Northern California Coastal & Inland Valleys
Feed roses after they have completed their first bloom cycle. Use a balanced slow-release fertilizer and mix in some chelated iron for good measure. Dibble the dry fertilizer into the surface of the soil, then water. Repeat every four to six weeks during the summer.
Prune Spring-Flowering Shrubs
The very best time to prune spring-flowering shrubs is right after they finish blooming. Lilac, forsythia, redbud, weigela, and spiraea all respond well to late-season pruning, plus you get to enjoy the maximum number of flowers. If you had pruned in the fall, you would have lost a major portion of the bloom.
Treat Plants to Moo Tea
I like to give my plants a variety of fertilizers. I wouldn't want to eat spaghetti every day and figure plants don't want the same thing all the time either. One of the fertilizer treatments I use is Moo Tea. I fill the leg of an old pair of panty hose with steer manure and place it in a 5-gallon bucket of water overnight. The following morning, I pour the solution into a watering can and apply it to my annuals, vegetables, and perennials. Everybody at my house seems to like tea time!
Be Alert for Insects
May brings warm weather and hatching insects. As the soil warms, insect eggs hatch and come to life with a voracious appetite. This is the time of year when armyworms, tent caterpillars, grubs, and whiteflies make their seasonal debut. The best offense is a good defense, so be on the lookout for insect signs. If you only have a few insects, live and let live. If you notice an infestation, rake the area clean, wash the foliage, and treat with a soap and oil spray.
Watch for Aphids on Roses
Aphid will suck the life out of your rose plants. Look for them on tender new growth or on unopened buds. To control aphids organically, use a strong jet of water to wash the insects off the foliage. If that doesn't do the trick try releasing ladybugs, which are eager consumers of aphids. If the ladybugs don't work, the next step is to use insecticidal soap mixed in a small spray bottle. Always use the least toxic method of treatment first. If that doesn't work, go on to the next step. Treat roses in the morning hours so the plants have time to dry off during the day.