Unwins Seeds

How to Grow Penstemons

How to Grow Penstemons

There’s no mistaking that Penstemons are fabulous border plants. Perennial, long-flowering and easy to grow thriving in fertile, moist, free-draining soil. They’re fairly easy to look after, only requiring occasional watering in very dry weather or if planted in very light, free draining soil.

They will flower from late summer until late autumn, when they die right down to the base. Unless there’s a very severe winter, they grow back the following year and flower again. Unlike more hardy perennials in your border, it’s best to keep their stems and foliage in tact throughout the winter to give them that little extra bit of protection from frost or snow. When the weather begins to warm in spring, you can cut the stems right down to the base and allow fresh new growth to take its place.

They prefer light shade or full sun and will attract Bees, Butterflies and other beneficial insects. Our Penstemons are grown from cuttings which give a larger, more vigorous plant with stronger, better developed roots.  They are quick to establish and upon arrival can be planted into their final growing positions providing all risk of frost has passed. However, we do recommend growing them on for a few weeks first.

When They Arrive

Remove the plants from the packing straight away and sit them in a tray of shallow water, allowing the plugs to fully soak.

Once the plugs are completely soaked, remove them from the tray of water and allow drain and rest in a light, frost-free place for the few hours.

Potting Your Plants Up & Growing Them On

One of the best things about our Young Plants is that it isn’t necessary to pot them up and grow them on before planting outside, although we recommend that you do for best results...

How to pot your plants up:

Once your plants have been watered and allowed to drain, they can be planted straight into 9m pots with a good multipurpose or container compost.

When doing so, ensure you handle each plant by the root ball, rather than the stem to avoid damage.

  • Fill each pot loosely with compost and make a large enough hole in the centre to fit the plants’ root ball. Allow one pot per plant.
  • Position the plant into the hole, top up with more compost if required and firm down with your hands.
  • Water after planting to settle to roots and leave to grow-on in a light, frost free place to grow on for 2 – 3 weeks to establish a strong root system before planting out.

Planting Young Plants straight outside:

If planting straight outside without potting on first, it’s best to wait until risk of frost is passed to give them the best chance. Late May is usually fairly safe, but different locations may vary.

Before planting your Young Plants, thoroughly dig and water the soil first. Doing this provides an easier environment for the young plants to establish their roots.

  • Dig an individual hole for each plug, deep and wide enough for the entire root ball.
  • Position the plant into the hole and backfill with soil.
  • Water-in after planting.

5 Tips on Planting Penstemon Plants

1) Enrich the soil with organic matter and general purpose fertiliser when planting out – this will aid good establishment. In subsequent years, add fertiliser and a mulch of well-rotted organic matter each spring.

2) Allow approx 45cm (18in) between plants and protect from slugs when plants are still small.

3) Deadhead spent flowering spikes to prolong the flowering season.

4) Trim back in the spring once the worst of the winter weather has passed (usually in late April or early May) – the old stems provide frost protection for the new shoots.

5) Keep well watered when first planted to make it a good environment for your Penstemon to establish a strong network of roots. In following years, it will only be necessary to water your Penstemon occasionally.

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