Southern gardeners have to be especially watchful at this time when it comes to insect pests, plant diseases, and drought. Northern gardeners should be watchful for these problems, too, but not to the same degree.
All Regions
Remove suckers from tomato plants. Prune shrubs that bloom on old wood after they are done flowering. Be on high alert for insect pests and diseases. These include but are not limited to aphids, asparagus beetles, cabbage worms, cutworms, tomato hornworms, scale, snails, slugs, leaf spot, mildew, and rust. Use mature compost or aged manure to side-dress plants. Prune wisteria after it finishes blooming. Place row covers or netting over bushes with ripening berries to keep the birds from eating them. Inspect plants for damage from four-lined plant bugs (Poecilocapsus lineatus). Inspect trees for nests of bagworms. Inspect plants for Japanese beetles (Popillia japonica), including roses, gourds, pumpkins, and squash.
Mid-Atlantic
Expect highs in the low- to mid-80s F and lows in the mid-50s to mid-60s. It is likely to rain 10 or 11 days this month. Take advantage of any dry, cooler days to stay ahead on your gardening chores.
Keep an eye out for pests such as groundhogs and rabbits so that they do not get to your harvest before you do. Plant squash, cucumbers, pumpkins, and gourds outside. Plant members of the nightshade family if you haven’t already. Divide spring-flowering bulbs while you can still tell where they are. Mark the location of any that you will be dividing in fall, instead, before their foliage dies back. Plug gaps left behind as spring bulb plants and early-blooming perennials, such as Pasque flower, disappear with annuals.
Midwest
You have a good chance of getting rain every third day in June in the Midwest. That is just about right to keep your plants happy but not so much as to keep you from getting your gardening tasks done. Be sure to work on the good days, though, unless you do not mind being wet while working.
Monitor potential June bug (Phyllophaga longispina) damage. To prevent them from wasting energy on producing seed, deadhead your spring bulbs after they are done blooming. Also, fertilize them. But wait till the leaves have yellowed before trimming them off. Plant members of the nightshade family outside if you have not already. Plant cucumbers, beans, squash, and gourds outside.
Northeast
Most days, it is still pleasant to work in the garden in June. But sudden heatwaves are possible; save beach trips for those days, and perform necessary garden tasks on the cooler days.
Monitor potential June bug (Phyllophaga longispina) damage.To prevent them from wasting energy on producing seed, deadhead your spring bulbs after they are done blooming. Also, fertilize them. But wait till the leaves have yellowed before trimming them off.Plant beans, squash, melons, gourds and cucumbers and make trellises for their vines to grow on.Plant members of the nightshade family outside if you have not already.Direct sow seeds for annuals outside.
Pacific Northwest
In June you get relatively little rain in the Pacific Northwest. The average high is 71 F and the average low 53 F.
Fertilize your annuals. Inspect daylily plants for the daylily gall midge (Contarinia quinquenotata). Its larvae feed on the buds of daylilies, distorting their appearance. Remove such distorted buds, bag them, and dispose of them properly (not in the compost pile). Plant beans, squash, melons, gourds and cucumbers and make trellises for their vines to grow on. Plant members of the nightshade family. Divide any patches of spring bulbs that you feel are starting to peter out. Deadhead them first, but leave the foliage alone until it yellows. Pick ripe strawberries. Plant summer-flowering bulbs such as dahlias.
Pacific Coast
June is sunny and dry in Northern California. The average high in San Francisco, for example, is 66 degrees F, the average low 53. Southern California is predictably warmer, with an average high of 78 degrees F, and an average low of 60 degrees F.
In Northern California
Stake your tomatoes, mulch them to help keep the soil evenly moist, and fertilize them with a low-nitrogen fertilizer. Keep an eye out for diseases (especially fungal diseases) ad insect pests on your rose bushes. Keep them fed and keep their soil evenly moist (mulching helps). Ensure that your automatic irrigation system is working properly.
In Southern California
Continue to direct sow the seeds for warm-season vegetables (beans, melons, squash, etc.). Ensure that your automatic irrigation system working properly. Fertilize your roses. Fertilize citrus and avocado trees.
Southwest
In the high desert, daytime temperatures will be quite hot, but the nights can be relatively cool. In Santa Fe, New Mexico, for example, expect an average high of 84 degrees F and an average low of 49 degrees F; you will get about six days of rain. It is a different story in Phoenix, Arizona, where you will have an average high of 104 degrees F, an average low 77 degrees F, and hardly any rain.
Ensure that your automatic irrigation system working properly.Mulch wherever possible to conserve moisture.Harvest your date palms (Phoenix dactylifera).
Southeast
It starts to become quite hot in June in the Southeast. Georgia, for example, has an average high of 86 degrees F and an average low of 68; this state will get 10 rainy days in June.
Watch for fungal disease and pests. Stake tomatoes, if you haven’t already Ensure that your automatic irrigation system working properly. Fertilize and deadhead your roses. Some perennials that bloom late in the growing season, such as Joe-Pye weed, can get so tall that they flop over. Either stake them or trim them back by half to keep them tidier.
