I have a buddleia (6 years old) which has declined over the last two years - it is now merely some dead twigs with very few leaves. I have contacted our local extension agent and she says that it is probably a 'short life' buddleia. I would like to know which buddleias are known to be long life plants so I can avoid this happening again.
Any information you can give will help me greatly!
I can speak from experience about B. davidii that it is unreliable although there may be instances of long-lived individual plants, having grown it for well over a decade in OH, and for about 8 years in AL. They all seem to have the short-lived reputation in general though, judging from what I've read on forums and websites over the years.
Since your question was asked at this time of year and seeing that you're in FL, I wonder if your plant in question has gotten too dried out? Something eating/tunneling around the roots? Although they like to be kind of dry, the more fertile the soil, the better. Have you got mostly sand? Maybe it needs some compost.
If you consider them temporary and transient, you may be less disappointed in the future. Since they propagate so easily, when I take cuttings each spring, I make sure to stick them in several places around the yard, or even near a "mama" if there's room. Since any particular plant is likely to die over winter, that's how I've managed to have some every year from one plant I was given around 20 years ago. Have you been pruning in the spring? That seems to invigorate them. I used to start the cuttings in pots first, but that's really an unnecessary step if you are able to provide temporary shade if it gets hot and keep moist until cuttings are established in situ. Plants that haven't experienced being moved from a pot do better (establish quicker, live longer,) IMO. Spots where it's more dry during the colder months (even when the ground doesn't freeze) seem to be best. Cold + wet = death to these shrubs.
It must depend on where you live, soil type, light etc as mine The B davidii and everyone I know who grows these same named type have been doing so for over 20 years, the same plant, not replants or cutting, Mine spread their seeds around and I have to now tug them out the ground as enough is enough.
What I have learned is, to keep these Shrubs / plant, flowering well, you need to cut the whole plant back to about 12 inches from the ground either end of summer or early spring depending on your zone a frost in winter. Also each year I throw about 3 inches of leaf mold mixed with a handful of general fertilizer and compost mixed together to help it kick start in spring. I have of late even had seedlings growing in the crevices of old walls and even seen some growing in the brickwork of old half demolished buildings though these may not be the davidii type as they are seen from motorways. I feel sure these you have must be either in the wrong soil or the humidity / hot sunshing get;s to the young tender leaf buds, therefore I would be puting up some form of shade for the first few months till the plant can take the elements they are growing in but water is a must, put your finger into the soil to see if it's too dry or dig out a little by using your small trowel.
Good luck, Hope this helps you out.
I agree, I expect it's something related to climate/cultural conditions not the particular variety that you were growing. There are ones out here that I see that have grown basically into trees so they're definitely much older than 6 yrs. The tree ones get that way when people don't cut them back and they just keep growing--they seem to bloom just fine that way too, I see them all the time covered in flowers. Personally though I prefer to cut mine back as WeeNel mentioned to keep them as smaller shrubs rather than big shrubs/small trees.
Totally agree about keeping them smaller, don't let mine get taller than I can reach to deadhead. With something that can grow 5-10 feet within a year, as my Mom lets hers do, height isn't necessarily an indicator of age. Seeing it in the same place every year would make me think they are the same shrubs, too, as they probably are.
Like I said above, first sentence, there are many instances of long-lived individual plants. The last time a friend drove by where I lived at the time, couple years ago, the mama bush I started with back in the 90's was still alive, as are many of the cuttings taken from it over the years, now in various yards in OH and AL. But many are not. Same yards, same care. I've been reading garden forums and websites since they came into existence and short-lived Buddleia is a universal, constant topic of conversation, many of which (conversations) are still out there, should a search sound interesting to anyone.
Takes just a few minutes to trim off some pieces in spring, then stick the cut end in the ground. They will grow unless they get dessicated before being able to establish some roots. Knowing your shrub should survive doesn't help if/when it doesn't. If there's 3, you have 2 more chances. Since they're all free after you get the mama, why not hedge your bets?