• Fertilize your late-spring flowering bulbs as soon as they finish blooming – use 5-10-5 or 5-10-10 fertilizer or a water-soluble fertilizer according to directions.
• Do not remove leaves from bulbs (or tie them in knots) until they have turned brown; however it’s best to deadhead daffodils and tulips to avoid them wasting energy on seeds you do not want.
• You can still scatter seed from cockscomb, portulaca, zinnia, cosmos, or small sunflowers for late-season bloom.
• Prune spring-blooming shrubs if not already done – azaleas, rhododendrons, forsythia, and spirea. Established plants can tolerate severe pruning if renovation is needed.
• Gap between ideal planting weather and summer heat is rapidly narrowing. You should mulch to protect developing roots from rapid dehydration.
• Remember to check new plantings through the summer. Trees and shrubs will need a good soaking every week through the first growing season. Herbaceous perennials will need regular watering at least for the first couple of months.
• Numerous summer-flowering plants, including echinacea, heliopsis, phlox, platycodon and veronica, among others, can be cut back to extend flowering of plant groups or to create staggered or delayed flowering.
• Bearded iris can be divided 6 to 8 weeks after they have bloomed e.g. in July or August. Remember to plant the rhizomes shallowly so that some of the top of the rhizome is exposed to sunlight. Siberian or Japanese iris can be divided in spring or fall when two months of below 90°F can be assured.
• Check needled evergreens for small bagworms. At this point they can be controlled with organic bacteria spray. By July you will have to use a more toxic insecticide or remove them by hand.
• Pinching back the growing tips on your chrysanthemums in early June (Memorial Day) and again around July 4th will yield a stronger, healthier, bushier flowering plant.
• Many plants, such as marigolds, zinnias, gomphrenas and even petunias will benefit from pinching to encourage branching.
• Avoid getting water on the leaves of annuals whenever possible. Powdery mildew can become a problem, especially on zinnias but can show up on a wide range of plants.
• Japanese beetles will arrive in late June. Handpick or use an appropriate insecticide. DO NOT use pheromone traps….they attract many more beetles than you would otherwise have.
• Continue to sow vegetables for a succession of summer crops. Plant out runner and french beans, leeks, tomatoes and peppers. Remember to water runner beans when they are flowering to ensure pods set well.
• Vegetable crops generally need another dose of fertilizer about 5 to 6 weeks after planting or when fruit starts to form.
• Vegetable gardens need one inch of water each week. Provide a good soaking if rain is not adequate. A rain gauge is a great gardener’s aid.
• Avoid blossom-end-rot (BER) in tomatoes, peppers, squash and watermelons by maintaining uniform soil moisture. BER is caused by inadequate calcium uptake by the plant and can be guarded against by incorporating calcitic lime, composted manure or bone-meal in the soil before planting. Be sure to not raise the pH above 6.5!
• Through June, you can still plant warm-weather vegetables including tomatoes, cucumbers, squash, green beans, winter squash and pumpkins.
• Be careful when harvesting. Use 2 hands to pull beans, cucumbers, squash, etc. to avoid breaking the plant.
• Check the label of all insecticides and fungicides before applying. Pay attention to the number of days to wait before harvesting and the crops and pests on the label.
• Try to mow frequently enough to remove no more than 1/3 of the blade at a time.
• Regular rainy weather will produce good conditions for brown patch, a fungus disease. If brown patches begin to occur, do not irrigate and do not mow when grass is wet as you can spread disease problems.
• Grass clippings left on the lawn are the best and cheapest way to return organic matter to the soil.
• Hanging baskets are especially prone to water loss. This is because they generally contain several different plants, all competing for the available water from a limited amount of soil. For this reason, hanging baskets require very frequent watering.
• Provide support for climbing plants, and tie in the shoots as they grow.
• As the summer progresses, shoots produced by shrubs earlier in the spring will begin to become firm and slightly woody towards their base. These shoots make good propagating material in mid to late summer.