Actual size and flowering may vary slightly based on season.
Bougainvillea Barbara Karst
Barbara Karst is a vigorous bougainvillea with magenta-red color in flushes from late spring through fall. Staked, it climbs a wall, fence or arbor to about 10 to 15 feet in the Valley. As a bush, it can be pruned into a shrub. It loves summer heat, takes reflected heat off hot walls and needs little water once rooted. Full sun brings out the brightest color.
Best for: covering hot west and south walls, fences and arbors, pruned shrubs in sunny beds, and big patio pots.
The staked form goes against a hot wall or fence and grows to about 10 to 20 feet tall in time. It does not cling, so tie the canes to wire or a trellis as they grow. Plant 6 to 8 feet apart along a long run.
The bush form can be kept as a shrub about 3 to 6 feet tall and 4 to 6 feet wide by pruning after each bloom flush. Give it the sunniest spot you have for the brightest color.
It grows well in a large pot with drainage holes and a free-draining mix. A pot is easy to cover on frost nights and keeps fallen bracts in one spot. Water when the top 2 to 3 inches dry.
Frost around 28 to 32°F burns the leaves and stems, though it usually regrows from the roots. The canes carry sharp thorns, and fallen bracts blow around, so keep it back from pools, paths and play areas.
- Along a wall or fence6-8 ft apart
- Low hedge (bush form)4-5 ft apart
Water regularly until it is rooted, starting often and spreading out to about once a week. Once established, water about every 7 to 10 days in summer and about once a month in winter. Let the soil dry between soakings.
Do the main pruning in spring after frost danger passes, and light trims after each bloom flush. It blooms on new growth. Tie staked canes to the support as they grow, and wear gloves and long sleeves.
Cover it with frost cloth, not plastic, on frost nights. A freeze drops the leaves and it rests until spring. Do not prune the damage until new growth shows.
Give one light feeding in spring and none in winter. More fertilizer means more leaves and fewer flowers.
Small green or brown inchworms chew ragged holes and leave black droppings, mostly at night. Healthy plants recover, so save BT for young plants or heavy damage.
Drainage test first. Dig the hole and fill it with water. If water is still sitting in the hole a day later, you likely hit caliche, clay or hard soil, so fix the drainage before planting. If it drains very fast, the soil is sandy. Standing water around roots is a common reason new plants fail.
Weed cloth. Cut it away from the planting hole and where the roots will spread. Remove any plastic sheeting completely, since it keeps water and air out of the soil.
Rock or decomposed granite with no soil underneath. Bring in soil close in texture to your native soil, mix it with the soil below, and build up enough depth for roots before planting.
If you can break through. Use a breaker bar, pick, or jackhammer. Dig through the caliche and break out the solid chunks. Backfill with the soil you dug out, with no compost or manure in the hole. Confirm drainage before planting.
If you cannot break through. Dig narrow holes through the hard layer beside the root ball, not under it, and refill them with the same soil, not gravel. If it still will not drain, plant on a low mound of the same soil.
Root ball. Check the outside edges for any roots circling around. Loosen or cut those so they grow outward. Do not break up the center of the root ball.
Depth. The top of the root ball should sit at or just slightly above the surrounding soil level. Planting too deep can lead to rot and kill the plant.
Drip emitters. At planting, put the emitters on the root ball, on different sides of the plant. After about 2 months, move them to the outer edge of the root ball. Over the first year, add emitters farther out toward the edge of the branches as roots grow. Once a plant is rooted, never water only at the trunk.
What color is Barbara Karst?
It has magenta-red bracts that come in flushes from late spring through fall. Plant it in full sun for the brightest color.
How big does Barbara Karst get?
Staked on a wall it reaches about 10 to 20 feet in the Valley, and more on a big support. As a pruned bush, keep it about 3 to 6 feet tall.
Should I buy the bush or the staked form?
Buy staked for a wall, fence or arbor, since it is already trained upright. Buy the bush form for a bed, hedge or pot you plan to keep pruned.
How cold hardy is it?
Its roots survive to about 20°F, but the leaves and stems burn around 28 to 32°F. Cover it with frost cloth, not plastic, on frost nights.
When should I prune off frost damage?
Wait until frost danger has passed, usually by March in Phoenix, or until new growth shows. Then cut back to just above the new growth.
How often should I water it?
Water regularly until it is rooted. After that, about every 7 to 10 days in summer and about once a month in winter, letting the soil dry between soakings.
Why is it all leaves and no color?
Too much water or fertilizer keeps it growing leaves. Water less often and feed only once, lightly, in spring. Drier soil pushes it into bloom.
How should I plant it?
Handle the root ball gently and do not break it apart, since the roots are fine and do not like to be disturbed.
How far apart should I plant it?
Plant them about 6 to 8 feet apart along a wall or fence, or 4 to 5 feet apart for a low hedge of the bush form. The Spacing tab shows the numbers.
Can I plant it by the pool?
Keep it back from the pool. The papery bracts drop and blow around, and the canes are thorny.
Is it safe for dogs and cats?
It is not known to be poisonous to pets. The sharp thorns are the main risk, so keep it off dog runs and paths.
What is eating the leaves?
Ragged, chewed leaf edges with small black droppings usually mean bougainvillea loopers. Healthy plants handle it, so only treat young plants or heavy damage with BT.
Bougainvillea Barbara Karst for sale in Arizona, delivered to you
Barbara Karst is a widely planted bougainvillea known for its magenta-red color and love of summer heat. Its roots survive to about 20°F. This page covers bush vs staked, size, spacing, watering, pruning after frost and how to get more color.
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Barbara Karst bougainvillea in Phoenix
Barbara Karst is a magenta-red bougainvillea that loves summer heat and takes reflected heat off hot walls. It blooms in flushes from late spring through fall, and its roots survive to about 20°F.
Bush vs staked Barbara Karst
The staked form is trained upright for walls, fences and arbors. The bush form is kept as a shrub by pruning, for beds and pots. Both are the same plant.
How big does Barbara Karst get?
On a wall it reaches about 10 to 20 feet in the Valley, and 8 to 10 feet wide. Pruned as a bush, it stays about 3 to 6 feet tall.
How far apart to plant bougainvillea on a fence
Plant about 6 to 8 feet apart along a wall or fence. Tie the canes to the support as they grow, since bougainvillea does not cling.
When to prune bougainvillea after a freeze
Wait until frost danger has passed, usually by March in Phoenix, or until new growth shows. Then cut back to just above the new growth.
How often to water bougainvillea in summer
Once it is established, water about every 7 to 10 days in summer and about once a month in winter. Too much water gives you leaves instead of color.
Why is my bougainvillea not blooming?
The usual cause is too much water or fertilizer. Water less often, feed it lightly once in spring, and give it full sun.
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