The finest Asters are frequently grown in the open air, entirely without the aid of artificial heat, and indeed without any special horticultural appliances.  Those who possess the best possible resources will find additional advantage in resorting also to this mode of culture.  It gives another string to the bow, and prolongs the season of flowering.  For open-air sowings in April make the soil level and fine, and about the middle of that month draw drills three inches deep.  In these place an inch of finely prepared rich soil, and if it is largely mixed with vegetable ashes, so much the better.  The distance between the drills should be regulated by the variety.  For tall-growing Asters twelve to fifteen inches between the rows will not be too much.  Ten inches will suffice for the dwarfs.  Sow the seed thinly and evenly, and cover carefully with fine soil.  Commence early to thin the plants, always leaving the strongest, and arrange that they finally stand at from eight to fifteen inches apart according to the sort.

Keep the ground clean, and before the flowering stage is reached gently stir the surface, but not deep enough to injure the roots.  An occasional application of weak manure water will be advantageous, but it must not be allowed to touch the foliage.

For tall varieties it may be needful to provide support.  If so, place a neat stick on that side of the plant towards which it leans, as this takes the strain off the tying material, and saves the plant from being cut or half-strangled.  In a dry season, and especially on light soils, there must be a bountiful supply of soft water, alternated every few days with the manure water already alluded to.  Evening is the best time to apply it.

For show purposes rather more room is required than we have stated.  Only about five buds should be matured by each plant, and these, of course, the finest.  To prepare flowers for exhibition is in itself an art, and each cultivator must be guided by his own resources and experience.

Asters in pots make excellent decorative subjects.  It is only necessary to lift them carefully from the borders with balls of earth surrounding the roots, and pot them just before the buds expand, or they may be potted up while in full flower without flagging.

The plants are liable to the attacks of aphis, both green and black.  While under glass the pests can be destroyed by fumigation; but in the open a solution of some good insecticide may be administered with the syringe at intervals of about three days, until a clearance is effected.  Other foes are the various grubs which attack plants at the collar.  On the first sign of failing vigour, gently remove with a pointed stick the soil around the plant, and in doing this avoid any needless disturbance of the roots.  Do not be satisfied until the enemy is destroyed.

==Aubrietia==

==Hardy perennial==