April 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)
• Some of your cool-season annuals may still be going strong, especially along the immediate coast. If so, leave them in. Otherwise, it’s time to replant these with warm-season varieties.
• Warm-season annuals should be in abundant supply and in all sizes right now. Choices include petunias, lobelia, verbena, marigold, ageratum, cosmos, impatiens, coleus, torenia and begonias.
• If you are in a warm inland garden this is the first good month for planting the real hot weather sizzlers like dahlias, zinnias, gomphrena, cleome, portulaca and lisianthus.
• 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.
• Many azaleas are blooming now. For these blooming plants be cautious of getting the flowers wet from overhead watering or a late season rain.
The flowers will turn to mush with water on them, especially pure white hybrids.
• Azaleas are nearly dormant while they are in bloom, so this is an excellent time to plant them. Since they are also in bloom, the selection is excellent as well.
• They don’t really require any pruning, but if you do need to shape them or reduce their size a bit as soon as they finish blooming is the best time to do it.
• Most bearded iris are now developing flower buds or even blooming.
• Apply another application of a good well-balanced, general-purpose organic fertilizer to them this month and the flower production will be even better. Any fertilizer labeled for roses (by not with insecticides or other added ingredients) will do fine.
• Trim off the faded flower stalk just above the foliage when the last flower fades.
Bulbs, rhizomes, tubers, etc
(See also Bearded Iris, Dahlias, Cannas and Tuberous Begonias)
• Bulbs that are in bloom in most parts of Orange County now include most alliums (late in the month), anemone, babiana, bletilla (just starting), calla, chasmanthe (finishing up), crocosmia (formerly called montbretia), daffodils, Dutch Iris, freesia, hippeastrum, hyacinth, iphieon (finishing up), ixia, narcissus, nectaroscordum, ornithogalum, ranunculus, scilla campanulata, sparaxis, sprekelia, tritonia, tulips and watsonia (just starting.
• If you didn’t last month, plant or re-plant dahlia tubers now (see Dahlias).
• This is the first opportunity to plant caladium. These need to be started when the soil is warm. Tuberose need even warmer soil, so wait at least another month for them.
Bulbs, rhizomes, tubers, etc (Cont.)
• Bedding cyclamen, although not generally referred to as a bulb, are still in full bloom, but are beginning to show signs of heat stress, especially in inland gardens.
• 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. These will not return reliably next year.
California Native Plants
• Some of these will still be blooming and growing well, but many other will already be slowing down and preparing for the long, hot and dry summer months.
• 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
• Some Japanese Camellias may still be in full bloom. Be sure to keep the old flowers picked up underneath the plant to eliminate the occurrence of a disease called Camellia Petal Blight (a fungal disease that causes the petals to turn brown and mushy).
• As soon as your camellia has finished blooming is the best time to do any shaping or other pruning to the plant.
• Apply your first of three feedings to your camellia about 4-6 weeks after it finished blooming. Use an “azalea/camellia” or acid based fertilizer, like cottonseed meal. Apply a light application (camellias are not heavy feeders) evenly around the base of the plant, but do not dig it into the soil. Camellias (and many other plants) have very delicate surface roots within the top inch of soil that are easily damaged by cultivation. You will feed again 4-6 weeks later and then you final feeding 4-6 weeks later again.
• They should be growing well this month, but probably won’t be blooming quite yet. Keep them fertilized with a general, well balanced organic fertilizer to help them along.
• Clematis are continuing to grow well and quickly now. Keep feeding them with a balanced organic fertilizer to keep them going.
• Most varieties will be blooming and those that are not should be heavily budded.
• Help them as they grow by guiding their fragile stems or carefully tying to the arch, trellis or obelisk as they grow.
Dahlias (tuberous types)
• Finish up planting (or re-planting) any dormant tubers. Choose a full sun location and drop a little fish bone meal or bone meal into each hole before planting.
• For tall varieties, put stakes in now, to avoid damaging the roots later.
• Keep newly planted tubers moist, but be careful not to overwater until growth shows above the soil.
• When the foliage is a few inches out of the ground begin fertilizing. Use a liquid or granular organic fertilizer that is low in nitrogen and high in phosphorus. Fish Bone Meal is excellent.
• When the stems are about eight or ten inches tall pinch off the top set of leaves. This will encourage the plant to branch and have more blooms.
