Blue Moon is a selection of American wisteria bred to survive harsh northern winters while still producing hanging lavender-blue flower clusters.1Henderson Garden Supply. Blue Moon Wisteria Cold tolerance is the main reason northern gardeners choose Blue Moon over Asian wisterias, because cold winters are less likely to kill its flower buds. It is gentler and smaller than the Asian wisterias many people picture, though it is still a vigorous vine that needs real support. Growing it well is mostly a matter of steering that vigor into flowers rather than leaves, through sunlight, pruning and restraint with fertilizer.
Where to Plant Blue Moon Wisteria
Blue Moon blooms best in full sun.2Missouri Botanical Garden. Wisteria macrostachya Blue Moon Aim for at least 6 to 8 hours of direct sunlight a day for heavy flowering.3The Sill. Blue Moon Wisteria In too much shade it grows weak and produces fewer flowers.4The Sill. Blue Moon Wisteria
Before you dig, watch how the sun moves across the spot over a full day. South- or west-facing walls and fences usually give the most sun. Keep the vine a few feet from house foundations, gutters and any windows it could climb into, and plant where you can reach it easily, since you’ll be pruning twice a year.
Soil matters more for drainage than for richness. Blue Moon grows best in slightly acidic, humus-rich, moderately fertile soil that stays moist but drains well.5Missouri Botanical Garden. Wisteria macrostachya Blue Moon It adapts to clay, loam and sandy soils as long as water doesn’t sit around the roots.6Henderson Garden Supply. Blue Moon Wisteria In strongly alkaline soil it can develop iron chlorosis, which shows as yellowing leaves with green veins.7Utah State University Extension. Wisteria in the Garden Avoid low spots where water pools after rain.
On planting day, dig a hole about twice as wide as the root ball and no deeper. Mix compost into heavy soil to improve drainage, and set the plant at the same depth it grew in its pot. Water deeply right after planting, then mulch around the base without letting the mulch touch the stem.
What to Expect From Blue Moon Flowers
The vine grows about 15 to 25 feet long.8Missouri Botanical Garden. Wisteria macrostachya ‘Blue Moon’ Its flowers come in hanging clusters 6 to 12 inches long of fragrant, pea-like lavender-blue blooms.9Missouri Botanical Garden. Wisteria macrostachya ‘Blue Moon’ The main bloom arrives in June in many areas.10Missouri Botanical Garden. Wisteria macrostachya ‘Blue Moon’ The flowers along each flower cluster open at about the same time, which gives a dramatic display.11Missouri Botanical Garden. Wisteria macrostachya ‘Blue Moon’
Once established, Blue Moon can bloom up to three times in one growing season.12Missouri Botanical Garden. Wisteria macrostachya ‘Blue Moon’ After the first big show, you can expect smaller flushes of flowers through summer.13Heyden’s Gardens. Wisteria ‘Blue Moon’ The clusters attract bees, butterflies and hummingbirds,14Nursery Management. Wisteria macrostachya ‘Blue Moon’ and the vine is a significant nectar source for bumblebees.15Henderson Garden Supply. Blue Moon Wisteria Avoid spraying insecticides while it’s flowering, to protect the pollinators visiting it.
Repeat blooms depend on the vine being established, not newly planted. A young plant may grow leaves and shoots for a year or more before it flowers well, so patience in the first seasons is normal and not a sign of failure.
Why Blue Moon Wisteria Won’t Bloom
- Too much shade, below the 6 hours of direct sun needed to form buds16Missouri Botanical Garden. Wisteria macrostachya Blue Moon
- A plant that is too young, especially one grown from seed17Missouri Botanical Garden. Wisteria macrostachya Blue Moon
- Pruning that removes the shoots where buds form18Missouri Botanical Garden. Wisteria macrostachya Blue Moon
- Too much fertilizer, especially nitrogen, which pushes leaves instead of flowers19Missouri Botanical Garden. Wisteria macrostachya Blue Moon
Wisteria raised from seed can take up to 20 years to flower.20RHS Gardening. How to grow wisteria Buy a named Blue Moon plant from a nursery instead.
Each cause has a fix. Move a young vine to a sunnier spot, or thin overhanging branches. Switch to the twice-yearly pruning routine described next, and stop nitrogen feeding, including lawn feed nearby. If the plant is simply young, give it another season before giving up.
How to Prune Blue Moon Wisteria
Blue Moon doesn’t need pruning to bloom.21Spring Hill Nursery. Blue Moon Reblooming Wisteria But holding back leafy growth and encouraging short flowering shoots produces more flowers.22RHS Advice. Wisteria Pruning Guide Shortening side shoots focuses the plant’s energy into forming buds along those short shoots.23UC Agriculture and Natural Resources. Pruning Wisteria
In July or August after flowering, cut the long whippy green shoots of this year’s growth back to five or six leaves.24RHS Advice. Wisteria Pruning Guide This keeps the vine out of gutters and windows and pushes it to set flower buds instead of more green growth.25RHS Advice. Wisteria Pruning Guide Because Blue Moon reblooms, make this cut after the main flush rather than before it. Lightly trimming a few shoots between flushes is fine.
