as may be necessary, and then it will be wise to consider whether there is space to grow the whole stock well.  If not, do not hesitate to sacrifice the surplus, and in doing so reject the rankest-growing specimens, for these are least likely to produce a fine display of bloom.  It is mistaken practice to take out the top shoot, as this checks the plant for no good end; but when about six inches high, each one will need the support of a stick.  Give water freely, and air on all suitable occasions.  The least tendency to curled leaves indicates something amiss, and demands immediate attention.  A cold blast may have stricken the plants, or the soil may be poor; lack of sufficient water will produce the mischief, or it may arise from the presence of aphis.  If the last-named assumption prove correct, fumigate on the first quiet evening, and omit watering on that day.  The mere mention of the other points will be sufficient to show the remedy for them.

As the time for transfer to the open air approaches, all that is possible should be done to harden the plants for the change.  They may be placed for a few days under the shelter of a wall or hedge, but on the least sign of frost be prepared to protect with hurdles or mats.  Full exposure during genial showers and fair weather is advisable, and an occasional examination of the plants will prevent their rooting through the pots into the soil.

The border for Dahlias can scarcely be made too rich, for they are hungry and thirsty subjects, and will amply repay in a profusion of bloom the manure that may be lavished upon them.  Slugs and snails are unfortunately too partial to newly planted Dahlias, but the vermin soon cease to care about them; therefore it is advisable to plant Lettuces plentifully at the same time, or previously, on the same ground, and to dust around the Dahlias with lime.  Insert at least one stake, about a yard long, near each plant, to give support, and two or three others will have to be given before the branches spread far.  Secure the first shoot when planting is completed, and follow up the tying as growth demands.