In the north, June is the first totally frost-free month and bedding plants and half-hardy plants may be set out. In most years, watering is necessary this month. In dry weather, water hanging baskets and containers daily, flower beds and vegetables weekly, but shrubs and deeprooted plants should not require additional water.
Weed growth continues to be rapid – hoe the soil regularly. As soon as bedding plants become established, start giving a weekly foliar feed. Deadhead perpetual-flowering plants to encourage further blooms. After the main spike of delphinium, foxgloves and lupins start to die, cut the spike back to a bud or the new emerging secondary spikes to encourage their development.
Feed roses with a proprietary rose feed and if necessary spray with combined fungicide and pesticide. When cutting roses, take the stem back to near the leader, cutting back to a leaf joint. A new flower-bearing stem will then develop from the bud in the leaf axil.
Seeds of perennials and biennials that can be sown outside include Aurinia saxitilis (syn. Alyssum saxatile), aubrietia, aquilegia, Canterbury bells, coreopsis, delphinium, gaillardia, honesty, lupin, phlox, statice and wallflowers. Plant hanging baskets and containers. Stop planting outdoor chrysanthemums half-way through the month.
Remove the dead blooms of shrubs that bear their flowers on the tips of the stems. Only prune them if they are overgrown or if there is any weak, spindly growth.
Forsythia and other shrubs that bear flowers along the stems of the previous year’s wood should be pruned back now to encourage new wood, which will ripen to produce blooms next year.
Strawberries and fruits grown against walls should be protected from birds by covering with netting. Begin propagating strawberries by pinning down one runner per plant from two-year-old plants. After three year-old plants have finished fruiting they should be dug out. Mulch raspberries, tayberries and cultivated blackberries to encourage strong new canes for the following season.
Open windows and the door during the day but close at night, especially at the beginning of the month. Damp down the floor in the morning to keep the house cool and humid. Raise pot plants including primulas, calceolarias and schizanthus from seed.
As semitender subjects such as fuchsia and geraniums are placed outside, use the room vacated to propagate them and other plants that require warm condition.
Tomatoes will be in flower but the first truss often produces only a small crop owing to poor fertilisation. The remedy is to touch the blooms with a camel hair brush until the pollen comes away and transfer it to another flower. After the first truss has set there will be sufficient natural
agents present for the pollination of other blooms.
Pests and diseases
Keep a sharp lookout for pests and diseases and treat before they have a chance to become established.
Any green algae present from replanting should be beginning to clear itself. If it does not, check the pH balance of the pond.
Plant outdoor tomatoes. Ideally they should be grown against a south-facing wall, but if this is not possible set in rows running east to west so that they receive day-long sunlight. Start removing side-growths immediately they are large enough to remove. Pinch out the tops of broad beans to discourage blackfly.
Set out marrows, pumpkins and ridge cucumbers. Sweetcorn plants raised in the greenhouse can be set out in blocks. Plant out Brussels sprouts, all winter greens and leeks. Continue to sow peas, dwarf beans, carrots, beetroot, spinach, turnips, endive and lettuce. Harvest early potatoes and continue to earth up late varieties.