June Gardening Checklist: Flowers & Flowering Plants cover

June Gardening Checklist: Flowers & Flowering Plants


With the help of many gardening friends I have attempted to offer on these pages some useful information to help you with your own garden. Gardening is sharing. Any corrections, comments or suggestions are appreciated and will improve future information. Flowers and Flowering Plants are the focus of this NoteStream. Also see our NoteStreams on Fruit Trees, Edibles, and more.

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June Gardening Checklist: Flowers & Flowering Plants

Fellow Gardeners,

The information, dates and techniques in this blog are as accurate as I can currently offer. During the past three decades I have cared for, nurtured and observed tens of thousands of plants.

With the help of many gardening friends I have attempted to offer on these pages some useful information to help you with your own garden. Gardening is sharing. Any corrections, comments or suggestions are appreciated and will improve future information.




• (See also Sweet Peas and Wildflowers)

• This is a month for warm-season annuals. The nights are consistently warmer, the days are longer sunnier and the thermometer is rising.

• Warm-season annuals are in abundant supply now. If you didn’t get them planted in the last month or two then get them planted now, before the really hot weather of July or August. Choices include celosia, petunias, lobelia, verbena, marigold, ageratum, cosmos, impatiens, coleus, torenia and begonias.

• Some real hot, hot, hot weather sizzlers are dahlias, zinnias, gomphrena, salvia, portulaca, cleome and lisianthus. This is a good month to plant these, since they absolutely love hot temperatures.

• Because of their quick growth and heavy flowering potential, annuals need more fertilizing than most other plants in the garden.

• Keep deadheading (removing spent flowers) from annuals to help them continue blooming abundantly.



• Keep azaleas well irrigated now that the weather is warming up.

• Azaleas are shallow rooted and will dry out quickly. Avoid cultivating or allowing other plants to grow under or in competition with the roots of your azalea.

Bearded Iris:

Bearded Iris:

• They should have finished their first bloom by now.

• Trim off the faded flower stalk just above the foliage when the last flower fades.

• If you are growing any of the new “repeat-blooming” varieties they may cycle again in as little as another month or two. Keep feeding these re-bloomers aggressively. Older “once-blooming” varieties can have their feeding reduced in half. Any fertilizer labeled for roses (by not with insecticides or other added ingredients) will do fine.



Bulbs, rhizomes, tubers, etc

(See also Bearded Iris, Dahlias, Cannas and Tuberous Begonias)

• Spring bulbs are long finished flowering by now, but several warm-weather varieties are putting on a good show now in Orange County. These include some alliums, calla (in cool and moist situations), galtonia (summer hyacinth), gladiolus, hippeastrum, many true lilies, tigridia (recommended), tritelleia (recommended) and watsonia.

• Caladium are continuing to sprout and grow nicely now. Keep them watered and fertilized and in bright but indirect light and sheltered from winds.

Bulbs, rhizomes, tubers, etc (Cont.)

• Now that the soil is very warm it is still a good time to plant tuberose tubers that you bought at the nursery in January or February, or from those you dug out of your garden last November. Give them a sunny site and slightly acid, well drained soil.

• As spring bulbs finish blooming do not hurry to cut back the foliage or ignore the plant. Keep the leaves in place and continue watering until the leaves naturally turn brown and dry, then you can cut them off. These leaves are sending energy to the bulb for next season. Of course, for one-year bulbs like most anemone, crocus, hyacinth, muscari, ranunculus and tulips, after they are done blooming, pull them and toss them out.

California Native Plants

California Native Plants

• Be very cautious irrigating most of our native plants during the summer.

Most of these are adapted to a winter wet – summer dry moisture cycle. Too frequent irrigations now (especially in soils with a clay content) will certainly cause problems.

Image by M. Dolly

(CC BY-SA 2.0)




• You will probably be toward the middle or end of your camellia fertilizing for the year. The first of three feedings to your camellia should have been applied about 4-6 weeks after it finished blooming. The second feeding is 4-6 weeks after the first and the final feeding is 4-6 weeks later again.

• If you did not apply a thick, fresh layer of organic mulch under your camellias last month do it now. This mulch will keep the roots cooler during the warm summer months, improve the soil quality and reduce watering requirements.

• Except for a couple of late blooming Japanese camellia varieties, they have finished their bloom period for this year.

• Keep camellias well irrigated now that the weather is warming up.

• Camellias are shallow rooted and will dry out quickly. Avoid cultivating or allowing other plants to grow under or in competition with the roots of your camellia.



• They should be flowering well now.

• Keep them well watered, cannas do not like dry soil.

• As cannas flower you may notice that each stalk produces a cluster of flowers at the top. After this cluster finishes the stalk grows a few more inches and produces another cluster. In some varieties, this can go on for four or five clusters and last almost two months from beginning to end. When the last cluster of flowers has finished, cut the entire stalk to the soil. This stalk will never bloom again and cutting it down will encourage more stalks, and flowers, to grow. Keep this process up all summer for the best results.



• Many clematis are still blooming. Keep them well fed with a balanced organic fertilizer to keep them going.

