When they're not in flower, perennials are enjoyed for their foliage, which is at least as important a consideration as the blooms.
Perennials may grow and expand each year, eventually filling more space than you might expect. To keep perennials under control and growing well, many need division (digging up the root clump, dividing it into sections, and replanting the best sections in freshened soil). This can provide a harvest of new plants for use elsewhere in the garden
This could cause the seeds to rot and may give very erratic germination.
This said it is important to keep your eye on them to make sure they don't dry out.
Bees and finches love lavender.
Daisies, whether in wild or cultivated form, are essential because their centres contain an abundance of nectar. Ivy provides nectar for insects and berries for the birds; it also offers shelter: blackbirds, robins and many other birds build their nests in its branches.
As the main aim of a plant is to produce a seed head, removing old blooms you will not only be enhancing the look of your plant you will be forcing it into producing more flowers.
Try using a pair of scissors to remove the dead flowers this can speed the job up.
When watering your baskets and pots take care to give them the right amount of water.
It can be just as damaging to over water your plants as leaving them to dry out.
Next time you water the garden try to become aware if any of your plants are becoming too wet and not growing very well.
Many times when people have a plant that looks sick they think it just needs a good water when all it really needs is to dry out, as a healthy plant will use the water you daily give it.
This will keep your plants healthy and promote good root development. Apply a general purpose fertiliser, being carefull not to damage emerging shoots, or to burn them when feeding. Avoid watering/feeding in the mid day sun.