Aug. 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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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 definitely a month for warm-season annuals, especially those that really love hot, hot, hot weather.
The nights are warm, the days are long and sunny, and the temperatures are high. Keep newly planted annuals well watered until they are thoroughly rooted. Choices include dahlias, zinnias, lisianthus, petunias, lobelia, verbena, marigold, ageratum, cosmos, gomphrena, salvia, New Guinea impatiens, coleus, torenia, portulaca and begonias.
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.
Continue to keep azaleas well irrigated now that the weather is warm.
Azaleas are shallow rooted and dry out quickly. Avoid cultivating or allowing other plants to grow under or in competition with the roots of your azalea.
This is a great month to dig, transplant and divide these.
Bearded Iris should be dug and divided about every four years (every two or three years for aggressive re-blooming varieties). If you are growing any of the new “repeat-blooming” varieties they may cycle again any time. Keep feeding these re-bloomers aggressively.
Older “once-blooming” varieties can have their feeding reduced in half. Any organic fertilizer labeled for roses (by not with insecticides or other added ingredients) will do fine. This is an excellent time to plant new bearded iris from rhizomes.
Bulbs, rhizomes, tubers, etc
(See also Bearded Iris, Dahlias, Cannas and Tuberous Begonias)
Even in the hot temperatures of August there are bulbs blooming now in Orange County. These include Amaryllis belladonna, eucomis (Pineapple lily), hymenocallis, some true lilies, urginia (Giant Squill) and tuberose. Fancy leaved caladiums are still doing great now. Keep them well watered and fertilized and in indirect, but bright light.
Plant bearded iris rhizomes now (see Bearded Iris). Plant fall blooming Colchicum (sometimes called “autumn crocus) and lycoris now, if you can find them in nurseries.
Amaryllis belladonna, commonly called “Naked Ladies”, can be dug and divided now if necessary. The best time to do this is after the flowers have finished, but prior to the foliage growing again this fall. However, only perform this chore if it is absolutely necessary since crowded condition provide better flowering.
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
Except for a few late-blooming varieties, you will probably be finished with 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.
Japanese camellias are about done with their “growth” cycle for the year and are now entering the period in which they set buds for next spring. Do not prune.
Sasanqua camellias have also finished their “growth” cycle for the year and are also setting buds for next spring. Do not prune. Continue to keep camellias well irrigated now that the weather is warm. Camellias are shallow rooted and dry out quickly. Avoid cultivating or allowing other plants to grow under or in competition with the roots of your camellia.
They should still be flowering well now.
Cannas are one of the longest blooming plants in a garden. Continue to keep them well watered in the hot summer weather, 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.
Clematis prefer cool roots, especially during the summer months.
Do all you can, especially during this month and next, to keep them sheltered from the heat.
To insulate the roots, maintain a thick 3-4 inch layer of organic mulch over them at all times, especially now. In the warm summer weather be sure to apply more frequent irrigations.
Continue fertilizing, to prepare the plant for potential late summer/fall blooms. Use a mild, organic fertilizer. If your soil is slightly alkaline (high pH) periodically alternate fertilizing with an acid product such as Cottonseed Meal.
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.
In the warm summer weather be sure to apply more frequent irrigations. Vigorous clematis varieties are still blooming. Keep them well fed with a balanced organic fertilizer to keep them going. If your soil is slightly alkaline (high pH) periodically alternate fertilizing with an acid product such as Cottonseed Meal. 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 still be in full bloom and enjoying the warm sunny weather. 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 throughout the hot summer months. Flooding the soil works best; overhead watering will cause broken stems and mushy flowers.
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. If powdery mildew appears on the lower leaves use organic Neem oil or E-Rase.
Your plants should still be blooming, although probably a bit less than a couple of months ago.
Keep fertilizing regularly with a balanced fertilizer or one slightly higher in phosphorus, to promote more flowering. Proper watering is still critical at this time of the year, especially for those plants in hanging baskets.
Water early in the morning or in the evening and check the soil moisture most every day. Never let the soil dry out completely. During a particularly dry, hot or windy period 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 will be encouraging root diseases.
Image by Audrey
Groom the plant periodically by removing dead flowers and any developing seedpods.
If your plants look gangly and unsightly try pruning them lightly. If you keep feeding them heavily they will put on new growth that you can pinch once or twice and then have a nice bloom again. Keep watching for any signs of Fuchsia Gall Mites 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.
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.
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 type, such as Cottonseed Meal.
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 through fall, but never very many at one time. Budworms may still be attacking the developing buds and new leaves. If necessary, spray with BT on a regular basis.
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, but may be look bit heat stressed. Keep up with removing spent flowers regularly to encourage more bloom. For the most part, Martha types have finished blooming for this year.
Martha types have finished up their big bloom for the year.