• Clematis prefer cool roots, especially during the summer months. If you can, grow another shrub directly to the south of your clematis to provide some shade over the roots. Alternatively, place a large decorative pot on the south side of the plant.

• To insulate the roots even more and moderate the warm summer soil temperatures maintain a thick 3-4 inch layer of organic mulch over the roots at all times, especially now.

• As the weather warms up apply more frequent irrigations.

• If you are growing a spring-only flowering variety (not as common in Orange County), these should be pruned soon after their spring bloom is finished, which may be this month.



Dahlias (tuberous types)

• Plants should be in full bloom, robust and vigorous now.

• Regularly cut off spent blooms to make the plants both look better and set more flowers.

• Keep the taller varieties carefully staked to prevent the heavy canes from toppling over. Heavy natural cane bamboo stakes work well.

• Water regularly and deeply, especially as they grow larger and the weather warms. Flooding the soil works best; overhead watering will cause broken stems and mushy flowers. Missed waterings now will cause gaps in the flower development later in the season.

• Fertilize them regularly throughout their growing and blooming period. Use a liquid or granular organic fertilizer that is low in nitrogen and high in phosphorus. Fish Bone Meal is excellent.



Image by Audrey

(CC BY 2.0)


• Your plants should still be in full bloom now.

• Keep fertilizing regularly with a balanced fertilizer or one slightly higher in phosphorus, to promote blooms.

• Keep the plants well watered, especially during a warm spell and any plants in hanging baskets.

• During any particularly dry, hot and windy periods a couple of mistings of the foliage is very beneficial. If the soil is already moist from an early morning watering (best), be careful not to soak the soil again or you may encourage root diseases.

• Groom the plant periodically by removing dead flowers and any developing seedpods.

• Watch for Fuchsia Gall Mites again this month. These nearly invisible pests are a serious threat to fuchsias. Look for any signs of puckered or distorted new growth. If you discover any, pinch it out and dispose of it immediately. A pesticide treatment is usually required.



• Gardenias should still be blooming and growing well this month.

• Keep them well fed through the summer months. Use a fertilizer with trace minerals, such as most organic types and alternate this with an acidic formula to keep the pH down.

• If the leaves are showing signs of green veins with yellow areas between the veins, especially on the new growth, they need additional iron. Iron is a supplement to the regular fertilizing program of your gardenia.


• This group includes Ivy geraniums, Zonal geraniums (also called “Common” geraniums), Martha geraniums and the various scented geraniums, but does not include true geraniums (sometimes called “Hardy” geraniums), which are discussed under Perennials.

• Ivy and Zonal types are still blooming well now. Keep up with removing spent flowers regularly to encourage more bloom.

• Martha types have finished up their big spring bloom. Unlike Ivy and Zonal types these are not generally everblooming plants. With regular deadheading, a bit of shade in hot inland gardens and continued feeding you will be able to encourage a few more sporadic blooms through summer. Keep removing any spent flower clusters.

Geraniums (Cont.)

Geraniums (Cont.)

• Ivy and Zonal geraniums do not like heavy pruning.

To keep the plants shapely and vigorous for a longer period of time prune back a few long stems every month or so from now through fall, but never very many at one time.

Geraniums (Cont.)

• Continue fertilizing all geraniums, except most scented types, regularly with a balanced fertilizer. Geraniums prefer a slightly acidic soil, so periodically alternate feedings with an acid fertilizer, such as Cottonseed Meal.

• Budworms may still be attacking the developing buds and new leaves. If necessary, spray with BT on a regular basis.

• Rust may continue to be a problem in some gardens, especially on Zonal and Martha varieties. However, it is usually only a springtime issue and with the warm weather approaching should be about over.




• These should still be blooming.

• Keep feeding them in order to produce more new growth (which will bloom next year).

• Remove any flowers that have faded by pruning as far as half way down the stem below the flower.

• Only prune stems that have flowered this season; leave all other stems alone since they will flower on their branch tips next season.


(See also Bearded Iris, Bulbs/Rhizomes/Tubers, Cannas, Dahlias, Fuchsias, Geraniums, Ornamental Grasses and Tuberous Begonias)

• If you are planting perennials this month be sure to keep them well watered as these young plants head into the warm summer months. Also, try to avoid overgrown or root bound plants, as they will be harder to establish.

• Keep fertilizing your perennials. The frequency and amount will depend upon the formulation that you are using. If you have been building up your soil health your fertilizing duties will be much reduced.

• Removing the many spent or old flowers regularly will help them to produce more new flowers. Add these to your compost bin.

Perennials (Cont.)

Perennials (Cont.)

• Irrigating your perennials now is a bit more important than it was just a month ago. The heat of summer is approaching and there are no rains to help you out. Your perennials will respond well to careful irrigations now.

• Sub-tropical perennials are at their happiest now and over the next two or three months. This is a good month to plant these heat lovers too.



• You should have pinched the tips of the new growth last month. If not, do so right away.

• Keep fertilizing the plant often with a well balanced food to encourage growth.

• Watch for whiteflies and treat as needed.




