Citrus

Overview

This project focuses on growing citrus from seed, developing experimental rootstocks, and evaluating how different citrus cultivars perform under Pacific Northwest conditions.

The long-term goal is to determine whether carefully selected seed-grown citrus can provide useful rootstock material while also testing whether grafting can improve growth, flowering, fruiting, and overall performance in my climate.

Rather than simply growing citrus for fruit production, the project treats each plant as experimental material. Seedlings can be evaluated for their own characteristics before eventually being used in grafting and breeding work.

Research Objectives

The project currently follows these five interconnected objectives.

1. Seed-Grown Citrus Development

Grow citrus from seed under local conditions and allow the seedlings to develop naturally before determining their eventual use.

2. Rootstock Development

Evaluate seed-grown citrus for characteristics that could make them useful as future rootstocks, rather than immediately grafting every seedling.

3. Reducing the Juvenile Period

Test whether grafting established cultivars onto selected seed-grown citrus can reduce the time required to reach flowering and fruiting.

The main question is whether grafting can reliably accelerate the transition from juvenile growth to reproductive growth under my conditions.

4. Climate Adaptation

Evaluate whether particular combinations of rootstock and scion can improve citrus performance in my climate, particularly with regard to cold tolerance, growth, flowering, and eventual fruit production.

5. Seed-Grown Controls

The seed-grown siblings will serve as controls against the grafted plants. This will allow me to compare whether the grafting methods actually produce a meaningful difference rather than simply assuming that grafting improves performance.

Current Citrus Collection

The established collection currently includes several different types of citrus, each serving a somewhat different purpose within the project.

• Cara Cara navel orange — future grafting material. <25°F
• Tarocco blood orange — still juvenile; planned for continued growth through the winter. 25-28°F
• Calamondin — Used to grow seedling rootstocks, and experimenting overwintering outdoors. 20-22°F
• Meyer lemon - Experimenting growing outdoors with minimal protection. 20-25°F
• Flying Dragon - Used for rootstock propagation. <-10°F
• Chandler grapefruit/pomelo — particularly cold hardy for pomelo/grapefruit. <28°F
• Seed-grown lemons — four currently growing. 30-35°F
• Seed-grown grapefruit — 28-32°F

Flying Dragon is one of the more important long-term plants in the collection.

The objective is not primarily to use the tree itself as a rootstock. Instead, I want to give it the space and growing conditions necessary to mature as quickly and as completely as possible so that it can produce fruit and, most importantly, seeds.

Those seeds can then be grown into new generations of citrus seedlings.

The long-term process is:

Flying Dragon → fruit → seeds → seed-grown plants → evaluation → grafting with improved cultivars

I also intend to experiment with crossing Flying Dragon with selected citrus cultivars, including Calamondin, once the plants are mature enough to flower.

Current Update: Seed-Grown Citrus and Future Grafting

The citrus project is currently in its early stages, but several seed-grown plants have already been successfully established.

I initially started approximately eight supermarket lemon seeds. I currently have four remaining and growing.

I also started four grapefruit seeds, with three remaining. The grapefruit has produced one particularly interesting observation: each of the three successful seeds produced two seedlings. This multiple-embryo behavior was unexpected and is something I intend to document further.

Repotting Grapefruit Seedlings

This is currently the most unusual observation within the seed-grown citrus group and will be followed as the seedlings mature. The seed-grown citrus will eventually become some of the most valuable experimental material in the project.

Rather than immediately grafting every seedling, I want to allow them enough time to develop their own characteristics. This provides an opportunity to observe differences in vigor, growth habit, cold tolerance, and other traits before selecting which plants are worth retaining as future rootstocks.

The ultimate goal is to graft desirable cultivars onto selected seedlings and compare their performance against ungrafted seed-grown controls.

This should allow me to determine whether particular rootstock/scion combinations can improve performance while also identifying seedlings that may have useful characteristics of their own.

Outdoor Hardiness Experiments

Some citrus will also be evaluated directly under outdoor conditions.

The initial candidates include Calamondin and Meyer lemon.

The objective is to determine what these plants can tolerate naturally before adding increasingly significant winter protection.

For the current experiments, protection will primarily focus on blocking wind and limiting cold rainfall and moisture around the root zone. Blankets or similar passive protection may also be used when necessary.

The plants will be monitored for minimum temperatures experienced, visible cold damage, survival, recovery, and subsequent growth.

Notable Observations

The purpose of growing these plants from seed is not simply to produce inexpensive citrus trees. Each seedling provides an opportunity to observe variation and potentially identify useful characteristics that could be carried forward into future generations.

All three grapefruit seeds that successfully germinated produced two seedlings each.

Future Additions

The collection is currently at structural capacity, so additional citrus acquisitions are being limited.

Potential future additions include:

• A hardy mandarin or another cold-tolerant mandarin-type citrus
• Smith's Red Valencia or Vaniglia Sanguigno blood orange

Currently on hold:

• Yuzu Lemon
• Melogold
• Citrumelo
• Clementine

These will remain potential additions rather than immediate purchases until additional space becomes available.

Looking Forward

The immediate priority is to allow the existing citrus collection to mature rather than continuously adding new plants.

The next stages of the project will focus on:

• Developing the seed-grown lemon and grapefruit seedlings.
• Monitoring the unusual multiple-seedling grapefruit behavior.
• Allowing Flying Dragon to mature enough to produce fruit and seeds.
• Continuing outdoor trials with Calamondin and Meyer lemon.
• Evaluating seedling characteristics before selecting future rootstocks.
• Beginning grafting experiments as suitable rootstocks mature.
• Eventually comparing grafted plants against their seed-grown controls.
• Expanding the genetic pool when additional space becomes available.

The overall objective is to build a progressively larger pool of locally evaluated citrus genetics rather than simply accumulating individual cultivars.