In January or February, when the vine is bare, cut those same shoots back further to two or three buds.26RHS Advice. Wisteria Pruning Guide Space the side shoots about 12 inches apart to leave room for the flowers.27UC Agriculture and Natural Resources. Pruning Wisteria That way flowers next season won’t be hidden by leaves.28RHS Advice. Wisteria Pruning Guide Avoid heavy cutting in fall, which removes next year’s buds.
In winter, flower buds are fatter and rounder than the slim, pointed leaf buds, and they cluster near the base of the short flowering shoots. Leave the fat buds when you make the cut.
Use clean, sharp bypass pruners. Choose a few strong main stems to train along the support and keep them, and remove shoots that grow toward the house or off the structure.
If an established vine has never been pruned and is a tangle, start with the winter cut, when the bare stems are easiest to see. Begin by removing anything dead, broken or crossing the main framework. Cut the long whippy shoots back to two or three buds, but don’t try to fix years of neglect in one season; spreading the cleanup over two winters is gentler on the vine. The following summer, begin the post-flowering cut so the vine gets used to the routine, and expect flowering to improve once the short flowering shoots build up.
Watering and Feeding Blue Moon Wisteria
Water regularly through the first growing season so the roots establish.29Henderson Garden Supply. Blue Moon Wisteria After that, established vines prefer soil that stays moist but never waterlogged.30Missouri Botanical Garden. Wisteria macrostachya Blue Moon
The first summer, water deeply once or twice a week rather than lightly every day. Check the soil a few inches down before watering. A layer of mulch holds moisture and reduces how often you need to water.
Wisteria pulls its own nitrogen from the air, so it usually doesn’t need extra nitrogen.31Utah State University Extension. Wisteria in the Garden Avoid fertilizers that contain nitrogen.32Plant Addicts. Wisteria Care Added phosphorus can help blooming if your soil is short of it, but many soils already have enough.33Utah State University Extension. Wisteria in the Garden A soil test before feeding tells you whether phosphorus will help.
The three numbers on a fertilizer bag stand for nitrogen, phosphorus and potassium, in that order. Choose a bag where the first number is low or zero. Bloom-booster products typically have a high middle number.
The visible result of surplus nitrogen is a lush, dark green vine with long shoots and few or no flowers. Runoff from a fertilized lawn reaching its roots can have the same leafy effect.
Supporting a Blue Moon Vine
The vine twines around its support and becomes heavy and woody with age, so it needs something strong enough for 15 to 25 feet of growth. Sturdy arbors, pergolas or heavy-gauge wire on a wall work better than light trellises. Install the support before planting so roots aren’t disturbed later. If you use wall wires, leave a small gap between the wires and the wall for air and pruning access. Set wood or metal posts firmly in the ground, and anchor any wall attachment into solid material, not just the siding.
Tie the main stems loosely to the support as they grow. Guide shoots sideways along wires, since horizontal stems tend to flower more. Check ties each year so they don’t cut into thickening stems, and keep the vine off downspouts and trees it could damage.
Is Blue Moon Wisteria Poisonous
The whole wisteria plant is considered poisonous because of the toxic compounds it contains.34Plantura. Is wisteria poisonous? The seeds and pods carry the most of these toxins.35Pollinator Patch App. Is Wisteria Poisonous to Dogs? Yes (ASPCA): Watch the Pods If children or dogs play nearby, pick off seed pods after flowering.
Dry pods may split open, sometimes with a popping sound, and scatter the flat seeds on the ground, so check under the vine as well as on it. Removing pods before they mature and cleaning up fallen ones takes away the part of the plant most likely to be eaten.
If someone does eat part of it, signs of poisoning commonly include vomiting and stomach upset. Call poison control or a vet promptly rather than waiting for symptoms, and bring a piece of the plant or a photo to help identify it.
Pests and Diseases to Watch For
Insects that feed on wisteria include Japanese beetles, aphids, leaf miners, scale and mealybugs.36NC State Extension Plants. Wisteria Diseases include dieback, crown gall and leaf spot.37NC State Extension Plants. Wisteria
Look over the new shoot tips and the undersides of leaves in spring and summer, and you’ll catch insects before they build up. Scale shows up as small bumps stuck to stems, and mealybugs look like tiny bits of white cotton in leaf joints. Chewed or lacy leaves with beetles on them are a sign of Japanese beetle feeding.
Aphids cluster on new shoot tips and can be hosed off with water. Hand-pick Japanese beetles into soapy water in early morning. Cut out dead or dying stems back to healthy wood. Good sun and air flow reduce leaf spot.
Growing Blue Moon in a Pot or From Cuttings
Wisteria tends to flower better when its roots are a bit crowded in a pot.38Bonsai Empire. Care guide for the Wisteria Bonsai tree Choose a large, heavy container, but don’t rush to repot.
Roots in pots are more exposed to cold than those in the ground. In winter, move pots against a sheltered wall or into an unheated garage. Potted vines also dry out faster and need more frequent watering.
Cuttings produce new plants identical to the parent, while seedlings may not be.39Plantura. Wisteria: flowers, characteristics & propagation You can layer stems in summer, take softwood cuttings in spring to midsummer, or take hardwood cuttings in winter.40RHS Gardening. How to grow wisteria Skip seed, which brings both slow flowering and uncertain results.
To layer, bend a low flexible stem to the soil. Nick the underside and bury that section with soil. Keep it moist until roots form, then cut it free and replant.