Image by Audrey
• You should have stopped pinching at the end of last month. Now you want your plants to grow out and begin flowering. If you pinched and fertilized regularly over the past couple of months your plants will be very full and set loads of flowers.
• Now that you are getting your plants ready to flower it is time to switch fertilizers. Put away the high nitrogen-high growth fertilizer that you were using and begin using a fertilizer that is more balanced or even slightly higher in phosphorus, to promote blooms.
• Keep the plants well watered, especially during a warm spell.
• Watch for Fuchsia Gall Mites, which are a serious pest of these plants. 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 are growing well now and may even be showing some blooms.
• If you didn’t apply fertilizer last month be sure to this month. Use a fertilizer with lots of trace minerals, such as most organic types and alternate with an acidic formula to keep the pH down.
• This is a great month to apply a good dose of an iron supplement to your plants. Iron only works well in warm soil temperature, so applying it now will have a significant benefit to the gardenias.
• 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 should be blooming well now. Remove spent flowers to the bottom of the stem regularly to encourage more blooms.
• Fertilize 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.
• 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.
• Stop pinching Martha types (but keep feeding) and allow them to go into full bloom. Remove spent flower clusters regularly just below the flower to encourage more blooms.
• This is the month that budworms usually begin attacking. They primarily feed on the developing buds, but also feed on new leaves as well. If necessary, spray with BT on a regular basis beginning now.
• Rust may appear about now, especially on Zonal and Martha varieties. First seen as small brown clustered and raised spots on the undersides of the foliage this is nearly impossible to control chemically. However, it is generally a short term springtime issue and can be managed through proper culture. Fresh air circulation, adequate sunlight and keeping the foliage dry in the evening are suggested.
• This is still a good time to take healthy three to four inch tip cuttings to propagate all varieties. For best results use sterile shears, let the cutting “cure” for a few hours in a dry shady area and root them in clean potting soil and clean pots. When thoroughly rooted plant them into the garden to replace old, tired and woody plants.
• These are continuing to wake up from the cool winter months and should be putting on nice new growth. They are growing nicely and a few may even be beginning to bloom.
• Apply a m
• Moderate feeding.
• Do not prune hydrangeas at all this time of the year. Hydrangeas bloom on one-year-old stems. Pruning now will eliminate most of the flowers.
• If you want to try to get blue or lavender flowers on your otherwise pink plant you need to continue applying Aluminum Sulfate to the soil. White flowered varieties will not be effected and not all pinks will be effected the same.
• Most cymbidiums are wrapping up their bloom cycle this month. Continue feeding with a high phosphorus fertilizer through the end of their bloom period.
• After your cymbidium has finished blooming
• As epidendrum orchid flowers fade, cut the individual stems to two or thee buds above the soil. This will keep them blooming almost year-round.
• Keep feeding epidendrums with a low nitrogen/high phosphorus fertilizer.
(See also Bearded Iris, Bulbs/Rhizomes/Tubers, Cannas, Dahlias, Fuchsias, Geraniums, Ornamental Grasses and Tuberous Begonias)
• There is a myriad of new and interesting plants at nurseries this month. A slow walk through the nursery now will stimulate lots of exciting plant possibilities.
• This is a good planting month for perennials. The selection is good and many will be in bud or bloom.
• 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.
• See separate entries for bearded iris, bulbs/rhizomes/tubers, cannas, fuchsia and ornamental grasses.
• Most of your perennial “chores” should have already been done and you can now enjoy your perennials in all their colorful glory.
• Sub-tropical perennial are beginning to perk up now. This is also a good month to plant these. These include begonias, heliotrope, impatiens, lamium, pentas (starflower) and plectranthus.
• By now most of the perennials that completely withdrew to below ground for the cool winter months have sprouting from the soil again. Some of the last perennials to sprout that you should still be on the lookout for include caladium, calla (colored types), chocolate cosmos and some true lilies (lilium).
• Tall, upright, spiking perennials like dahlia (tuberous perennial types), delphinium, foxglove (digitalis), kniphofia (red hot poker), liatris, true lilies (lilium), monkshood (aconitum), oriental poppy and most thalictrum (meadow rue) should have stakes in place to support the flower stalks and prevent breaking. Tie the stalks to the stakes as they grow.
• Removing the myriad of spent or old flowers regularly always helps them to produce more new flowers. This is a good time to cut some fresh flowers for a vase as well.
