Summer is the time of propagation by stem cuttings. Many plants can be propagated by stem cuttings starting with softwood cuttings in late spring to mid summer and continuing with semi-ripe cuttings from late summer to early autumn.
If you are going to grow your own herbs from seeds next year than you will have to collect the seeds of annuals as they ripen. Collect seeds for use or sowing from annuals like: poppies, pot marigolds, nasturtiums, sunflowers, dill and coriander, and from biennials and perennials like: angelica, caraway, sweet cicely, fennel and lovage.
Clean the seeds, remove the husks and store in clearly marked paper envelopes. Never store the seeds in plastic containers as moisture will form and the seeds will rot or start into growth. Sow the seeds you have collected within a year of collection and angelica seeds within a few months as the seeds soon lose their viability.
Weeding and watering
Continue the weeding to prevent any undesirable plants to become established in your beds or borders. If you are growing any herb that selfseed you can allow some of them to selfseed and then to transplant the seedlings later. If necessary you should top up mulches to retain moisture around plants over the hot summer months.
Water well newly-planted herbs and any moisture-loving ones that may be suffering from drought. Do not forget to water containers daily, preferably early in the morning, as the restricted quantity of soil dries fast in hot summer days.
Harvesting and pruning
Summer is the time to make maximum use of fresh-cut herbs in the kitchen and to harvest leaves for drying for winter use. Collect the leaves for winter use before the plants have come into flower. For a second crop on leafy herbs such as lovage and mint you should cut them down to the ground level in early to mid summer, before they start to seed.
Cut back chive flowers and stems for new leafy growth and deadhead roses and annuals to encourage new blooms. Cut aromatic foliage and flowers for drying to make pot-pourri.
For plants with variegated leaves like variegated lemon balm you should cut any reverted stems to prevent the whole plant from reverting, as the reverted stem are stronger than the variegated ones.
Trim fast-growing herbal hedges like wall germander and cotton lavender as often as necessary to keep them in shape during the growing season.