Unlike Ivy and Zonal types these are not everblooming plants. With regular deadheading, a bit of shade in hot inland gardens and continued feeding you may be able to coax a few more blooms through summer. 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.
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. Martha’s are done blooming for the year. Budworms may still be attacking the developing buds and new leaves. If necessary, spray with BT on a regular basis.
Most of the flowering should be about done. Even dried hydrangea flowers can be attractive on the plant as they change color and take on a unique appearance.
The first week of the month is about your last good chance to remove any flowers that have faded.
Pruning by then will still give the plant enough time to produce some new growth (which is where the flowers will be next season). Prune as far as half way down the stem below the faded flower. Only prune stems that have flowered this season, leave all other stems alone since they will flower on their tips next season.
Any pruning after the beginning of this month will interfere with the plants ability to bloom well next year. Don’t cut the plant again until next summer. Feed them one more time in order to produce more new growth (which will bloom next year).
Orchids (Outside Grown)
Keep feeding cymbidiums with high nitrogen to promote growth.
Be sure to keep them well watered in the warm summer months.
(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. Try to avoid buying 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 spent or old flowers regularly will help them to produce more new flowers.
This is especially important at this time of the year as many of these plants are attempting to set seeds.
Most of your time in the perennial garden now will be occupied with general cleaning, some trimming, lots of deadheading and mostly enjoying your garden.
The summer heat will take it toll on some plants while other will seem to grow even stronger.
Irrigating your perennials now is important. The heat of summer is bearing down on these plants and the plants will respond well to careful irrigations.
Begin preparing space now for new plantings, during the upcoming fall planting season.
Do not pinch or prune the plant. Keep fertilizing the plant often with a well balanced food to encourage growth.
Watch for whiteflies and treat as needed. Protect the plant from high winds to avoid breaking the stems. Keep the plants well watered.
Although they may still be blooming, the heat of this and next month are taking a bit of a toll on roses, especially in inland gardens.
A moderate summer pruning will really help revive your roses now and will encourage a big bloom display over the next few months. Early in the month is the best time to do this pruning. Remove about 1/3 of the plant and any crossing or awkward growth.
Be sure to fertilize well immediately after pruning. If you haven’t already, check the mulch layer under the roses and add more as needed.
Disease should not be much of an issue now, except along the immediate coast.
Rose slugs are still a problem, but should be less now. 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.
Roses are heavy feeders; continue regular fertilizing. Rather than use fertilizer/insecticide combinations (which severely disrupt soil life), use a well-balanced organic product.
Keep deadheading roses as they fade. Stay on the lookout for pests.
Rose Slug problems may be less by now, but spider mites like the warm, dry summer temperatures. Irrigations should be frequent and deep in the warm summer weather.
Hose off the foliage of roses frequently. Contrary to popular myth, this will actually reduce the likelihood of powdery mildew and discourages spider mites as well.
Seeds will be in good supply at the end of the month.
This is an especially good time to plant seeds of early-blooming (also called “short-day”) varieties that may bloom by Christmas. These varieties include ‘Winter Elegance’ (our favorite) and ‘Early Multiflora’.
Potted, blooming plants are now available in nurseries. Plants should be in full bloom.
Most tuberous begonias produce both male (single) and female (double) flowers separately, but on the same plant. Double flowers are much showier and many gardeners 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, especially during the hot summer months.
The surface of the soil should dry slightly between watering. 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 the wrong time to be thinking about wildflowers now.
However, if you will be planting again this winter keep the area free of weeds between now and then. If the area has no other plants in it do not water. Irrigations will only encourage weed growth.
If you want to get a head start on weed control in the wildflower area try this:
Irrigate the area lightly but several times a day for about 10 to 14 days. This will germinate many of the weed seeds. Once they germinate, control them with a either a very shallow Hula-Hoe (also called a “Wiggle Hoe”) or spray with a non residual herbicide like Roundup. Repeat the process a couple of times more before scattering the wildflowers, about November. You will then have far less weed seed germination.
Pruning established plants: Established wisterias need considerable pruning each year to encourage flowers and maintain a manageable plant. A good schedule for these three prunings is June, August and December.
This will be the second pruning of the year. First, prevent any new growth from twining around itself in a hopeless mass. Next, cut again (as you did in June) all stems to just above the second or third bud above last years resting point. This is easy to spot by noticing the color of the outer layer of the stem/bark.
Established wisterias need only an occasional deep summer watering and little, if any, fertilizer. However, iron is occasionally needed to correct chlorosis.
Training young plants: Continue guiding the long, twining stems carefully in the direction that you want.
Prune off any wayward stems completely at their source and eliminate stems that are tangling together. Make sure that the support you are training the plant onto is very strong, as wisterias are extremely heavy plants.
Also on young plants, be sure to provide plenty of water and fertilizer it to encourage quick coverage and deep roots. It is not unusual to have some random summer and fall flowers on wisterias, especially if you are following the pruning instructions given here.