(See also the information under the individual plants)
• Trees, shrubs, perennials, flowers, vegetables.
• This is another good month to plant warm-season flowers from color pacs or small pots. Good choices for putting in the ground now are marigolds, lobelia, petunia, ageratum, alyssum, cosmos, verbena, coleus, begonias and impatiens. It is still a month or two too early for the super heat lovers like zinnia, portulaca, vinca, and lisianthus (eustoma).
• Cool-season flowers like primrose, pansies, violas, Iceland poppies, bedding cyclamen, stock and snapdragons are still going strong. Keep these fertilized and deadheaded.
• Potted holiday poinsettias should be outdoors by now. They may be looking pretty rough now.
• If you didn’t last month, cut the tops off to two or three buds near the base (probably about 3-4 inches high).
• Gradually transition to plant to a full sun location.
• Begin fertilizing the plant with a well balanced food and new growth will begin sprouting from the dormant buds at the base of the plant.
• Roses are making their first big bloom this month. This “first bloom” is the most spectacular of the entire year. The flowers will be huge and the color rich. The flowers will hold well in the cooler temperatures of April and the foliage should be lush and healthy as well. Enjoy the show.
• Continue fertilizing roses. They are heavy feeders. 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.
• Granular, well-balanced, organic fertilizers work especially well for roses and most of these will encourage beneficial soil life.
• Begin deadheading roses as they fade. The rule of thumb is to prune to just above a leaf with five leaflets. Floribunda’s, many English roses and some others are deadheaded on very short stems until the last of the flowers in the cluster have faded. Then cut down to just above the first leaf with five leaflets.
• Be on the lookout for pests. Aphids can usually b hosed off with a strong jet of water. Flower thrips may require an insecticide.
• Keep on the lookout for diseases. Powdery mildew and rust are the primary concerns. Regular grooming, early removal of infested leaves, good air circulation and full sun will help considerably.
• If diseases do require a fungicide, use one of the newer, safer, organic products available. These include Rose Defense (a neem oil extract), E-Rase (jojoba oil) or Saf-T-Cide (straight paraffinic oil).
• Potted roses are in good supply and the selection is excellent now at the nursery. It is a good time to add more or upgrade any that you are struggling with.
• Make notes now in your garden journal about which roses are performing well and which are now. Notes on disease tolerance will be useful later if you decide to switch to improved varieties.
• One of the most obvious pests, especially in coastal gardens is now beginning to show up. Commonly called “Rose slug”, it is not a slug at all, but the larval form of a fly relative, called a Sawfly. These tiny little caterpillar-like pests are hard to spot, but feed by chewing on the undersides of foliage. Eventually, irregular holes are eaten through the leaves. Neem oil will work on them as will organic Pyrethrin sprays, but the application must be thorough and applied to the undersides of the foliage.
• Irrigations will be more frequent now as the weather warms and the days lengthen.
• For the biggest flowers pinch out some of the competing buds while they are very small.
• Weed as needed, but avoid most herbicides around roses.
• These should still be in full bloom about now. Keep the flowers trimmed regularly to encourage more flowers. This may be as often as twice a week. Sweet peas are one of the plants that really benefit from having their flowers trimmed.
• Feed regularly.
• Assist them with climbing and support if necessary.
• Tubers should be sprouting in the flats that you put then into last month.
• When there is about two to three inches of growth on each tuber gently scoop it out of the stay with a spade and a bit of soil under it. Place it into a basket, pot or well drained bedding area where it will grow and bloom for the rest of the summer and into the fall.
• Begin fertilizing. Tuberous begonias are heavy feeders, especially in containers. Use a well balanced fertilizer and periodically mix in an acid fertilizer, since these prefer a low soil pH.
• 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.
• Most of these will be over their bloom peak and beginning to look a little stressed. You may be able to extend their season a bit with some additional irrigations.
• If you want some of your wildflowers to re-seed for next year, leave them in place for a while and allow the seed to fall to the soil.
• This is the main month of bloom for wisterias. If proper pruning was followed all year, established plants should be in full, glorious bloom now. Enjoy.
• No pruning now or you may interfere with the blooms.
• Select and plant new wisterias now, while they are in bloom. Grafted plants are preferred, since they will almost always bloom at a much younger age.
• There is still no need to fertilize now and irrigation is only needed on young, newly installed plants.