Growing Rhododendrons from Seed
Start seeds indoors in fall, winter or early spring. We also grow native azaleas from seed entirely outdoors, sowing in spring.
- Flourescent lights (Shop Lights) with Cool White bulbs.
- Suitable indoor space or greenhouse.
- Optional heating mat and thermostat set to 70 F if in unheated space.
- Milled sphagnum moss (available in bulk from wholesale suppliers, or in small quantities as "No Dampoff")
- Peat Moss
- Plastic Shoe Boxes with Clear Lids. Drainage holes are optional and not necessary.
- Flats approximately 3" deep for transplanting.
- Transplanting medium (screened composted pine bark).
- Optional fungicide, such as Captan.
- Add milled sphagnum and peat moss to water in separate buckets, adding a small amount of Dawn detergent (as wetting agent and mild disinfectant).
- Allow to soak overnight for thorough wetting.
- Add to a shoebox 3 double handfuls of peat moss, squeezing out tightly to remove excess water.
- Add to the shoebox, sprinkling atop the peat moss, 1 double handful of milled sphagnum, also squeezing hard to remove excess water.
- Thinly sow the rhodo seed on top of the sphagnum layer, so that individual seeds are about 1/4 - 1/2 inch apart. *
- Lightly water in the sown rhodo seed (may mist with fungicide), and seal the clear lid of the shoebox.
- Add small amounts of water as necessary to avoid drying out of the sphagnum surface.
- Place seed germination containers under fluorescent lights.
- Germination should begin in 2-3 weeks. Cotyledons appear initially, followed by true leaves in a week or so.
- Seedlings may be transplanted as soon as the first true leaves appear, although they may also be transplanted as cotyledons if sufficient care is taken not to dry out.
- Transplant to Flats, approximately 3-4" apart. Flats may be under lights or in a greenhouse (we use a passive solar heated greenhouse).
- Do not allow transplants to dry out. Water at least daily.
- Transplants may be fertilized weekly with 1/3 strength Miracid or other soluble fertilizer. A thin top dressing of slow release granular fertilizer may also be applied.
- Seedlings may be moved outdoors in early fall, when they are large enough to withstand hard rains. Remove excess tree leaves in fall, to avoid damage to the young seedlings.
- Seedlings may be transplanted to containers or beds after one or two years. Large numbers of seedlings are produced, more than can be reasonably managed, necessitating intentional selection in addition to the natural selection which will occur.
* Fungicide treatment is optional. Seeds may be misted with fungicide solution such as Captan.
Copyright © 2014-2019.
Southeastern Chapter of the American Rhododendron Society.
All rights reserved.
Unless otherwise noted, original content on the SE-ARS website is released under a Creative Commons Attribution 3.0 License.