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If you have a wilting buddleia it’s usually something I often see with newly planted buddleia and buddleia that have put on new growth in spring. Generally, it’s usually water related, either not getting enough, more on this below or drowning, often in clay soil with bad drainage.
Various things are to blame for the wilting of your butterfly bushes, and I will cover them below starting with the most likely:
Not getting enough water or to much water
Are they getting enough water?
A plant that does not have enough water is bound to wilt but also, a plant with too much will do the same. If the leaves are also starting to curl and crisp, this is often a soil its not getting enough water.
If your plant is wilting and the soil is bone dry, then the plant just needs water. Newly planted buddleia are often more affected than more established plants. I recommend watering newly planted buddleia at least once a day, even twice a day on very warm days. Remember that have a very limited root system when first planted so need watering right at the base of the plant. You could also consider getting an automated watering system.
After watering, put your fingers into the first couple of inches of soil and see if the soil is dry underneath. Often gardeners will give them a quick water and the soil looks wet on the surface but it’s dry underneath. The best way to water is to leave the hose pipe dripping at the base of the plant for 20-30 minutes. This will allow the water to get right down to the roots.
Are they drowning due to poor draining soil
If the soil is moist and the plant is still wilting, it could have been overwatered or you could have had a lot of heavy rain and it’s literally drowning if the water can’t drain away. The leaves are often limp and NOT crispy when they are suffering from too much water.
Roots sitting in waterlogged soils develop root rot, which as mentioned above, is fatal. Grow your buddleia in well-drained soils. If you have clay soil, mix in lots of horticultural grit and peat into the soil to improve drainage.
Does your buddleia have yellow leaves? learn what the problem might be in my guide here on why your buddleia leaves are turning yellow
Newly planted buddleia can sometimes suffer what is known as transplant shock, this could be caused by damage to the roots during planting or simply the plant being planted in a new position it’s not used to. They usually recover fairly quickly. If your buddleia was otherwise healthy, the drainage is good and you have watered them regularly, this could be the issue.
Buddliea grown in pots can often become root bound, this simply means that the roots have become so compact that there is no soil left in the pot and the pot is now just full of roots, usually very compact to the shape of the pot. The problem with this is twofold, there is no soil left around the roots so there are very few nutrients. The second problem is usually the cause of wilting, because there is very little soil left to maintain moisture for the roots, they suffer from lack of water and no matter how often you water them, it just doesn’t get to the roots as it simply runs around the compact roots or over the side of the pot.
The answer is to simply repot the plant into a larger pot and to only grow dwarf varieties of buddleia in pots that don’t get too large. Also, don’t forget to use a John Innes potting compost as it retains moisture better because it soil based.
Pest and Diseases
Your plants may be wilting because they are sick from fungal or bacterial diseases. Plants affected by diseases present symptoms in the stems, roots, or foliage; therefore, be on the lookout. Downy mildew, rhizoctonia, and root rot are common diseases that impact buddleias; however, root rot and rhizoctonia are fatal.
If your plants have powdery mildew, spray with a fungicide at the first signs of infection and remove badly affected leaves.
Severely affected plants usually need to be removed and destroyed and don’t put them in your compost bin as you risk spreading the disease. Solarization and leaving the soil bare for a while is a good way of killing harmful organisms from the soil before attempting to replant.
Also, be the lookout for aphids, they often attack new fresh growth and can also cause wiling is the attack is server enough. I recommend spraying with a pesticide or even soap and water can do the trick.
Late or early frost
So generally, you prune buddleia in early spring as the new growth emerges, this promotes more growth at the base of the plant and means you get a nice bushy plant with lots of flowers while making sure it doesn’t grow too big. Sometimes if we get some nice weather in spring followed by a sharp frost, this can cause the new growth to wilt from frost damage. The same can happen if you prune later in the year which ideally you wouldn’t do because it promotes new growth late in the season and then the new growth is at risk from frost. This is usually not fatal and it will just take a little longer for the new growth to shoot again.
To much fertiliser
This is usually a problem with newly planted buddleia. When planting, I always recommend mixing a small handful of bone meal or fish blood and bone into the soil to give them the best start. However, make sure you mix the fertiliser into the soil well and don’t just put a handful of fertiliser into the planting hole and then put the root directly on top of it. This can burn the roots and will cause wilting. Make sure it’s well mixed in.
Buddleia bushes are strong plants and often indestructible, therefore, they can spring back after wilting as long the issue was not fatal. Always check the soil for moisture levels and always be on the lookout for infections.
his goes especially for young buddleia bushes because they are more susceptible than the already established plants.