• This is still a big bloom month, but by now the “first bloom” is about done and side branches are in bud and bloom. The flowers may be just a bit smaller, but still terrific.

• Old-garden roses (also called heirloom roses) only bloom on “old wood”. What this means is that they only produce flowers on the tips of the branches that were left in place from the previous summer. By contrast, almost all modern roses bloom on “new growth”.

Old-garden roses (popular examples are ‘Cecil Brunner’, ‘Grus an Auchen’, ‘Reine des Violettes’ and ‘Lady Banks’ Rose – Rosa banksiae) need their annual pruning immediately following their big spring bloom – about now. Do not prune these varieties again in the winter or you will eliminate most of the flowers for next year.

Roses (Cont.)

• Do not use soil-applied fertilizers combined with systemic insecticide. These products are very disruptive to soil life (beneficial microorganisms, bacteria, mycorrhizal fungi, earthworms, etc.). Many rosarians also believe they reduce the vigor of the rose.

• Another good month to get out and visit other rose gardens. Nearby, visit Rose Hills Memorial Park (Whittier) and the Richard Nixon Library (Yorba Linda).

• Roses are heavy feeders; continue fertilizing them regularly. Do not use soil-applied fertilizers that are combined with a systemic insecticide. These products are very disruptive to soil life (beneficial microorganisms, bacteria, mycorrhizal fungi, earthworms, etc.). Many rosarians also believe they reduce the vigor of the rose.

Roses (Cont.)

• Granular, well-balanced, organic fertilizers work especially well for roses and most of these will encourage beneficial soil life.

• Keep deadheading roses as they fade.

• Stay on the lookout for pests, although by now pests will be less of an issue.

• One pest that is quite common now, especially in coastal gardens, is the “Rose slug”. Not a slug at all, or a caterpillar, which it resembles, this is the larval form of a fly relative, called a Sawfly. These little green caterpillar-like pests are hard to spot, but chew on the undersides of foliage.

If you have them, by now you will see lots of irregular holes eaten through the leaves. Neem oil will work on them as will organic Pyrethrin sprays, but the applications must be thorough, frequent and applied to the undersides of the leaves.

Roses (Cont.)

• Disease problems, especially in inland gardens, should be much reduced by now and through the rest of summer.

• Irrigations should be frequent now as the weather warms and the days lengthen.

• Hose off the foliage of roses frequently. Contrary to popular myth, this will actually reduce the likelihood of powdery mildew and keeps the foliage clean and healthy looking.

• Weed as needed, but avoid most herbicides around roses.

Sweet Peas

Sweet Peas

• These are about done for this year. If they are still looking good and blooming then enjoy them. They will probably be showing a quite a bit of heat stress now, particularly at their bases where yellowing and drying will eventually become overwhelming.

• It is also common to have a lot of powdery mildew developing on the foliage this time of the year. Rather than attempt to control it, which will prove impossible, this is a sign that the season is about over for this year.

• If you have any particularly outstanding varieties you can attempt to harvest some seed and store it until this fall. However, Sweet Peas often do not grow “true” from their seed.

Tuberous Begonias

• Plants are still growing and should have buds and maybe even some flowers Some gardeners pinch out the first set or two of flowers to focus more energy on the growth of the plant.

• Most tuberous begonias produce both male (single) and female (double) flowers separately on the same plant. The double flowers are much showier and many people pinch off the single (male) flowers as they appear.

• Keep fertilizing regularly. They are heavy feeders, especially in containers. Use a well balanced fertilizer and periodically mix in an acid fertilizer, to keep the soil pH low.

Tuberous Begonias (Cont.)

• Keep them well watered, but not soggy. The soil should be rich and well-drained. The surface of the soil should dry slightly between watering.

• If in a breezy location, staking upright varieties with a small bamboo stake will reduce the possibility of breakage.

• Pinch off faded flowers regularly and rotate container grown plants to insure even growth.

• If powdery mildew appears treat it by improving air circulation around the plants. Usually this will correct the problem, if not use a fungicide.



• It is far too late for wildflowers now.

If you will be planting again this winter keep the area free of weeds between now and then. If the area is free of other plants do not water it. Irrigations will only encourage weed growth.



• On established plants, this is the time of the first of three annual pruning. A good schedule for these three prunings is June, August and December. This is the first pruning of the year. Cut any and all unwanted new growth to three buds above last years resting point. The point where the current years growth began and last years ended can be located by noticing the change in the stem/bark color. This pruning should be done to encourage flower bud development and to contain the size of the plant.

Wisteria (Cont.)

• Established wisterias are better with only an occasional deep summer watering and little, if any, fertilizer other than possibly iron (to correct chlorosis). Wisterias are large, aggressive vines; additional water and fertilizer will only create more rampant growth and more pruning needs.

• On young plants, continue guiding the long, twining stems carefully in the direction that you want.

• Also on young plants, be sure to provide plenty of water and fertilizer it to encourage quick coverage and deep roots.

• If you haven’t already, cutting off the small developing seedpods now will make a more attractive plant through the summer.